Interacting effects of elevated atmospheric CO2 and hydrology on the growth and carbon sequestration of Sphagnum moss

Interacting effects of elevated atmospheric CO2 and hydrology on the growth and carbon... Wetlands Ecol Manage https://doi.org/10.1007/s11273-018-9607-x OR IGINAL PAPER Interacting effects of elevated atmospheric CO and hydrology on the growth and carbon sequestration of Sphagnum moss . . . Thomas R. Newman Neal Wright Barbara Wright Sofie Sjo¨gersten Received: 21 September 2017 / Accepted: 19 March 2018 The Author(s) 2018 Abstract Peatlands are a critical carbon store com- Elevated CO levels increased Sphagnum height and prising 30% of the Earth’s terrestrial soil carbon. dry weight but the magnitude of the response differed Sphagnum mosses comprise up to 90% of peat in the among species. The most responsive species, S. fallax, northern hemisphere but impacts of climate change on yielded the most biomass compared to S. papillosum Sphagnum mosses are poorly understood, limiting and S. capillifolium. Water levels and the CO development of sustainable peatland management and treatment were found to interact, with the highest restoration. This study investigates the effects of water level (1 cm below the surface) seeing the largest elevated atmospheric CO (eCO ) (800 ppm) and increase in dry weight under eCO compared to 2 2 2 hydrology on the growth of Sphagnum fallax, Sphag- ambient (400 ppm) concentrations. Initially, CO flux num capillifolium and Sphagnum papillosum and rates were similar between CO treatments. After greenhouse gas fluxes from moss–peat mesocosms. week 9 there was a consistent three-fold increase of the CO sink strength under eCO . At the end of the 2 2 experiment, S. papillosum and S. fallax were greater Electronic supplementary material The online version of sinks of CO than S. capillifolium and the - 7cm this article (https://doi.org/10.1007/s11273-018-9607-x) con- water level treatment showed the strongest CO sink tains supplementary material, which is available to authorized strength. The mesocosms were net sources of CH but users. 4 the source strength varied with species, specifically S. T. R. Newman (&) fallax produced more CH than S. papillosum and S. School of Geography, Geology and the Environment, capillifolium. Our findings demonstrate the impor- University of Leicester, Leicester, UK tance of species selection on the outcomes of peatland e-mail: trn2@leicester.ac.uk restoration with regards to Sphagnum’s growth and S. Sjo ¨ gersten GHG exchange. School of Biosciences, The University of Nottingham, Nottingham NG7 2RD, UK Keywords C sequestration  Elevated CO e-mail: Sofie.Sjogersten@nottingham.ac.uk Greenhouse gas fluxes  Peatland  Sphagnum N. Wright  B. Wright Climate change Micropropagation Services, Ley Springs, Loughborough Road, East Leake, Loughborough, Leicestershire LE12 6NZ, UK e-mail: Neal@microprop.co.uk B. Wright e-mail: Barbara@microprop.co.uk 123 Wetlands Ecol Manage Introduction Atmospheric CO concentration has increased since pre-industrial times to ca. 408 ppm (ESRL Peatlands are important in the global carbon (C) cycle NOAA 2015) and is predicted to increase to 800 ppm due to their function as a long-term carbon store. This by the year 2100 (IPCC 2013). The effects of this store has built up through millennia due to very low elevation of atmospheric CO on Sphagnum moss are decomposition rates that are surpassed by productivity currently disputed, with studies indicating an increase rates (Clymo and Hayward 1982) making peatlands in growth rate (Jauhiainen and Silvde 1999; Heijmans net carbon sinks. It’s been estimated that today’s et al. 2001a; Saarnio et al. 2003), decreases in growth peatlands store ca 30% (* 550 Pg C) of the Earth’s rate (Grosvernier et al. 2001; Fenner et al. 2007) and terrestrial soil carbon while comprising only 3% of the no response (Van der Hejiden et al. 2000; Hoosbeek Earths land area (Gorham 1991;Yu 2012). et al. 2002; Toet et al. 2006). Contrasting responses Within peatlands in the northern hemisphere, between Sphagnum species are thought to be the cause Sphagnum mosses are often the dominant species, of some of the variation. Toet et al. (2006), found comprising up to 90% of peat (Clymo 1987). Sphag- increased abundance in S. recurve and no difference in num plays an important role in peatland formation and S. palustre when they were subjected to an elevation of ecological resilience, through its low decomposition 180 ppm above ambient, while S. fuscum did not rate due to its recalcitrant and antibacterial nature respond to elevated CO (350, 700, 1000 and (Kroken et al. 1996) and by creating acidic, anoxic and 2000 ppm) at all (Jauhiainen et al. 1997). Further- nutrient-poor conditions within peatlands (Amesbury more, contrasting responses have been seen between 2013; Hajek and Vicherova 2014). Sphagnum’s studies conducted on the same species. For example, S. extraordinary physiology allows it to hold 16–26 magellanicum, was found to increase in growth rate by times its weight in water (Bold 1973; Amesbury Heijmans et al. (2001b) when subjected to 560 ppm 2013), in both live and dead non-decomposed Sphag- CO , while Heijmans et al. (2001a) reported a greatly num, depending on species. This buffers the impact of reduced growth rate. This suggests factors other than dry weather conditions on peat moisture levels, species are affecting Sphagnum’s response to elevated preventing the peat from drying out and decomposing. CO . Peatlands are classified as such once an organic soil Hydrology has been identified as one of the most layer of 30 cm or greater has formed; for northern important factors controlling Sphagnum growth and peatlands, the average peat depth is 1.3–2.3 m, but peatland carbon dynamics (Strack and Waddington peat depth can extend to 15–20 m in some peatlands 2007; Turetsky et al. 2012; Lanta and Kantorova 2015 (Clymo et al. 1998; Turunen et al. 2002). Accumula- etc.). Water availability impacts both C sequestration tion rates of Sphagnum peat are approximately and growth rate (Glime 2007), due to there being an -1 0.61–3.9 mm year (Royles et al. 2012; Amesbury optimum moisture content for Sphagnum photosyn- 2013), due to Sphagnums slow growth rate within the thesis (Rice and Giles 1996). Varying physiologies cold, nutrient poor peatlands (Strack 2008). The slow mean that different Sphagnum species vary in sensi- growth rate is important in the context of peatland tivity to changes in water level, each often growing management as once the peat is lost, the peatland will best within their own hydrological niche (Rydin and only recover slowly over centuries/millennia. Degra- Mcdonald 1985; Grosvernier et al. 1997; Taylor et al. dation of peatlands through drainage, mining and 2015). For example, mature S. fallax is observed to removal of Sphagnum allows stored C to be released struggle at low water levels (Carroll et al. 2009), while back into the atmosphere CO , through decomposition having higher growth rates than any other species in of the exposed peat. It is estimated that UK peatlands wet conditions (Buttler et al. 1998). Recent studies -1 are a net source of 3.72 Mtn CO year (Worrall 2eq have also highlighted the importance of precipitation et al. 2011), with only 1% of Englands deep peats on Sphagnum dominated peatlands carbon dynamics considered to be in an undamaged state (Natural and species distribution (Robroek et al. 2009; Radu England 2010). This makes restoring peatlands a and Dual 2018). Nijp et al. (2014) found precipitation priority, as restored peatlands not only protect the reduced the negative impacts of drought, while already sequestered carbon, but can reinstate their Robroek et al. (2007) found precipitation allowed carbon sink capacity (Strack 2008). species to survive outside of their hydrological niche. 123 Wetlands Ecol Manage Materials and methods Precipitation also affects Sphagnum C uptake, with species responding differently to varying precipitation Experimental set up frequencies (Nijp et al. 2014). Water limitation has also been found to affect the impacts of other factors, Peat cores were collected from Cadishead and Little such as temperature and vegetation’s impact on CO and CH fluxes (Silvola et al. 1996; Leppala et al. Woolden Mosses (North West England, UK M44 5LR of Grid ref: SJ697953). This site is typical of drained 2011). Currently large tracts of damaged peatlands are and degraded cut over peatlands in the UK. The site is being restored in the UK via application of Sphagnum currently under restoration and some areas have been containing beads and gel to encourage growth on re-flooded. It is characterized by predominantly bare degraded peatland sites (Hinde et al. 2010; Wittram peat with cotton grass and birch growing around the et al. 2015). However, information is limited with edges with Sphagnum growing only in areas where regards to which species are most effective in quickly reintroduction has been attempted. To account for variation within the peat substrate, establishing and recreating peatland functions such as C sequestration, particularly in the context of global all 72 peat cores (approximately 18 cm 9 16 cm) were collected from random locations within the non- change, e.g., elevated atmospheric CO concentra- tions. Such information is urgently needed to ensure flooded part of the peatbog. Collection and transporta- tion of cores took place within 8 h, after collection that restoration efforts are as effective as possible under future elevated atmospheric CO levels. For cores were refrigerated at ? 4 C. example, some studies indicate that elevated CO Three weeks after collection, peat cores were then levels may result in increased CH fluxes peatlands cut into 17.4 cm 9 11 cm cylinders and transplanted dominated by Sphagnum species (Saarnio et al. into 17.4 cm 9 15.6 cm clear plastic, cylindrical polypropylene containers. The treatments were 2000, 2003; Ellis et al. 2009) but effects differ among studies made across European peatland sites (Silvola applied in a randomised block design (n = 4) with species (S. fallax, S. papillosum and S. capillifolium) et al. 2003). To date, a hand full of studies have considered a possible interaction between hydrology and water level (1, 4 and 7 cm below the peat surface) as the treatments. Each combination of species and and raised atmospheric CO on the growth of Sphag- num moss (e.g., Jauhiainen et al. 1997; Toet et al. water level was repeated four times within each 2006) despite that interactions with hydrology may growth room. The randomized block design was used control how different Sphagnum species respond to to account for any possible variations of conditions elevated CO . Indeed, interactions between hydrology within each growth room. The two CO treatments 2 2 and elevated atmospheric CO concentrations may used were 400 and 800 ppm CO (ambient and cause the contrasting responses of Sphagnum species elevated), 800 ppm is the predicted 2100 concentra- tion (IPCC 2013), due to the slow growth rates of to elevated CO found in previous studies. Such interaction would have important implications for Sphagnum this was chose as a good analogue for future restoration attempts. To achieve the two CO peatland restoration, suggesting that selecting the correct species for the environment is critical for treatments cores were randomly allocated to one of two growth rooms in which the atmosphere was restoration success. The aim of this study was to determine whether adjusted to the target CO concentration. Apart from the CO concentration the settings in the growth room there is an interaction between hydrology and elevated atmospheric CO on the growth and greenhouse gas were identical: Day length consisted of a 16 h -2 -1 (GHG) exchange of three Sphagnum moss species photoperiod (300 lmol m s ), including a 1 h -2 -1 grown on peat-monoliths. To achieve this aim two dawn/dusk and 8 h night (0 lmol m s ). Daytime specific hypotheses were tested: (i) elevated atmo- conditions were set to a temperature of 21 C and a relative humidity of 50%, while night-time conditions spheric CO will have a greater positive effect on S. fallax growth and GHG fluxes than other species; (ii) were set to 15 C and 75% respectively. low water table will inhibit the effect of elevated CO on Sphagnum growth. 123 Wetlands Ecol Manage Water levels within the growth rooms where consistent throughout the course of the experiment: Temperature was Once the peat cores were placed in the growth rooms, measured at 27.5 ± 0.1 C in direct light with an air the three water level treatments were applied to the temperature of 21.2 ± 0.1 C, relative humidity, cores, which were then allowed to equilibrate for 52 ± 1% and finally light was 234 ± 0.4 lmol -2 -1 1 week. All water applied to the cores initially and m s . throughout the experiment was rainwater that was Sphagnum height was measured using an adaption firstly collected as runoff from glasshouses located in of the cranked wire method detailed by Clymo (1970). East Leake, Loughborough, Leicestershire. The rain- Initial height of the moss (peat level) was marked on water was then filtered through a sand gravity filter, the side of the clear plastic container; from this the leaving the rainwater free of particulate contaminants height of the tallest Sphagnum plant in each individual such as dirt washed from the glasshouse surface. container was measured to the nearest mm. Rainwater was used to simulate ombrotrophic peat- As Sphagnum was grown from micro propagated land conditions. Water level treatments were moni- plants, the establishment rates of the different Sphag- tored daily for the first month and then once every num species could be quantified. This was inferred 2 days thereafter via visual inspection. If needed water through the Normalized Difference Vegetation Index was applied to the cores using a pressurised water (NDVI), a numerical indicator that uses the visible and sprayer to reduce disturbance to the peat surface. This near-infrared bands of the electromagnetic spectrum kept variation in water level to within 1 cm throughout to assess crop healthiness (Govaerts and Verhulst the course of the experiment. 2010). This was done using a hand held device (GreenSeeker , Trimble Navigation Ltd., Sunnyvale Sphagnum application California, USA), which gave a reading between 0 and 1 where 0 indicates bare soil and 1, established green After 1 week, each species of Sphagnum was applied vegetation (FSNAU 2016). The Green Seeker was to the relevant core using liquid gels, currently used held approximately 10 cm above the Sphagnum for application to peatlands as part of restoration surface, with a reading for each core taken over 5 s programmes, containing micro propagated material of while the device was continually moved over the each species. The Sphagnum suspended within the gel whole surface of the core, giving an average reading was micropropagated from source material originating for each core. from the Peak Districk, UK, by MicroPropagation The total Sphagnum biomass production from each Services (MicroPropagation Services (EM) Ltd 2015). container was quantified at the end of the experiment. The micro-propagated Sphagnum was suspended For this all Sphagnum growth in each container was within a gel containing basic nutrients, at an approx- removed, weighed (wet weight), dried at 70 C and imate concentration of 150,000 individual plants per weighed again (dry weight). L, which ranged from 1 to 5 mm in length (for CO flux and evaporation rate from each core was example gel see SI. 1). The gel was applied at a rate of measured using an EGM-4 Infrared Gas Analyser 3L per m (0.072L per core) using a large pipette (IRGA) connected to a CPY-3 using an open dynamic before being spread evenly over the core surface. The system (PP systems, Hitchin, UK). CO flux rates were application rate is the same as trials conducted using recorded every minute over a 10 min period. IRGA the same gel in the restoration of the Cadishead time wishing was every 8 s, from which a linear peatland (Wright et al. 2012). regression is calculated to determine CO flux over each 1 min period. To ensure fluxes were not affected Measurements of Sphagnum performance by disturbance following the installation of the CPY-3 and GHG fluxes chamber over the mesocosms, we used only the final three readings, these were averaged and used for Measurements of Sphagnum performance and CO subsequent data analysis. Positive fluxes represent a fluxes were made bi-weekly for each parameter apart net release of CO from the mesocosms. from CH gas samples and dry weight, which were For CH flux determination, gas samples were determined at the end of the experiment. Conditions collected from each container using a modified version 123 Wetlands Ecol Manage of the closed static chamber method (Collier et al. 2014). Each container was carefully sealed using a lid with a septum in its centre giving a headspace of 0.11 dm . Then, using a 30 ml syringe with a 25 gauge hypodermic needle, gas samples were then taken after 1, 30 and 60 min. Samples were then transferred into 12 ml pre-evacuated exetainers before each sample was analysed via gas chromatography (GC-2014; Shimadzu, UK) using a Flame Ionization Detector (FID), with hydrogen as the carrier gas. The oven temperature was 40 C, the injector 80 C and the FID -1 Fig. 1 The effect of elevated CO and species on NDVI 250 C. The flow rate was 30 ml min ; the column (mean ± SE) over the 13 week experimental period. Black was a HayeSEp N packed column, 60/80 mesh. lines represent atmospheric CO of 400 ppm; light grey lines Measurements for each container were analysed using represent atmospheric CO of 800 ppm. Diamonds and solid lines represent S. fallax; squares and dashes lines represent S. a linear regression model and the ideal gas law to papillosum; triangles and dotted lines represent S. capillifolium calculate gas flux rate for each container, which was -2 -1 then used to calculate CH flux in mg m h where capillifolium established slower than under the ambi- positive gas fluxes represent net CH emissions. ent treatment (F = 2.96, P = 0.061). (2,51) Sphagnum grew taller under eCO (F = 16.34, 2 (1,51) Statistical analysis P\ 0.001) but this effect varied among species (F = 5.31, P= 0.008) with S. fallax responding (2,270) The effects of time, hydrology, species and CO most significantly to eCO (F = 48.78, P\ 0.001) 2 (2,51) treatment and their interactions on height, evapora- (Fig. 2a). S. papillosum height was also found to tion, CO flux and NDVI were tested using repeated increase growth under eCO (2.9 mm taller by week 2, measures analysis of variance (ANOVA) after box- 13) the effect was not as large as S. fallax (7.4 mm cox transformations had been performed where nec- taller by week 13), while S. capillifolium indicated no essary, to normalize the data. Time was treated as a difference in height between the treatments (Fig. 2a). categorical variable, with each measurement week The lowest water level (7 cm below peat surface) had treated as a separate category. Treatment effects on shorter plants (near significant water level effect: dry weight and CH flux were tested using ANOVA F = 2.49, P = 0.093) than both the medium (4 cm (2,51) with hydrology, species, and CO treatment as fixed below peat surface) and high (1 cm below peat effects, where CO flux was normalised to the CO 2 2 surface) water levels (Fig. 2b). flux from the first set of measurements (week 3). This The eCO treatment yielded 90.3% increase in removed the impact of variation in the initial CO flux biomass (294.2 ± 47.2 g m ) compared to the ambient rates from the cores. All calculations were performed treatment (154.6 ± 23.7 g m )(F = 30.94, P \ (1,51) using the data analysis program GenStat 17th Edition 0.001). However, the effect size varied among species for windows 10.1 (VSN International 2011). (F = 4.17, P = 0.021), with S. fallax showing a (2,51) 129.7% increase in biomass production under eCO -2 (eCO 142.4 ± 17.1 g m , ambient Results -2 62.0 ± 9.8 g m ), followed by a 101.0% increase -2 for S. capillifolium (eCO 66.8 ± 16.1 g m , ambi- Growth -2 ent 33.2 ± 6.4 g m ) and finally a 43.2% increase -2 for S. papillosum (eCO 85.068 ± 14.0 g m , ambi- Different establishment rates were found between -2 ent 59.4 ± 7.6 g m ) (Fig. 3a). species (F = 7.20, P = 0.002), with S. fallax (2,51) Sphagnum grown at higher water level treatments establishing fastest with NDVI [ 0.8 in week 7, which produced more biomass (F = 7.64, P = 0.001) (2,51) was 2 weeks earlier than S. papillosum and 3 weeks (Fig. 3a). The eCO and water level treatments earlier than S. capillifolium (Fig. 1). Under eCO S. interacted (F = 4.13, P = 0.022) with the high (2,51) fallax and S. papillosum established faster, while S. 123 Wetlands Ecol Manage Fig. 2 a The effect of elevated CO and species on plant height b The effect of water level on plant height (mean ± SE) over the (mean ± SE) over the 13 week experimental period. Black lines 13 week experimental period. Diamonds and black line represent atmospheric CO of 400 ppm; light grey lines represents a water level 1 cm below peat surface; squares and represent atmospheric CO of 800 ppm. Diamonds and solid dark grey line represent a water level 4 cm below peat surface; lines represent S. fallax; squares and dashes lines represent S. triangles and light grey line represent a water level 7 cm below papillosum; triangles and dotted lines represent S. capillifolium. peat surface Fig. 3 a The effect of species on dry weight (mean ± SE) (mean ± SE) recorded at the end of the 13 week experimental recorded at the end of the 13 week experimental period. For period. For each water level, black bars represent growth under each species, black bars represent growth under 400 ppm 400 ppm atmospheric CO ; light grey bars represent 800 ppm atmospheric CO ; light grey bars represent 800 ppm atmo- atmospheric CO 2 2 spheric CO b The effect of water level on dry weight water level resulting in the largest increase of 142.0% flux rates over the first 7 weeks period. After 7 weeks -2 (79.9 ± 9.2 g m ) in biomass under eCO compared there was a large increase in the CO uptake (increas- 2 2 -2 to a 66.0% increase (35.6 ± 8.1 g m ) at the 4 cm ingly negative CO flux) under eCO (F = 14.59, 2 2 (1,51) -2 and 19.2% (8.5 ± 5.4 g m ) increase at the 7 cm P \ 0.001). Specifically, CO uptake was more than water level treatments (Fig. 3b). 5-times greater in week 7 and consistently 3-times greater than the ambient treatment from week 9 to the Gas flux end of the experiment (Fig. 4a; Time 9 eCO inter- action: F = 27.28, P \ 0.001). Increasingly (5,270) In parallel with the NDVI and height data, elevated lower water levels were found to have a significantly and ambient CO treatments had almost identical CO larger CO uptake (F = 5.00, P = 0.010) (Fig. 4b). 2 2 2 (2,51) 123 Wetlands Ecol Manage Fig. 4 a The effect of elevated CO on CO flux (mean ± SE) represent 4 cm below the surface; triangles and light grey line 2 2 over the 13 week experimental period. Diamonds and black line represent 7 cm below the surface. c The effect of species on CO represent 400 ppm atmospheric CO ; squares and grey line flux (mean ± SE) over the 13 week experimental period. represent 800 ppm atmospheric CO . b The effect of water level Diamonds and solid line represent S. fallax; squares and dashed (cm below the peat surface) on CO flux (mean ± SE) over the line represent S. papillosum; triangles and dotted line represent 13 week experimental period. Diamonds and black line S. capillifolium. d The effect of species on CH flux represent 1 cm below peat surface; squares and dark grey line (mean ± SE) -2 -1 CO fluxes were found to differ between species m h ) (Fig. 4d); the species and eCO treatments 2 2 (F = 4.29, P = 0.019), with S. capillifolium did not interact with the water level treatments. (2,51) having the smallest uptake of CO -2 -1 (- 69.12 ± 14.74 mg m h ) compared to S. -2 -1 papillosum (- 101.30 ± 15.47 mg m h ) and S. Discussion -2 -1 fallax (- 91.56 ± 16.43 mg m h ) by week 13 (Fig. 4c). Over the course of the experiment, CO Growth responses uptake increased more for S. fallax and S. papillosum over the course of the experiment than S. capillifolium Our finding that eCO increased Sphagnum growth are (F = 6.24, P \ 0.001) (Fig. 4c). in agreement with multiple studies (Jauhiainen and (10,270) Only the species treatment was found to have an Silvola 1999; Heijmans et al. 2001a; Saarnio et al. effect on CH flux (F = 3.66, P = 0.029), 2003), however as this area of research is contested, 4 (2,123) with S. fallax producing the most CH the results are also in disagreement with several -2 -1 (5.28 ± 2.22 mg m h ), twice as much as S. studies (Berendse et al. 2001; Grosvernier et al. 2001; -2 -1 papillosum (2.09 ± 1.09 mg m h ) and 10 times Fenner et al. 2007). as much as S. capillifolium (0.48 ± 0.18 mg 123 Wetlands Ecol Manage The greater effect of elevated CO on S. fallax S. capillifolium (Carroll et al. 2009). One reason for growth and establishment than either of the other this could be the impact of precipitation rewetting on species supports the first hypothesis which predicted reducing the impact of drought by precipitation that fast growing S. fallax would respond most increasing the water contents of the top layer (Nijp positively to the eCO treatment. This is in agreement et al. 2014), negating the impacts of a lower water with previous studies (Berendse et al. 2001; Mitchell table. However, differences between species utiliza- et al. 2002; Granath et al. 2012) which suggested that tion of precipitation was seen by Nijp et al. (2014) increased CO will increase the growth of certain between S. majus, S. balticum and S. fuscum, which species more than others. Variation in species was not seen within our findings. This suggests that responses may be caused by differences in the our experiment did not differentiate water level to a effectiveness of species to utilize the increased high enough degree to examine differences between atmospheric CO concentration. Under elevated CO the species. 2 2 it’s possible that water became the limiting factor for growth, even under the highest water level treatments. CO and CH flux responses 2 4 Silvola (1991) showed that the differences in water needed for photosynthesis vary between species. Greater CO assimilation under eCO was found in S. 2 2 Additionally, Nijp et al. (2014), found that Sphagnum fallax and S. papillosum than S. capillifolium, this species vary in their ability to exploit transient water lends additional support to our first hypothesis which resources. This could account for the differences seen predicted that elevated CO would increase C seques- in growth rates under increased CO between the tration due to increased growth rates but that responses species, with some species better able to exploit the would differ among species. Our finding of increased elevated CO under the hydrological conditions. CO uptake under eCO agrees in part with findings by 2 2 2 Sphagnum also have higher water level limits due to Van der Heijden et al. (2000), who found that blocking of CO diffusion to the leaf via the layer of photosynthesis in mature plants of S. fallax was water surrounding the leaf, with species differing on initially stimulated by elevated CO (700 ppm). the extent of water level found limiting (Glime 2007). However, in contrast to our findings, acclimation For example, optimum water content for photosyn- was observed with stimulated S. fallax returning to the thesis for S. fuscum are lower than those required for S. levels of the controls after 3 days. This could have angustifolium. This could have impacted Sphagnum been due to differences between establishing and growth within our experiment due to the high mature S. fallax. frequency of precipitation and surface water this Our findings somewhat contrasted with Harpensla- provided to the Sphagnum. ger et al. (2015), who grew four Sphagnum species on We found that higher water levels coupled with peat monoliths incubated between 18 and 23 C over a eCO caused a greater increase in dry weight support- 12 week period. Harpenslager et al. (2015), found that ing our second hypothesis, which predicted that low S. fallax and S. palustre had positive net C effluxes water tables would inhibit the effect of elevated CO similar to bare peat in spite of increased biomass. on Sphagnum growth. Similar results were found for S. Harpenslager et al. (2015) suggested that these results fuscum by Jauhiainen et al. (1997), who suggested that were due to the release of CO derived from this was due to water limitation of photosynthesis of bicarbonate due to lowering of the monoliths pH. Sphagnum at low water levels. We did not find an While this is dissimilar to our findings, these releases interaction effect of hydrology on species, in contrary were species dependant, highlighting how different to previous studies, which have identified that each species can impact total CO flux beyond sequestra- species of Sphagnum grows best within its own tion. These differences in growth and C fixation hydrological niche (Grosvernier et al. 1997). It’s also between the species were in congruence with our been found that each species responds to variation in results. water tables differently (Jauhiainen et al. 1997; Carroll Overall our findings suggest that in the context of et al. 2009) due to differences in their physiologies. In future elevated CO , all three species of Sphagnum particular, S. fallax has been found to be highly will increase in CO assimilation due to increased dependent on water level, holding 30% less water than growth, however, it is suggested that not all species 123 Wetlands Ecol Manage will react the same, with certain species seeing a much while the plots in the other two studies encompassed greater increase in CO assimilation (in this case S. both Sphagnum mosses, sedges and dwarf shrubs fallax and S. papillosum) compared to others. Whilst making it difficult to isolate Sphagnum species our study did not find acclimation (such as Van der responses in the two field studies. Heijden et al. (2000), this could be due to our focus on The species-specific effects on CH fluxes of the establishing Sphagnum and not mature plants. three Sphagnum species used in this study is important Greenhouse gas budgets for peatlands are often as it suggests that the Sphagnum species composition complex, with most peatlands being sources of CH per se, and not just the mix of functional groups (Strom (Moore and Roulet 1995; Saarnio et al. 2007; Leppala et al. 2005; Leppala et al. 2011) is an important control et al. 2011). As CH has a Global Warming Potential of CH . Although the mechanisms behind the species- 4 4 (GWP) of 28 over 100 years (IPCC 2013), the specific effects on CH fluxes are unclear. They may increased CO sink strength in response to eCO relate to differences in production of labile carbon and/ 2 2 shown here could be offset if CH emissions increase. or phenolic compounds among Sphagnum species In our 13-week study CH emissions remained low, (Ellis et al. 2009). Transportation of C to the although they increased slightly at the end of the rhizosphere has been shown to vary with species experiment. (Reich et al. 2001). It’s possible that similar variation The GWP of the CH4 emissions over 100 years may account for the differences seen in emissions (CO equivalents (CO )) of the three species was between the Sphagnum species. 2 2eq 147.84 ± 62.12, 58.52 ± 23.98 and Furthermore, relationships between species and -2 -1 13,44 ± 5.04 mg m h for S. fallax, S. papillosum specific methanogenic and methanotrophic communi- and S. capillifolium respectively. If emissions of CO ties could have also had an impact. This has been and CH from each species are taken into account, S. shown for plant functional types within peatlands by fallax would have a positive net emission Robroek et al. (2015), which showed removal of plant -2 -1 (56.28 mg m h CO ), while S.papillosum and functional types (gramminoids and ericoids) signifi- 2eq S.capillifolium would have a negative net emissions cantly alter microbial community structure. This fit’s -2 -1 (- 42.78 and -55.68 mg m h CO respec- with Opelt et al. (2007) who found that diversity of 2eq tively). This suggests that while S. fallax was shown bacterial communities was higher in S. fallax than S. to have the greatest C assimilation over the course of magellanicum. the experiment, S. papillosum and S. capillifolium had lower net emissions. This highlights the importance of CH release within these systems which can offset Conclusions carbon uptake to a substantial amount and even become a net source of emissions. Our study highlights the importance of Sphagnum The increase in CH emissions towards the end of species selection when undertaking restoration of a the experiment was likely due to recovery of peatland. The clear differences in species establish- methanogenic populations following the increased ment and growth under increased CO and CH flux 2 4 moisture content of the peat (Bellisario et al. 1999; between the species indicates that selecting the correct Leppala et al. 2011) and increased C availability due to Sphagnum species or combination of species is critical increased photosynthesis (Megonigal and Schlesinger to the success and GHG balance of recolonization 1997) and C transportation to the rhizosphere (Orem- attempts. While water level was not shown to interact land 1988; Williams et al. 2000). The lack of response with species, it’s interaction with CO suggests that CH fluxes to eCO in our study contrasts with environmental factors may also play an important role 4 2 findings from FACE studies on UK and Finnish in establishment success. ombrotrophic peatlands which found modest increases Furthermore, differences between the species CO in peatland CH fluxes in response to eCO (Saar- and CH fluxes within the initial establishment period, 4 2 4 nio and Silvola 1999; Ellis et al. 2009). An important suggests that using different species will impact the difference between our study and those of Saarnio and overall GHG balance the peatland once restored. Silvola (1999) and Ellis et al. (2009) are the fact that Within the establishment phase, the increase in CO our mesocosms contained a sole Sphagnum species uptake found in response to eCO suggests that the 123 Wetlands Ecol Manage for the restoration of cut-over bogs. J Appl Ecol capacity to sequester C by Sphagnum dominated 35:800–810. https://doi.org/10.1046/j.1365-2664.1998. peatbogs may increase under future CO rich atmo- 355351.x spheric conditions. Nevertheless, there may be trade- Carroll J, Anderson, P, Caporn S, Eades P, O’Reilly C, Bonn A offs between plant performance and GHG emissions (2009) Sphagnum in the peak district. Current status and potential for restoration. Moors for the future. Report as our fastest growing species S. fallax also had the 16:1–121 highest CH emissions, which offset assimilation and Clymo RS (1970) The growth of Sphagnum: methods of mea- caused net GHG emission. While the estimation of the surement. J Ecol 58:13–49. https://doi.org/10.2307/ impacts to the final GHG balance of a restored Clymo RS (1987) The ecology of peatlands. Sci Prog peatland are beyond the scope of this paper, this 71:593–614 highlights that species may be and important consid- Clymo RS, Hayward PM (1982) The ecology of Sphagnum. In: ered when determining which Sphagnum species Smith AIE (ed) Bryophyte ecology. Springer, Netherlands, should be used for peatland restoration. pp 229–289 Clymo RS, Turunen J, Tolonen K (1998) Carbon accumulation in peatland. Oikos 81:368–388. https://doi.org/10.2307/ Acknowledgements This work was completed at The University of Nottingham. Thank you to The Lancashire Collier SM, Ruark MD, Oates LG, Jokela WE, Dell CJ (2014) Wildlife Trust for allowing the use of peat from Cadishead & Measurement of greenhouse gas flux from agricultural soils Little Woolden Mosses, Anna Keightley her help with peat using static chambers. J Vis Exp 90:e52110. https://doi. collection and expertise of Cadishead & Little Woolden Mosses org/10.3791/52110 and the lab staff at The University of Nottingham for their Ellis T, Hill PW, Fenner N, Williams GG, Godbold D, Freeman assistance with equipment and helping to solve technical issues C (2009) The interactive effects of elevated carbon dioxide when they arose. This study was supported by and water table draw-down on carbon cycling in a Welsh MicroPropagation Services (EM) Ltd (T.R.N). ombrotrophic bog. Ecol Eng 35:978–986 ESRL NOAA (2015) Trends in atmospheric carbon dioxide. Compliance with ethical standards http://www.esrl.noaa.gov/gmd/ccgg/trends/. Accessed 03 Nov 2015 Conflict of interest The authors declare that they have no Fenner N, Ostle NJ, Mcnamara N, Sparks T, Harmens H, Rey- conflict of interest. nolds B, Freeman C (2007) Elevated CO effects on peat- land plant community carbon dynamics and DOC Open Access This article is distributed under the terms of the production. Ecosystem 10:635–647 Creative Commons Attribution 4.0 International License (http:// FSNAU (2016) Understanding the normalized difference veg- creativecommons.org/licenses/by/4.0/), which permits unre- etation index (NDVI). https://www.google.co.uk/url?sa = stricted use, distribution, and reproduction in any medium, t&rct = j&q = &esrc = s&source = web&cd = 2&sqi = provided you give appropriate credit to the original 2&ved = 0ahUKEwj3u4Kf9_jMAhXDChoKHYRpBdQQ author(s) and the source, provide a link to the Creative Com- FggkMAE&url = http%3A%2F%2Fwww.fsnau.org%2F- mons license, and indicate if changes were made. downloads%2FUnderstanding_the_Normalized_Vegetation_ Index_NDVI.pdf&usg = AFQjCNH7xIkJg2mjblyralvxpxRL u7lV2w&sig2 = 0scVtLMrBFmV_kPX7goVrw&bvm = bv. 122852650,d.d2 s&cad = rja. Accessed 3 May 2016 Glime MJ (2007) Bryophyte ecology, volume 1, physical References ecology. Michigan Technological University: International Association of Bryologists. http://www.bryoecol.mtu.edu/. Amesbury M (2013) Sphagnum moss: bog plant extraordinaire! Accessed 6 Nov 2015 http://bogology.org/2013/09/27/sphagnum-moss-bog- Gorham E (1991) Northern Peatlands—role in the carbon-cycle plant-extraordinaire. Accessed 24 Oct 2015 and probable responses to climatic warming. Ecol Appl Bellisario LM, Bubier JL, Moore TR, Chanton JP (1999) Con- 1:182–195. https://doi.org/10.2307/1941811 trols on CH emissions from a northern peatland. Glob Govaerts B, Verhulst N (2010) The normalized difference Biogeochem Cycles 13(1):81–91 TM vegetation index (NDVI) greenseeker handheld sensor: Berendse F, Van Breemen N, Rydin H, Buttler A, Heijmans M, toward the integrated evaluation of crop management. Part Hoosbeek MR, Lee JA, Mitchell E, Saarinen T, Vasander A-concepts and case studies. CIMMYT, Mexico H, Wallen B (2001) Raised atmospheric CO levels and Granath G, Strengbom J, Rydin H (2012) Direct physiological increased N deposition cause shifts in plant species com- effects of nitrogen on Sphagnum: a greenhouse experiment. position and production in Sphagnum bogs. Glob Change Funct Ecol 26:353–364. https://doi.org/10.1111/j.1365- Biol 7:591–598 2435.2011.01948.x Bold HC (1973) Morphology of plants, 3rd edn. Harper and Grosvernier P, Matthey Y, Buttler A (1997) Growth potential of Row, New York three Sphagnum species in relation to water table level and Buttler A, Grosvernier P, Matthey Y (1998) Development of peat properties with implications for their restoration in Sphagnum fallax diaspores on bare peat with implications 123 Wetlands Ecol Manage cut-over bogs. J Appl Ecol 34:471–483. https://doi.org/10. CO supply on two keystone species in peatland restoration 2307/2404891 and implications for global change. J Ecol 90:529–533. Grosvernier PR, Mitchell EAD, Buttler A, Gobat JM (2001) https://doi.org/10.1046/j.1365-2745.2002.00679.x Effects of elevated CO and nitrogen deposition on natural Moore TR, Roulet NT (1995) Methane emissions from Cana- regeneration processes of cut-over ombrotrophic peat bogs dian peatlands. In: Lal R, Kimble J, Levine E, Stewart BA in the Swiss Jura mountains. Glob Change Prot Areas (eds) Advances in soil science: soils and global change. 9:347–356 CRC Press, Boca Raton, pp 153–164 Hajek T, Vicherova E (2014) Desiccation tolerance of Sphag- Natural England (2010) England’s peatlands carbon storage and num revisited: a puzzle resolved. Plant Biol 16:765–773 greenhouse gases. Natural England Report NE257 Harpenslager SF, Van Dijk G, Kosten S, Roelofs JGM, Nijp JJ, Limpens J, Metselaar K, van der Zee SEATM, Berendse Smolders AJP, Lamers LPM (2015) Simultaneous high C F, Robroek BJM (2014) Can frequent precipitation mod- fixation and high C emissions in Sphagnum mires. Bio- erate the impact of drought on peatmoss carbon uptake in geosciences 12:4739–4749. https://doi.org/10.5194/bg-12- northern peatlands? New Phytol 203:70–80 4739-2015 Opelt K, Berg C, Scho ¨ nmann S, Eberl L, Berg G (2007) High Heijmans M, Arp WJ, Berendse F (2001a) Effects of elevated specificity but contrasting biodiversity of Sphagnum-as- CO and vascular plants on evapotranspiration in bog sociated bacterial and plant communities in bog ecosys- vegetation. Glob Change Biol 7:817–827 tems independent of the geographical region. ISME J Heijmans M, Berendse F, Arp WJ, Masselink AK, Klees H, De 1(502):516. https://doi.org/10.1038/ismej.2007.58 Visser W, Van Breemen N (2001b) Effects of elevated Oremland RS (1988) Biogeochemistry of methanogenic bacte- carbon dioxide and increased nitrogen deposition on bog ria. Wiley, New York vegetation in the Netherlands. J Ecol 89:268–279. https:// Radu DD, Dual TP (2018) Precipitation frequency alters peat- doi.org/10.1046/j.1365-2745.2001.00547.x land ecosystem structure and CO exchange: contrasting Hinde S, Rosenburgh A, Wright N, Buckler M, Caporn S, Fox L effects on moss, sedge, and shrub communities. Glob (2010) Sphagnum re-introduction project: a report on Change Biol. https://doi.org/10.1111/gcb.14057 research into the re-introduction of Sphagnum mosses to Reich PB, Tilman D, Craine J, Ellsworth D, Tjoelker MG, degraded moorland. Moors for the Future Research Report, Knops J, Wedin D, Naeem S, Bahauddin D, Goth J (2001) vol 18, pp 1–31 Do species and functional groups differ in acquisition and Hoosbeek MR, Van Breemen N, Vasander H, Buttler A, use of C, N and water under varying atmospheric CO and Berendse F (2002) Potassium limits potential growth of N availability regimes? A field test with 16 grassland bog vegetation under elevated atmospheric CO and N species. New Phytol 150:435–448 deposition. Glob Change Biol 8:1130–1138. https://doi. Rice SK, Giles L (1996) The influence of water content and leaf org/10.1046/j.1365-2486.2002.00535.x anatomy on carbon isotope discrimination and photosyn- IPCC (2013) Climate change 2013: the physical science basis, thesis in Sphagnum. Plant Cell Environ 19:118–124 contribution of working group 1 to the fifth assessment Robroek BJ, Limpens J, Breeuwer A, van Ruijven J, Schouten report of the intergovernmental panel on climate change. MG (2007) Precipitation determines the persistence of Cambridge University Press, Cambridge hollow Sphagnum species on hummocks. Wetlands Jauhiainen J, Silvola J (1999) Photosynthesis of Sphagnum 27(4):979–986 fuscum at long-term raised CO concentrations. Annales Robroek BJM, Schouten MGC, Limpens J, Berendse F, Poorter Botanici Fennici 36:11–19 H (2009) Interactive effects of water table and precipitation Jauhiainen J, Silvola J, Tolonem K, Vasander H (1997) on net CO assimilation of three co-occurring Sphagnum Response of Sphagnum fuscum to water levels and CO mosses differing in distribution above the water table. Glob concentration. J Bryol 19:391–400. https://doi.org/10. Change Biol 15:680–691. https://doi.org/10.1111/j.1365- 1179/jbr.1997.19.3.391 2486.2008.01724.x Kroken SB, Graham LE, Cook ME (1996) Occurrence and Robroek BJM, Jassey VEJ, Kox MAR, Berendsen RL, Mills evolutionary significance of resistant cells in charophytes RTE, Cecillon L, Puissant J, Meima-Franke M, Bakker and bryophytes. Am J Bot 83:1241–1254 PAHM, Bodelier PLE (2015) Peatland vascular plan Lanta V, Kantorova J (2015) Niche separation of two grass functional types affect methane dynamics by altering species along a moisture gradient in a post-mined peatland. microbial community structure. J Ecol 103:925–934. Wetlands 35:923–929. https://doi.org/10.1007/s13157- https://doi.org/10.1111/1365-2745.12413 015-0683-x Royles J, Ogee J, Wingate L, Hodgson DA, Convey P, Griffiths Leppala M, Oksanen J, Tuittila ES (2011) Methane flux H (2012) Carbon isotope evidence for recent climate-re- dynamics during mire succession. Oecologia 165:489–499. lated enhancement of CO assimilation and peat accumu- https://doi.org/10.1007/s00442-010-1754-6 lation rates in Antarctica. Glob Change Biol emission Megonigal J, Schlesinger WH (1997) Enhanced CH 18:3112–3124. https://doi.org/10.1111/j.1365-2486.2012. from a wetland soil exposed to elevated CO . Biogeo- 02750.x chemistry 37:77–88 Rydin H, Mcdonald AJS (1985) Tolerance of Sphagnum to Micropropagation Services (EM) LTD. (2015) BeadaMoss. water level. J Bryol 4:571–578. https://doi.org/10.1179/jbr. http://www.beadamoss.co.uk/page8.html. Accessed 23 1985.13.4.571 Oct 2015 Saarnio S, Silvola J (1999) Effects of increase CO and N on Mitchell EAD, Buttler A, Grosvernier P, Rydin H, Siegenthaler CH efflux from a boreal mire: a growth chamber A, Gobat JM (2002) Contrasted effects of increased N and 123 Wetlands Ecol Manage experiment. Oecologia 19:349–356. https://doi.org/10. peatland. Ecohydrology 9:1017–1027. https://doi.org/10. 1007/s004420050795 1002/eco.1699 Saarnio S, Saarinen T, Vasander H, Silvola J (2000) A moderate Toet S, Cornelissen JH, Aerts R, van Logtestijn RS, de Beus M, increase in the annual CH efflux by raised CO or NH Stoevelaar R (2006) Moss responses to elevated CO and 4 2 4- 2 NO supply in a boreal oligotrophic mire. Glob Change variation in hydrology in a temperate lowland peatland. Biol 6:137–144. https://doi.org/10.1046/j.1365-2486. Plants and climate change. Springer, Netherlands, 2000.00294.x pp 27–42 Saarnio S, Jarvio S, Saarinen T, Vasander H, Silvola J (2003) Turetsky MR, Bond-lamberty B, Euskirchen E, Talbot J, Minor changes in vegetation and carbon gas balance in a Frolking S, Mcguire AD, Tuittila ES (2012) The resilience boreal mire under a raised CO or NH NO supply. and functional role of moss in boreal and arctic ecosystems. 2 4 3 Ecosystems 6:46–60. https://doi.org/10.1007/s10021-002- New Phytol 196:49–67. https://doi.org/10.1111/j.1469- 0208-3 8137.2012.04254.x Saarnio S, Morero M, Shurpali NJ, Tuittila ES, Ma ¨kila ¨ M, Alm J Turunen J, Tomppo E, Tolonen K, Reinikainen A (2002) Esti- (2007) Annual CO and CH fluxes of pristine boreal mires mating carbon accumulation rates of undrained mires in 2 4 as a background for the lifecycle analyses of peat energy. Finland—application to boreal and subarctic regions. Boreal Environ Res 12:101–113 Holocene 12:69–80. https://doi.org/10.1191/ Silvola J (1991) Moisture dependence of CO exchange and it’s 0959683602hl522rp recovery after drying in certain boreal forest and peat Van Der Heijden E, Verbeek SK, Kuiper PJC (2000) Elevated mosses. Lindbergia 17:5–10 atmospheric CO and increased nitrogen deposition: Silvola J, Alm J, Ahlholm U, Nykanen H, Martikainen P (1996) effects on C and N metabolism and growth of the peat moss CO fluxes from peat in boreal mires under varying tem- Sphagnum recurvum P. Beauv. var. mucronatum (Russ.) perature and moisture conditions. J Ecol 84:219–228 Warnst. Glob Change Biol 6:201–212. https://doi.org/10. Silvola J, Saarnio S, Foot J, Sundh I, Greenup A, Heijmans M, 1046/j.1365-2486.2000.00303.x Ekberg A, Mitchell E, Van Breemen N (2003) Effects of VSN International (2011) GenStat for Windows, 14th edn. VSN elevated CO and N deposition on CH emissions from International, Hemel Hempstead 2 4 European mires. Global Biogeochem Cycles 17(2):1068. Williams MA, Rice CW, Owensby CE (2000) Carbon dynamics https://doi.org/10.1029/2002GB001886 and microbial activity in allgrass prairie exposed to ele- Strack M (2008) Peatlands and climate change. International vated CO for 8 years. Plant Soil 227:127–137. https://doi. Peat Society, Saarijarven org/10.1023/a:1026590001307 Strack M, Waddington JM (2007) Response of peatland carbon Wittram BW, Roberts G, Buckler M, King L, Walker JS (2015) dioxide and methane fluxes to a water table drawdown A practitioners guide to Sphagnum reintroduction. Moors experiment. Global Biogeochem Cycles 21:13. https://doi. for the Future Partnership, Edale org/10.1029/2006GB002715 Worrall F, Chapman P, Holden J, Evans C, Artz R, Smith P, Strom L, Mastepanov M, Christensen TR (2005) Species- Grayson R (2011) A review of current evidence on carbon specific effects of vascular plants on carbon turnover and fluxes and greenhouse gas emissions from UK peatlands methane emissions from wetlands. Biogeochemistry Wright N, Caporn S, Rosenburgh A, Hinde S, Buckler M (2012) 75:65–82. https://doi.org/10.1007/s10533-004-6124-1 Large-scale bog restoration with Sphagnum species. Taylor N, Price J, Strack M (2015) Hydrological controls on MicroPropagation Services, East Leake productivity of regenerating Sphagnum in a cutover Yu ZC (2012) Northern peatland carbon stocks and dynamics: a review. Biogeosciences 9:4071 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Wetlands Ecology and Management Springer Journals

Interacting effects of elevated atmospheric CO2 and hydrology on the growth and carbon sequestration of Sphagnum moss

Free
12 pages
Loading next page...
 
/lp/springer_journal/interacting-effects-of-elevated-atmospheric-co2-and-hydrology-on-the-2BGaBbf3KV
Publisher
Springer Netherlands
Copyright
Copyright © 2018 by The Author(s)
Subject
Life Sciences; Freshwater & Marine Ecology; Conservation Biology/Ecology; Environmental Law/Policy/Ecojustice; Marine & Freshwater Sciences; Hydrology/Water Resources; Water Quality/Water Pollution
ISSN
0923-4861
eISSN
1572-9834
D.O.I.
10.1007/s11273-018-9607-x
Publisher site
See Article on Publisher Site

Abstract

Wetlands Ecol Manage https://doi.org/10.1007/s11273-018-9607-x OR IGINAL PAPER Interacting effects of elevated atmospheric CO and hydrology on the growth and carbon sequestration of Sphagnum moss . . . Thomas R. Newman Neal Wright Barbara Wright Sofie Sjo¨gersten Received: 21 September 2017 / Accepted: 19 March 2018 The Author(s) 2018 Abstract Peatlands are a critical carbon store com- Elevated CO levels increased Sphagnum height and prising 30% of the Earth’s terrestrial soil carbon. dry weight but the magnitude of the response differed Sphagnum mosses comprise up to 90% of peat in the among species. The most responsive species, S. fallax, northern hemisphere but impacts of climate change on yielded the most biomass compared to S. papillosum Sphagnum mosses are poorly understood, limiting and S. capillifolium. Water levels and the CO development of sustainable peatland management and treatment were found to interact, with the highest restoration. This study investigates the effects of water level (1 cm below the surface) seeing the largest elevated atmospheric CO (eCO ) (800 ppm) and increase in dry weight under eCO compared to 2 2 2 hydrology on the growth of Sphagnum fallax, Sphag- ambient (400 ppm) concentrations. Initially, CO flux num capillifolium and Sphagnum papillosum and rates were similar between CO treatments. After greenhouse gas fluxes from moss–peat mesocosms. week 9 there was a consistent three-fold increase of the CO sink strength under eCO . At the end of the 2 2 experiment, S. papillosum and S. fallax were greater Electronic supplementary material The online version of sinks of CO than S. capillifolium and the - 7cm this article (https://doi.org/10.1007/s11273-018-9607-x) con- water level treatment showed the strongest CO sink tains supplementary material, which is available to authorized strength. The mesocosms were net sources of CH but users. 4 the source strength varied with species, specifically S. T. R. Newman (&) fallax produced more CH than S. papillosum and S. School of Geography, Geology and the Environment, capillifolium. Our findings demonstrate the impor- University of Leicester, Leicester, UK tance of species selection on the outcomes of peatland e-mail: trn2@leicester.ac.uk restoration with regards to Sphagnum’s growth and S. Sjo ¨ gersten GHG exchange. School of Biosciences, The University of Nottingham, Nottingham NG7 2RD, UK Keywords C sequestration  Elevated CO e-mail: Sofie.Sjogersten@nottingham.ac.uk Greenhouse gas fluxes  Peatland  Sphagnum N. Wright  B. Wright Climate change Micropropagation Services, Ley Springs, Loughborough Road, East Leake, Loughborough, Leicestershire LE12 6NZ, UK e-mail: Neal@microprop.co.uk B. Wright e-mail: Barbara@microprop.co.uk 123 Wetlands Ecol Manage Introduction Atmospheric CO concentration has increased since pre-industrial times to ca. 408 ppm (ESRL Peatlands are important in the global carbon (C) cycle NOAA 2015) and is predicted to increase to 800 ppm due to their function as a long-term carbon store. This by the year 2100 (IPCC 2013). The effects of this store has built up through millennia due to very low elevation of atmospheric CO on Sphagnum moss are decomposition rates that are surpassed by productivity currently disputed, with studies indicating an increase rates (Clymo and Hayward 1982) making peatlands in growth rate (Jauhiainen and Silvde 1999; Heijmans net carbon sinks. It’s been estimated that today’s et al. 2001a; Saarnio et al. 2003), decreases in growth peatlands store ca 30% (* 550 Pg C) of the Earth’s rate (Grosvernier et al. 2001; Fenner et al. 2007) and terrestrial soil carbon while comprising only 3% of the no response (Van der Hejiden et al. 2000; Hoosbeek Earths land area (Gorham 1991;Yu 2012). et al. 2002; Toet et al. 2006). Contrasting responses Within peatlands in the northern hemisphere, between Sphagnum species are thought to be the cause Sphagnum mosses are often the dominant species, of some of the variation. Toet et al. (2006), found comprising up to 90% of peat (Clymo 1987). Sphag- increased abundance in S. recurve and no difference in num plays an important role in peatland formation and S. palustre when they were subjected to an elevation of ecological resilience, through its low decomposition 180 ppm above ambient, while S. fuscum did not rate due to its recalcitrant and antibacterial nature respond to elevated CO (350, 700, 1000 and (Kroken et al. 1996) and by creating acidic, anoxic and 2000 ppm) at all (Jauhiainen et al. 1997). Further- nutrient-poor conditions within peatlands (Amesbury more, contrasting responses have been seen between 2013; Hajek and Vicherova 2014). Sphagnum’s studies conducted on the same species. For example, S. extraordinary physiology allows it to hold 16–26 magellanicum, was found to increase in growth rate by times its weight in water (Bold 1973; Amesbury Heijmans et al. (2001b) when subjected to 560 ppm 2013), in both live and dead non-decomposed Sphag- CO , while Heijmans et al. (2001a) reported a greatly num, depending on species. This buffers the impact of reduced growth rate. This suggests factors other than dry weather conditions on peat moisture levels, species are affecting Sphagnum’s response to elevated preventing the peat from drying out and decomposing. CO . Peatlands are classified as such once an organic soil Hydrology has been identified as one of the most layer of 30 cm or greater has formed; for northern important factors controlling Sphagnum growth and peatlands, the average peat depth is 1.3–2.3 m, but peatland carbon dynamics (Strack and Waddington peat depth can extend to 15–20 m in some peatlands 2007; Turetsky et al. 2012; Lanta and Kantorova 2015 (Clymo et al. 1998; Turunen et al. 2002). Accumula- etc.). Water availability impacts both C sequestration tion rates of Sphagnum peat are approximately and growth rate (Glime 2007), due to there being an -1 0.61–3.9 mm year (Royles et al. 2012; Amesbury optimum moisture content for Sphagnum photosyn- 2013), due to Sphagnums slow growth rate within the thesis (Rice and Giles 1996). Varying physiologies cold, nutrient poor peatlands (Strack 2008). The slow mean that different Sphagnum species vary in sensi- growth rate is important in the context of peatland tivity to changes in water level, each often growing management as once the peat is lost, the peatland will best within their own hydrological niche (Rydin and only recover slowly over centuries/millennia. Degra- Mcdonald 1985; Grosvernier et al. 1997; Taylor et al. dation of peatlands through drainage, mining and 2015). For example, mature S. fallax is observed to removal of Sphagnum allows stored C to be released struggle at low water levels (Carroll et al. 2009), while back into the atmosphere CO , through decomposition having higher growth rates than any other species in of the exposed peat. It is estimated that UK peatlands wet conditions (Buttler et al. 1998). Recent studies -1 are a net source of 3.72 Mtn CO year (Worrall 2eq have also highlighted the importance of precipitation et al. 2011), with only 1% of Englands deep peats on Sphagnum dominated peatlands carbon dynamics considered to be in an undamaged state (Natural and species distribution (Robroek et al. 2009; Radu England 2010). This makes restoring peatlands a and Dual 2018). Nijp et al. (2014) found precipitation priority, as restored peatlands not only protect the reduced the negative impacts of drought, while already sequestered carbon, but can reinstate their Robroek et al. (2007) found precipitation allowed carbon sink capacity (Strack 2008). species to survive outside of their hydrological niche. 123 Wetlands Ecol Manage Materials and methods Precipitation also affects Sphagnum C uptake, with species responding differently to varying precipitation Experimental set up frequencies (Nijp et al. 2014). Water limitation has also been found to affect the impacts of other factors, Peat cores were collected from Cadishead and Little such as temperature and vegetation’s impact on CO and CH fluxes (Silvola et al. 1996; Leppala et al. Woolden Mosses (North West England, UK M44 5LR of Grid ref: SJ697953). This site is typical of drained 2011). Currently large tracts of damaged peatlands are and degraded cut over peatlands in the UK. The site is being restored in the UK via application of Sphagnum currently under restoration and some areas have been containing beads and gel to encourage growth on re-flooded. It is characterized by predominantly bare degraded peatland sites (Hinde et al. 2010; Wittram peat with cotton grass and birch growing around the et al. 2015). However, information is limited with edges with Sphagnum growing only in areas where regards to which species are most effective in quickly reintroduction has been attempted. To account for variation within the peat substrate, establishing and recreating peatland functions such as C sequestration, particularly in the context of global all 72 peat cores (approximately 18 cm 9 16 cm) were collected from random locations within the non- change, e.g., elevated atmospheric CO concentra- tions. Such information is urgently needed to ensure flooded part of the peatbog. Collection and transporta- tion of cores took place within 8 h, after collection that restoration efforts are as effective as possible under future elevated atmospheric CO levels. For cores were refrigerated at ? 4 C. example, some studies indicate that elevated CO Three weeks after collection, peat cores were then levels may result in increased CH fluxes peatlands cut into 17.4 cm 9 11 cm cylinders and transplanted dominated by Sphagnum species (Saarnio et al. into 17.4 cm 9 15.6 cm clear plastic, cylindrical polypropylene containers. The treatments were 2000, 2003; Ellis et al. 2009) but effects differ among studies made across European peatland sites (Silvola applied in a randomised block design (n = 4) with species (S. fallax, S. papillosum and S. capillifolium) et al. 2003). To date, a hand full of studies have considered a possible interaction between hydrology and water level (1, 4 and 7 cm below the peat surface) as the treatments. Each combination of species and and raised atmospheric CO on the growth of Sphag- num moss (e.g., Jauhiainen et al. 1997; Toet et al. water level was repeated four times within each 2006) despite that interactions with hydrology may growth room. The randomized block design was used control how different Sphagnum species respond to to account for any possible variations of conditions elevated CO . Indeed, interactions between hydrology within each growth room. The two CO treatments 2 2 and elevated atmospheric CO concentrations may used were 400 and 800 ppm CO (ambient and cause the contrasting responses of Sphagnum species elevated), 800 ppm is the predicted 2100 concentra- tion (IPCC 2013), due to the slow growth rates of to elevated CO found in previous studies. Such interaction would have important implications for Sphagnum this was chose as a good analogue for future restoration attempts. To achieve the two CO peatland restoration, suggesting that selecting the correct species for the environment is critical for treatments cores were randomly allocated to one of two growth rooms in which the atmosphere was restoration success. The aim of this study was to determine whether adjusted to the target CO concentration. Apart from the CO concentration the settings in the growth room there is an interaction between hydrology and elevated atmospheric CO on the growth and greenhouse gas were identical: Day length consisted of a 16 h -2 -1 (GHG) exchange of three Sphagnum moss species photoperiod (300 lmol m s ), including a 1 h -2 -1 grown on peat-monoliths. To achieve this aim two dawn/dusk and 8 h night (0 lmol m s ). Daytime specific hypotheses were tested: (i) elevated atmo- conditions were set to a temperature of 21 C and a relative humidity of 50%, while night-time conditions spheric CO will have a greater positive effect on S. fallax growth and GHG fluxes than other species; (ii) were set to 15 C and 75% respectively. low water table will inhibit the effect of elevated CO on Sphagnum growth. 123 Wetlands Ecol Manage Water levels within the growth rooms where consistent throughout the course of the experiment: Temperature was Once the peat cores were placed in the growth rooms, measured at 27.5 ± 0.1 C in direct light with an air the three water level treatments were applied to the temperature of 21.2 ± 0.1 C, relative humidity, cores, which were then allowed to equilibrate for 52 ± 1% and finally light was 234 ± 0.4 lmol -2 -1 1 week. All water applied to the cores initially and m s . throughout the experiment was rainwater that was Sphagnum height was measured using an adaption firstly collected as runoff from glasshouses located in of the cranked wire method detailed by Clymo (1970). East Leake, Loughborough, Leicestershire. The rain- Initial height of the moss (peat level) was marked on water was then filtered through a sand gravity filter, the side of the clear plastic container; from this the leaving the rainwater free of particulate contaminants height of the tallest Sphagnum plant in each individual such as dirt washed from the glasshouse surface. container was measured to the nearest mm. Rainwater was used to simulate ombrotrophic peat- As Sphagnum was grown from micro propagated land conditions. Water level treatments were moni- plants, the establishment rates of the different Sphag- tored daily for the first month and then once every num species could be quantified. This was inferred 2 days thereafter via visual inspection. If needed water through the Normalized Difference Vegetation Index was applied to the cores using a pressurised water (NDVI), a numerical indicator that uses the visible and sprayer to reduce disturbance to the peat surface. This near-infrared bands of the electromagnetic spectrum kept variation in water level to within 1 cm throughout to assess crop healthiness (Govaerts and Verhulst the course of the experiment. 2010). This was done using a hand held device (GreenSeeker , Trimble Navigation Ltd., Sunnyvale Sphagnum application California, USA), which gave a reading between 0 and 1 where 0 indicates bare soil and 1, established green After 1 week, each species of Sphagnum was applied vegetation (FSNAU 2016). The Green Seeker was to the relevant core using liquid gels, currently used held approximately 10 cm above the Sphagnum for application to peatlands as part of restoration surface, with a reading for each core taken over 5 s programmes, containing micro propagated material of while the device was continually moved over the each species. The Sphagnum suspended within the gel whole surface of the core, giving an average reading was micropropagated from source material originating for each core. from the Peak Districk, UK, by MicroPropagation The total Sphagnum biomass production from each Services (MicroPropagation Services (EM) Ltd 2015). container was quantified at the end of the experiment. The micro-propagated Sphagnum was suspended For this all Sphagnum growth in each container was within a gel containing basic nutrients, at an approx- removed, weighed (wet weight), dried at 70 C and imate concentration of 150,000 individual plants per weighed again (dry weight). L, which ranged from 1 to 5 mm in length (for CO flux and evaporation rate from each core was example gel see SI. 1). The gel was applied at a rate of measured using an EGM-4 Infrared Gas Analyser 3L per m (0.072L per core) using a large pipette (IRGA) connected to a CPY-3 using an open dynamic before being spread evenly over the core surface. The system (PP systems, Hitchin, UK). CO flux rates were application rate is the same as trials conducted using recorded every minute over a 10 min period. IRGA the same gel in the restoration of the Cadishead time wishing was every 8 s, from which a linear peatland (Wright et al. 2012). regression is calculated to determine CO flux over each 1 min period. To ensure fluxes were not affected Measurements of Sphagnum performance by disturbance following the installation of the CPY-3 and GHG fluxes chamber over the mesocosms, we used only the final three readings, these were averaged and used for Measurements of Sphagnum performance and CO subsequent data analysis. Positive fluxes represent a fluxes were made bi-weekly for each parameter apart net release of CO from the mesocosms. from CH gas samples and dry weight, which were For CH flux determination, gas samples were determined at the end of the experiment. Conditions collected from each container using a modified version 123 Wetlands Ecol Manage of the closed static chamber method (Collier et al. 2014). Each container was carefully sealed using a lid with a septum in its centre giving a headspace of 0.11 dm . Then, using a 30 ml syringe with a 25 gauge hypodermic needle, gas samples were then taken after 1, 30 and 60 min. Samples were then transferred into 12 ml pre-evacuated exetainers before each sample was analysed via gas chromatography (GC-2014; Shimadzu, UK) using a Flame Ionization Detector (FID), with hydrogen as the carrier gas. The oven temperature was 40 C, the injector 80 C and the FID -1 Fig. 1 The effect of elevated CO and species on NDVI 250 C. The flow rate was 30 ml min ; the column (mean ± SE) over the 13 week experimental period. Black was a HayeSEp N packed column, 60/80 mesh. lines represent atmospheric CO of 400 ppm; light grey lines Measurements for each container were analysed using represent atmospheric CO of 800 ppm. Diamonds and solid lines represent S. fallax; squares and dashes lines represent S. a linear regression model and the ideal gas law to papillosum; triangles and dotted lines represent S. capillifolium calculate gas flux rate for each container, which was -2 -1 then used to calculate CH flux in mg m h where capillifolium established slower than under the ambi- positive gas fluxes represent net CH emissions. ent treatment (F = 2.96, P = 0.061). (2,51) Sphagnum grew taller under eCO (F = 16.34, 2 (1,51) Statistical analysis P\ 0.001) but this effect varied among species (F = 5.31, P= 0.008) with S. fallax responding (2,270) The effects of time, hydrology, species and CO most significantly to eCO (F = 48.78, P\ 0.001) 2 (2,51) treatment and their interactions on height, evapora- (Fig. 2a). S. papillosum height was also found to tion, CO flux and NDVI were tested using repeated increase growth under eCO (2.9 mm taller by week 2, measures analysis of variance (ANOVA) after box- 13) the effect was not as large as S. fallax (7.4 mm cox transformations had been performed where nec- taller by week 13), while S. capillifolium indicated no essary, to normalize the data. Time was treated as a difference in height between the treatments (Fig. 2a). categorical variable, with each measurement week The lowest water level (7 cm below peat surface) had treated as a separate category. Treatment effects on shorter plants (near significant water level effect: dry weight and CH flux were tested using ANOVA F = 2.49, P = 0.093) than both the medium (4 cm (2,51) with hydrology, species, and CO treatment as fixed below peat surface) and high (1 cm below peat effects, where CO flux was normalised to the CO 2 2 surface) water levels (Fig. 2b). flux from the first set of measurements (week 3). This The eCO treatment yielded 90.3% increase in removed the impact of variation in the initial CO flux biomass (294.2 ± 47.2 g m ) compared to the ambient rates from the cores. All calculations were performed treatment (154.6 ± 23.7 g m )(F = 30.94, P \ (1,51) using the data analysis program GenStat 17th Edition 0.001). However, the effect size varied among species for windows 10.1 (VSN International 2011). (F = 4.17, P = 0.021), with S. fallax showing a (2,51) 129.7% increase in biomass production under eCO -2 (eCO 142.4 ± 17.1 g m , ambient Results -2 62.0 ± 9.8 g m ), followed by a 101.0% increase -2 for S. capillifolium (eCO 66.8 ± 16.1 g m , ambi- Growth -2 ent 33.2 ± 6.4 g m ) and finally a 43.2% increase -2 for S. papillosum (eCO 85.068 ± 14.0 g m , ambi- Different establishment rates were found between -2 ent 59.4 ± 7.6 g m ) (Fig. 3a). species (F = 7.20, P = 0.002), with S. fallax (2,51) Sphagnum grown at higher water level treatments establishing fastest with NDVI [ 0.8 in week 7, which produced more biomass (F = 7.64, P = 0.001) (2,51) was 2 weeks earlier than S. papillosum and 3 weeks (Fig. 3a). The eCO and water level treatments earlier than S. capillifolium (Fig. 1). Under eCO S. interacted (F = 4.13, P = 0.022) with the high (2,51) fallax and S. papillosum established faster, while S. 123 Wetlands Ecol Manage Fig. 2 a The effect of elevated CO and species on plant height b The effect of water level on plant height (mean ± SE) over the (mean ± SE) over the 13 week experimental period. Black lines 13 week experimental period. Diamonds and black line represent atmospheric CO of 400 ppm; light grey lines represents a water level 1 cm below peat surface; squares and represent atmospheric CO of 800 ppm. Diamonds and solid dark grey line represent a water level 4 cm below peat surface; lines represent S. fallax; squares and dashes lines represent S. triangles and light grey line represent a water level 7 cm below papillosum; triangles and dotted lines represent S. capillifolium. peat surface Fig. 3 a The effect of species on dry weight (mean ± SE) (mean ± SE) recorded at the end of the 13 week experimental recorded at the end of the 13 week experimental period. For period. For each water level, black bars represent growth under each species, black bars represent growth under 400 ppm 400 ppm atmospheric CO ; light grey bars represent 800 ppm atmospheric CO ; light grey bars represent 800 ppm atmo- atmospheric CO 2 2 spheric CO b The effect of water level on dry weight water level resulting in the largest increase of 142.0% flux rates over the first 7 weeks period. After 7 weeks -2 (79.9 ± 9.2 g m ) in biomass under eCO compared there was a large increase in the CO uptake (increas- 2 2 -2 to a 66.0% increase (35.6 ± 8.1 g m ) at the 4 cm ingly negative CO flux) under eCO (F = 14.59, 2 2 (1,51) -2 and 19.2% (8.5 ± 5.4 g m ) increase at the 7 cm P \ 0.001). Specifically, CO uptake was more than water level treatments (Fig. 3b). 5-times greater in week 7 and consistently 3-times greater than the ambient treatment from week 9 to the Gas flux end of the experiment (Fig. 4a; Time 9 eCO inter- action: F = 27.28, P \ 0.001). Increasingly (5,270) In parallel with the NDVI and height data, elevated lower water levels were found to have a significantly and ambient CO treatments had almost identical CO larger CO uptake (F = 5.00, P = 0.010) (Fig. 4b). 2 2 2 (2,51) 123 Wetlands Ecol Manage Fig. 4 a The effect of elevated CO on CO flux (mean ± SE) represent 4 cm below the surface; triangles and light grey line 2 2 over the 13 week experimental period. Diamonds and black line represent 7 cm below the surface. c The effect of species on CO represent 400 ppm atmospheric CO ; squares and grey line flux (mean ± SE) over the 13 week experimental period. represent 800 ppm atmospheric CO . b The effect of water level Diamonds and solid line represent S. fallax; squares and dashed (cm below the peat surface) on CO flux (mean ± SE) over the line represent S. papillosum; triangles and dotted line represent 13 week experimental period. Diamonds and black line S. capillifolium. d The effect of species on CH flux represent 1 cm below peat surface; squares and dark grey line (mean ± SE) -2 -1 CO fluxes were found to differ between species m h ) (Fig. 4d); the species and eCO treatments 2 2 (F = 4.29, P = 0.019), with S. capillifolium did not interact with the water level treatments. (2,51) having the smallest uptake of CO -2 -1 (- 69.12 ± 14.74 mg m h ) compared to S. -2 -1 papillosum (- 101.30 ± 15.47 mg m h ) and S. Discussion -2 -1 fallax (- 91.56 ± 16.43 mg m h ) by week 13 (Fig. 4c). Over the course of the experiment, CO Growth responses uptake increased more for S. fallax and S. papillosum over the course of the experiment than S. capillifolium Our finding that eCO increased Sphagnum growth are (F = 6.24, P \ 0.001) (Fig. 4c). in agreement with multiple studies (Jauhiainen and (10,270) Only the species treatment was found to have an Silvola 1999; Heijmans et al. 2001a; Saarnio et al. effect on CH flux (F = 3.66, P = 0.029), 2003), however as this area of research is contested, 4 (2,123) with S. fallax producing the most CH the results are also in disagreement with several -2 -1 (5.28 ± 2.22 mg m h ), twice as much as S. studies (Berendse et al. 2001; Grosvernier et al. 2001; -2 -1 papillosum (2.09 ± 1.09 mg m h ) and 10 times Fenner et al. 2007). as much as S. capillifolium (0.48 ± 0.18 mg 123 Wetlands Ecol Manage The greater effect of elevated CO on S. fallax S. capillifolium (Carroll et al. 2009). One reason for growth and establishment than either of the other this could be the impact of precipitation rewetting on species supports the first hypothesis which predicted reducing the impact of drought by precipitation that fast growing S. fallax would respond most increasing the water contents of the top layer (Nijp positively to the eCO treatment. This is in agreement et al. 2014), negating the impacts of a lower water with previous studies (Berendse et al. 2001; Mitchell table. However, differences between species utiliza- et al. 2002; Granath et al. 2012) which suggested that tion of precipitation was seen by Nijp et al. (2014) increased CO will increase the growth of certain between S. majus, S. balticum and S. fuscum, which species more than others. Variation in species was not seen within our findings. This suggests that responses may be caused by differences in the our experiment did not differentiate water level to a effectiveness of species to utilize the increased high enough degree to examine differences between atmospheric CO concentration. Under elevated CO the species. 2 2 it’s possible that water became the limiting factor for growth, even under the highest water level treatments. CO and CH flux responses 2 4 Silvola (1991) showed that the differences in water needed for photosynthesis vary between species. Greater CO assimilation under eCO was found in S. 2 2 Additionally, Nijp et al. (2014), found that Sphagnum fallax and S. papillosum than S. capillifolium, this species vary in their ability to exploit transient water lends additional support to our first hypothesis which resources. This could account for the differences seen predicted that elevated CO would increase C seques- in growth rates under increased CO between the tration due to increased growth rates but that responses species, with some species better able to exploit the would differ among species. Our finding of increased elevated CO under the hydrological conditions. CO uptake under eCO agrees in part with findings by 2 2 2 Sphagnum also have higher water level limits due to Van der Heijden et al. (2000), who found that blocking of CO diffusion to the leaf via the layer of photosynthesis in mature plants of S. fallax was water surrounding the leaf, with species differing on initially stimulated by elevated CO (700 ppm). the extent of water level found limiting (Glime 2007). However, in contrast to our findings, acclimation For example, optimum water content for photosyn- was observed with stimulated S. fallax returning to the thesis for S. fuscum are lower than those required for S. levels of the controls after 3 days. This could have angustifolium. This could have impacted Sphagnum been due to differences between establishing and growth within our experiment due to the high mature S. fallax. frequency of precipitation and surface water this Our findings somewhat contrasted with Harpensla- provided to the Sphagnum. ger et al. (2015), who grew four Sphagnum species on We found that higher water levels coupled with peat monoliths incubated between 18 and 23 C over a eCO caused a greater increase in dry weight support- 12 week period. Harpenslager et al. (2015), found that ing our second hypothesis, which predicted that low S. fallax and S. palustre had positive net C effluxes water tables would inhibit the effect of elevated CO similar to bare peat in spite of increased biomass. on Sphagnum growth. Similar results were found for S. Harpenslager et al. (2015) suggested that these results fuscum by Jauhiainen et al. (1997), who suggested that were due to the release of CO derived from this was due to water limitation of photosynthesis of bicarbonate due to lowering of the monoliths pH. Sphagnum at low water levels. We did not find an While this is dissimilar to our findings, these releases interaction effect of hydrology on species, in contrary were species dependant, highlighting how different to previous studies, which have identified that each species can impact total CO flux beyond sequestra- species of Sphagnum grows best within its own tion. These differences in growth and C fixation hydrological niche (Grosvernier et al. 1997). It’s also between the species were in congruence with our been found that each species responds to variation in results. water tables differently (Jauhiainen et al. 1997; Carroll Overall our findings suggest that in the context of et al. 2009) due to differences in their physiologies. In future elevated CO , all three species of Sphagnum particular, S. fallax has been found to be highly will increase in CO assimilation due to increased dependent on water level, holding 30% less water than growth, however, it is suggested that not all species 123 Wetlands Ecol Manage will react the same, with certain species seeing a much while the plots in the other two studies encompassed greater increase in CO assimilation (in this case S. both Sphagnum mosses, sedges and dwarf shrubs fallax and S. papillosum) compared to others. Whilst making it difficult to isolate Sphagnum species our study did not find acclimation (such as Van der responses in the two field studies. Heijden et al. (2000), this could be due to our focus on The species-specific effects on CH fluxes of the establishing Sphagnum and not mature plants. three Sphagnum species used in this study is important Greenhouse gas budgets for peatlands are often as it suggests that the Sphagnum species composition complex, with most peatlands being sources of CH per se, and not just the mix of functional groups (Strom (Moore and Roulet 1995; Saarnio et al. 2007; Leppala et al. 2005; Leppala et al. 2011) is an important control et al. 2011). As CH has a Global Warming Potential of CH . Although the mechanisms behind the species- 4 4 (GWP) of 28 over 100 years (IPCC 2013), the specific effects on CH fluxes are unclear. They may increased CO sink strength in response to eCO relate to differences in production of labile carbon and/ 2 2 shown here could be offset if CH emissions increase. or phenolic compounds among Sphagnum species In our 13-week study CH emissions remained low, (Ellis et al. 2009). Transportation of C to the although they increased slightly at the end of the rhizosphere has been shown to vary with species experiment. (Reich et al. 2001). It’s possible that similar variation The GWP of the CH4 emissions over 100 years may account for the differences seen in emissions (CO equivalents (CO )) of the three species was between the Sphagnum species. 2 2eq 147.84 ± 62.12, 58.52 ± 23.98 and Furthermore, relationships between species and -2 -1 13,44 ± 5.04 mg m h for S. fallax, S. papillosum specific methanogenic and methanotrophic communi- and S. capillifolium respectively. If emissions of CO ties could have also had an impact. This has been and CH from each species are taken into account, S. shown for plant functional types within peatlands by fallax would have a positive net emission Robroek et al. (2015), which showed removal of plant -2 -1 (56.28 mg m h CO ), while S.papillosum and functional types (gramminoids and ericoids) signifi- 2eq S.capillifolium would have a negative net emissions cantly alter microbial community structure. This fit’s -2 -1 (- 42.78 and -55.68 mg m h CO respec- with Opelt et al. (2007) who found that diversity of 2eq tively). This suggests that while S. fallax was shown bacterial communities was higher in S. fallax than S. to have the greatest C assimilation over the course of magellanicum. the experiment, S. papillosum and S. capillifolium had lower net emissions. This highlights the importance of CH release within these systems which can offset Conclusions carbon uptake to a substantial amount and even become a net source of emissions. Our study highlights the importance of Sphagnum The increase in CH emissions towards the end of species selection when undertaking restoration of a the experiment was likely due to recovery of peatland. The clear differences in species establish- methanogenic populations following the increased ment and growth under increased CO and CH flux 2 4 moisture content of the peat (Bellisario et al. 1999; between the species indicates that selecting the correct Leppala et al. 2011) and increased C availability due to Sphagnum species or combination of species is critical increased photosynthesis (Megonigal and Schlesinger to the success and GHG balance of recolonization 1997) and C transportation to the rhizosphere (Orem- attempts. While water level was not shown to interact land 1988; Williams et al. 2000). The lack of response with species, it’s interaction with CO suggests that CH fluxes to eCO in our study contrasts with environmental factors may also play an important role 4 2 findings from FACE studies on UK and Finnish in establishment success. ombrotrophic peatlands which found modest increases Furthermore, differences between the species CO in peatland CH fluxes in response to eCO (Saar- and CH fluxes within the initial establishment period, 4 2 4 nio and Silvola 1999; Ellis et al. 2009). An important suggests that using different species will impact the difference between our study and those of Saarnio and overall GHG balance the peatland once restored. Silvola (1999) and Ellis et al. (2009) are the fact that Within the establishment phase, the increase in CO our mesocosms contained a sole Sphagnum species uptake found in response to eCO suggests that the 123 Wetlands Ecol Manage for the restoration of cut-over bogs. J Appl Ecol capacity to sequester C by Sphagnum dominated 35:800–810. https://doi.org/10.1046/j.1365-2664.1998. peatbogs may increase under future CO rich atmo- 355351.x spheric conditions. Nevertheless, there may be trade- Carroll J, Anderson, P, Caporn S, Eades P, O’Reilly C, Bonn A offs between plant performance and GHG emissions (2009) Sphagnum in the peak district. Current status and potential for restoration. Moors for the future. Report as our fastest growing species S. fallax also had the 16:1–121 highest CH emissions, which offset assimilation and Clymo RS (1970) The growth of Sphagnum: methods of mea- caused net GHG emission. While the estimation of the surement. J Ecol 58:13–49. https://doi.org/10.2307/ impacts to the final GHG balance of a restored Clymo RS (1987) The ecology of peatlands. Sci Prog peatland are beyond the scope of this paper, this 71:593–614 highlights that species may be and important consid- Clymo RS, Hayward PM (1982) The ecology of Sphagnum. In: ered when determining which Sphagnum species Smith AIE (ed) Bryophyte ecology. Springer, Netherlands, should be used for peatland restoration. pp 229–289 Clymo RS, Turunen J, Tolonen K (1998) Carbon accumulation in peatland. Oikos 81:368–388. https://doi.org/10.2307/ Acknowledgements This work was completed at The University of Nottingham. Thank you to The Lancashire Collier SM, Ruark MD, Oates LG, Jokela WE, Dell CJ (2014) Wildlife Trust for allowing the use of peat from Cadishead & Measurement of greenhouse gas flux from agricultural soils Little Woolden Mosses, Anna Keightley her help with peat using static chambers. J Vis Exp 90:e52110. https://doi. collection and expertise of Cadishead & Little Woolden Mosses org/10.3791/52110 and the lab staff at The University of Nottingham for their Ellis T, Hill PW, Fenner N, Williams GG, Godbold D, Freeman assistance with equipment and helping to solve technical issues C (2009) The interactive effects of elevated carbon dioxide when they arose. This study was supported by and water table draw-down on carbon cycling in a Welsh MicroPropagation Services (EM) Ltd (T.R.N). ombrotrophic bog. Ecol Eng 35:978–986 ESRL NOAA (2015) Trends in atmospheric carbon dioxide. Compliance with ethical standards http://www.esrl.noaa.gov/gmd/ccgg/trends/. Accessed 03 Nov 2015 Conflict of interest The authors declare that they have no Fenner N, Ostle NJ, Mcnamara N, Sparks T, Harmens H, Rey- conflict of interest. nolds B, Freeman C (2007) Elevated CO effects on peat- land plant community carbon dynamics and DOC Open Access This article is distributed under the terms of the production. Ecosystem 10:635–647 Creative Commons Attribution 4.0 International License (http:// FSNAU (2016) Understanding the normalized difference veg- creativecommons.org/licenses/by/4.0/), which permits unre- etation index (NDVI). https://www.google.co.uk/url?sa = stricted use, distribution, and reproduction in any medium, t&rct = j&q = &esrc = s&source = web&cd = 2&sqi = provided you give appropriate credit to the original 2&ved = 0ahUKEwj3u4Kf9_jMAhXDChoKHYRpBdQQ author(s) and the source, provide a link to the Creative Com- FggkMAE&url = http%3A%2F%2Fwww.fsnau.org%2F- mons license, and indicate if changes were made. downloads%2FUnderstanding_the_Normalized_Vegetation_ Index_NDVI.pdf&usg = AFQjCNH7xIkJg2mjblyralvxpxRL u7lV2w&sig2 = 0scVtLMrBFmV_kPX7goVrw&bvm = bv. 122852650,d.d2 s&cad = rja. Accessed 3 May 2016 Glime MJ (2007) Bryophyte ecology, volume 1, physical References ecology. Michigan Technological University: International Association of Bryologists. http://www.bryoecol.mtu.edu/. Amesbury M (2013) Sphagnum moss: bog plant extraordinaire! Accessed 6 Nov 2015 http://bogology.org/2013/09/27/sphagnum-moss-bog- Gorham E (1991) Northern Peatlands—role in the carbon-cycle plant-extraordinaire. Accessed 24 Oct 2015 and probable responses to climatic warming. Ecol Appl Bellisario LM, Bubier JL, Moore TR, Chanton JP (1999) Con- 1:182–195. https://doi.org/10.2307/1941811 trols on CH emissions from a northern peatland. Glob Govaerts B, Verhulst N (2010) The normalized difference Biogeochem Cycles 13(1):81–91 TM vegetation index (NDVI) greenseeker handheld sensor: Berendse F, Van Breemen N, Rydin H, Buttler A, Heijmans M, toward the integrated evaluation of crop management. Part Hoosbeek MR, Lee JA, Mitchell E, Saarinen T, Vasander A-concepts and case studies. CIMMYT, Mexico H, Wallen B (2001) Raised atmospheric CO levels and Granath G, Strengbom J, Rydin H (2012) Direct physiological increased N deposition cause shifts in plant species com- effects of nitrogen on Sphagnum: a greenhouse experiment. position and production in Sphagnum bogs. Glob Change Funct Ecol 26:353–364. https://doi.org/10.1111/j.1365- Biol 7:591–598 2435.2011.01948.x Bold HC (1973) Morphology of plants, 3rd edn. Harper and Grosvernier P, Matthey Y, Buttler A (1997) Growth potential of Row, New York three Sphagnum species in relation to water table level and Buttler A, Grosvernier P, Matthey Y (1998) Development of peat properties with implications for their restoration in Sphagnum fallax diaspores on bare peat with implications 123 Wetlands Ecol Manage cut-over bogs. J Appl Ecol 34:471–483. https://doi.org/10. CO supply on two keystone species in peatland restoration 2307/2404891 and implications for global change. J Ecol 90:529–533. Grosvernier PR, Mitchell EAD, Buttler A, Gobat JM (2001) https://doi.org/10.1046/j.1365-2745.2002.00679.x Effects of elevated CO and nitrogen deposition on natural Moore TR, Roulet NT (1995) Methane emissions from Cana- regeneration processes of cut-over ombrotrophic peat bogs dian peatlands. In: Lal R, Kimble J, Levine E, Stewart BA in the Swiss Jura mountains. Glob Change Prot Areas (eds) Advances in soil science: soils and global change. 9:347–356 CRC Press, Boca Raton, pp 153–164 Hajek T, Vicherova E (2014) Desiccation tolerance of Sphag- Natural England (2010) England’s peatlands carbon storage and num revisited: a puzzle resolved. Plant Biol 16:765–773 greenhouse gases. Natural England Report NE257 Harpenslager SF, Van Dijk G, Kosten S, Roelofs JGM, Nijp JJ, Limpens J, Metselaar K, van der Zee SEATM, Berendse Smolders AJP, Lamers LPM (2015) Simultaneous high C F, Robroek BJM (2014) Can frequent precipitation mod- fixation and high C emissions in Sphagnum mires. Bio- erate the impact of drought on peatmoss carbon uptake in geosciences 12:4739–4749. https://doi.org/10.5194/bg-12- northern peatlands? New Phytol 203:70–80 4739-2015 Opelt K, Berg C, Scho ¨ nmann S, Eberl L, Berg G (2007) High Heijmans M, Arp WJ, Berendse F (2001a) Effects of elevated specificity but contrasting biodiversity of Sphagnum-as- CO and vascular plants on evapotranspiration in bog sociated bacterial and plant communities in bog ecosys- vegetation. Glob Change Biol 7:817–827 tems independent of the geographical region. ISME J Heijmans M, Berendse F, Arp WJ, Masselink AK, Klees H, De 1(502):516. https://doi.org/10.1038/ismej.2007.58 Visser W, Van Breemen N (2001b) Effects of elevated Oremland RS (1988) Biogeochemistry of methanogenic bacte- carbon dioxide and increased nitrogen deposition on bog ria. Wiley, New York vegetation in the Netherlands. J Ecol 89:268–279. https:// Radu DD, Dual TP (2018) Precipitation frequency alters peat- doi.org/10.1046/j.1365-2745.2001.00547.x land ecosystem structure and CO exchange: contrasting Hinde S, Rosenburgh A, Wright N, Buckler M, Caporn S, Fox L effects on moss, sedge, and shrub communities. Glob (2010) Sphagnum re-introduction project: a report on Change Biol. https://doi.org/10.1111/gcb.14057 research into the re-introduction of Sphagnum mosses to Reich PB, Tilman D, Craine J, Ellsworth D, Tjoelker MG, degraded moorland. Moors for the Future Research Report, Knops J, Wedin D, Naeem S, Bahauddin D, Goth J (2001) vol 18, pp 1–31 Do species and functional groups differ in acquisition and Hoosbeek MR, Van Breemen N, Vasander H, Buttler A, use of C, N and water under varying atmospheric CO and Berendse F (2002) Potassium limits potential growth of N availability regimes? A field test with 16 grassland bog vegetation under elevated atmospheric CO and N species. New Phytol 150:435–448 deposition. Glob Change Biol 8:1130–1138. https://doi. Rice SK, Giles L (1996) The influence of water content and leaf org/10.1046/j.1365-2486.2002.00535.x anatomy on carbon isotope discrimination and photosyn- IPCC (2013) Climate change 2013: the physical science basis, thesis in Sphagnum. Plant Cell Environ 19:118–124 contribution of working group 1 to the fifth assessment Robroek BJ, Limpens J, Breeuwer A, van Ruijven J, Schouten report of the intergovernmental panel on climate change. MG (2007) Precipitation determines the persistence of Cambridge University Press, Cambridge hollow Sphagnum species on hummocks. Wetlands Jauhiainen J, Silvola J (1999) Photosynthesis of Sphagnum 27(4):979–986 fuscum at long-term raised CO concentrations. Annales Robroek BJM, Schouten MGC, Limpens J, Berendse F, Poorter Botanici Fennici 36:11–19 H (2009) Interactive effects of water table and precipitation Jauhiainen J, Silvola J, Tolonem K, Vasander H (1997) on net CO assimilation of three co-occurring Sphagnum Response of Sphagnum fuscum to water levels and CO mosses differing in distribution above the water table. Glob concentration. J Bryol 19:391–400. https://doi.org/10. Change Biol 15:680–691. https://doi.org/10.1111/j.1365- 1179/jbr.1997.19.3.391 2486.2008.01724.x Kroken SB, Graham LE, Cook ME (1996) Occurrence and Robroek BJM, Jassey VEJ, Kox MAR, Berendsen RL, Mills evolutionary significance of resistant cells in charophytes RTE, Cecillon L, Puissant J, Meima-Franke M, Bakker and bryophytes. Am J Bot 83:1241–1254 PAHM, Bodelier PLE (2015) Peatland vascular plan Lanta V, Kantorova J (2015) Niche separation of two grass functional types affect methane dynamics by altering species along a moisture gradient in a post-mined peatland. microbial community structure. J Ecol 103:925–934. Wetlands 35:923–929. https://doi.org/10.1007/s13157- https://doi.org/10.1111/1365-2745.12413 015-0683-x Royles J, Ogee J, Wingate L, Hodgson DA, Convey P, Griffiths Leppala M, Oksanen J, Tuittila ES (2011) Methane flux H (2012) Carbon isotope evidence for recent climate-re- dynamics during mire succession. Oecologia 165:489–499. lated enhancement of CO assimilation and peat accumu- https://doi.org/10.1007/s00442-010-1754-6 lation rates in Antarctica. Glob Change Biol emission Megonigal J, Schlesinger WH (1997) Enhanced CH 18:3112–3124. https://doi.org/10.1111/j.1365-2486.2012. from a wetland soil exposed to elevated CO . Biogeo- 02750.x chemistry 37:77–88 Rydin H, Mcdonald AJS (1985) Tolerance of Sphagnum to Micropropagation Services (EM) LTD. (2015) BeadaMoss. water level. J Bryol 4:571–578. https://doi.org/10.1179/jbr. http://www.beadamoss.co.uk/page8.html. Accessed 23 1985.13.4.571 Oct 2015 Saarnio S, Silvola J (1999) Effects of increase CO and N on Mitchell EAD, Buttler A, Grosvernier P, Rydin H, Siegenthaler CH efflux from a boreal mire: a growth chamber A, Gobat JM (2002) Contrasted effects of increased N and 123 Wetlands Ecol Manage experiment. Oecologia 19:349–356. https://doi.org/10. peatland. Ecohydrology 9:1017–1027. https://doi.org/10. 1007/s004420050795 1002/eco.1699 Saarnio S, Saarinen T, Vasander H, Silvola J (2000) A moderate Toet S, Cornelissen JH, Aerts R, van Logtestijn RS, de Beus M, increase in the annual CH efflux by raised CO or NH Stoevelaar R (2006) Moss responses to elevated CO and 4 2 4- 2 NO supply in a boreal oligotrophic mire. Glob Change variation in hydrology in a temperate lowland peatland. Biol 6:137–144. https://doi.org/10.1046/j.1365-2486. Plants and climate change. Springer, Netherlands, 2000.00294.x pp 27–42 Saarnio S, Jarvio S, Saarinen T, Vasander H, Silvola J (2003) Turetsky MR, Bond-lamberty B, Euskirchen E, Talbot J, Minor changes in vegetation and carbon gas balance in a Frolking S, Mcguire AD, Tuittila ES (2012) The resilience boreal mire under a raised CO or NH NO supply. and functional role of moss in boreal and arctic ecosystems. 2 4 3 Ecosystems 6:46–60. https://doi.org/10.1007/s10021-002- New Phytol 196:49–67. https://doi.org/10.1111/j.1469- 0208-3 8137.2012.04254.x Saarnio S, Morero M, Shurpali NJ, Tuittila ES, Ma ¨kila ¨ M, Alm J Turunen J, Tomppo E, Tolonen K, Reinikainen A (2002) Esti- (2007) Annual CO and CH fluxes of pristine boreal mires mating carbon accumulation rates of undrained mires in 2 4 as a background for the lifecycle analyses of peat energy. Finland—application to boreal and subarctic regions. Boreal Environ Res 12:101–113 Holocene 12:69–80. https://doi.org/10.1191/ Silvola J (1991) Moisture dependence of CO exchange and it’s 0959683602hl522rp recovery after drying in certain boreal forest and peat Van Der Heijden E, Verbeek SK, Kuiper PJC (2000) Elevated mosses. Lindbergia 17:5–10 atmospheric CO and increased nitrogen deposition: Silvola J, Alm J, Ahlholm U, Nykanen H, Martikainen P (1996) effects on C and N metabolism and growth of the peat moss CO fluxes from peat in boreal mires under varying tem- Sphagnum recurvum P. Beauv. var. mucronatum (Russ.) perature and moisture conditions. J Ecol 84:219–228 Warnst. Glob Change Biol 6:201–212. https://doi.org/10. Silvola J, Saarnio S, Foot J, Sundh I, Greenup A, Heijmans M, 1046/j.1365-2486.2000.00303.x Ekberg A, Mitchell E, Van Breemen N (2003) Effects of VSN International (2011) GenStat for Windows, 14th edn. VSN elevated CO and N deposition on CH emissions from International, Hemel Hempstead 2 4 European mires. Global Biogeochem Cycles 17(2):1068. Williams MA, Rice CW, Owensby CE (2000) Carbon dynamics https://doi.org/10.1029/2002GB001886 and microbial activity in allgrass prairie exposed to ele- Strack M (2008) Peatlands and climate change. International vated CO for 8 years. Plant Soil 227:127–137. https://doi. Peat Society, Saarijarven org/10.1023/a:1026590001307 Strack M, Waddington JM (2007) Response of peatland carbon Wittram BW, Roberts G, Buckler M, King L, Walker JS (2015) dioxide and methane fluxes to a water table drawdown A practitioners guide to Sphagnum reintroduction. Moors experiment. Global Biogeochem Cycles 21:13. https://doi. for the Future Partnership, Edale org/10.1029/2006GB002715 Worrall F, Chapman P, Holden J, Evans C, Artz R, Smith P, Strom L, Mastepanov M, Christensen TR (2005) Species- Grayson R (2011) A review of current evidence on carbon specific effects of vascular plants on carbon turnover and fluxes and greenhouse gas emissions from UK peatlands methane emissions from wetlands. Biogeochemistry Wright N, Caporn S, Rosenburgh A, Hinde S, Buckler M (2012) 75:65–82. https://doi.org/10.1007/s10533-004-6124-1 Large-scale bog restoration with Sphagnum species. Taylor N, Price J, Strack M (2015) Hydrological controls on MicroPropagation Services, East Leake productivity of regenerating Sphagnum in a cutover Yu ZC (2012) Northern peatland carbon stocks and dynamics: a review. Biogeosciences 9:4071

Journal

Wetlands Ecology and ManagementSpringer Journals

Published: Jun 1, 2018

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off