Coupling soil–plant–atmosphere exchange of ammonia with ecosystem functioning in grasslands

Coupling soil–plant–atmosphere exchange of ammonia with ecosystem functioning in grasslands The exchange of ammonia (NH 3 ) between the atmosphere and the land surface is controlled by both atmospheric and land surface processes and can thus be bi-directional. Whether emission or deposition occurs depends on the nitrogen (N) status of the ecosystem. Resistance models have been developed to represent this bi-directional pattern of NH 3 exchange. Major pathways include exchange with leaf cuticles, plant tissues (via stomata) and with the soil surface. However, the parameters that quantify the emission potential of the foliage and ground surface, the NH 3 stomatal compensation point, χ s , and the soil surface NH 3 concentration, χ soil , respectively, are entirely empirical in these models and do not consider the influence of the plant and soil N status. On the other side, grassland ecosystem models simulate the ecosystem N dynamics, but until now NH 3 biosphere–atmosphere exchange was only treated in a very simple manner. A two-layer resistance model for NH 3 exchange has thus been combined with the grassland ecosystem model PaSim in order to link NH 3 exchange with the ecosystem N dynamics. For this purpose, the plant substrate N pool in previous versions of PaSim has been divided between apoplastic and symplastic compartments, and the apoplastic substrate N pool has been linked to the stomatal NH 3 exchange. In addition, soil ammoniacal N (NH x ) has been partitioned between the soil surface and several soil layers, and the soil surface NH 3 exchange has been linked to the soil surface ammonium (NH 4 + ). The new combined model has been parameterised and applied to an intensively managed grassland site in Southern Scotland. The comparison with micrometeorological measurements of NH 3 fluxes has shown that the model can qualitatively reproduce the effects of cutting and fertilisation on the net NH 3 exchange above the canopy. In particular, the model reproduces the expected strong coupling of the NH 3 exchange with the dynamics of the apoplastic substrate N pool. However, peak NH 3 emissions are underestimated, and it is postulated that this could be related to the representation of leaf litter emissions from the soil surface in the model, and to the simulated soil NH x dynamics. Nevertheless, this new version of PaSim is a valuable tool for investigating the influence of different management scenarios or of climate change on NH 3 exchange. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecological Modelling Elsevier

Coupling soil–plant–atmosphere exchange of ammonia with ecosystem functioning in grasslands

Loading next page...
 
/lp/elsevier/coupling-soil-plant-atmosphere-exchange-of-ammonia-with-ecosystem-jtZQUHN1Ps
Publisher
Elsevier
Copyright
Copyright © 2002 Elsevier Science B.V.
ISSN
0304-3800
eISSN
1872-7026
DOI
10.1016/S0304-3800(02)00169-2
Publisher site
See Article on Publisher Site

Abstract

The exchange of ammonia (NH 3 ) between the atmosphere and the land surface is controlled by both atmospheric and land surface processes and can thus be bi-directional. Whether emission or deposition occurs depends on the nitrogen (N) status of the ecosystem. Resistance models have been developed to represent this bi-directional pattern of NH 3 exchange. Major pathways include exchange with leaf cuticles, plant tissues (via stomata) and with the soil surface. However, the parameters that quantify the emission potential of the foliage and ground surface, the NH 3 stomatal compensation point, χ s , and the soil surface NH 3 concentration, χ soil , respectively, are entirely empirical in these models and do not consider the influence of the plant and soil N status. On the other side, grassland ecosystem models simulate the ecosystem N dynamics, but until now NH 3 biosphere–atmosphere exchange was only treated in a very simple manner. A two-layer resistance model for NH 3 exchange has thus been combined with the grassland ecosystem model PaSim in order to link NH 3 exchange with the ecosystem N dynamics. For this purpose, the plant substrate N pool in previous versions of PaSim has been divided between apoplastic and symplastic compartments, and the apoplastic substrate N pool has been linked to the stomatal NH 3 exchange. In addition, soil ammoniacal N (NH x ) has been partitioned between the soil surface and several soil layers, and the soil surface NH 3 exchange has been linked to the soil surface ammonium (NH 4 + ). The new combined model has been parameterised and applied to an intensively managed grassland site in Southern Scotland. The comparison with micrometeorological measurements of NH 3 fluxes has shown that the model can qualitatively reproduce the effects of cutting and fertilisation on the net NH 3 exchange above the canopy. In particular, the model reproduces the expected strong coupling of the NH 3 exchange with the dynamics of the apoplastic substrate N pool. However, peak NH 3 emissions are underestimated, and it is postulated that this could be related to the representation of leaf litter emissions from the soil surface in the model, and to the simulated soil NH x dynamics. Nevertheless, this new version of PaSim is a valuable tool for investigating the influence of different management scenarios or of climate change on NH 3 exchange.

Journal

Ecological ModellingElsevier

Published: Dec 15, 2002

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 folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off