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doi: 10.1002/saj2.20720pmid: N/A
This paper contains a brief overview of contents of 13 North American Forest Soils Conferences.
Holub, Scott M.; Cattnach, Glenn; Littke, Kimberly M.; Hatten, Jeff A.
doi: 10.1002/saj2.20740pmid: N/A
Forests around the world, and in the case of this study, the coastal Pacific Northwest United States, store large amounts of carbon, both above ground in the trees and below ground in soils. Understanding the effects of forest disturbance, including timber harvesting, is important in order to evaluate the role that forestry plays in the global carbon cycle. Soil carbon can be difficult to assess with enough precision to detect the kinds of changes that are expected, yet a series of small changes over time in the same direction could have important cumulative effects. In this study, eight randomly selected Douglas‐fir forest stands in Oregon and Washington were sampled at 300 points each using a fixed‐depth sampling approach to attempt to detect a 5% or higher change in soil carbon storage to 1 m, longitudinally from pre‐harvest to 10 years post‐harvest. There was moderate variability in results over time at individual sites, with some sites decreasing slightly and others increasing slightly. Only two sites achieved lower than the 5% minimum detectible difference target. The remaining six sites were able to detect 5.7%–10.7% differences. In one case, an unexpectedly large increase in mineral soil carbon 10 years post‐harvest occurred without clear explanation. On average, forest floor carbon stores were 20% larger 10 years post‐harvest than pre‐harvest. Even with the large increases excluded, both the fixed‐depth approach and equivalent soil mass correction showed there was no significant change in mineral soil carbon stores to 1 m at 10 years post‐harvest in the region.
Fedenko, Jennifer; D'Amore, David; Spinola, Diogo; Portes, Raquel; Dere, Ashlee; Lybrand, Rebecca A.
doi: 10.1002/saj2.20695pmid: N/A
A dense concentration of old‐growth forest and a wet, cold climate promote mineral weathering and leaching in coastal temperate rainforest soils. Our objective was to assess soil development and soil organic carbon (SOC) distribution across 18 soil profiles in remote, upland terrain of southeast Alaska where pedon data are sparse. We made soil morphological observations, collected samples, and completed laboratory analyses to measure SOC content, pH, and particle size distribution. The survey of upland backslope soils included north‐ and south‐facing hillslopes derived from three lithologies (slate, metavolcanic, and phyllite). The soils across all sites were very gravelly (51.8 ± 20.4% coarse fragments), acidic (mineral soil pH 4.85 ± 0.45), and moderately deep (96.56 ± 37.80 cm); thin, broken E horizons were underlain by thick, carbon‐rich spodic horizons. Soil development was relatively consistent as demonstrated by the Profile Development Index with values from 15 to 26 and Podzolization Index values spanning 8 to 14. A mean pedon SOC stock of 198.02 ± 81.42 Mg C ha−1 (n = 18) was calculated using data collected for all upland organic and mineral soils from our work. The accumulation of SOC was similar among soils formed from contrasting lithologies with averages of 182 ± 15.70 Mg C ha−1 for slate, 188 ± 53.80 Mg C ha−1 for metavolcanic, and 218 ± 124 Mg C ha−1 for phyllite. Our work contributes to soil morphological observations, laboratory data, and SOC stock estimates required to better constrain and model pedogenic processes and SOC stock in remote forests where data sets are limited.
Pitumpe Arachchige, Pavithra S.; Hettiarachchi, Ganga M.; Rice, Charles W.; Dynes, James J.; Maurmann, Leila; Kilcoyne, A. L. David; Attanayake, Chammi P.
doi: 10.1002/saj2.20701pmid: N/A
Direct evidence‐based approaches are vital in understanding the involvement of abiotic/biotic factors and evaluating the newly proposed theories on soil carbon (C) stabilization. Microaggregates (150–250 µm) collected from a corn system (>22 years; Kansas, USA), which had been under no‐till with different nitrogen (N) treatments were analyzed (N treatments: manure/compost, urea, zero fertilizer). We studied C stabilization in free soil microaggregates (with preserved aggregate architecture), directly using scanning transmission X‐ray microscopy coupled with near edge X‐ray absorption fine structure (STXM‐NEXAFS) spectroscopy. Submicron scale findings were complemented with bulk chemical analysis. The STXM‐NEXAFS analysis revealed soil organic carbon (SOC) preservation inside nano‐ and micro‐pores and organo–mineral association, various degrees of humification, and high molecular diversity. The presence of microbial‐derived C was found in manure‐/compost‐added microaggregates highlighting the contribution of organic amendments in facilitating microbial diversity. The incidence of aragonite‐like minerals suggested the biologically/chemically active nature of microaggregate cores. Bulk analysis of free microaggregates showed a higher concentration of SOC (6.5%), ammonium oxalate extractable Fe/Al/Si), and higher aliphaticity of humic acid in manure‐/compost‐added soils compared to inorganic fertilizer (3% SOC) and control (2.7% SOC) treatments. The co‐existence of elements (calcium [Ca]/C, iron [Fe]/N, Fe/C, aluminum [Al]/C, and silicon [Si]/C) was partially supported by bulk chemical analysis that indicated a strong association between ammonium oxalate extractable Fe/Al/Si and SOC (R2 = 0.63—0.77). Overall, our study provided direct/indirect evidence for the complex and interactive involvement of chemical, mineralogical, and biological mechanisms that may have been stimulated by the long‐term addition of compost/manure in stabilizing SOC.
Calleja‐Huerta, A.; Lamandé, M.; Heck, R. J.; Green, O.; Munkholm, L. J.
doi: 10.1002/saj2.20719pmid: N/A
Soil structure dynamics during a season depend on management practices and environmental factors. A lightweight autonomous robot (total mass: 3300–4100 kg, wheel load: 700–1200 kg, contact areas: 0.125 m2, inflation pressures: 60–280 kPa) was used for sowing (October 2021) and weeding (May 2022) operations on an annually plowed sandy loam field. We took 579 cm3 soil cores at 10‐ to 18‐cm depth in the crop area and wheel tracks before and after the operations to assess the impact from traffic and the potential recovery of topsoil structural properties. We measured air permeability and effective air‐filled porosity in the laboratory, and X‐ray CT scanned the samples to evaluate soil pore functionality. The first operation (conducted on a moist seedbed) had the largest impact, significantly compacting and reducing the air‐filled porosity by 42% (from 0.21 to 0.12 m3 m−3) and decreasing air permeability by 75.8% (from 130 to 31.5 µm2). After 7 months, the crop area and wheel track showed signs of soil consolidation due to environmental factors but not decompaction. The second operation occurred on drier (water content 0.06 g g−1), stronger soil conditions (degree of compactness 100.8%), and recompaction of the wheel track was not observed. Traffic in weak soils can result in seasonal topsoil compaction despite the lighter wheel loads. However, due to the milder impacts, recovery rates might be faster for lightweight machinery than for heavy tractors. Multi‐season studies are needed to assess the real potential of lightweight robots to minimize soil compaction risk.
García‐Ramírez, P.; Guillén, K.; Sedov, S.; Golden, C.; Morell‐Hart, S.; Scherer, A.; Pi, T.; Solleiro‐Rebolledo, E.; Dine, H.; Rivera, Y.
doi: 10.1002/saj2.20723pmid: N/A
The soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long‐term human impacts of ancient Maya agriculture. To understand the interaction between natural and human‐induced soil‐forming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land‐use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro‐ and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfide‐sulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil‐geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals.
Luo, Pengcheng; Su, Lijun; Tao, Wanghai; Shan, Yuyang; Deng, Mingjiang; Wang, Quanjiu; Yan, Haokui
doi: 10.1002/saj2.20725pmid: N/A
This study addresses the problem of 2D soil water movement under ponding radii of 1, 2, and 3 cm. The soil water movement characteristics (shape parameters of the water content profile, ratio of horizontal wetting front to vertical wetting front, relationship between infiltration time and horizontal wetting front, and relationship between infiltration time and cumulative infiltration) under the above three kinds of water ponding radius were analyzed. On the basis of the assumption that the soil wetting body is a semi‐ellipse and the analytical solution of the 1D soil water movement equation at any angle, the approximate analytical solution of the 2D soil water movement equation under ponding conditions is optimized. The function relationships between infiltration time, wetting front, and cumulative infiltration are established. We applied the numerical data simulated by HYDRUS‐3D to validate the parameters in proposed analytical solutions and evaluated the relationships between the wetting front and hydraulic parameters. The results indicate that as the water ponding radius increases, the wetting body and 2D water content distribution becomes larger. When the water ponding radius was 2 cm, the numerical and analytical solution of 1D soil water distribution showed the best comparison results, and the model error was the smallest. The ratio of wetting fronts was linearly increased with the increase of air‐entry suction with R2 = 0.9969.
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