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Predicted climate change extremes, such as severe or prolonged drought, may considerably impact carbon (C) and nitrogen (N) cycling in water-limited ecosystems. However, we lack a clear and mechanistic understanding of how extreme climate change events impact ecosystem processes belowground. This study investigates the effects of five years of reoccurring extreme growing season drought (66% reduction, extreme drought treatment) and two-month delay in monsoon precipitation (delayed monsoon treatment) on belowground productivity and biogeochemistry in two geographically adjacent semi-arid grasslands: Chihuahuan Desert grassland dominated by Bouteloua eriopoda and Great Plains grassland dominated by B. gracilis. After five years, extreme drought reduced belowground net primary productivity (BNPP) in the Chihuahuan Desert grassland but not in the Great Plains grassland. Across both grasslands, extreme drought increased soil pH and available soil nutrients nitrate and phosphate. The delayed monsoon treatment reduced BNPP in both grasslands. However, while available soil nitrate decreased in the Chihuahuan Desert grassland, the delayed monsoon treatment overall had little effect on soil ecosystem properties. Extreme drought and delayed monsoon treatments did not significantly impact soil microbial biomass, exoenzyme potentials, or soil C stocks relative to ambient conditions. Our study demonstrates that soil microbial biomass and exoenzyme activity in semi-arid grasslands are resistant to five years of extreme and prolonged growing season drought despite changes to soil moisture, belowground productivity, soil pH, and nutrient availability
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Deeper topsoils enhance ecosystem productivity and climate resilience in arid regions, but not in humid regions
Abstract Understanding the controlling mechanisms of soil properties on ecosystem productivity is essential for sustaining productivity and increasing resilience under a changing climate. Here we investigate the control of topsoil depth (e.g., A horizons) on long‐term ecosystem productivity. We used nationwide observations (n = 2401) of topsoil depth and multiple scaled datasets of gross primary productivity (GPP) for five ecosystems (cropland, forest, grassland, pasture, shrubland) over 36 years (1986–2021) across the conterminous USA. The relationship between topsoil depth and GPP is primarily associated with water availability, which is particularly significant in arid regions under grassland, shrubland, and cropland (r = .37, .32, .15, respectively,p < .0001). For every 10 cm increase in topsoil depth, the GPP increased by 114 to 128 g C m−2 year−1in arid regions (r = .33 and .45,p < .0001). Paired comparison of relatively shallow and deep topsoils while holding other variables (climate, vegetation, parent material, soil type) constant showed that the positive control of topsoil depth on GPP occurred primarily in cropland (0.73, confidence interval of 0.57–0.84) and shrubland (0.75, confidence interval of 0.40–0.94). The GPP difference between deep and shallow topsoils was small and not statistically significant. Despite the positive control of topsoil depth on productivity in arid regions, its contribution (coefficients: .09–.33) was similar to that of heat (coefficients: .06–.39) but less than that of water (coefficients: .07–.87). The resilience of ecosystem productivity to climate extremes varied in different ecosystems and climatic regions. Deeper topsoils increased stability and decreased the variability of GPP under climate extremes in most ecosystems, especially in shrubland and grassland. The conservation of topsoil in arid regions and improvements of soil depth representation and moisture‐retention mechanisms are critical for carbon‐sequestration ecosystem services under a changing climate. These findings and relationships should also be included in Earth system models.
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- Award ID(s):
- 2017870
- PAR ID:
- 10541243
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Global Change Biology
- Volume:
- 29
- Issue:
- 23
- ISSN:
- 1354-1013
- Page Range / eLocation ID:
- 6794 to 6811
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/gcb.16944
