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Abstract Interactions between plants and soil microbes influence plant nutrient transformations, including nitrogen (N) fixation, nutrient mineralization, and resource exchanges through fungal networks. Physical disturbances to soils can disrupt soil microbes and associated processes that support plant and microbial productivity. In low resource drylands, biological soil crusts (“biocrusts”) occupy surface soils and house key autotrophic and diazotrophic bacteria, non‐vascular plants, or lichens. Interactions among biocrusts, plants, and fungal networks between them are hypothesized to drive carbon and nutrient dynamics; however, comparisons across ecosystems are needed to generalize how soil disturbances alter microbial communities and their contributions to N pools and transformations. To evaluate linkages among plants, fungi, and biocrusts, we disturbed all unvegetated surfaces with human foot trampling twice yearly from 2013–2019 in dry conditions in cyanobacteria‐dominated biocrusts in the Chihuahuan Desert grassland and shrubland ecosystems. After 5 years, disturbance decreased the abundances of cyanobacteria (especiallyMicrocoleus steenstrupiiclade) and N‐fixers (Scytonemasp., andSchizothrixsp.) by >77% and chlorophyllaby up to 55% but, conversely, increased soil fungal abundance by 50% compared with controls. Responses of root‐associated fungi differed between the two dominant plant species and ecosystem types, with a maximum of 80% more aseptate hyphae in disturbed than in control plots. Although disturbance did not affect15N tracer transfer from biocrusts to the dominant grass,Bouteloua eriopoda, disturbance increased available soil N by 65% in the shrubland, and decreased leaf N ofB. eriopodaby up to 16%, suggesting that, although rapid N transfer during peak production was not affected by disturbance, over the long‐term plant nutrient content was disrupted. Altogether, the shrubland may be more resilient to detrimental changes due to disturbance than grassland, and these results demonstrated that disturbances to soil microbial communities have the potential to cause substantial changes in N pools by reducing and reordering biocrust taxa.
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The competitive advantage of a constitutive CAM species over a C 4 grass species under drought and CO 2 enrichment
Abstract Plants with crassulacean acid metabolism (CAM) are increasing in distribution and abundance in drylands worldwide, but the underlying drivers remain unknown. We investigate the impacts of extreme drought and CO2enrichment on the competitive relationships between seedlings ofCylindropuntia imbricata(CAM species) andBouteloua eriopoda(C4grass), which coexist in semiarid ecosystems across the Southwestern United States. Our experiments under altered water and CO2water conditions show thatC. imbricatapositively responded to CO2enrichment under extreme drought conditions, whileB. eriopodadeclined from drought stress and did not recover after the drought ended. Conversely, in well‐watered conditionsB. eriopodahad a strong competitive advantage onC. imbricatasuch that the photosynthetic rate and biomass (per individual) ofC. imbricatagrown withB. eriopodawere lower relative to when growing alone. A meta‐analysis examining multiple plant families across global drylands shows a positive response of CAM photosynthesis and productivity to CO2enrichment. Collectively, our results suggest that under drought and elevated CO2concentrations, projected with climate change, the competitive advantage of plant functional groups may shift and the dominance of CAM plants may increase in semiarid ecosystems.
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- PAR ID:
- 10458928
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 10
- Issue:
- 5
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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