More than just water limited: Microbial respiration responds to multiple limiting resources in dryland soils

Authors: Young, Kristina; CHUCKRAN, PETE - University Of California Berkeley; REIBOLD, ROBIN - Us Geological Survey (USGS); GAUTHIER, DYLAN - University Of Texas - El Paso; REED, SASHA - Us Geological Survey (USGS); MCLAREN, JENNIE - University Of Texas - El Paso; Holguin, Jennifer; Webb, Nicholas

Submitted to: Ecological Society of America Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2025
Publication Date: 7/31/2025
Citation: Young, K.E., Chuckran, P., Reibold, R., Gauthier, D., Reed, S.C., McLaren, J., Holguin, J., Webb, N.P. 2025. More than just water limited: Microbial respiration responds to multiple limiting resources in dryland soils. Ecological Society of America Proceedings. Abstract.

Interpretive Summary:

Technical Abstract: Anthropogenic changes to resource availability are fundamentally altering biogeochemical cycles, with significant implications for carbon (C) cycling and storage in terrestrial ecosystems. Drylands, covering over 42% of the Earth's terrestrial surface, are particularly vulnerable to these shifts due to naturally low resource levels. Despite their extensive global coverage and critical role in C sequestration, dryland ecosystems remain understudied, especially regarding the microbial mechanisms governing soil respiration and organic carbon storage. A key but often overlooked component of dryland C cycling is bare soil, which constitutes approximately 24% of the Earth’s terrestrial surface. In these systems, microbial communities mediate C cycling, yet the extent to which resource availability—especially nitrogen (N) and phosphorus (P)—controls microbial respiration remains poorly understood. To investigate the role of resource availability in dryland soil respiration, we conducted a factorial wet incubation experiment using soils collected from a sandy desert shrubland in the Jornada Experimental Range, Chihuahuan Desert, USA. We manipulated labile C, N, and P availability in 27 treatment combinations, plus a control, to simulate a range of stoichiometric conditions. CO2 efflux was measured over 48 hours to quantify microbial respiration responses, and microbial biomass C, N, and P were assessed via liquid chloroform extraction. Contrary to the prevailing hypothesis that dryland respiration is predominantly water-limited, water addition alone resulted in negligible increases in CO2 efflux. Instead, microbial respiration varied significantly with nutrient additions, particularly C and N, indicating a more complex interaction of limiting factors than previously assumed. Notably, while respiration rates responded strongly to resource inputs, microbial biomass C remained relatively stable across treatments. This suggests that changes in soil respiration were driven by shifts in microbial metabolic activity rather than total microbial biomass, highlighting the need for metagenomic and metatranscriptomic analyses to resolve microbial functional responses. These findings challenge traditional dryland C cycling paradigms and underscore the necessity of incorporating microbial activity and resource availability into ecosystem models. As drylands continue to experience increased aridity and nutrient alterations due to global change, understanding the microbial drivers of C cycling will be critical for predicting future carbon dynamics. Our study provides novel insights into the biogeochemical controls on dryland respiration and emphasizes the need for further investigation into microbial community functional dynamics in resource-limited environments.