Contrasting mechanisms underlie short‐ and longer‐term soil respiration responses to experimental warming in a dryland ecosystem

• Published in: Global change biology 2020-09, Vol.26 (9), p.5254-5266
• Main Authors: Dacal, Marina, García‐Palacios, Pablo, Asensio, Sergio, Cano‐Díaz, Concha, Gozalo, Beatriz, Ochoa, Victoria, Maestre, Fernando T.
• Format: Article
• Language: English
• Subjects: Acclimation; Acclimatization; Arid zones; biocrusts; Carbon; dryland; Ecosystem; microbial thermal acclimation; Organic carbon; Organic soils; Prairies; Respiration; short‐term versus longer‐term warming; Soil; Soil dynamics; Soil Microbiology; soil moisture; soil respiration; Soil temperature; Soils; Temperature
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.15209

Soil carbon losses to the atmosphere through soil respiration are expected to rise with ongoing temperature increases, but available evidence from mesic biomes suggests that such response disappears after a few years of experimental warming. However, there is lack of empirical basis for these temporal dynamics in soil respiration responses, and for the mechanisms underlying them, in drylands, which collectively form the largest biome on Earth and store 32% of the global soil organic carbon pool. We coupled data from a 10 year warming experiment in a biocrust‐dominated dryland ecosystem with laboratory incubations to confront 0–2 years (short‐term hereafter) versus 8–10 years (longer‐term hereafter) soil respiration responses to warming. Our results showed that increased soil respiration rates with short‐term warming observed in areas with high biocrust cover returned to control levels in the longer‐term. Warming‐induced increases in soil temperature were the main drivers of the short‐term soil respiration responses, whereas longer‐term soil respiration responses to warming were primarily driven by thermal acclimation and warming‐induced reductions in biocrust cover. Our results highlight the importance of evaluating short‐ and longer‐term soil respiration responses to warming as a mean to reduce the uncertainty in predicting the soil carbon–climate feedback in drylands. We investigated the temporal dynamics of soil respiration responses to temperature, and the mechanisms underlying them, in a biocrust‐dominated dryland ecosystem, coupling data from a 10 year field warming experiment with laboratory incubations. Our results showed that increased soil respiration rates with short‐term warming observed in areas with high biocrust cover returned to control levels in the longer‐term. Contrasting mechanisms underlie such responses. Specifically, warming‐induced increases in soil temperature were the main drivers of the short‐term soil respiration responses, whereas longer‐term soil respiration responses to warming were primarily driven by thermal acclimation and warming‐induced reductions in biocrust cover.