Journal
SOIL BIOLOGY & BIOCHEMISTRY
Volume 148, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2020.107871
Keywords
Birch effect; Modeling; Moisture; Carbon dynamics; Carbon-use efficiency; Microbial mechanisms; EcoSMMARTS (the ecological version of a soil microbial model to account for responses to stress)
Categories
Funding
- Knut and Alice Wallenberg Foundation [KAW 2017.171]
- Swedish Research Council Vetenskapsradet [2015-04942, 2016-04146, 2016-06327]
- Formas [2015-468, 2018-01315, 2018-00425]
- Swedish Research Council [2016-06327] Funding Source: Swedish Research Council
- Forte [2018-01315] Funding Source: Forte
- Formas [2018-00425, 2018-01315] Funding Source: Formas
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Soils are continuously exposed to cycles of drying and rewetting (D/RW), which drive pronounced fluctuations in soil carbon (C) fluxes. These C dynamics are characterized by a decoupled behavior between microbial biomass synthesis (growth) and CO2 production (respiration). In general, respiration rates peak shortly after RW and subsequently decrease, while the growth peaks lag several hours behind. Despite the significance of these dynamics for the soil C budget and the global C cycle, this feature has so far been overlooked in biogeochemical models and the underlying mechanisms are still unclear. We present a new process-based soil microbial model that incorporates a wide range of physical, chemical and biological mechanisms thought to affect D/RW responses. Results show that the model is able to capture the respiration dynamics in soils exposed to repeated cycles of D/RW, and also to single events in which moisture was kept constant after RW. In addition, the model reproduces, for the first time, the responses of microbial growth to D/RW. We have identified the C accumulation during dry periods, the drought-legacy effect on the synthesis of new biomass, and osmoregulation as the strongest candidate mechanisms to explain these C dynamics. The model outputs are further compared to earlier process-based models, highlighting the advances generated by the new model. This work thus represents a step towards unravelling the microbial responses to drought and rainfall events, with implications for our understanding of C cycle and C sequestration in soils.
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