Lower Soil Carbon Loss Due to Persistent Microbial Adaptation to Climate Warming
Abstract
Soil microbial respiration is a major positive feedback triggered by climatic warming in a coupled climate-carbon system, and is the main source of uncertainty in climate projections. Despite intensive studies for two decades, the magnitude, direction, and duration of such feedbacks are uncertain, and their underlying microbial mechanisms are still poorly understood, especially in multiple years with large interannual environment variations. Accordingly, we established a field warming (+2.8oC) experiment in the temperate grassland ecosystem of the US Great Plains in Central Oklahoma in 2009. During 7 years of experiment, we monitored many ecosystem variables, including ecosystem carbon fluxes (i.e., GPP, ER and NEE), soil total respirations (Rt) and its components (i.e., microbial heterotrophic respiration (Rh) and plant root autotrophic respiration (Ra)), soil temperature, moisture, total organic carbon, to evaluate long-term warming effects on ecosystem carbon cycling. Soil samples were collected annually and analyzed by multiple metagenomics technologies to detect the soil microbial community structure and function in response to warming. Our results indicated that the temperature sensitivity of soil microbial respiration persistently decreased by 8-23% over 7 years of warming. Integrated metagenomic and functional analyses showed that warming-induced respiratory acclimation is mainly due to adaptive changes in microbial community functional structure. Incorporating microbial functional community structure and gene abundance data into a microbially-enabled ecosystem model significantly improved the modeling performance of soil microbial respiration by 5-19%, compared to the traditional non-microbial model. Model parametric uncertainty was also reduced by 55-71% when gene abundances were used, which thereby greatly increases the confidence in model simulations. In addition, our modeling analyses suggested that decreased temperature sensitivity could lead to considerably less heterotrophic respiration (11.6±7.5%), and hence less soil C loss. If such microbially mediated dampening effects occur generally across different spatial and temporal scales, the potential positive feedback of soil microbial respiration in response to climate warming may be less than predicted.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B43C..08Z
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0465 Microbiology: ecology;
- physiology and genomics;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES