Microbial community responses reduce soil carbon loss in Tibetan alpine grasslands under short‐term warming

Abstract

Changes in labile carbon (LC) pools and microbial communities are the primary factors controlling soil heterotrophic respiration (R h ) in warming experiments. Warming is expected to initially increase R h but studies show this increase may not be continuous or sustained. Specifically, LC and soil microbiome have been shown to contribute to the effect of extended warming on R h . However, their relative contribution is unclear and this gap in knowledge causes considerable uncertainty in the prediction of carbon cycle feedbacks to climate change. In this study, we used a two-step incubation approach to reveal the relative contribution of LC limitation and soil microbial community responses in attenuating the effect that extended warming has on R h . Soil samples from three Tibetan ecosystems-an alpine meadow (AM), alpine steppe (AS), and desert steppe (DS)-were exposed to a temperature gradient of 5-25°C. After an initial incubation period, soils were processed in one of two methods: (a) soils were sterilized then inoculated with parent soil microbes to assess the LC limitation effects, while controlling for microbial community responses; or (b) soil microbes from the incubations were used to inoculate sterilized parent soils to assess the microbial community effects, while controlling for LC limitation. We found both LC limitation and microbial community responses led to significant declines in R h by 37% and 30%, respectively, but their relative contributions were ecosystem specific. LC limitation alone caused a greater R h decrease for DS soils than AMs or ASs. Our study demonstrates that soil carbon loss due to R h in Tibetan alpine soils-especially in copiotrophic soils-will be weakened by microbial community responses under short-term warming.

Unaltered soil microbial community composition, but decreased metabolic activity in a semiarid grassland after two years of passive experimental warming

“…Previous studies showed that warming could stimulate microbial respiration due to increased microbial biomass C (Liu et al., 2019), soil nutrient availability (Ali et al., 2018), root exudates (Li et al., 2013), enzymatic activity (Bragazza et al., 2012; Li et al., 2017), or plant production (Euskirchen et al., 2009). Some other studies showed opposite results; that is, microbial respiration inhibited by warming, which resulted from decreased soil water availability (Fang et al., 2018; Liu et al., 2009), labile C (Li et al., 2019), microbial biomass C (Chen, et al., 2016), or enzymatic activity (Garcia‐Palacios et al., 2018). As a result, these contrasting responses of microbial metabolic rate to warming led to large uncertainties and contradictory predictions of climate‐C feedbacks (Bradford et al., 2010; Hartley et al., 2007, 2009).…”

High microbial diversity stabilizes the responses of soil organic carbon decomposition to warming in the subsoil on the Tibetan Plateau

“…Recent studies have attempted to uncover possible mechanisms by which changes in microbial traits (biomass, physiology, community composition, etc.) or key processes such as enzyme production regulate the response of SOC to warming (e.g., Alvarez et al, 2018; Ding et al, 2016; Guo et al, 2020; Karhu et al, 2014; Li et al, 2019; Nottingham et al, 2019; Walker et al, 2018). However, the results are context dependent and vary among different ecosystems.…”

Distinct Elevational Patterns and Their Linkages of Soil Bacteria and Plant Community in An Alpine Meadow of the Qinghai–Tibetan Plateau

“…Acidobacteria was the most common group at low-elevation, possibly due to their low C turnover, which allows them to adapt to the low-nutrient soil environment as “stress tolerators” [ 61 ]. Of course, not all taxa in a phylum will be either copiotrophic or oligotrophic [ 60 ], hence other classifier levels should be used to predict soil C loss [ 62 ]. In our study, Beta - and Gamma - proteobacteria decreased as elevation decreased; however, Acidobacteria GP4 and GP6 increased.…”