Responses of Bacterial Communities to Simulated Climate Changes in Alpine Meadow Soil of the Qinghai-Tibet Plateau

Abstract

e The soil microbial community plays an important role in terrestrial carbon and nitrogen cycling. However, microbial responses to climate warming or cooling remain poorly understood, limiting our ability to predict the consequences of future climate changes. To address this issue, it is critical to identify microbes sensitive to climate change and key driving factors shifting microbial communities. In this study, alpine soil transplant experiments were conducted downward or upward along an elevation gradient between 3,200 and 3,800 m in the Qinghai-Tibet plateau to simulate climate warming or cooling. After a 2-year soil transplant experiment, soil bacterial communities were analyzed by pyrosequencing of 16S rRNA gene amplicons. The results showed that the transplanted soil bacterial communities became more similar to those in their destination sites and more different from those in their "home" sites. Warming led to increases in the relative abundances in Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria and decreases in Acidobacteria, Betaproteobacteria, and Deltaproteobacteria, while cooling had opposite effects on bacterial communities (symmetric response). Soil temperature and plant biomass contributed significantly to shaping the bacterial community structure. Overall, climate warming or cooling shifted the soil bacterial community structure mainly through species sorting, and such a shift might correlate to important biogeochemical processes such as greenhouse gas emissions. This study provides new insights into our understanding of soil bacterial community responses to climate warming and cooling. G lobal climate change greatly affects terrestrial ecosystems, particularly in polar or alpine regions (1). However, due to the complexity of soil microbiome, how global warming affects their diversity, abundance, and structure is poorly understood (2, 3). To show the responses of microorganisms to climate changes, we must identify those microbes sensitive or acclimated to temperature and their relationships to biogeochemical processes, such as greenhouse gas emissions.Warming is able to directly affect soil bacterial physiology (4) and indirectly affect microbes through changing plant and soil properties (5). For example, an increase in temperature may lead to a preponderance of thermally adapted microorganisms (6). Artificial warming is widely used to study the effects of warming on soil ecosystems. Integrated metagenomic and functional analyses of a long-term warming experiment in a grassland ecosystem show that one of the outcomes of climate warming is a shift of the microbial community composition, which most likely leads to the reduced temperature sensitivity of heterotrophic soil respiration (3). Also, multifactorial warming experiments show that warming and precipitation alter the microbial community composition in a constructed natural grass prairie (7). Likewise, another long-term in situ warming experiment experiences a moderate natural drought, and warming decreases the diversity and sig...

Microbial community composition and abundance after millennia of submarine permafrost warming

“…The observed significant negative rank-based correlation between increasing temperature and total cell counts (TCCs) contradicts our hypothesis that millennial-scale permafrost warming directly increases microbial abundance. It is, however, in line with related studies on arctic and subarctic soil microbial communities in which a negative effect of increasing temperature on microbial abundance was assigned to freeze-thaw cycles (Schimel et al, 2007;Skogland et al, 1988) and substrate depletion (Walker et al, 2018). Both effects are, however, unlikely here.…”

Arbuscular mycorrhizal fungal community composition affected by original elevation rather than translocation along an altitudinal gradient on the Qinghai-Tibet Plateau

“…Therefore, it is suggested that reciprocal translocation experiment is the most rigorous way of demonstrating impacts of climate change because this experiment allows applying both warming and cooling processes and is believed to reduce chemical and mechanical disturbances to a minimum29. Several reciprocal translocation experiments have been conducted on plant survival and productivity30, soil properties and respiration2934, and soil microbial community333536 in natural grassland ecosystems. However, the AM fungal response to soil-plant reciprocal translocation along an altitudinal gradient remains largely unexplored.…”

Prolonged exposure does not increase soil microbial community response to warming along geothermal gradients

“…This implies that the observed patterns in bacterial community composition may, to a certain extent, be explained by the decrease in abundance of Betaproteobacteria. Several other studies have reported a consistent response to environmental drivers, including temperature elevation, for Betaproteobacteria (Fierer et al 2007;Rui et al 2015;Zhang et al 2016) indicating that members of this group may largely share environmental requirements.…”

“…Given the recent concern regarding the stability of ecological systems under a changing climate, there 63 have been numerous studies investigating the effects of warming on microbial community composition 64 (Zogg et al 1997;Zhang et al 2005;Frey et al 2008;Weedon et al 2012;Luo et al 2014;Karhu et al 65 2014;Xu et al 2015;Rui et al 2015). The rationale behind these studies is that sensitivity of soil 66 microbial community composition to increasing soil temperatures will indicate a corresponding 67 sensitivity of the biogeochemical processes these communities are involved in (Zogg et al 1997;68 Strickland et al 2009).…”