Global drivers and patterns of microbial abundance in soil

Abstract

Aim While soil microorganisms play key roles in Earth's biogeochemical cycles, methodological constraints and sparse data have hampered our ability to describe and understand the global distribution of soil microbial biomass. Here, we present a comprehensive quantification of the environmental drivers of soil microbial biomass. Location Global. Methods We used a comprehensive global dataset of georeferenced soil microbial biomass estimates and high‐resolution climatic and soil data. Results We show that microbial biomass carbon (CMic) is primarily driven by moisture availability, with this single variable accounting for 34% of the global variance. For the microbial carbon‐to‐soil organic carbon ratio (CMic/COrg), soil nitrogen content was an equally important driver as moisture. In contrast, temperature was not a significant predictor of microbial biomass patterns at a global scale, while temperature likely has an indirect effect on microbial biomass by influencing rates of evapotranspiration and decomposition. As our models explain an unprecedented 50% of the global variance of CMic and CMic/COrg, we were able to leverage gridded environmental information to build the first spatially explicit global estimates of microbial biomass and quantified the global soil microbial carbon pool to equal 14.6 Pg C. Main Conclusions Our unbiased models allowed us to build the first global spatially explicit predictions of microbial biomass. These patterns show that soil microbial biomass is not primarily driven by temperature, but instead, biomass is more heterogeneous through the effects of moisture availability and soil nutrients. Our global estimates provide important data for integration into large‐scale carbon and nutrient models that may imply a major step forward in our ability to predict the global carbon balance, now and in a future climate.

Spatial variability of soil microbial biomass and its relationships with edaphic, vegetational and climatic factors in the Three-River Headwaters region on Qinghai-Tibetan Plateau

“…Nevertheless, the low microbial biomass observed in TRH is in accordance with the results of previous macro-scale studies which concluded that the spatial pattern of soil microbial biomass at broad scales was driven by macro-climate and plant traits (Fierer et al, 2009;Insam, 1990;Serna-Chavez et al, 2013;Wardle, 1992;Wright and Coleman, 2000;Xu et al, 2013;Zak et al, 1994). The TRH region has extremely harsh climate with high temperature variability (Sang et al, 2013;van Gestel et al, 2011), Fig.…”

“…This is because a low turnover rate can lead to the accumulation of microbial biomass in soils (Insam, 1990;Serna-Chavez et al, 2013;Wardle, 1992;Xu et al, 2013). This explanation is only valid if temperature change along the altitudinal gradient would not decrease the substrate supply for microbes.…”

“…Many studies on soil MB have been conducted in the past few decades (Dempster et al, 2012;Kaschuk et al, 2010;Xu et al, 2013), and the focus has recently changed from site/ecosystem level Wright and Coleman, 2000;Zak et al, 1994) to regional (Dequiedt et al, 2011;Drenovsky et al, 2010) and global scales (Serna-Chavez et al, 2013;Xu et al, 2013). These large-scale studies examined microbial biomass storage and the mechanisms determining its spatial patterns.…”

“…For example, a recent study (Xu et al, 2013) found that soil MB showed substantial variation across various biomes at global scale and the spatial patterns of MBC and MBN were in line with those of soil C and N with higher densities in northern high latitudes and lower densities in low latitudes and the Southern Hemisphere. Serna-Chavez et al (2013) suggested that the global pattern of soil MB was driven by moisture and soil nutrient contents, not temperature. Using meta-analysis, Fierer et al (2009) showed that soil MB was highly correlated with soil organic C and belowground plant NPP across global biomes.…”

“…Using meta-analysis, Fierer et al (2009) showed that soil MB was highly correlated with soil organic C and belowground plant NPP across global biomes. Nevertheless, MB studies have rarely been conducted above 3000 m in elevation, therefore, previous studies estimating the global soil MB pattern and its dominant factors lack support from high elevation sites (Serna-Chavez et al, 2013;Wardle, 1992;Xu et al, 2013).…”