How global changes affect soil microbial biodiversity and function
Dr. Zhenghu Zhou
Northeast Forestry University, Harbin, China
Biodiversity of plants and animals on the Earth is changing at an unprecedented rate due to a variety of global change factors, such as warming, carbon-dioxide enrichment, altered precipitation, atmospheric nitrogen deposition, nutrient fertilization, land-use change, and their combinations.
Soil microbial communities are surprisingly diverse and abundant. In specific, 1 trillion (1012) microbial species harbor on the Earth, and 1 g soil contains up to 1 billion (109) bacterial cells consisting of tens of thousands of taxa.
Soil microbial communities play a critical role in almost all of the biogeochemical cycling processes in terrestrial ecosystems, such as organic matter decomposition, nutrient cycling, plant diversity, and productivity. Scientists have attempted to examine whether microbial diversity displays an environmental gradient (along temperature, resources, stoichiometry, and so on) like plant diversity, and whether microbial community assembly follows the macroecological theories. Yet, such attempts often fail for soil microorganisms. These knowledge gaps swamp our predictions of global changes impacts on microbial diversity and their ecosystem functions.
Responses of microbial diversity and community structure (from Zhou et al., 2020, Nat. Comm.).
Here, we conducted a global synthesis of 1235 global-change experimental observations from more than 40 countries that measured microbial alpha diversity (number of species coexisting within a local site), beta diversity (the magnitude of similarity in species composition among different sites), and community structure with high-throughput sequencing techniques. Our study attempts to answer the following three questions: first, what are the effects of global changes on microbial diversity and community structure worldwide? Are the effects similar to those reported for plants and animals? Second, what are the potential drivers of these responses? Finally, how do global changes induced changes in microbial alpha diversity affect the microbial functionality in the ecosystems?
In this paper, we show that microbial community structure is sensitive to global changes, while global changes affect microbial diversity inconsistently and do not always lead to the loss of microbial diversity. Conversion from highly diverse natural ecosystems to homogeneous agricultural monocultures has a positive effect on microbial alpha diversity. Soil pH is the most important factor to predict the global changes effects on microbial alpha diversity. Generally, if a global change factor increases the soil pH, the alpha diversity would increase; if it decreases the soil pH, the alpha diversity would reduce; if it has no effect on soil pH, it would not change the alpha diversity. The response of soil functionality to global changes can be explained by the responses of microbial community structure and biomass rather than the response of microbial alpha diversity.
In the end, we highlight that the responses of microbial communities to global changes are fundamentally different from those of macro-communities, which are crucial to the policy-making to preserve microbial diversity hotspots under global environmental changes.
Publication: Zhou, Z., Wang, C. & Luo, Y. Meta-analysis of the impacts of global change factors on soil microbial diversity and functionality. Nat Commun 11, 3072 (2020). https://doi.org/10.1038/s41467-020-16881-7