Understanding the diversity and distribution of soil microbes towards sustainable resource management

With an increasing human population and global climate change, there is a pressing need to understand how environmental disturbances affect ecosystem properties and functioning. Soil microbes (including bacteria and fungi, two major groups of microbes) play key roles for nutrient cycling in terrestrial ecosystems. In addition, some microbes promote nutrient uptake by plants and their resistance to pest and diseases, while other microbes can cause serious crop and tree damage as pathogens. Climate warming, and the resulting changes in habitat conditions, will alter nutrient cycling and ecosystem functioning in soils. In addition, most forests, grasslands and agricultural soils are subject to extensive land-use changes. However, it is largely unknown how the diversity and ecosystem functioning of soils may be affected by such changes. To address these knowledge gaps, a key step is to determine the main mechanisms that underlie the diversity and distribution of soil microbes.

Compared to plants and animals, microbes have remained understudied in ecological and biogeographical studies, largely owing to their small size, immense diversity and thereby identification difficulties. Recent advances in molecular methods have greatly facilitated the identification and advanced studies of microbes. In particular, current high-throughput sequencing techniques enable us to determine millions of genes and identify thousands of microbial taxa from a single sample. Such information can provide useful insights to disentangle the effects of specific environmental requirements (environmental filtering) and biotic interactions in structuring microbial communities. I have used these methods with the goal to understand microbial diversity patterns, and the underlying mechanisms, across different ecosystems. The major findings from this line of research include:

• The finding that soil harbors the greatest diversity of bacteria and fungi across all habitat types and is a major source of plant-associated microbes.
  
  
• The identification of a global latitudinal gradient in soil microbial diversity, where the highest bacterial gene and phylogenetic diversity can be found in temperate zones across all major biome types.
  
  
• The discovery that variations in soil microbial community structure are mainly driven by soil and climatic factors, rather than geographic distance, on a global scale.

Overall, our data indicate that the community structure of soil microbes strongly vary with environmental variation, suggesting that climate change and anthropogenic disturbances may affect the ecosystem functioning of microbial communities and their biotic interactions. My current research focuses on question of how environmental changes can affect the interactions between soil microbes and plants. A better understanding of this question can eventually help to exploit plant-microbe interactions towards more sustainable management of production systems.