Soil organisms are fundamental for maintaining ecosystem functions and services such as nutrient cycling, waste decomposition and plant productivity, and therefore, contribute to human well-being and ecosystem sustainability. Their role in maintaining ecosystem functioning is well-known in natural ecosystems, yet their importance in driving the functioning of croplands is still under debate. In our recent study, we investigated the importance of soil biodiversity and key-stone species in driving long-term wheat production after four decades of continued cropping. We hypothesized that soil biodiversity is essential for wheat production as it controls processes such as nutrient uptake, organic matter decomposition, pathogen control, and the release of micro-nutrients and plant growth hormones. We used a 35-year fertilization experiment from Mengcheng County, China to address our research questions (Fig. 1).
Fig. 1. Soil sampling in the long-term fertilized and unfertilized fields.
We found that the biodiversity of key-stone soil microbial species thriving within ecological networks is fundamental to maintain wheat production in long-term croplands (Fig. 2). These microbial taxa include members of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and nematode. In other words, microbial assemblies (groups of taxa) including a higher richness of key-stone species will have a more positive association with wheat yield, but also with the abundance of soil functional genes associated with carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) cycles. We further investigated the functional profiles associated with key-stone species by approaching their whole genomes. The retrieved whole genomes associated with key-stone species presented higher per-genome gene copies of oxidoreductases (participating most biogeochemical cycles of ecosystems and linking to microbial energetics) and 71 functional genes associated with C, N, P and S cycling, when compared with the genomes clustered within other groups of taxa. Some of these taxa includes members of Chloroflexi, Nitrosospira, Mesorhizobium which are associated with plant-growth promoting processes.
Together, our findings highlighted the essential roles of the biodiversity of key-stone taxa in maintaining soil functions and crop production, this knowledge is important because it opens the door to isolate and apply these microbial communities aiming to improve crop production to feed a continue growing human population worldwide.
Fig. 2. (A) Network diagram of the main groups of taxa (Modules #0–3); (B) The normalized per-genome gene copies of genes associated with C, N, P, S cycles and oxidoreductases; (C) Ecological relationships between the biodiversity of key-stone taxa, soil functional potentials and crop production.
Our paper is available in https://www.nature.com/articles/s41396-020-00796-8