Soil organisms, such as bacteria, nematodes and earthworms, might not be as attractive to the eye as plants, humans or birds; however, if it weren’t for them, plants and animals or any macro life on Earth, would simply not exist. In many ways, microbes and invertebrates are machines for toxin degradation, pathogen control, waste decomposition, climate regulation, antibiotics, fermentation, and the release of nutrients. These nutrients are then taken up by plants while growing, and that support the production of food and timber, critical for human well-being. So, please, next time you are drinking your beer or thinking about a healthy and productive environment, keep in mind that these, a priori, less nice-looking organisms are responsible for all of that, and more. Interestingly, until recently, despite their importance, little was known about the role of soil biodiversity in controlling ecosystem functioning. Some of the reasons for this are that microbes have been traditionally considered highly redundant organisms in soil (they are expected to be doing similar types of things), and that technology was not prepared to test this type of question. 

Over the last decade, some foundational studies started to highlight the role of soil biodiversity in controlling terrestrial ecosystem functioning within specific regions on Earth (e.g., deserts) and in experiments including different degrees of soil trophic complexity (1-3). However, we were still lacking global cross-biome studies, and microcosm experiments specific to microbial species, aiming to support the link between soil biodiversity and ecosystem functions. In this post, I will introduce some of the work that we (an amazing group of collaborators and myself) have been conducting over the last few years, which combines experimental approaches and global surveys to fill out this important gap of knowledge. The results were just published in Nature Ecology and Evolution (4). 

Back in 2014, I moved to Sydney, AU, where I worked as a postdoc at Western Sydney University for a few years. At the Hawkesbury Institute for the Environment in WSU, we conducted some cool microcosm experiments aiming to identify the role of soil microbial diversity in regulating ecosystem functions. These results, included in our recent paper, provide experimental evidence that the diversity of soil bacteria and fungi are fundamental to maintain the rates of functioning of nutrient cycling and organic matter decomposition in terrestrial environments. Moreover, they suggested that there is an overall lack of microbial functional redundancy when controlling multiple ecosystem functions (multiple soil species are needed!). 

A couple of years later, I started a collaborative global field survey (the CLIMIFUN survey) aiming to better understand the functioning and biodiversity of terrestrial ecosystems. You can read more about other work derived from this survey at https://cordis.europa.eu/project/rcn/201008/brief/en. Using the CLIMIFUN survey, we were able to test the link between the biodiversity of multiple soil organisms and ecosystem functions across contrasting global biomes ranging from deserts to tropical forests. What we found was that the biodiversity of multiple groups of soil organisms (from bacteria to annelids) is essential to maintain the functioning of terrestrial ecosystems across global biomes, and that the biodiversity of highly functional and connected soil taxa within the soil food web was especially important to support healthy and productive environments. To wrap it up, our work advances the necessity to introduce management programs and conservational policies for soil biodiversity, such as those which have existed for plants and animals for decades, and calls for public awareness of the importance of soil biodiversity. 

1. Wagg C. et al. Soil biodiversity and soil community composition determine ecosystem multifunctionality. Proc Natl Acad Sci U S A. 111, 5266-70 (2014).
2. Jing X. et al. (2015). The links between ecosystem multifunctionality and above- and belowground biodiversity are mediated by climate. Nat Comm 6, 8159 (2015).
3. Delgado-Baquerizo, M. et al. Microbial diversity drives multifunctionality in terrestrial ecosystems. Nat Comm 7, 10541 (2016).
4. Delgado-Baquerizo, M. et al. Multiple elements of soil biodiversity drive ecosystem functions across biomes. Nature Ecology & Evolution 4, 210–220 (2020). 

To read more, read the paper following the link: https://www.nature.com/articles/s41559-019-1084-y