Community ecology seeks to untangle structural patterns and underlying biological mechanisms across time and space. Though developed for studies above ground, community ecology provides an equally relevant framework for looking at the below ground world, a realm that’s now understood to store and cycle most of Earth’s organic carbon.
Although it has its critics, the niche concept is a dominant framework in community ecology that examines species position in the ecosystem based on comparative advantages their traits convey and ability to persist contingent on biotic interactions and abiotic conditions. To understand the niche concept plant ecologists invest tremendous effort studying communities through the lens of functional traits. In 2013, 78% of the articles in the Journal of Ecology focused on species traits, rather than just species identities to explain patterns observed in experimental and observational studies.
Despite considerable advances using trait-based approaches in above ground ecology, microbial ecologists have preferred to view communities through the taxonomic lens, with a focus on species identities that compromises ecological understanding. (For example, the observation that ‘fast-growing cord-forming fungi are more combative than the litter-dwelling microfugi’ is more useful than ‘Resinicium bicolor out-competes Mortierella verticillata in soil’.) By focusing on biological properties, and how they vary between individuals, the trait-based approach can improve our capacity to extrapolate to other species and systems, based on the relative expression of those functional traits.
To bring microbial ecology into the realm of classic ecological theory, and to better understand how communities are structured across time and space, Lennon et al. measured a set of microbial physiological traits for a diverse collection of soil bacteria and fungi to quantify how microbial respiration (which produces CO2 as a by-product) varies with changes in soil moisture. They showed that, via trade offs in drought tolerance, soil microbes are filtered into specific niche spaces along the moisture gradient, providing the most robust evidence for the niche-based community structuring in these below ground communities. By identifying functional groups of microorganisms, whose distributions respond predictably to changes in the environment, this study begins to help predict how communities and ecosystems will respond to climate change with predictable consequences for ecosystems.