Disentangling the mechanisms underlying functional differences among decomposer communities

Home‐field advantage (HFA) is a commonly used sports analogy, which has seen recent growth within the ecosystem ecology literature. It is most often invoked in litter transplant studies, where local adaptation (HFA) explains higher decomposition rates of leaf litter on ‘home’ soil communities. In exploring the mechanisms driving functional differences among soil decomposer communities, a consistent quantitative framework is lacking. We review methods for calculating HFA, propose a consolidated regression approach and demonstrate why HFA must be calculated along with a new ‘ability’ metric if we are to test definitively the competing hypotheses that soil decomposer communities are functionally equivalent versus dissimilar. We demonstrate that qualitative interpretations of HFA differ when the ability of a decomposer community is calculated simultaneously with HFA. For example, communities may differ in their ability to degrade litter in the absence of HFA, or apparent HFA may instead be caused by differing abilities, changing our ecological interpretation of the factors generating functional differences among decomposer communities. Synthesis: We propose a single, statistical approach to help evaluate how and why soil decomposer communities differ in functional abilities. Our approach should help formalize mechanistic interpretations of why soil community composition commonly influences litter decomposition rates.