Are leaf litter and microbes team players? Interpreting home-field advantage decomposition dynamics

In the ecological literature, a 'home-field advantage' (HFA) describes the phenomenon where plant litters are broken down more quickly in their native versus a foreign environment due to a hypothesized specialised decomposer -litter relationship. Climate change is expected to spatially shift plant communities at an imbalanced rate compared to their decomposers, resulting in previously unexperienced above- and belowground pairings. Understanding decomposition dynamics has implications for global climate and carbon models, yet a clear predictive framework for the HFA has not been proposed. The ecological HFA concept is borrowed from the sports realm where extensive research has found a consistent, greater-than-random chance that teams in sports competitions win games played at their home venue because players are in better physical and psychological states. While research continues to show the sports HFA present in all types of sports independent of playing level or region, the ecological HFA has been shown inconsistently and cannot currently be generalised across scales and ecosystems. In this review, we map the ecological HFA onto a framework used to interpret the HFA in sports. First, we identify and outline the 'game' of decomposition, the 'teams' of decomposer organisms, how plants 'coach' this game, and also how ecological researchers are involved in their role as game 'officials'. Second, we place parallels between the game location factors established in the sports analogy and their ecological counterparts to reveal a greater mechanistic understanding of the ecological HFA. Here we explore microbial adaptation to abiotic environments, the role of historical resource inputs, and how degree of ecosystem contrast and definitional ambiguity affect the HFA. In doing so, we discuss how microbial functional breadth, plant strategy and temporal effects play into the HFA. Using the sports HFA framework provides a novel and promising approach to understanding the ecological HFA that has been lacking, and helps identify potential factors that may not traditionally have been considered. Our framework incorporates multiple theories and views the HFA as a 'team effort' involving multiple components.