Litter quality and environmental controls of home-field advantage effects on litter decomposition

The home-field advantage (HFA) hypothesis' predicts that plant litter is decomposed faster than expected in the vicinity of the plant where it originates from (i.e. its home') relative to some other location (i.e. away') because of the presence of specialized decomposers. Despite growing evidence for the widespread occurrence HFA effects, what drives HFA is not understood as its strength appears highly variable and context-dependent. Our work advances current knowledge about HFA effects by testing under what conditions HFA is most important. Using published data on mass loss from 125 reciprocal litter transplants from 35 studies, we evaluated if HFA effects were modulated by macroclimate, litter quality traits, and the dissimilarity between home' and away' of both the quality of reciprocally exchanged litters and plant community type. Our results confirmed the occurrence of an overall, worldwide, HFA effect on decomposition with on average 7.5% faster decomposition at home. However, there was considerable variation in the strength and direction (sometimes opposite to expectations) of these effects. While macroclimate and average litter quality had weak or no impact on HFA effects, home-field effects became stronger (regardless of the direction) when the quality of home' and away' litters became more dissimilar (e.g. had a greater dissimilarity in N:P ratio; F-1,F-42 = 6.39, p = 0.015). Further, home-field effects were determined by the degree of difference between the types of dominant plant species in the home' versus away' communities (F-2,F-105 = 4.03, p = 0.021). We conclude that home-field advantage is not restricted to particular litter types or climate zones, and that the dissimilarity in plant communities and litter quality between the home' and away' locations, are the most significant drivers of home-field effects.