The consistency of home-field advantage effects with varying climate conditions

Abstract

The home-field advantage (HFA) hypothesis predicts that plant litters decompose faster in the vicinity of the plant from which they are derived than away from ‘home’. Although we are aware that both litter quality and the efficiency of decomposers within soil communities (hereafter, “soil ability”) are important drivers of HFA effects, we know little on variation in HFA effects and underlying processes of these changes across years with varying climates. In order to address these questions, we repeated four years with varying climates (two mild years, 2016 & 2018 and two stressed years, 2017 & 2019) a reciprocal transplant experiment with four litter types, crossing vegetation structure and soil fertility contrasts of both litter and ecosystems (forest and grassland litters from both fertile and unfertile soils). We used the Decomposer Ability Regression Test for both types of years to search for evidence of HFA effects and conducted ANOVAs on the cross effects of vegetation structure and soil fertility contrasts to further identifying the underlying processes of changes in HFA across climates. HFA effects were only significant for the most recalcitrant litter of Pinus pinaster, and much more significant during the mild years. Litter quality was stable across species and years, whereas differences in soil ability among ecosystems of the four species were strongly affected by climate, with highly significant differences among ecosystems occurring only during the mild years. Changes in soil ability across climates (decreasing HFA effects during stressed years) were explained by an overall increase in litter decomposition in forests as compared to grasslands during the stressed years, due to the facilitation of soil decomposers by forest canopies. Our study showed that HFA effects vary across climates as a result of changes in soil ability and that forest canopies may buffer the negative effects on litter decomposition of increasing stress with climate change.