Home-field advantage accelerates leaf litter decomposition in a high-elevation forest ecosystem

Background/Question/Methods While climate and litter quality explain 65-80% of the variation in leaf litter decomposition rates, that leaves 20-35% unexplained. We investigated whether interactions between the soil biotic community and leaf litter from different plant species could explain some of this variation in decomposition. Specifically we tested the hypothesis that soil biotic communities beneath different tree species specialize in the decomposition of leaf litter from the tree species above them. If so, litter should decompose faster than expected when it decomposes at home (i.e. beneath the tree species from which it was derived) versus away, which we call ‘home-field advantage.' We conducted a reciprocal litter transplant experiment in a high elevation forest ecosystem in the San Juan Mountains, southwest Colorado. Leaf litter from each of three common tree species (trembling aspen, lodgepole pine, and Engelmann spruce) was allowed to decompose in stands of each tree species, and mass, carbon, and nitrogen loss was measured over time. A related laboratory experiment was established to determine if differences in the soil biotic community beneath the different tree species caused home-field advantage. Results/Conclusions During the first year of decomposition, litter mass loss was 8% faster at home than away, indicating that home-field advantage occurs in this ecosystem (i.e. leaf litter decomposed faster than expected when it was placed in a stand of the tree species from which it was derived). Preliminary data from the laboratory experiment suggests that differences in the soil biotic community associated with the different tree species are responsible for this home-field advantage. Global change is expected cause species range shifts that will separate some species that have historically co-existed within a community. If tree species in this high elevation ecosystem become separated from their associated soil biota, litter decomposition rates may decrease in the future with implications for carbon cycling and nutrient availability.