Abstract
Aboveground-belowground linkages are recognized as divers of community dynamics and ecosystem processes, but the impacts of plant-neighbor interactions on these linkages are virtually unknown. Plant-neighbor interactions are a type of interspecific indirect genetic effect (IIGE) if the focal plant’s phenotype is altered by the expression of genes in a neighboring heterospecific plant, and IIGEs could persist after plant senescence to affect ecosystem processes. This perspective can provide insight into how plant-neighbor interactions affect evolution, as IIGEs are capable of altering species interactions and community composition over time. Utilizing genotypes of Solidago altissima and Solidago gigantea, we experimentally tested whether IIGEs that had affected living focal plants would affect litter decomposition rate, as well as nitrogen (N) and phosphorous (P) dynamics after the focal plant senesced. We found that species interactions affected N release and genotype interactions affected P immobilization. From a previous study we knew that neighbor genotype influenced patterns of biomass allocation for focal plants. Here we extend those previous results to show that these changes in biomass allocation altered litter quality, that then altered rates of decomposition and nutrient cycling. Our results provide insights into above- and belowground linkages by showing that, through their effects on plant litter quality (e.g., litter lignin:N), IIGEs can have afterlife effects, tying plant-neighbor interactions to ecosystem processes. This holistic approach advances our understanding of decomposition and nutrient cycling by showing that evolutionary processes (i.e., IIGEs) can influence ecosystem functioning after plant senescence. Because plant traits are determined by the combined effects of genetic and environmental influences, and because these traits are known to affect decomposition and nutrient cycling, we suggest that ecosystem processes can be described as gene-less products of genetic interactions among the species comprising ecological communities.
Highlights
Until recently, above- and belowground subsystems had been studied separately, but the processes that occur in each subsystem are tightly linked [1,2,3] with plants serving as a major intermediary
Our results indicate that rates of decomposition and subsequent nutrient release are, in part, a legacy of indirect genetic effects (IIGEs) that affected plant phenotypes during the growing season
We found that initial litter chemistry varied between S. altissima and S. gigantea, and among genotypes within S. gigantea (Fig. 1), leading to S. altissima decomposing up to 40% faster than S. gigantea (Fig. 2a)
Summary
Above- and belowground subsystems had been studied separately, but the processes that occur in each subsystem are tightly linked [1,2,3] with plants serving as a major intermediary. Environmental impacts on a plant’s phenotype during the growing season have the potential to cross the ‘‘living-dead’’ barrier when, after senescence, plants shed leaves containing important nutrients that enter the belowground system. These ‘‘afterlife’’ effects describe how species- or genotype-based differences in litter quality (e.g., [4], [5]), interactions with herbivores [6,7,8,9], ozone [7] and UV radiation [10] will feed back to affect ecosystems [11]. IIGEs occur when interactions between plants and their neighbors have a genetic basis, though to our knowledge the possibility that IIGEs could initiate ‘‘afterlife’’ effects remains untested
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