Litter, Plant Competition, and Ecosystem Dynamics: A Theoretical Perspective

AbstractCommunity structure depends jointly on species' responses to, and effects on, environmental factors. Many such factors, including detritus, are studied in ecosystem ecology. Detritus in terrestrial ecosystems is dominated by plant litter (nonliving organic material), which, in addition to its role in material cycling, can act as a niche factor modulating interactions among plants. Litter thus links traditional community and ecosystem processes, which are often studied separately. We explore this connection using population dynamics models of two plant species and a litter pool. We first find conditions determining the outcome of interactions between these species, highlighting the role that litter plays and the role of broader ecosystem parameters, such as decomposition rate. Species trade-offs in tolerance to direct competition and litter-based interference competition allow for coexistence, provided the litter-tolerant species produces more litter at the population level; otherwise, priority effects may result. When species coexist, litter-mediated interactions between plants disrupt the traditional relationship between biomass accumulation and decomposition. Increasing decomposition rate may have no effect on standing litter density and, in some cases, may even increase litter load. These results illustrate how ecosystem variables can influence community outcomes that then feed back to influence the ecosystem.