Which enemies mediate distance- and density-dependent mortality of tree seeds and seedlings? A meta-analysis of fungicide, insecticide, and exclosure studies
Song, Xiaoyang; Corlett, Richard (2020), Which enemies mediate distance- and density-dependent mortality of tree seeds and seedlings? A meta-analysis of fungicide, insecticide, and exclosure studies, Dryad, Dataset, https://doi.org/10.5061/dryad.51c59zw6v
Conspecific negative distance- and density-dependence is believed to be one of the most important mechanisms controlling forest community assembly and species diversity globally. SoilPlant pathogens, and insect and mammalian herbivores, are the most common natural enemy types that have been implicated in this phenomenon, but their relative importancegeneral effects at different plant life stages isare still unclear. Here, we conduct a meta-analysis of studies that involved robust manipulative experiments, using fungicides, insecticides, and exclosures, to assess the contributions of different natural enemy types to distance- and density-dependent effects at seed and seedling stages. We found that natural enemies cause stronger distance- and density-dependent mortality caused by natural enemies was most likely at the seedling stage than the seed stage. Fungicide treatments can change significantand was greater at higher mean annual temperatures. Seedling mortality was significantly weakened when fungi were removed. By contrast, negative distance- and density-dependent mortality to non-significance at the seedling stage. Negative conspecific distance- and density-dependence is not a general pattern at the seed stage. High seed mass reduced distance- and density-dependent mortality. Seed studies excluding only large mammals found significant negative conspecific distance-dependent mortality, but exclusion of all mammals resulted in a non-significant mortality.effect of conspecifics. Our study suggests that soilplant pathogens are a major cause of distance- and density-dependent mortality at the seedling stage, althoughwhile the impacts of herbivores on seedlings have been understudied. At the seed stage, large and small mammals respectively weaken and enhance negative conspecific distance-dependent mortality. Future research should identify specific agents of mortality, investigate the interactions among different enemy types, and assess how global change drivers may affect the dynamics of natural enemies and thus influence the strength of conspecific distance- and density-dependence.