Feedbacks between plants and their soil microbial communities often drive negative density dependence in rare, tropical tree species, but their importance to common, temperate trees remains unclear. Additionally, whether negative density dependence is driven by natural enemies (e.g., soil pathogens) or by high densities of seedlings has rarely been assessed. Density dependence may also depend on seedling size, as smaller and/or younger seedlings may be more susceptible to mortality agents. We monitored seedlings of Quercus rubra, a common, canopy‐dominant temperate tree, to investigate how the density of neighboring adults and seedlings influenced their survival over two years. We assessed how the soil microbial community influenced seedling survival by growing seedlings in a glasshouse inoculated with soil collected from beneath conspecific and heterospecific mature trees. In the field, seedling survival was lower in areas with high densities of mature conspecifics but was unrelated to either conspecific or heterospecific seedling density. Smaller seedlings were also more sensitive than larger seedlings to neighboring adult conspecifics. In the glasshouse, seedlings grown with soil from beneath a conspecific adult had a higher mortality rate than seedlings grown with soil from beneath heterospecific adults or sterilized soil, suggesting that soil microbial communities drive the patterns of mortality in the field. These results illustrate the importance of negative density‐dependent feedbacks resulting from the soil microbial community in a common and ecologically important temperate tree species.

中文翻译：

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在普通温带树中，幼苗存活率随同种密度的增加而降低

植物及其土壤微生物群落之间的反馈通常导致稀有热带树种对密度的依赖性降低，但它们对普通温带树种的重要性仍不清楚。另外，很少评估负密度依赖性是由天敌（例如土壤病原体）还是由高密度的幼苗引起的。密度依赖性还可能取决于幼苗的大小，因为较小和/或较年轻的幼苗可能更易受死亡因素的影响。我们监测了栎树的幼苗这是一棵常见的冠层温带树，用于研究邻近的成年和幼苗的密度如何影响其两年的生存。我们评估了土壤微生物群落如何通过在温室中接种从同种和异种成熟树下面收集的土壤的幼苗来影响幼苗存活。在田间，具有高密度成熟同种的区域幼苗的存活率较低，但与同种或异种幼苗密度无关。较小的幼苗对邻近的成年种也比较大的幼苗敏感。在温室中，同种异体成虫下方土壤生长的幼苗的死亡率高于异种异种成虫下方或无菌土壤中生长的幼苗的死亡率，这表明土壤微生物群落驱动了田间的死亡模式。这些结果说明了在常见且对生态重要的温带树种中土壤微生物群落产生的负密度依赖性反馈的重要性。