The mechanisms driving species diversity in the context of Janzen–Connell model are best understood by evaluating not only conspecific distance-dependent (CDD) seedling performance, but also replacement of conspecific seedlings by heterospecific seedlings beneath adult trees. We evaluated CDD and replacement as a log response ratio of seedling performance (height, age) directly beneath and at a distance from adult plants in a temperate forest, and examined the log response ratio of that between conspecifics and heterospecifics beneath adults for five hardwood species with different ecological traits (e.g., seed size, mycorrhizal type, relative abundance). CDD was greater in three small-seeded species with arbuscular mycorrhizae (AM) associations than it was in two large-seeded species with ectomycorrhizae (EM) associations. Replacement was also higher for small-seeded AM species compared to large-seeded EM species, resulting in a strong, positive relationship between CDD and replacement. The traits suggest that small-seeded AM seedlings are more likely to be replaced by heterologous seedlings beneath the adults than large-seeded EM seedlings, probably due to that the small-seeded AM species are more susceptible to attack by plant natural enemies (e.g., soil pathogens, leaf diseases). As a result, small-seeded AM species had lower relative abundances compared to large-seeded EM species. This study suggests that either seed size or associations with microorganisms play an important role in driving forest diversity by regulating replacement and CDD, although relative importance of the two traits (i.e., seed size, mycorrhizal type) remains unclear, because of the autocorrelation between the two traits for the five species studied.

在Janzen-Connell模型的背景下，不仅通过评估同种距离依赖性（CDD）幼苗性能，而且还可以用成年树下的异种幼苗替代同种幼苗来更好地理解驱动物种多样性的机制。我们将CDD和置换作为温带森林中成年植物正下方和与成年植物之间距离的幼苗性能（高度，年龄）的对数响应比进行了评估，并研究了5种硬木树种的成虫与异种之间的对数响应比。具有不同的生态特征（例如，种子大小，菌根类型，相对丰度）。在具有丛枝菌根（AM）关联的三个小种子物种中，CDD比在具有外生菌根（EM）关联的两个大种子物种中更大。与大种子的EM物种相比，小种子的AM物种的置换也更高，从而导致CDD与置换之间具有牢固的正相关关系。性状表明，与大种子的EM幼苗相比，成年以下的小种子AM幼苗更有可能被异种幼苗取代，这可能是由于小种子的AM物种更容易受到植物天敌的攻击（例如，土壤病原体，叶病）。结果，与大种子的EM物种相比，小种子的AM物种的相对丰度较低。这项研究表明，种子大小或与微生物的结合通过调节置换和CDD在驱动森林多样性方面起着重要作用，尽管尚不清楚两个特征（即种子大小，菌根类型）的相对重要性，