Abstract：
Conspecific negative density dependence (CNDD) is thought to be a key process in maintaining plant diversity. However, the strength of CNDD is highly variable in space and time as well as among species, and correlates of this variation that might help to understand and explain it remain largely unquantified. Using Bayesian hierarchical models, we took advantage of 10-year seedling monitoring data that were collected annually in every dry and rainy season in a seasonal tropical forest. We quantified the interspecific variation in the strength of CNDD and its temporal variation. We also examined potential correlates of this interspecific and temporal variation, including species functional traits (such as drought-tolerant traits, defense-related traits, and recourse acquisition traits) and species abundances. In the dry season, we found a negative relationship between the density of neighboring conspecific seedlings on seedling survival, while in the rainy season, there was a negative relationship between the density of neighboring conspecific adults on seedling survival. In addition, we found that interspecific variation in CNDD was related to drought-tolerant traits in the dry season but not in the rainy season. Across years, we found that drought-intolerant species suffer less CNDD during the dry seasons that have higher rainfall, whereas drought-tolerant species suffer less CNDD when the dry season has lower rainfall. We also found that rare species suffered stronger CNDD in the dry season. Overall, our study highlights that CNDD is highly variable among species and through time, necessitating a deeper appreciation of the environmental and functional contexts of CNDD and their interactions.
摘要：
特定负密度依赖性（CNDD）被认为是维持植物多样性的关键过程。然而,CNDD的强度在空间和时间以及物种之间都有很大差异，以及这种可能有助于理解和解释它的变化的相关性在很大程度上仍未量化。使用贝叶斯分层模型，我们利用了每年在季节性热带森林的每个干旱和雨季收集的10年幼苗监测数据。我们量化了CNDD强度的种间变化及其时间变化。我们还检查了种间和时间变化的潜在相关性，包括物种功能性状(如耐旱性状，防御相关的特征，和追索权获取性状)和物种丰度。在干旱的季节，我们发现邻近同种幼苗的密度与幼苗存活之间存在负相关关系，而在雨季，邻近同种成虫密度对幼苗成活率呈负相关。此外,我们发现CNDD的种间变异与旱季的耐旱性有关，而与雨季无关。多年来，我们发现，在降雨量较高的干旱季节，不耐受干旱的物种遭受的CNDD较少，而当旱季降雨量较低时，耐旱物种遭受的CNDD较少。我们还发现，稀有物种在旱季遭受更强的CNDD。总的来说,我们的研究强调了CNDD在物种之间和时间上的差异很大，需要更深入地了解CNDD的环境和功能背景及其相互作用。
