Conspecific negative density dependence (CNDD) could be one of the most important local-scale mechanisms shaping plant species coexistence. However, the spatial and temporal changes in the strength CNDD and the implications for the plant diversity remain unknown. We used 10 years of seedling data, in a seasonal tropical rainforest, to discover how CNDD influences tree seedling survival across habitats and seasons. We also evaluated the relation between CNDD and species diversity. We found the strength of CNDD in the valley habitat was significantly stronger than in ridge habitat in rainy season, but not significantly different in dry season. Corresponding to expectations of CNDD as mechanism of diversity maintenance, seedling species diversity was significantly higher in valley habitat than in ridge habitat and significantly correlated with CNDD. Additionally, conspecific and heterospecific seedling neighbour densities positively affected the survival of tree seedlings, but heterospecific adult neighbour density had a weak effect. Our study finds that CNDD varied significantly across habitats and was correlated with local seedling diversity. Our results highlight the importance of CNDD in driving species diversity at the local scale. Recognizing the spatial and temporal variation in the strength of CNDD will aid efforts to model and understand species coexistence.

同种负密度依赖（CNDD）可能是影响植物物种共存的最重要的地方尺度机制之一。但是，CNDD强度的时空变化及其对植物多样性的影响仍然未知。我们在季节性热带雨林中使用了10年的幼苗数据，以发现CNDD如何影响生境和季节的树木幼苗生存。我们还评估了CNDD与物种多样性之间的关系。我们发现，在雨季，CNDD在山谷栖息地的强度明显强于山脊栖息地，而在旱季则没有显着差异。与CNDD作为维持多样性的机制的预期相对应，山谷生境中的幼苗物种多样性显着高于山脊生境，并且与CNDD显着相关。此外，同种和异种幼苗邻域密度积极影响树木幼苗的存活，但异种成年邻居密度影响较弱。我们的研究发现，CNDD在各个生境之间差异很大，并且与当地幼苗的多样性相关。我们的结果凸显了CNDD在推动本地规模物种多样性方面的重要性。认识到CNDD强度的时空变化将有助于对物种共存进行建模和理解。我们的结果凸显了CNDD在推动本地规模物种多样性方面的重要性。认识到CNDD强度的时空变化将有助于对物种共存进行建模和理解。我们的结果凸显了CNDD在推动本地规模物种多样性方面的重要性。认识到CNDD强度的时空变化将有助于对物种共存进行建模和理解。