College of Agriculture and Biological Science, Dali University, Dali, Yunnan, China.
Yunnan Academy of Forestry and Grassland, Kunming, China.
Sci Rep. 2024 Sep 9;14(1):21019. doi: 10.1038/s41598-024-72374-3.
The neighborhood effect has become an important framework with which to study the mechanisms that maintain the coexistence of tree species. Phylogenetic relatedness among neighboring plants directly affects species coexistence and the maintenance of tree diversity. And some studies have reported that seedling performance is negatively correlated with phylogenetic relatedness, which termed phylogenetic negative density dependence. Soil-borne fungal pathogens affected seedling performance of phylogenetically related host species, i.e., phylogenetic Janzen-Connell effect. Seedlings may be particularly vulnerable to habitat and neighbor characteristics. Although previous studies have demonstrated the influence of neighborhood effects, phylogenetic relatedness, and habitat filtering on seedling survival, growth, and mortality, the effect of variation in these factors on seedling abundance remains unclear. To address this question, we used a 4-ha (200 m × 200 m) and monitored four-year (2020-2023) seedling dataset from a mid-montane humid evergreen broad-leaved subtropical forest in the Gaoligong Mountains, Yunnan, Southwestern China, and which consisted of 916 seedlings belonging to 56 species. The results of generalized linear mixed models showed no significant effect of conspecific adult neighbors on seedling abundance at any of the intervals evaluated. In contrast, we found evidence of phylogenetic distance density dependence in the forests of the Gaoligong Mountains. Specifically, there was a significant positive effect of the relative average phylogenetic distance between heterospecific adult neighbors and focal seedlings on focal seedling abundance in 2020; however, the relative average phylogenetic distance between heterospecific seedling neighbors and focal seedlings had a significant negative effect on seedling abundance over the four-year period (2020-2023). Among the habitat factors, only light (canopy opening) had a negative effect on seedling abundance in all four years. Light resources may be a limiting factor for seedlings, and determine seedling dynamics in subtropical forests. Overall, our results demonstrated that phylogenetic density dependence and habitat filtering affected subtropical seedling abundance. Our findings provide new evidence of the impact of phylogenetic density dependence on seedling abundance in a subtropical mid-montane humid evergreen broad-leaved forest and highlight the need to incorporate the neighborhood effect, phylogenetic relatedness, and habitat factors in models assessing seedling abundance.
邻域效应已成为研究维持树种共存机制的重要框架。邻近植物之间的系统发育关系直接影响物种共存和树木多样性的维持。一些研究报告称，幼苗性能与系统发育关系呈负相关，这被称为系统发育负密度依赖性。土壤传播的真菌病原体影响亲缘关系宿主物种的幼苗性能，即系统发育詹森-康奈尔效应。幼苗可能特别容易受到生境和邻居特征的影响。尽管先前的研究已经证明了邻域效应、系统发育关系和栖息地过滤对幼苗存活、生长和死亡的影响，但这些因素变化对幼苗丰度的影响仍不清楚。为了解决这个问题，我们使用了来自中国西南高黎贡山海拔 200 米×200 米的 4 公顷（200×200 米）和监测了四年（2020-2023 年）的幼苗数据集，该数据集由属于 56 个物种的 916 株幼苗组成。广义线性混合模型的结果表明，在任何评估间隔内，同种成年邻居对幼苗丰度均无显著影响。相比之下，我们在高黎贡山的森林中发现了系统发育距离密度依赖性的证据。具体来说，在 2020 年，异种种群成年邻居与焦点幼苗之间的相对平均系统发育距离对焦点幼苗丰度有显著的正影响；然而，在四年期间（2020-2023 年），异种种苗邻居与焦点幼苗之间的相对平均系统发育距离对幼苗丰度有显著的负影响。在生境因素中，只有光照（树冠开度）在所有四年都对幼苗丰度有负影响。光照资源可能是幼苗的限制因素，并决定了亚热带森林的幼苗动态。总体而言，我们的结果表明，系统发育密度依赖性和栖息地过滤会影响亚热带幼苗的丰度。我们的研究结果提供了新的证据，证明系统发育密度依赖性对亚热带中海拔湿润常绿阔叶林幼苗丰度的影响，并强调需要将邻域效应、系统发育关系和生境因素纳入评估幼苗丰度的模型中。
