Research Institute of Forestry, Chinese Academy of Forestry, Key Laboratory of Tree Breeding and Cultivation, State Forestry Administration, Beijing, 100091, China.
Fengyangshan National Nature Reserve, Longquan, Zhejiang province, 323700, China.
Sci Rep. 2018 Jun 14;8(1):9149. doi: 10.1038/s41598-018-27140-7.
Negative conspecific density dependence is one of the principal mechanisms affecting plant performance and community spatial patterns. Although many studies identified the prevalence of density dependent effects in various vegetation types by analyzing conspecific spatial dispersal patterns (spatial patterning) of forest trees, interactions between individuals and heterospecific neighboring trees caused by density-dependent effects are often neglected. The effects of negative density dependence lead us to expect that neighbourhood species segregation would increase with increasing tree size and that larger trees would be surrounded by more heterospecific neighbours than would smaller trees. We studied four mapped 1-Ha plots on Changbaishan Mountain in North-eastern China and used marked point pattern analysis to explore whether trees of different sizes exhibited differences in neighbourhood species segregation; we also determined whether larger trees were more likely to have heterospecific neighbours than smaller trees were. Our results show that bigger trees generally have higher species mingling levels. Neighborhood species segregation ranged from lower than expected levels to random or nearly random patterns at small scales as tree size classes increased under heterogeneous Poisson null model tests. This study provides some evidence in support of negative density dependent effects in temperate forests.
负密度制约是影响植物性能和群落空间格局的主要机制之一。尽管许多研究通过分析森林树木的同种空间扩散模式（空间格局）来确定各种植被类型中密度制约效应的普遍性，但由于密度制约效应导致的个体与异种邻树之间的相互作用往往被忽视。负密度制约的影响使我们预计，随着树木大小的增加，邻域物种隔离程度会增加，而且与小树相比，大树周围的异种邻树会更多。我们在中国东北长白山的四个 1 公顷的地图上进行了研究，并使用标记点格局分析来探索不同大小的树木在邻域物种隔离方面是否存在差异；我们还确定了大树比小树更有可能有异种邻树。我们的结果表明，大树通常具有更高的物种混合水平。在异质泊松零模型检验中，随着树大小类别的增加，在小尺度上，邻域物种隔离程度从低于预期水平到随机或近乎随机模式。这项研究为温带森林中存在负密度制约效应提供了一些证据。
