Dou Xiao-Wen, Tang Meng-Ping
State Key Laboratory of Subtropical Silviculture/College of Environmental and Resource Sciences, Zhejiang A&F University, Lin'an 311300, Zhejiang, China.
Ying Yong Sheng Tai Xue Bao. 2022 Oct;33(10):2695-2704. doi: 10.13287/j.1001-9332.202210.004.
Whether the gravitational model can be used to analyze tree competition in forest community is a valuable question. A tree relative vitality circle based on the gravitational model can illustrate the magnitude of competitive tree vitality. A gravitational competition index based on the relative vitality circle of competitive trees can accurately depict the relationship between growth and competition. This study was conducted in the coniferous and broadleaf mixed forest of Tianmu Mountain National Nature Reserve in Zhejiang Province. We carried out correlation analyses between the V_Hegyi competition index and diameter at breast height (DBH), between the gravitational competition index and DBH, and between the two competition indices and the basal area increment. We further analyzed the correlation between the growth rate of DBH and the ratio of the two-phase gravitational competition index, that is, the ratio of the 2021 gravitational competition index to that of 2006. In addition, the correlation analysis was applied between the relative vitality circle diameter and DBH. We also compared the magnitudes of the competition indices between the living standing trees and the dead trees. The results showed that both competition indices were negatively correlated with DBH, and followed a power function relationship. The basal area increment was negatively correlated with each of the two competition indices. However, the gravitational competition index was better than V_Hegyi competition index for indicating the relationship between tree growth and tree competition. Compared with the ratio of the V_Hegyi competition indices, the ratio of the two-phase gravitational competition indices could better demonstrate the relationship between tree growth and tree competition. In the coniferous and broadleaved mixed forests, the correlation coefficient between the growth and competition of broadleaved species was greater than that of coniferous species. The dead trees were significantly influenced by competition. Tree relative vitality circle size was negatively correlated with DBH. The gravitational model was one of the critical models that reflect spatial interactions and could be applied to examine forest competition. The gravitational competition index could be used as a spatially structured indicator to evaluate tree competition and tree vitality, which could better indicate the relationship between tree growth and tree competition than the V_Hegyi competition index.
引力模型是否可用于分析森林群落中的树木竞争是一个有价值的问题。基于引力模型的树木相对活力圈能够说明竞争树木活力的大小。基于竞争树木相对活力圈的引力竞争指数可以准确描述生长与竞争之间的关系。本研究在浙江省天目山国家级自然保护区的针阔混交林中开展。我们对V_Hegyi竞争指数与胸径（DBH）、引力竞争指数与DBH，以及两个竞争指数与断面积增量之间进行了相关性分析。我们进一步分析了DBH生长速率与两期引力竞争指数之比（即2021年引力竞争指数与2006年引力竞争指数之比）之间的相关性。此外，还对相对活力圈直径与DBH之间进行了相关性分析。我们还比较了活立木与枯立木之间竞争指数的大小。结果表明，两个竞争指数均与DBH呈负相关，且呈幂函数关系。断面积增量与两个竞争指数中的每一个均呈负相关。然而，在指示树木生长与树木竞争之间的关系方面，引力竞争指数优于V_Hegyi竞争指数。与V_Hegyi竞争指数之比相比，两期引力竞争指数之比能更好地说明树木生长与树木竞争之间的关系。在针阔混交林中，阔叶树种生长与竞争之间的相关系数大于针叶树种。枯立木受竞争的影响显著。树木相对活力圈大小与DBH呈负相关。引力模型是反映空间相互作用的关键模型之一，可用于研究森林竞争。引力竞争指数可作为一个空间结构指标来评估树木竞争和树木活力，在指示树木生长与树木竞争之间的关系方面，它比V_Hegyi竞争指数表现更好。
