桂西北干热河谷天然次生林群落个体密度对木本植物枝叶关系的影响

Effects of Individual Density of Natural Secondary Forest Communities on Twig-leaf Relationships of Woody Plants in the Dry-hot Valley of Northwest Guangxi

以雅长林场12个个体密度具有差异的天然次生林群落为对象,采用标准化主轴估计法比较不同个体密度群落木本植物枝叶大小及数量差异,分析密度制约因素对植物枝叶关系的影响。结果表明:不同密度植物的小枝横截面积与总叶面积均存在显著正向的异速生长关系,且回归方程存在共同斜率。中、高密度群落植物的小枝横截面积-总叶面积回归方程的截距显著高于低密度,说明高密度群落植物的单位面积枝条上所支撑的总叶面积大于低密度群落植物。不同密度群落植物的小枝横截面积与分梢密度均存在显著负向的异速生长关系,且存在显著小于1的共同斜率。各密度间小枝横截面积-分梢密度回归方程的截距无显著差异,说明在资源竞争加剧的情况下,植物并未改变枝条大小和数量的生物量投资比例。不同密度植物枝叶关系的回归方程在全部个体水平和大个体水平中均存在共同斜率,表明密度竞争无法改变植物的枝叶关系。在个体密度变化情况下,Corner法则对桂西北干热河谷天然次生林群落木本植物仍具有普适性。不同密度小枝横截面积与总叶面积的回归方程截距存在差异,说明群落个体密度增大,植物会重新权衡枝条与叶片的生物量及资源利用策略。

Taking 12 natural secondary forest communities with different individual densities in Yachang Forest Farm as objects,standardized principal axis estimation method was used to compare the differences in the relationship of size between twig and leaf among different densities,and the effects of density constraints on the relationship between twigs and leafs was analyzed.The results showed that there was a significant positive allometry relationship between twig cross-sectional area and total leaf area of plants in different densities,and there was a common slope in those regression equations.The intercept of the regression equation of twig cross-sectional area-total leaf area of plants in medium and high density communities was significantly higher than that of plants in low density communities,which indicated that the total leaf area supported by branches per unit area of plants in high density communities was larger than that of plants in low density communities.Significant negative allometry relationships appeared between twig cross-sectional area and branching density of plants in different densities,and the common slope was significantly smaller than 1.The intercepts of the regression equations of twig cross-sectional area-branching density between densities were not significantly different,confirmed that plants did not change the proportion of biomass investment in branch size and number when resource competition intensified.The regression equations of the twig-leaf relationships with different densities showed that there were common slopes at both the all-individual level and the large-individual level,indicating that density competition could not change the twig-leaf relationships of plants.The Corner’s rules is still suitable to woody plants in the natural secondary forest community in the dry-hot valley of northwest Guangxi under the condition of individual density changes.The differences in the intercepts of regression equations between twig cross-sectional area and total leaf area with different densities,suggesting that plants will rebalance the allocation for twig-leaf and the strategy for resource utilization when the individual density of the community increases.