Stand density is a critical factor in the variation of crown structure and biomass, and can significantly change the growing space and resource acquisition of trees. However, an understanding of the interactive mechanisms of this effect with stand characteristics and environmental conditions is still lacking. In this study, our goal was to quantify the responses of crown structure and biomass to stand density and explore how shade tolerance, tree species functional group, tree age and climate affect these responses. We synthesized the outcomes of 356 observations from 60 studies published since 2000 using a meta-analysis approach. The results showed that stand density did not change the ratio of branch plus leaf biomass to aboveground biomass (CB:TB) but did have a significant effect on the crown structure and the branch and leaf biomass. This indicates that in the face of density stress, trees are generally less able to adjust biomass allocation among different organs than they are to alter the morphology of organs. The effect of stand density on crowns varied greatly among different shade-tolerant species, tree species functional groups and tree age, while climatic gradients had no significant effect on the response of crowns to stand density, which reflected the change in tree growth strategies in response to the combined effect of many factors. Overall, our meta-analysis indicates that crown growth can be regulated by changing stand density but that the interaction of stand characteristics and environmental conditions with stand density results in different tree growth strategies. This meta-analysis helps to deepen the understanding of the adaptation strategies of trees in response to competition and environmental stress and serves to promote sustainable management of forest ecosystems.

林分密度是影响树冠结构和生物量变化的关键因素，可以显着改变树木的生长空间和资源获取。然而，仍然缺乏对这种效应与林分特征和环境条件的相互作用机制的理解。在这项研究中，我们的目标是量化树冠结构和生物量对林分密度的响应，并探索耐荫性、树种功能组、树龄和气候如何影响这些响应。我们使用荟萃分析方法综合了自 2000 年以来发表的 60 项研究的 356 项观察结果。结果表明，林分密度不会改变枝叶生物量与地上生物量的比值（CB：TB），但对树冠结构和枝叶生物量有显着影响。这表明在面对密度压力时，树木通常更不能调整不同器官之间的生物量分配，而不是改变器官的形态。林分密度对树冠的影响在不同耐荫树种、树种功能组和树龄之间差异很大，而气候梯度对树冠对林分密度的响应没有显着影响，反映了树木生长策略响应的变化。多因素综合作用。总体而言，我们的荟萃分析表明，树冠生长可以通过改变林分密度来调节，但林分特征和环境条件与林分密度的相互作用会导致不同的树木生长策略。