College of Urban and Environmental Science and MOE Laboratory for Earth Surface Processes, Peking University, 100871, Beijing, China.
Satellite Environmental Application Center, Ministry of Ecology and Environment, 100094, Beijing, China.
Commun Biol. 2020 Jul 30;3(1):405. doi: 10.1038/s42003-020-01144-4.
Tree allometry in semi-arid forests is characterized by short height but large canopy. This pattern may be important for maintaining water-use efficiency and carbon sequestration simultaneously, but still lacks quantification. Here we use terrestrial laser scanning to quantify allometry variations of Quercus mongolica in semi-arid forests. With tree height (Height) declining, canopy area (CA) decreases with substantial variations. The theoretical CA-Height relationship in dynamic global vegetation models (DGVMs) matches only the 5 percentile of our results because of CA underestimation and Height overestimation by breast height diameter (DBH). Water supply determines Height variation (P = 0.000) but not CA (P = 0.2 in partial correlation). The decoupled functions of stem, hydraulic conductance and leaf spatial arrangement, may explain the inconsistency, which may further ensure hydraulic safety and carbon assimilation, avoiding forest dieback. Works on tree allometry pattern and determinant will effectively supply tree drought tolerance studying and support DGVM improvements.
半干旱森林的树木生长是高径比较小而冠层较大的特征。这种模式可能对同时维持水分利用效率和碳封存很重要，但仍缺乏量化。本研究利用地面激光扫描技术对半干旱森林蒙古栎的树木生长进行了量化。随着树高（Height）的降低，冠层面积（CA）呈显著下降趋势。由于胸径（DBH）低估了 CA，高估了 Height，动态全球植被模型（DGVMs）中的理论 CA-Height 关系仅与我们结果的 5%位数相匹配。水分供应决定了 Height 的变化（偏相关分析中 P=0.000），但不决定 CA（P=0.2）。茎、水力导度和叶片空间排列的功能分离，可能解释了这种不一致性，这可能进一步确保了水力安全和碳同化，避免了森林衰退。关于树木生长模式和决定因素的研究将有效地为树木耐旱性研究提供支持，并有助于改进 DGVM。
