伏牛山北坡不同生境栓皮栎的年内径向生长节律及对气候变化的响应

The period when xylem is developing corresponds to the time window during which trees and their wood cells are open to directly receive environmental signals. Its response to climatic factors is an essential basis for predicting the evolvement trends of forest ecosystem. Oak (Quercus variabilis Bl.) is one of the most important tree species in China, which dominates in warm temperate deciduous broad-leaved forest. The focus of this study therefore are (i) to monitor intra-annual dynamics of cambial activity and xylem differentiation in oak during three consecutive years by microcores method, with an emphasis on some crucial stages of radial growth, i.e. onset, time of maximum growth, end and duration of wood formation; (ii) to establish a relationship between synchronous phenological phases and cambial processes during wood formation by observing simultaneous phenological events, as well as relationships among the time of cambial reactivation, the start of first row of earlywood vessels and the phase of earlywood-latewood transition; (iii) to contrast the differences between both ages and habitats that could account for their different radial growth rhythm; (ⅳ) to assess main climatic factors influencing oak xylogenesis and its thresholds by using micrometeorological data monitored synchronously, it is necessary for better understanding the mechanisms underlying the climatic response of xylem anatomy. This research will enrich the content of dendroecology and dendroclimatology; provide a scientific basis for scientific management of forest under the background of global warming.

树木的径向生长是记录环境变化的时间窗户，它对气候的响应是预测森林生态系统演变趋势的重要依据。本项目以暖温带落叶阔叶林建群树种栓皮栎为研究对象，采用微树芯法对年内栓皮栎形成层活动和木质部分化各阶段的特征进行定量描述，开展栓皮栎年内径向生长节律的研究。在物候观察、生境因子调查和气象因子同步监测的基础上，分析径向生长关键期与物候变化的同步性，对比不同树龄和不同生境下栓皮栎径向生长节律的差异性，探讨影响栓皮栎径向生长的主导气候因子及相关阈值特征，揭示栓皮栎年内径向生长对气候变化的响应机制。研究结果将进一步丰富树轮生态学和树轮气候学的内容体系，为全球气候变暖背景下森林的科学经营提供理论参考。

本项目以伏牛山北坡暖温带落叶阔叶林建群树种栓皮栎为研究对象，对其年内径向生长节律及其对气象因子的响应关系进行了研究。通过物候观察、气象因子同步监测、微树芯样品采集、石蜡切片制作及实验数据对比分析，得出以下结论：（1）不同年份形成层细胞开始分裂、停止分裂以及木质部生长结束的时间节点差异较大，而第一轮早材导管环形成的时间相接近。年径向生长量的多少以及生长速率的大小与降雨量特征关系密切。坡向和年龄对栓皮栎径向生长节律的影响不显著。（2）栓皮栎径向生长的关键节点与叶片物候期存在较大差异。第一轮早材导管环的启动时间早于叶芽萌发15d左右；叶芽萌发的时间与第一轮早材导管环木质化的时间基本相同；第一轮早材导管环形成后20d左右，树木完成展叶。（3）栓皮栎形成层启动、第一轮早材导管环形成、木质部形成层细胞停止分裂的主导环境因子不同，分别为空气温度、降水量和降水量。