东北三大硬阔树轮对气候变化响应的时空规律研究

Broadleaved Korean pine forest (BKPF), the climax vegetation in eastern mountain areas of northeastern China, is critical to maintain the ecological security in northeast China and even whole China. Three hardwoods-Phellodendron amurense, Juglans mandshurica and Fraxinus mandshurica are important broadleaved species in BKPF. Their responses to climate change will affect the dynamic of the entire BKPF. Three sampling gradients (longitudinal, latitudinal and altitudinal) will be established by temperature and precipitation variations in the distribution area of BKPF in northeast China. The spatio-temporal variations of three hardwood tree rings response to climate change will be investigated by identifying the spatial variability and temporal stability of the relationships between climatic factors and tree-ring width, density and cell parameters under environmental gradients. The spatio-temporal variation mechanism of climate-growth relationships for three hardwoods will be explored from local climate, global climate and non-climatic factors. Meanwhile, tree-ring cell parameters will be used to interpret ring width-climate relationships, which may be one of the major innovations of this project. Finaly, the climate-growth relationships between Korean pine and three hardwoods in different sites are compared to identify the effect of global warming on the whole BKPF. This project will be very important to compensate for the lack of broadleaved tree-ring studies, compare the differences between broadleaved and conifer tree rings response to climate, and predict the dynamic of BKPF under climate change in the future.

阔叶红松林是东北东部山区地带性顶极植被，维系着东北乃至整个中国的生态安全。三大硬阔-黄檗、胡桃楸、水曲柳是阔叶红松林中的重要组成树种，它们对气候变化的响应会影响整个阔叶红松林的动态。本项目在阔叶红松林分布区内以温度、水分及海拔设立3个环境采样梯度，通过分析年轮宽度、密度及细胞参数与气候因子关系在环境梯度下的空间变异性，以及不同时间尺度下三大硬阔年轮-气候关系的时间稳定性，来研究三大硬阔年轮对气候变化响应的时空规律。从局地气候、全球气候、非气候因素等来探讨三大硬阔年轮-气候关系时空变异的驱动机制，以及用年轮细胞参数来解释树轮宽度与气候关系的变异,这也是本项目的一个特色和创新。最后，综合比较红松、三大硬阔年轮与气候关系的异同，来判定气候变暖对整个阔叶红松林的影响。本项目为弥补阔叶树种树轮研究的不足，对比针阔叶树种年轮-气候响应差异，及预测气候变化下阔叶红松林的动态都具有重要意义。

三大硬阔是阔叶红松林中的重要组成树种，它们对气候变化的响应会影响整个阔叶红松林的动态。本项目在东北以经度、纬度和海拔梯度进行树轮宽度和微树芯取样，分析了宽度及细胞参数与气候关系的时空变异性，以及大尺度气候涛动对生长-气候关系的影响。结果表明：在小兴安岭南部，黄菠萝和水曲柳生长随着经度增加，其生长末期受降水影响逐渐减弱。胡桃楸随着纬度增加，生长与温度的关系逐渐增强，而与降水关系则由正变负相关。方正、西大圈、凤凰山黄菠萝的空间响应差异不明显，3个样点生长与温度均正相关。水曲柳生长主要受温度影响，降水影响较弱，3个样点随纬度增加与温度相关性出现了“两头高中间低”的现象。在小兴安岭中部，黄菠萝生长对生长季温度变化敏感，而蒙古栎生长受温度和降水的共同限制。随经度增加，蒙古栎生长与水分的相关性逐渐减弱，而黄菠萝没有明显变化。水曲柳导管早材数量多、孔径大，晚材数量少、孔径小，主要是纤维细胞。黄菠萝早材多为单导管，晚材多个导管聚集成管孔团。胡桃楸无早晚材之分，导管与散孔材类似，从早材到晚材逐渐变小。应对生长季高温，三大硬阔都产生更少更大的导管，减小流阻。水曲柳和胡桃楸通过减少纤维细胞生物量分配，使纤维细胞数量减少，导管细胞个数不变从而比例上升。黄菠萝减少晚材生物量分配，纤维细胞和导管个数减少，晚材和导管比例下降。ENSO指数与东北温度在低频上显著相关，说明ENSO对东北气候存在长期影响。ENSO对老白山水曲柳生长呈正影响、而对鹤北水曲柳生长呈负影响；对长白山蒙古栎生长呈正影响、对小兴安岭蒙古栎生长呈负影响。1977年后，PDO与水曲柳生长关系显著增强。但是，PDO与蒙古栎生长关系不显著。PDO影响整个东北黄菠萝生长-气候关系的空间变异性。PDO调节生长开始、结束和有效积温的时空变化，进而影响生长-气候关系的空间变异。本结果弥补了阔叶树种树轮研究的不足，对预测气候变化下阔叶红松林动态具有重要意义。