腾格里沙漠南缘优势针叶树种径向生长对气候变化的响应稳定性评估

Tree-ring is the historical evidence of climate change and the internal performance of influences by the environment, and the response stability to climate change in radial growth of tree is a necessary complement to the study of dendrochronology. Picea crassifolia and Pinus tabuliformis are the most important trees and more sensitive to climate in Changling Mountains of south margin of Tengger Desert, where is located in northwest China with environmental vulnerability. The study contents indicate as follows: (1) the dynamic relationships between the radial growth of trees and climate factors were analyzed by the traditional empirical statistical methods such as using GLK (Gleichlaufigkeit), Pearson correlation, moving correlation function; (2) the response stabilities of trees radial growth to climate change were examined by the process-based model of VS-oscilloscope; (3) the radial growth model of the dominant coniferous tree species and the vulnerability threshold of forest were predicted by the tree-ring width chronologies (TRW) and basal area increment (BAI). Under the background of climate change, this study focus on stability of the growth-climate relationships to build the models between different altitudes, times and species of tree radial growth and climate factors, to determine the driving factors for affecting the growth of Picea crassifolia and Pinus tabuliformis, to clarify growth strategies and physiological adjustment mechanisms of trees for coping with the heterogeneous environments in Changling Mountains. This study results will establish the experimental basis for assessing the responses stability of the advantage conifer to climate change in northwest China, rich new theories on dendroclimatology, and provide scientific basis for historical climate reconstruction, tree growth trend prediction, diversity pattern maintaining and ecological management of forest ecosystems in arid and semi-arid mountains under global warming.

树轮是气候变化的历史证据，也是树木受环境影响的内在表现，其对气候变化的响应稳定性是树轮年代学研究的必要补充。本项目拟以环境脆弱的腾格里沙漠南缘昌灵山为研究区域，以对气候敏感的优势针叶树青海云杉和油松为研究对象，以气候变化下不同海拔和树种生长—气候关系为研究切入点，通过传统经验统计法分析树木径向生长与气候的动态关系，确定树木生长的驱动因子；通过VS-oscilloscope生长过程模型检验树木径向生长对气候变化的响应稳定性，揭示树木的生理适应机理；通过树轮宽度年表（TRW）和断面积增量（BAI）变化趋势预测未来气候变暖背景下树木径向生长模式，评估树木适应性和森林脆弱性。研究结果为青海云杉和油松对气候变化响应稳定性的评估奠定实验基础，为树轮年代学发展增加新的理论体系，同时为基于树轮的历史气候重建、未来气候变化下干旱区亚高山树木生长趋势预测、森林生态系统多样性格局维持和生态经营管理提供科学依据。

全球气候变化对于西北森林生态系统的结构和功能影响较大，特别是不同树种、不同海拔树木径向生长对于气候变化的响应稳定性还存在不确定性。因此，本项目以环境脆弱的腾格里沙漠南缘昌灵山为研究区域，以对气候敏感的优势针叶树青海云杉和油松为研究对象，构建了不同海拔青海云杉（2742m、2562m和2328m）和油松（2562m、2446m和2328m）树轮宽度年表与气候的动态关系模型，形成了适合模型模拟的树木最优生理过程参数值，检验了树木径向生长对气候变化响应的稳定性，解释了树木对气候变化的生态适应机制，揭示了气候变化背景下树木径向生长模式和森林未来发展趋势。. 主要研究结论有：1）两个树种不同海拔树轮年表的信噪比都比较高，说明获取的年表质量好，适合开展树轮年代学研究；发现青海云杉平均敏感度高于油松，说明青海云杉对气候的敏感性更强。2）昌岭山树木比祁连山中段和东段受干旱胁迫更强，两个树种3个海拔树木均受生长季干旱胁迫，随海拔降低生长受到的干旱胁迫加剧；且两个树种在年际和年内间对生长季气候变化都发生了不稳定的分异响应。3）温度和土壤湿度共同影响着两个树种径向生长过程，温度对生长季中期和高海拔树木生长起关键作用，而土壤湿度对生长季前后期和低海拔树木生长贡献更大。4）青海云杉的年内径向生长速率高于油松，且两个树种生长季长度在年际间呈增加趋势，中海拔青海云杉和油松生长启动提前显著，低海拔青海云杉和高海拔油松生长结束推迟显著。5）从1960年油松呈现先上升后下降生长趋势，而青海云杉呈持续下降趋势，且两个树种高海拔下降福大最大；且未来生长趋势发现油松和青海云杉在2060-2100年间各海拔均呈下降趋势，尤其是高海拔树木和RCP8.5高增温情境下降的幅度最大。根据本项目的研究结果，应该更加关注西北亚高山浅根性青海云杉和未来高海拔森林的动态监测，且重点做好研究区整个森林生态系统的水分管理。