全球环境变化对地带性常绿阔叶林结构与主要服务功能的影响及机理

The recent findings by the applicants showed significant directional changes in DBH growth rate and individual mortality and recruitment of old-growth evergreen broadleaved forests. The directional changes are not symmetrical among functional groups, species and individuals with different sizes, and thus result in the shrinkage of average DBH and a transition from the climax forest communities into these with more shrub individuals, which will, without doubt, alter forest ecosystem services, including these core services of carbon sequestration and water resources regulation. The forces that drive the directional changes forward should be global warming, alterations in precipitation pattern and increasing nitrogen deposition as some studies reported. However, two of the numerous uncertainties still remain. One is “how do the changing environmental factors drive the directional changes in community structures forward ?”, the other is “what will the carbon sequestration and water resources regulation be with the directional changes in community structures?”. Based on the preliminary studies, the proposed project tries to clarify the above two uncertainties using long-term observational data from more than 20 field stations in this region with theoretical analysis. The expected achievements may promote the development of community ecology and global change ecology, and support the policy decision for sustainable development.

申请者的近期研究表明，地带性常绿阔叶林群落个体死亡率、更新率、胸径生长速度等正发生趋势性变化，这种变化在功能群之间、物种之间及大小不同的个体之间是不均衡的，其结果是群落的平均胸径持续减小，群落向着灌丛化方向发展，结构的改变无疑将影响其服务功能特别是固碳与水资源调蓄等核心服务功能。初步研究表明，全球气候变化与区域N沉降上升是这个趋势性变化的驱动因子，但驱动机制不清楚；同时，伴随着常绿阔叶林群落结构趋势性变化，该生物群系碳贮量、固碳功能和水资源调蓄等核心服务功能如何变化更是亟待阐明的科学问题。本项目在前期研究的基础上，以长期定位研究和理论创新为手段，通过弄清全球环境变化在区域内的变化特征，试图揭示地带性常绿阔叶林群落结构趋势性变化的驱动机制、阐明其碳贮量、碳汇以及水资源调蓄等主要服务功能对群落结构趋势性变化的响应规律，推动群落生态学与全球变化生态学的发展，为该区域可持续发展提供宏观决策依据。

气候变化背景下地带性常绿阔叶林群落正发生趋势性变化。该生物群系在气候变化背景下，其碳贮量与固碳功能、水资源调蓄、小气候调节、生物多样保育与土壤肥力保持等核心服务功能如何变化及其驱动机制等是亟待阐明的科学问题。本项目以长期定位研究及生态网络联网监测、广泛的野外调查与遥感技术和理论模型为手段，系统揭示了常绿阔叶林及其自然演替系列与人工恢复系列等不同森林生态系统碳储量与碳汇功能对全球气温上升、降水格局改变、N沉降升高的响应趋势和机理，阐明了群落结构对不同森林生态系统碳汇功能的影响。发现过去几十年内，常绿阔叶林适应全球气候变化所产生的趋势性改变。项目在阐明植被变化与水资源关系全球格局的基础上，系统研究了不同森林生态系统的水资源调节功能及其机制、包括常绿阔叶林生态系统水分利用随林分结构空间异质性的变化规律，揭示了在气候变化、群落结构改变与森林覆盖变化的背景下常绿阔叶林区域水资源的响应趋势。项目成果发表在National Science Review、Nature Communications、PNAS综合性刊物上等（共48篇论文），在理论上推动全球变化生态学和生态系统生态学基础理论的发展，在应用上为生态公益林建设、大范围提升生态系统固碳潜力和兼顾水资源效益的生态恢复提供坚实的理论支撑。项目核心成果获广东省自然科学一等奖一项。