演替和气候对我国纬度梯度上森林的个体和群落尺度相关生长的影响机制

Allometric relationships of plant individuals and communities are not only theoretical focus of ecology, but also are important tools for estimating forest dynamics and carbon sink under global change. However, there are still some critical (major) questions on allometric relationships remained unresolved: 1) the mechanisms of how forest succession influence allometries have not been well understood; 2) the abiotic and biotic modulators of allometries at community scale are much less examined compared with that at individual scale; 3) empirical studies are largely conducted independent of existing theoretical models. This study is designed to examine some allometric relationships at individual and community scales, across both the latitudinal and successional gradients of Chinese forests, to explore questions as follows. 1) How do various abiotic and biotic factors affect allometries at individual and community scales, directly and indirectly? The potential modulators examined including: climate gradient (energy and water availability, and winter coldness), phylogeny, development stage of individuals and communities, local environmental factors, and ecological processes in forest communities (e.g. competition and regeneration). 2) When and how do observed allometric exponents deviate from predictions of Metabolic scaling theory (MST)? Which of the above-mentioned abiotic and biotic factors are the major drivers of deviations from theory predictions? Answering these questions is not only critical for understanding the mechanisms underlying geographic patterns of scaling relationships, but also important for improving the existing allometric models so that they can predict patterns beyond primary forests. Chinese Forests in China are mainly composed of secondary forests and plantations, and thus improved understandings of allometric laws are especially important for the restoration and management of our forests in response to global change.

相关生长规律既是当前理论研究的热点，又对全球变化下的森林碳汇估算、群落动态预测有重要的现实意义。但目前研究还存在一些问题，如：1)对随演替和气候变化的生态过程对相关生长的影响机理，研究亟待深入，2)群落尺度相关生长机理的研究相对不足，3)观测研究和理论模型研究尚未统一。我们在长期研究的基础上，选择我国森林区寒温带直至热带的地带性森林及其完整的演替序列，系统研究个体和群落水平相关生长的大尺度格局。重点探讨：1)气候、局域环境、进化、发育阶段、群落生态过程(竞争、更新等)，如何直接或间接起作用、共同影响个体和群落尺度的相关生长？2)相关生长关系偏离生态学代谢理论预测的规律，以及上述5类因素哪些是导致偏离理论值的主导机制？项目的研究不仅有助于阐明干扰和气候对不同尺度相关生长的影响机理，还可望为改进现有理论找到关键方向，以更好地为我国森林(以次生林、人工林为主)的经营、恢复和应对全球变化服务。

相关生长规律不仅森林碳汇估算、森林经营的重要理论工具, 也是影响多种生态系统功能和过程、及生物多样性的关键机制。但目前相关生长模型(MST)只适用于原始林, 对于干扰、气候如何影响相关生长, 进而影响生态系统的功能、过程, 还缺乏足够认识, 严重影响了理论对我国森林(以次生林、人工林为主)定量经营的指导价值。在我们以往研究基础上, 本项目从东北寒温带到云南热带林的8个地点选择了完整的演替阶段系列, 研究了从性状到群落尺度的相关生长随演替、气候变化的影响机制, 以及相关生长、功能性状、多样性、气候、演替等因素对生态系统功能及其稳定性的相对影响大小。结果表明: 1)多种地上、地下的个体和群落尺度相关生长关系均都在演替早期偏离MST预测更远, 演替进程中树木大小、生态过程(竞争、更新等)及功能性状的变化是相关生长变化的主因; 而气候等环境因子对相关生长直接影响不大, 可能是通过上述生物因素而间接影响相关生长。2)从局域到宏观尺度的证据都表明, 生物量、生产力等生态系统功能主要受相关生长、功能性状而不是多样性、气候的影响, 而气候变化下生态系统稳定性则受功能性状、林分因子通过相关生长的作用、生物多样性的共同影响, 但后两者的作用在不同地点、不同稳定性指标的研究结果还不一致, 其机理还需研究。3)应用对相关生长的研究认识, 对一些样地碳源汇测算关键方法进行了校验、或研发了新方法, 研编了数据测定和收集的规范, 建立了全球森林碳源汇数据库并进行了校验, 用于大尺度相关生长等研究, 并开展了一些其他探索性的研究工作。研究结果不仅为将MST拓展到次生林探明了关键方向, 创新性地利用相关生长等理论探讨了生态系统功能及其稳定性的影响机制, 对全球变化下我国大面积次生林恢复的定量经营也有重要理论意义。.通过项目的实施, 发表论文20篇, 其中SCI论文16篇; 出版专著1部; 培养1名博士后、3名博士和8名硕士研究生。