广西南部喀斯特与非喀斯特季节性雨林凋落物动态与机制的比较研究

The tropical karst seasonal rain forest is a typical forest type formed and developed on the carbonate bedrock with the climatic conditions of tropical northern margin. It is unique in the world with a high level of diversity and endemic species. In order to adapt to the fertile soil and strong alkaline karst environment, there might be a faster energy conversion and nutrient cycling of litterfall dynamic in this karst geologic setting. However, the mechanism of formation and development of litterfall dynamics of this forest is still unclear. To answer this question, the first step should be analyzing the litter fall dynamics and transformation of substances, which are important in understanding specific processes and mechanism of the material decomposition and transformation in the karst seasonal forest. In the proposed project, the litterfall production and decomposition rate of fallen leaves will be analyzed based on data from multiple years, investigations of biological and abiotic factors, and continuous monitoring data in the karst and non-karst representative forest dynamics plots in seasonal rain forests in Southern Guangxi. Specifically, we will focus on the comparative study on component structure and spatial-temporal pattern of litterfall, decomposition rate and spatial-temporal pattern of litterfall of leaves, and the potential influential factors on them and their ecological mechanism between karst and non-karst seasonal rain forests. Moreover, we will also study about the dynamics of litterfall in the forest ecosystem and reveal the general rules and specificities of material cycle and energy flow of litterfall in karst seasonal rain forest. Furthermore, results of this study will provide scientific basis and theoretical foundation for biodiversity conservation of karst seasonal rain forest and rehabilitation of karst rocky desertification.

喀斯特季节性雨林是在热带北缘湿润气候条件、碳酸盐岩基质上形成的独特森林类型。在贫瘠、强碱性等严酷的岩溶环境下，这种生态系统可能会表现出较快的物质循环与能量流动等特征。目前对该生态系统凋落物的动态和机制仍缺乏了解，而对凋落物动态及物质转化过程等科学问题的探索，是明晰喀斯特物质循环和能量流动过程及机制特殊性的关键。本项目以广西南部喀斯特与非喀斯特代表性森林动态监测样地为研究平台，以样地中凋落物的凋落量和凋落叶的分解速率为研究对象，以多年累积的凋落物、生物因子、非生物因子等监测数据为基础，对不同地质背景下凋落量的时空格局和凋落叶分解速率的时空格局及其形成的潜在因素和生态学机制等开展比较研究，探讨不同地质背景森林生态系统中凋落物动态的普遍性和特殊性规律，进而揭示喀斯特季节性雨林中与凋落物有关的物质循环和能量流动的特殊性，为独特的喀斯特季节性雨林生物多样性保护和退化生态系统修复提供理论和实践依据。

喀斯特季节性雨林是在热带北缘湿润气候条件、碳酸盐岩基质上形成的独特森林类型。在贫瘠、强碱性等严酷的岩溶环境下，这种生态系统可能会表现出较快的物质循环与能量流动等特征。目前对该生态系统凋落物的动态和机制仍缺乏了解，而对凋落物动态及物质转化过程等科学问题的探索，是明晰喀斯特物质循环和能量流动过程及机制特殊性的关键。项目以广西南部喀斯特与非喀斯特代表性森林动态监测样地为研究平台，以样地中凋落物的凋落量和凋落叶的分解速率为研究对象，以多年累积的凋落物、生物因子、非生物因子等监测数据为基础，对不同地质背景下凋落量的时空格局和凋落叶分解速率的时空格局及其形成的潜在因素和生态学机制等开展比较研究，探讨不同地质背景森林生态系统中凋落物动态的普遍性和特殊性规律，进而揭示喀斯特季节性雨林中与凋落物有关的物质循环和能量流动的特殊性。. 北热带季节性雨林不同年际间凋落量和凋落节律存在明显区别，且不同地质背景（喀斯特与非喀斯特）的凋落量差异显著；生态因子对叶凋落量年际动态存在显著影响，其累计解释偏差为69.3%，其中海拔的影响最强，解释偏差为46.5%，而生物因子则影响较弱；喀斯特季节性雨林凋落叶分解速率低于非喀斯特地质背景的同纬度和高纬度亚热带常绿落叶阔叶混交林；喀斯特季节性雨林不同生境类型代表的微环境因子对凋落叶的分解具有重要影响，其中海拔引起的温度和湿度的差异是影响喀斯特季节性雨林凋落叶分解速率和C、N含量变化的主要因素；不同生境间凋落叶分解速率存在显著差异，其中洼地分解速率最快、峰顶最慢。这表明，喀斯特季节性雨林中凋落叶分解过程并未表现出通过凋落物的快速分解来补偿因淋溶作用造成的营养元素流失，克服喀斯特森林贫瘠的土壤环境。这可能是因为喀斯特中低坡位以上部位相对干旱环境制约了凋落物的分解。研究喀斯特与非喀斯特不同地质背景下土壤微生物和土壤动物组分的差异性及其对凋落物分解过程的影响是今后重要研究方向。