桂西南喀斯特季节性雨林凋落叶分解速率和养分含量特征分析

森林凋落物是森林生态系统极其重要的组成部分, 了解凋落物分解过程有助于理解森林生态系统的物质循环和养分平衡的机理。本研究以桂西南喀斯特季节性雨林凋落叶为研究对象, 将2018年全年收集的凋落叶混合均匀后采用分解袋法进行原位分解实验, 探讨桂西南喀斯特季节性雨林凋落物的分解特征。结果发现: 凋落叶在分解过程中整体失重模式呈现先快后慢的变化趋势, 且不同生境类型下凋落叶失重率为: 洼地＞坡地＞峰顶; 分解过程中C含量呈波动状态, 但总体表现为下降趋势, 而N含量呈无规则波动; 失重率与海拔呈显著负相关, 并在分解初期和中后期与坡度呈显著负相关, C含量变化同海拔呈显著正相关, 而与其他环境因子的相关性则随分解时间的变化而变化。桂西南喀斯特季节性雨林凋落叶分解速率低于亚热带常绿落叶阔叶混交林, 但与同类型的喀斯特森林退化区相当; 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。

Analysis of the Leaf Litter Decomposition Rate and Nutrient Content in a Karst Seasonal Rainforest in Southwest Guangxi

Forest litter is an important part of forest ecosystem. Knowledge of the nutrient release characteristics of litter leaves during decomposition is needed to understand the mechanism underlying the material cycle and nutrient balance in forest ecosystems. In this study, the litter leaves in the karst seasonal rainforest in Southwest Guangxi were mixed evenly in 2018; an in-situ decomposition test was then performed using the decomposition bag method to evaluate the decomposition characteristics of litter in the karst seasonal rainforest. The results revealed that the whole weight loss pattern during the decomposition process of litter leaves was first fast and then slow. Under different habitat types, the rate of leaf weight loss was in this order: depression > slope > peak; the content of leaf C was in this order: peak > slope > depression; and the content of leaf N was in this order: slope > depression > peak. The rate of weight loss of litter leaves during the whole decomposition process negatively correlated with altitude and negatively correlated with slope at the early and middle late stages of de-composition. The C content of litter leaves positively correlated with altitude; however, its correlation with other environmental factors changed with the decomposition time. The results of the present study showed that the de-composition rate of litter leaves in the karst seasonal rainforest in Southwest Guangxi was lower than that in sub-tropical evergreen deciduous broad-leaved mixed forests, but similar to that in the degradation area of the same type of karst forest. The microenvironment factors represented by different habitat types in the karst seasonal rainforest had an important influence on the litter decomposition. The difference in temperature and humidity caused by altitude is the main factor affecting the litter decomposition rate, C content, and N content in the karst seasonal rainforest.