桂西南喀斯特季节性雨林叶凋落量的时空动态

森林凋落物是森林生态系统极其重要的组成部分, 关系着森林生态系统的物质循环和养分平衡。然而, 有关异质性自然森林生态系统中生物与非生物因子对凋落物凋落量的影响机制还存在较大争议。本文以广西弄岗15 ha森林动态监测样地中设置的90个凋落物收集器所收集的凋落叶为研究对象, 选取2013‒2018年连续6年的凋落叶数据探讨了森林叶凋落量的时空动态, 旨在深入了解该地区森林生态系统的物质循环过程及凋落量的影响因子。结果显示: 2013‒2018年的年均叶凋落量为4,099.44 kg/ha, 标准误为232.34, 变异系数为0.15, 这表明不同年际间叶凋落量存在明显差异; 不同年际间叶凋落量的节律性变化为双峰型、三峰型或多峰型, 说明不同年份的叶凋落量存在明显的节律性差异, 但总体而言高峰期主要出现在每年的春季(3‒4月)和秋季(8‒10月); 生态因子对叶凋落量年际动态存在显著影响, 其累计解释率为69.3%, 其中海拔对叶凋落量的影响最强, 解释率为46.5%; 而生物因子如胸径变异系数、单位面积胸高断面积之和和物种丰富度则对叶凋落量的影响较弱。多年的连续监测表明, 喀斯特季节性雨林不同年际间叶片的凋落量和节律性存在显著差异, 而非生物因子, 如海拔是形成叶凋落量空间变异的主要因素。

Spatio-temporal dynamics of leaf litter in a karst seasonal rainforest in southwest Guangxi

Leaf litter production is a major contributor to ecosystem net primary productivity and biogeochemical cycles. However, various abiotic and biotic drivers influence leaf litter production in heterogeneous natural forests. In this study, we quantified leaf litter production, composition, and spatio-temporal dynamics in a 15 ha forest dynamics plot in Nonggang National Nature Reserve, Guangxi. We set up 90 litter fall traps and collected leaf litter weekly beginning in May 2012. We explored the spatial and temporal dynamics of leaf litter production in order to gain an in-depth understanding of the material circulation process of forest ecosystem in this region. Ecological factors had significant influence on the inter-annual dynamics of leaf litter volume and explained 69.3% of the cumulative deviation. The effect of altitude on leaf litter was the strongest, explaining 46.5% of the deviation. However, biological factors, such as the coefficient of variation of DBH, the sum of stand basal area per unit area, and species-richness, had smaller effect sizes on annual leaf litter production. Years of continuous monitoring show that there are obvious differences in the leaf litter production between years in karst seasonal rainforests, but abiotic factors, such as altitude, heavily influence leaf litter production.