三峡地区香溪河流域叶片凋落物分解过程中N、P含量动态研究

Dynamics of Nitrogen and Phosphorus Content during Leaf Litter Decomposition in Xiangxi River Watershed,the Three Gorges Region

在香溪河流域1160、930、658 m 3个海拔梯度,利用凋落物分解袋法,研究黄栌(Cotinus coggygriavar.pu-bescens)、五裂槭(Acer oliverianum)和扇叶槭(Acer flabellatum)3个物种叶片凋落物的分解速率和主要营养元素N、P含量动态。结果表明,凋落物分解过程中干物质流失动态符合指数衰减方程;叶片初始N含量对分解速率没有显著影响,初始P含量与分解速率呈显著负相关;N、P含量动态在不同属物种间存在显著差异;海拔梯度的差异对N、P含量变化没有显著影响;凋落物在河岸陆地分解比较稳定,分解速度慢于同海拔河流;叶片分解N含量动态在河流与陆地中没有显著差异,而P含量变化差异显著。

Litter from riparian vegetation has long been recognized as an important energy flow in aquatic systems. Many researches on litter breakdown in drainage areas have been conducted, which could be used for assessing for the health of streams. To provide information for understanding nutrient cycling and energy flow in fluvial ecosystem, this paper focused on the leaf litter decomposition in Xiangxi River watershed, the Three Gorges region. The objective of this research was to examine the dynamics of nitrogen and phosphorus content of leaf litter decomposition in three plant species（ Cotinus coggygria var. pubescen,Acer oliverianum and Acer flabellatum） along an elevation gradient using mesh bags. Three altitudinal plots were located in headwater at altitute of 1160 m,930 m and 658 m in Xiangxi River watershed. Leaf litter bags had been deposited in stream water and on the riparian woodland for 90 days. Our results showed that after 90 days, the dynamics of dry mass loss followed the declining exponential equation. No significant differences were found between original N content of leaf litter and leaf litter decomposition rates. The initial P content was strongly negatively correlated with decomposition rates. N and P content of leaf litter in Cotinus coggygria var. pubescens have a significant differences between Acer oliverianum and Acerflabellatum. However, elevation had no significant influence on dynamics of N and P content of leaf litter. Acer flabellatum leaf litter decomposed significantly much slowly in the woodland than in the stream. P content of Acer flabellatum leaf litter had a significant difference between in the stream and on the woodland, but N content had no significant differences.