华西雨屏区慈竹林凋落叶分解过程养分释放对模拟氮沉降的响应

Nutrient Release in Decomposition of Leaf Litter in Neosinocalamus affinis Stands in Response to Simulated Nitrogen Deposition in Rainy Area of Western China

通过原位试验,研究华西雨屏区慈竹林凋落叶养分释放对模拟氮沉降的响应。试验设4个施氮水平:对照(CK,0kg·hm-2a-1)、低氮(LN,50kg·hm-2a-1)、中氮(MN,150kg·hm-2a-1)和高氮(HN,300kg·hm-2a-1)。结果表明:1)在凋落叶分解过程中,C,P和Mg元素含量总体上呈下降趋势,N元素表现为下降—上升—下降,K元素则为上升—下降—上升,Ca元素先升后降。各处理C,P,Ca和Mg元素都表现为直接释放,K元素为富集—释放,而N元素CK呈现淋溶—富集—释放,LN,MN和HN却为直接释放。2)氮沉降可促进凋落叶C,N,P,K,Ca,Mg元素的释放,其中MN促进作用最强;氮沉降对N元素的影响程度最大,LN,MN和HN周转期分别比CK(2.835a)缩短0.090,0.816和0.709a。3)分解过程中各处理C/N变化趋势为先升高后降低;总体上,分解前2个月N沉降可降低凋落叶C/N值,而2个月后提高其C/N值。

An in situ experiment was conducted in a Neosinocalamus affinis plantation in rainy area of western China to study nutrient release of leaf litter in response to simulated nitrogen deposition. Four treatments were set,i. e. ,null N level （CK,0 kg·hm -2a -1）,low N level （LN,50 kg·hm -2a -1）,moderate N level （MN,150 kg·hm -2a -1） and high N level （HN,300 kg·hm -2 a -1 ）. The results showed as follows： Different elements showed different trends in the whole process： The concentrations of C,P and Mg decreased with N increasing; the N initially decreased,then increased,and finally decreased; the K showed a curve which first increased,then decreased,and increased again at the end; the Ca increased at the beginning and then decreased. The characteristics of nutrient release patterns were as the following： K accumulated at early stage and released later; C,P,Ca and Mg released all through the process; N showed a curve of leaching-accumulation-releasing in CK treatment while it was directly releasing in LN,MN,HN. N deposition exerted a positive effect on the release of C,N,P,K,Ca,Mg with the highest release rate in MN. It suggests that it might take 2. 019 - 2. 853 years to decompose 95% of N element. During the process of leaf litter decomposing under N deposition, the C /N ratios showed a up-down trend. On the whole,C /N ratios decreased at the first 2 months,and then increased.