放牧和氮添加对半干旱沙质草地优势种糙隐子草及群落功能性状的影响

为探究氮沉降背景下放牧对半干旱沙质草地植物功能性状的影响，本试验探究了放牧和短期氮添加(20 g·m^-2·a^-1)对半干旱沙质草地优势种糙隐子草(Cleistogenes squarrosa)和群落功能性状的影响。结果表明：放牧和氮添加增加了糙隐子草的重要值，放牧降低了糙隐子草叶面积，氮添加显著降低了围封草地中糙隐子草叶干物质含量，增加了围封和放牧草地中糙隐子草叶氮含量(P<0.05)；相同氮素水平下放牧降低了植物群落高度，氮添加增加了围封样地植物叶面积和叶氮含量，增加了放牧样地植物比叶面积和叶氮含量，降低了叶干物质含量(P<0.05)；回归分析表明，糙隐子草叶面积和叶氮含量能较好地解释群落水平植物叶面积和叶氮含量的变化。半干旱沙质草地植物群落通过改变植株大小和主要叶性状来响应放牧和氮沉降，对预测未来草地生态系统结构与功能具有重要意义。

Effects of Grazing and Nitrogen Addition on Functional Traits of Dominant Species Cleistogenes squarrosa and Community in Semi-arid Sandy Grassland

To explore the effects of grazing on plant functional traits of semi-arid sandy grassland under the background of nitrogen deposition,we studied the effects of grazing and short-term nitrogen addition (20 g·m^-2·a^-1) on functional traits of the dominant species Cleistogenes squarrosa and community in semi-arid sandy grassland. The results showed that grazing and nitrogen addition increased the important value of C. squarrosa,while grazing reduced leaf area of C. squarrosa,and nitrogen addition significantly reduced C. squarrosa leaf dry matter content in enclosed grassland and increased leaf nitrogen content in enclosed and grazing grassland (P<0.05). Grazing significantly reduced height of the plant community at the same nitrogen level. Nitrogen addition significantly increased leaf area and leaf nitrogen content of plant community in enclosed grassland,and nitrogen addition significantly increased specific leaf area and leaf nitrogen content and decreased leaf dry matter content in grazing grassland (P<0.05). Regression analysis showed that the leaf area and leaf nitrogen content of C. squarrosa could better explain the changes of leaf area and leaf nitrogen content of community. The plants in semi-arid sandy grassland respond to grazing disturbance and nitrogen deposition by changing plant size and main leaf traits,which is of great significance for predicting the structure and function of grassland ecosystems in the future.