内蒙古典型草原凋落物分解对不同草地利用方式的响应

摘要

The study was carried out in the Sino-German grazing experiment site, which was established in June 2005, and located in the typical steppe region of Inner Mongolia grassland In order to explore twoOur objective, 1) how litter decomposition vary with grazing intensity and haymaking in typical steppe of Inner Mongolia grassland, and 2) how the litter decomposition rate, weightless rate, relative carbon and nitrogen loss rates respond to grazing intensity. The experimental treatments included traditional grazing, traditional haymaking and alternate mixed utilization of grazing & haymaking, and seven levels of grazing intensity (i.e., 0, 1.5, 3.0, 4.5, 6.0, 7.5, 9.0 sheep·hm-2). Our results showed that grazing accelerated decomposition and weightless of litters in both traditional and mixed grazing plots after one growing season. In flat area of traditional grazing plots, the decomposition and weightless rates of litters in 7.5 sheep·hm-2plots were significantly higher than that in control plots by 45.0% and 40.0%, respectively. In flat area of mixed grazing plots, the decomposition rate of litters in 6.0 sheep·hm-2plots was significantly higher than control plot by 35.0%. While in slop area of mixed grazing plots, the decomposition and weightless rates of litters in 9.0 sheep·hm-2plots were significantly higher than that in control plots by 82.4% and 62.0%, respectively. With the increases of grazing intensity, the variations of carbon and nitrogen loss in litters were similar in traditional system, whereas they showed divergent trends in mixed system. But as a whole, grazing accelerated carbon and nitrogen releasing during litter decomposition. At high grazing intensity, the decomposition, weightless and relative carbon loss rates of litters in mixed grazing plots were significantly higher than that in the traditional grazing plots. Our results were partially in agreement with the grazing optimization hypothesis.%以2005年设置的中德放牧控制试验为平台，研究了内蒙古典型草原群落凋落物的分解速率、失重率及其碳氮损失率在不同草地利用方式和放牧强度下的变化规律。草地利用方式包括：传统放牧、传统割草和放牧、割草轮换利用（混合利用）。放牧强度包括7个：0、1.5、3.0、4.5、6.0、7.5、9.0 sheep·hm-2。结果表明：传统放牧和混合利用方式下，放牧都不同程度地加速了群落凋落物的分解和失重。在传统放牧平地系统中，放牧强度为7.5 sheep·hm-2小区群落凋落物的分解速率和失重率均显著高于对照区，分别高出45.0%和40.0%；在混合利用平地系统中，放牧强度为6.0 sheep·hm-2小区群落凋落物的分解速率显著高于对照区，高出35.0%；在混合利用坡地系统中，放牧强度为9.0 sheep·hm-2小区群落凋落物的分解速率和失重率均显著高于对照区，分别高出82.4%和62.0%。群落凋落物碳损失率和氮损失率在传统放牧系统中，随放牧强度的增加呈现出相似的变化趋势，而在混合利用系统中，随放牧强度的增加呈现出相反的变化趋势，但是总体表现为，增加放牧强度会加速群落凋落物中碳氮的释放。高放牧强度下，群落凋落物的分解速率、失重率和碳损失率差异显著，表现为：混合利用>传统割草>传统放牧，这一试验结果在一定程度上验证了放牧优化假说。