Hou Fujiang, Nan Zhibiao, Xiao Jingyu, Chang Shenghua
College of Pastoral Agriculture Science and Technology, Lanzhou University, Gansu Grassland Ecological Research Institute, Lanzhou.
Ying Yong Sheng Tai Xue Bao. 2002 Aug;13(8):915-22.
This paper presented the characteristics of the vegetation, soil, and their coupling in the gradient of grazing pressure of the degraded alpine grassland in Sunan county and of the typical arid grassland in Huanxian county, Gansu province. The abundance index of species, Simpson index, Shannon-Wiener index, Cody index, nutrient functional diversity index and life type diversity index increased, while the Bray-Curtis index and nitrogen fixation diversity index decreased with the reduced grazing intensity in both types of degraded grassland. With reduced grazing pressure, the contents of total nitrogen, available nitrogen and organic matter in both grasslands and the content of available phosphorus in arid grassland at 0-40 cm soil depth were increased, and that of total phosphorus in alpine grassland was decreased, while phosphorus concentration in arid grassland showed no regular pattern of change. The total and available nitrogen, available phosphorus and the ratio of available phosphorus to total phosphorus and of organic carbon to nitrogen were all higher in alpine grassland than in arid grassland. The grey correlativity of vertical distribution pattern between soil elements and living root biomass was positively related to grazing pressure, while the coupling intensity of soil-herbage subsystem was increased with decreased grazing pressure. There existed a significant correlation between poor soil elements and abundance of poisonous and poor-nutritional plants in both degraded grasslands. The degradation process of grassland resulted not only from the degeneration of vegetation and soil subsystems, but also from the disappearance of coupling between both subsystems and the development of their discordance. The ecological process could be quantified by coupling intensity and discordance intensity. It is concluded that the studied arid grassland was degraded more seriously than alpine grassland.
本文介绍了甘肃省肃南县退化高寒草地和环县典型干旱草地在放牧压力梯度下植被、土壤及其耦合特征。在两种退化草地中，随着放牧强度降低，物种丰富度指数、辛普森指数、香农 - 威纳指数、科迪指数、养分功能多样性指数和生活型多样性指数均升高，而布雷 - 柯蒂斯指数和固氮多样性指数降低。随着放牧压力减小，两种草地0 - 40 cm土层深度的全氮、碱解氮和有机质含量增加，干旱草地有效磷含量增加，高寒草地全磷含量降低，干旱草地磷浓度变化无规律。高寒草地的全氮、碱解氮、有效磷、有效磷与全磷之比以及有机碳与氮之比均高于干旱草地。土壤元素与活根生物量垂直分布格局的灰色关联度与放牧压力呈正相关，而土壤 - 草本亚系统的耦合强度随放牧压力减小而增加。两种退化草地中土壤养分贫瘠与有毒及营养差的植物丰度之间存在显著相关性。草地退化过程不仅源于植被和土壤亚系统的退化，还源于两个亚系统之间耦合关系的消失及其不协调的发展。生态过程可用耦合强度和不协调强度来量化。研究得出结论，所研究的干旱草地退化比高寒草地更严重。
