天山北坡夏季放牧场植物功能群对不同放牧管理制度的响应

Response of plant functional groups to different grazing management systems in summer grasslands on the northern slope of Tianshan Mountains

草原生态系统生产力和功能多样性对放牧管理制度的响应过程是高度复杂的,这是研究群落对环境变化响应的一个主要挑战,将具有相似特征的物种分为植物功能类群,是降低生态群落研究复杂性的一种有效方法。本研究将研究区群落植物划分为莎草、禾草、豆科草、杂草4个植物功能群,以研究群落对“不降低放牧强度、不减少放牧天数的前提下,调整牲畜进入放牧场时间”这一放牧管理制度的响应。结果显示:相较于传统的5月进入放牧场放牧60 d,牲畜推迟至6月和7月进入放牧场放牧,增加了优良牧草功能群在群落中的优势地位,而降低了杂草功能群在群落中的地位;经偏最小二乘回归分析(PLS)分析发现,放牧管理、土壤变量、气候变量各自对功能群有较弱的直接影响,通过方差分解分析(VPA)得出结论,气候变量对各功能群相关变量的独立解释率为0,而放牧管理变量和土壤变量共同解释率为78.6%,这两者的协同作用才是各功能群生产力、多样性特征变化的主要驱动力;灵活放牧管理制度优于传统放牧管理制度,它既保持了牲畜生产的长期性和盈利性,又保持和发展了草原高生物多样性和多功能性,值得进一步推广研究。

The response process of grassland ecosystems,in terms of productivity and functional diversity,to grazing management systems is highly complex.This poses a major challenge in studying the response of plant communities to environmental changes.An effective approach to reducing the complexity of ecological community research is categorizing species with similar characteristics into plant functional groups.In this paper,the plant communities in the study area were divided into four functional groups(sedges,grasses,leguminous grasses,and weeds)to study the response of the community to a grazing management system that adjusted the entry time of livestock into the grasslands,without reducing grazing intensity and grazing duration.Compared with the traditional grazing for 60 days in May,delaying livestock grazing to June and July increased the dominant position of fine herbage and reduced the position of forbs in the community’s functional groups.Partial Least Square(PLS)analysis indicated that grazing management,soil variables,and climate variables had weak direct effects on functional groups.In addition,variance decomposition analysis(VPA)showed that the independent explanation rate of climate variables on the variables related to each functional group was 0,and that the combined explanation rate of grazing management variables and soil variables was 78.6%.The synergy between the two is the main driving force for changes in the productivity and diversity characteristics of each functional group.The flexible grazing management system is superior to the traditional grazing management system.It not only maintains the long-term sustainability and profitability of livestock production,but also maintains and develops a high biodiversity and the multifunctionality of grasslands,which is worthy of further research.