文献类型：期刊文献

英文题名：Grazing Altered the Pattern of Woody Plants and Shrub Encroachment in a Temperate Savanna Ecosystem

作者：Zhang, Zhiyong[1,2] Zhang, Bo[3] Zhang, Xiao[1] Yang, Xiaohui[1] Shi, Zhongjie[1] Liu, Yanshu[1]

第一作者：张志永

通信作者：Shi, ZJ[1];Liu, YS[1]

机构：[1]Chinese Acad Forestry, Inst Desertificat Studies, Beijing 100091, Peoples R China;[2]Chinese Acad Forestry, Res Inst Forestry Policy & Informat, Beijing 100091, Peoples R China;[3]Beijing Stn Forestry Sci & Technol Extens, Beijing 100029, Peoples R China

年份：2019

卷号：16

期号：3

外文期刊名：INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH

收录：;Scopus(收录号：2-s2.0-85060543996);WOS:【SSCI(收录号:WOS:000459113600036)，SCI-EXPANDED(收录号:WOS:000459113600036)】；

基金：This research was supported by the National Key Research and Development Program of China (2016YFC0500801; 2016YFC0500804), the National Natural Science Foundation of China (31670715; 41471029; 41701249), and Project of Institute of Desertification Studies, CAF (IDS2017JY-4).

语种：英文

外文关键词：Ulmus pumila-dominated temperate savanna; population structures; spatial patterns; spatial association; grazing pressure; shrub encroachment

摘要：Ulmus pumila-dominated temperate savanna is an important tree-grass complex ecosystem in the Otindag sand land, northern China. To date, few investigations have been undertaken on the spatial patterns and structure of this ecosystem and its driving factors under different grazing pressures. The objective of our study therefore is to explore whether grazing has affected the population structure/pattern of woody plants and shrub encroachment in a temperate savanna ecosystem. Results indicate that species richness and seedlings decreased with increasing grazing pressure. An increase in grazing pressure did not significantly affect adult-tree density, but it hindered the normal regeneration of U. pumila seedlings, further inducing population decline. U. pumila seedlings had a more significant aggregated distribution than juvenile or adult trees. The adult and juvenile trees had an aggregated distribution at the small scale and a random distribution at the large scale. Shrubs also showed a significant aggregated distribution. No clear effect on the spatial patterns of adult trees was observed; however, there was a noticeable effect for juveniles and seedlings under different grazing pressures. U. pumila seedlings had a positive association with their juveniles and Spiraea aquilegifolia, but a negative association with Caragana microphylla. Shrub encroachment occurred with decreasing grazing pressures. In conclusion, overgrazing led to the decline of U. pumila population, but the decrease in grazing pressure increased shrub encroachment in the temperate savanna ecosystem. Moderate grazing management may be a better way to enhance the stability of U. pumila population and reduce shrub encroachment.