草原灌丛化入侵:过程、机制和效应

摘要

Woody-plant encroachment in grasslands has been a much-studied topic in ecology and animal husbandry over the past few decades.This paper clarifes the causes and consequences of this encroachment by reviewing recent progress in the study of invasion stages,invasion mechanisms,the impacts of this encroachment on grassland ecosystems and their aftereffects.The means of woody-plant encroachment include both anthropophyte and natural invasion.In general,this encroachment divides into three stages:dispersal,colonizing and establishing and diffusing.The causes of encroachment have been identified as fire suppression,climate change,changes in nutrient availability and over grazing.These factors effect encroachment through changing plant coverage,soil water use efficiency and allelopathy.We conclude that woody-plant encroachment changes many interfaces in grassland ecosystems and influences the ecological and hydrological processes that lead to grassland degradation and desertification.%草原灌丛化已成为全球性问题,也是生态学、畜牧学研究的热点问题.紧扣草原灌丛化过程、发生机理及其生态学后效等关键问题,介绍了国内外的最新研究进展.灌木入侵途径包括有意识引进入侵和自然入侵2类,入侵过程分为传播到达、定居建群和扩散入侵3个阶段.放牧、火烧、温室气体增加,干旱以及降水格局改变等均可导致草本向木本的转化,且机制复杂,主要有影响草本,木本植物盖度、水分利用效率、化感作用等.木本植物入侵打破了草原生态系统的稳定,表现出沃岛效应,影响动植物的分布以及生态系统的功能和服务.阐明草原“草本—木本”群落演替机制,可为我国研究草原灌丛化和管理提供理论借鉴.