黄土高原草地植被的嬗变

The evolution of grassland vegetation on the Loess Plateau

草地是我国最大的陆地生态系统,草原安全与国家生态安全息息相关。黄土高原作为我国重要的草原分布地,是世界上水土流失最严重的区域之一,探究黄土高原草地植被演变历程对该地植被的恢复重建及生态保护具有重要意义。本文通过文献查阅、史料探究等方法系统研究了黄土高原草地植被的嬗变历程。研究表明:在地质历史时期,黄土高原植被类型以草原为主。更新世到全新世中期,黄土高原草地植被随气候变迁经历了森林草原、草原、荒漠草原的多次转变。到全新世晚期,由于暖期结束、气候总体变冷变干、人口基数增加和农耕文明的发展,黄土高原森林草原向干草原转变,草原带逐渐南移,草地植被破坏严重,面积不断减少,荒漠草原分布范围变广。随着黄土高原水土保持工作的展开,生态建设成效逐渐凸显。20世纪80年代以来,在三北防护林体系建设、退耕还林(草)、天然草原植被恢复与建设和山水林田湖草系统保护修复试点等生态项目实施下,黄土高原的草地退化和水土流失等问题得到了有效控制。如今黄土高原山青草盛,绿意盎然,植被恢复已经到达区域水资源承载的极限,生态建设迈入了新的发展阶段,仍需要探索新的治理思路与模式。

Grassland is the largest terrestrial ecosystem in China,and consequently,grassland security closely mirrors national ecological security.As an important area of grassland distribution in the country,the Loess Plateau is one of the most seriously affected areas in the world in terms of soil erosion.Accordingly,with respect to the restoration and reconstruction of vegetation and ecological protection,it is of considerable significance to examine the evolution of grassland vegetation on the Loess Plateau.In this study,we systematically studied the transmutation of grassland vegetation on the Loess Plateau based on a literature review and examination of the historical data.The results indicate that grassland has been the main vegetation type on the Loess Plateau during geological history.From the Pleistocene to the mid-Holocene,grassland vegetation on the plateau underwent numerous changes in the characteristics of forest-grassland,grassland,and desert grassland in response to climate change.Coinciding with an end to the warm period during the late Holocene,there was an overall cooling and drying of the climate,an increase in the human population base,and the development of agricultural civilization.Furthermore,forest steppe on the Loess Plateau changed to dry steppe and the steppe belt migrated southward,whereas the grassland vegetation became severely damaged and reduced in area,and the distribution of desert grassland expanded.Since modern times,with the gradual development of soil and water conservation work on the Loess Plateau,ecological restoration initiatives have gradually been highlighted from the 1980s.Under the implementation of ecological projects such as the construction of the three-north shelterbelt system,the return of farmland to forest and grassland,the restoration and reconstruction of natural grassland vegetation,and a pilot project for the protection and restoration of the mountains,rivers,forests,farmlands,lakes,and grassland systems,there has been an effective control of environmental problems,such as grassland degradation and soil erosion,on the Loess Plateau.Currently,vegetation coverage on the Loess Plateau grasslands and mountains has been markedly promoted,and the degree of vegetation restoration has satisfied the requirements of the regional water resource capacity.Despite these achievements,however,this essentially represents a new phase of development in the ecological reconstruction of Loess Plateau grassland,and one that needs to be continually monitored.