天山北麓历史时期的环境演变信息

近 2 0 0 0年以来 ,天山北麓的气候有冷暖干湿波动 ,但总体干旱的基本面貌未发生根本变化。植被在森林的上下界限、平原河谷林的发育程度、平原低地草甸的面积上 ,随气候的变化而发生波动。山地生态系统比较稳定 ,平原生态系统相对不稳定。尤其是平原河流和湖泊抗干扰性极差 ,容易发生改变 ,同时也引起局地小气候及生物群的变化。由于气候变化和人类活动的影响 ,平原地区的水系变化很大 ,河流流量减少、流程缩短、尾闾湖消失、地下水位降低、扇缘溢出带北移等成为普遍现象。天山北麓是自然绿洲发育比较好的地带 ,由于人类活动的影响 ,自然绿洲大多为人工绿洲取代 ,自然绿洲功能弱化 ,基本失去了改善荒漠环境、生物栖息地、保护荒漠区生物多样性等多种生态功能。该区新石器时代以来就有人为活动 ,早期以狩猎、牧业活动为主 ;中期以牧业为主 ,农业为辅 ;后期以农业为主 ,牧业为辅 ,人类对环境的影响有相当长的时间。清朝以来 ,尤其是解放后 ,人类对环境的影响作用急剧加强 ,成为近代环境变化的主导因素 ,主要表现在对水的控制而产生的一系列水系、植被、沙漠变化

THE INFORMATION OF ENVIRONMENTAL EVOLVEMENT OF THE NORTHERN PIEDMONTS OF THE TIANSHAN MTS. IN THE HISTORY

During the last 2000 years, the climate of the northern piedmont of Tianshan mountain has varied between cold and warm, arid and humidity, but the whole arid condition has not changed. It has varied with the change of climate, as for plants, the limit of forests, the growth degree of plain valley forest and the area of the lower plain meadow. The mountain ecosystem is more stable contrary to the plain ecosystem. Rivers and lakes of the plains is not very stable and easily changed as a result of the change of the regional climate and the biology of the community. The water system in the plain has largely changed because of the variation of the climate and the human activity. It is a common phenomenon that the water quality is reducing, the flow is shortening and the ending lakes are disappearing. Because the artificial oasis took the place of the natural oasis, the function of natural oasis is weakening and nearly lost the ability of improving the environment, the habitat of wildlife and preserving the biological diversity in wild area. Since the Neolithic Age, the human being has emerged and evolved in this area, living mainly on hunting and herding, followed by herding and farming, and finally farming and herding. Therefore the human influence on the environment last a considerable long period of time. Since Qing dynasty, especially after the foundation of new China (1949), the effect has increased sharply and been the dominant factor of the variation of environment in the latter_day, which presented on controlling of water resource, and so caused the change of water system, vegetation and desert etc.