基于覆被变化的纳帕海生态系统稳定性研究

A Study on the Napahai Ecosystem Stability based on Changes of Vegetation Cover

以覆被变化情况作为判断纳帕海季节性湿地生态系统稳定性的指标,利用1985年、2005年、2011年3个时段的纳帕海覆被分布格局,在Arcgis9.3平台上研究纳帕海覆被历史变化情况。研究结果表明:(1)30多年来,在承受农业、畜牧业、旅游业等强烈的人为干扰下,纳帕海覆被覆盖率无显明显下降,土地面积未扩大,水生群落面积减小,牧草面积扩大,保持了较好的生态功能,显示出较好的生态系统稳定性;(2)纳帕海生态系统稳定性,以纳帕海独特的水因子变化为基础,同时各类群落构成物种对水因子有很大的适应性,保证了各种水因子条件下覆被的存在,周期性淹水有利于生态系统的修复和抵抗各类干扰;(3)如果人为干扰持续破坏周期性淹水的条件,纳帕海生态系统有可能加速旱化,被大量大戟群落入侵,甚或沙化,失去相关的生态功能。

This study took the dynamic changes of vegetation cover as indicator to evaluate the ecosystem stability of Napahai Lake,used3historical pattern of vegetation distribution of1985,2005,2011in Napahai lake as basic material,analysed the ecosystem stability of Napahai Lake by Arcgis9.3.The results showed that:(1)In the past30years,under the intense artificial interferences such as agriculture,graziery,tourism,Napahai Lake keep a relatively good ecological functions,showed a good ecosystem stability.The total area of vegetation cover did not decrease obviously,the area and the locations of farm lands nearly keep the same as before,area of aquatic communities decreased while the area of pasture increased.(2)The ecosystem stability of Napahai Lake depends on local special seasonal water flooding condition,all kinds of the herbal species in plant communities have flexible adaptation to various water condition,which ensures the vegetation can survive regardless how the water conditions change,meanwhile seasonal water flooding is beneficial for both ecosystem rehabilitation and resisting disturbance.(3)If artificial interferences damage the seasonal water flooding continuously,the drought process will speed up and Napahai ecosystem will suffer invasion of Euphorbia jolkinii at large scale,or will degrade into bare sandy land and loss its basic ecological functions.