基于MODIS-NDVI的乐安湿地植被覆盖动态分析

Dynamic Analysis of Vegetation Cover in Le’an Wetland Based on MODIS-NDVI

乐安湿地作为长江上游生态屏障的重要组成部分,是大凉山生态建设的重点区域;也是高原湿地在海拔2 500 m^3 000 m典型生态系统。植被覆盖度(植被的垂直投影面积与单位面积之比)是反映湿地植物生长状况的重要生态学参数,在评估和监测湿地生态环境方面发挥着重要的作用。本文利用2011-2015年的MODIS归一化植被指数数据,应用像元二分法估算了布托乐安湿地保护区的植被覆盖度及其变化趋势,分析了乐安湿地保护区内植被覆盖度变化,旨在为保护区生态环境评价及管理提供科学依据。研究表明乐安湿地保护区植被覆盖度状况良好,中度及其以上等级植被覆盖区占研究区比重较大,超过50%;5年间,保护区植被覆盖度总体上呈现稳定状态,但是不同等级,不同时段的植被覆盖变化趋势不同;植被覆盖度在空间上呈现以万吨山、四棵乡一线向两侧降低的总体趋势。与海拔3 500 m左右的若尔盖湿地相比,乐安湿地植被覆盖度分布主要受地形、水热条件限制,以及人为活动因素的影响。

As an important part of ecological barrier in the upper reaches of the Yangtze River,Le’an Wetland was the key area of ecological development in the Daliang Mountain.It was also a typical ecosystem of plateau wetlands at elevation 2500~3000 m.The vegetation cover(the ratio of vertical projection area of vegetation to unit area) was an important ecological parameter to reflect the growth status of wetland plants.It played an important role in the assessment and monitoring of the wetland ecological environment.Based on the data of MODIS normalized vegetation index in 2011-2015 years,the vegetation cover and its changing trend of Bhutto Le’an Wetland Reserve were estimated by using the two sub-pixel model.And the change of vegetation cover in Le’an Wetland Reserve was analyzed in order to provide scientific basis for ecological environment evaluation and management in protected areas.The results showed that the vegetation cover of Le’an Wetland Reserve was in good condition,and the proportion of vegetation covering area in moderate and above grade was more than 50%.During the 5 years,the vegetation coverage of protected areas showed a stable state in general,but the change trend of vegetation cover was different at different levels and different periods.The vegetation cover in space presented a descending trend from Wandun Mountain-Sike Township to their two sides.Compared with Ruoergai wetland at about 3500 m above sea level,the distribution of vegetation cover in Le’an wetland was mainly affected by topography,hydrothermal conditions and human activity factors.