鄱阳湖自然保护区湿地植被生物量空间分布规律

探明区域湿地植被生物量的空间分布规律及其变化趋势,对于更好地保护候鸟生境、制定合理的湿地保护政策具有重要的意义。以鄱阳湖国家级自然保护区为研究对象,基于2000—2011年研究区MODIS植被指数产品和同期的植被生物量调查资料,建立了湿地植被生物量的遥感估算模型。在此基础上利用GIS空间分析方法,系统分析了保护区近10年来湿地植被生物量的空间分布规律及其季节变化特征。研究结果表明:(1)MODIS增强型植被指数的乘幂模型可以较好地模拟研究区湿地植被生物量的鲜重,拟合模型总体精度达到91.7%。(2)多年平均生物量呈现"岛屿型"空间分布模式:各子湖泊及洼地中心处,表现为水生植被群落为主的低生物量区(285 g/m2);湖心水体外围14—15m的高程区域,分布着以苔草群落为主的中生物量区(285—830 g/m2);高程位于16—18m的河口三角洲及天然堤坝区域,表现为以蒿、荻和芦苇群落为主的高生物量区。(3)保护区植被群落分布具有特定的季相变化特征,高、中、低生物量区在不同的月份呈现出不同的空间生消和演进规律,鄱阳湖水位的周期性涨落是影响其变化的一个重要扰动因子。

Spatial distribution of wetland vegetation biomass in the Poyang Lake National Nature Reserve, China

Vegetation is one of the important components of wetland, and vegetation biomass is a key indicator of the health status of the wetland ecosystem. Comphrehensive understanding of spatial distribution of vegetation biomass and its temporal variation is a pre-requirement for effective protection of bird habitats and scientific planning of wetland conservation. In this regard, it has been one of central topics in hydro-ecology, wetland ecology and vegetation ecology in past decades. In recent years, vegetation change has become one of major concerns with frequently occurred extreme droughts in the Poyang Lake National Nature Reserve (PLNRR) of China. To investigate the spaital changes of vegetation, MODIS (Moderate resolution Imaging Spectrordiometer) vegetation index products (MOD13Q1) were used to construct a model for retrieval of vegetation biomass with the coincident field data in PLNRR for the period from 2000-2011. GIS spatial analysis techniques were used to analyze the spatial patterns and seasonal variations of wetland vegetation biomass. Our findings can be summerizes as follows: (1) the power function best describe the relationship between MODIS-EVI (Enhanced Vegetation Index) and green yield of vegetaiton in PLNRR, with an overall accuracy of 91.7%. (2) Multi-year average of vegetation biomass displayed an island-like spatial pattern and can be classified into three zones. Vegetation biomass was lower than 285g/m², dominant with aquatic vegetation communities, for the bottom areas near the center of lakes. It ranged from 285 to 830 g/m², dominant with sedge communities, for the periphery of the lakes with an elevation of 14-15 m. The biomass was higher than 830 g/m² dominant with wormwood and reed communities, for surrounding delta or dyke areas with an elevation of 16-18 m. (3) Vegetation biomass showed different seasonal variations in each zone, which was jointly affected by multiple factors. Lake stage is the most important factor in regulating the spatial development of the vegetation biomass. Overall, the results should be not only helpful for understanding the change in biodiversity and ecosystem stability, but also provide a scientific basis for effective management and protection of wetland resources in the PLNRR.