官厅水库库区水生植物演变格局时空变化特征分析

Analysis of Hydrophytes for Spatial Evolution Pattern in Guanting Reservoir,China

利用中等分辨率长时间序列的TM遥感影像(1995—2007年),采用面向对象的分类方法,以多尺度分割技术为核心,提取了官厅水库水生植物空间分布信息,在斑块类型和景观级别尺度上,共筛选了8个高度浓缩景观格局信息的定量指标,结合水生植物空间分布的质心变化,分析了水生植物演变格局的时空变化特征。研究表明:(1)1995—2007年,受水域面积的扩张和萎缩的影响,库区水生植物面积及其平均斑块面积呈明显地增加和减少趋势:沉水植物波动幅度比较明显,呈先小幅扩张后急剧萎缩的趋势,2000年之前,随水域的扩张,其面积增加了30.2 km2,相对动态度达116.87%;之后,随着水域面积的持续萎缩,沉水植物面积以每年4.2%呈大幅递减趋势,减少了43.02 km2;挺水植物所占比例较小,其面积呈小幅扩张趋势,增加了4.58 km2。(2)沉水植物和挺水植物随水域面积的波动呈现不同的景观格局演变特征。库区沉水植物的景观优势度高,最高达56.09%,占库区水生植物景观类型的主体;挺水植物的平均斑块面积、聚集度指数均低于同年沉水植物,具有离散度高、破碎度高、连通性低的特点。挺水植物的斑块形状相对复杂,其分维度指数平均比同年沉水植物高0.29。(3)水生植物的质心12 a来发生了不同程度的偏移变化,挺水植物质心整体向库区东北方向移动了1.88 km,偏移方向为东偏北12.78°;沉水植物质心整体向库区西南方向移动了4.66 km,偏移方向为南偏西43.04°。

It is an important part in wetland ecosystem that hydrophytes have the important function of habitat construction. Using remote sensing techniques to derive hydrophytes is one of the significant way to monitor the hydrophytes in large-scale spatial pattern. This paper adapted object-oriented classification method to derive the types of hydrophytes in Guanting reservoir.Multi-scale segmentation technology was the core. The medium-resolution TM and ETM＋ multi-spectral remote sensing images were selected as the data source of the classifica- tion from 1995 to 2000. In this research ,we selected indices such as patch number, average patch area, landscape percentage, patch density, contagion indices, dimension indices, and combined the changes in centroids of hydrophyte to analyze the spatio-temporal pattern of hy- drophytes. The results showed：a）Hydrophytes＇ area and the average patch area in the reservoir area had significantly increasing and decreas- ing trends due to the expansion and shrink of water area from 1995 to 2007. Submerged maerophytes had a dramatic fluctuations, showed small expansion during the period 1995-2001, and represented an obviously decline from 2002 to 2007. With the expansion of water, sub- merged macrophytes＇ area increased by 30.2 km2, the relative dynamic de~＇ee was 116.87% from 1995 to 2000. With water area continually shrank, the annual decrease rate was 4.2%. Submerged maerophytes area reduced 43.02 km2 from 2000 to 2007. There would only a smallproportion of emergent macrophytes in hydrophytes. Emergent macrophytes had a slight expansion trend which increased by 4.58 km2.b） Submerged macrophytes and emergent macrophytes presented dynamic characteristics in landscape pattern, under effect of the fluctuations of water area. The dominance of landscape patterns of submerged macrophytes was high, about 56.09%. The average patch area and the conta- gion indices of emergent macrophytes were lower than submerged macrophytes in the same year, with the high discrete and low connectivity. The patch shape of emergent macrophytes was complex. The dimension indices were average higher 0.29 than submerged macrophytes in the same year. c）The centroid of hydrophytes had dramatic changes in the 12 years. The centroid of emergent macrophytes moved 1.88 km to- wards the east-north direction in 12.87~. The centroid of submerged macrophytes moved 4.66 km towards the southwest direction in 43.04~.