1987-2008年南四湖湿地植被碳储量时空变化特征

利用研究区1987、1997和2008年的LandsatTM／ETM＋卫星遥感数据，结合实地采样调查和收集的资料，计算3个时期山东省南四湖湿地各植被类型的面积和碳储量；同时依照不同覆被类型（植被类型）的平均碳储量将各覆被类型的斑块划分为不同储碳等级，绘制3个时期的南四湖湿地植被碳格局图，分析植被碳储量的时空变化特征、变化产生的原因和变化对湿地的潜在影响。研究结果表明：研究前期（1987年）植被储碳格局存在着明显的植被碳储量以湖南北中心线向两岸增大的带状特征，研究中后期（1997-2008年）带状储碳格局不断破碎化并最终消失。整个研究期高储碳等级的斑块面积不断减小，低储碳等级的斑块面积增加。湿地植被碳储量呈现前期基本稳定后期显著减少的特征，1987、1997和2008年湿地植被碳储量均值分别为1．07、1．08和O．64TgC，1987-1997年湿地植被碳储量平均年增加0．001TgC，变化幅度不大；1997-2008年年减少0．04TgC，下降较明显。其中自然植被碳储量在整个研究期内持续减少，人工植被碳储量呈现先增加后减少的波动变化特征，分析认为这一变化特征产生的主要原因是南四湖地区多因子驱动的土地覆被变化活动。通过区域湿地植被的碳平衡动态分析认为，植被碳储量（碳库）的减少可能会导致整个湿地碳储量的入不敷出，使整个湿地碳汇能力下降甚至可能变为碳源。

Spatial and temporal variation of vegetation carbon storage in Nansihu lake wetland from 1987 to 2008

Using vegetation carbon density data of Nansihu lake wetland coming from field survey and previous literatures, and combining with Landsat TM/ETM＋ remote sensing data of the three periods in 1987, 1997 and 2008, this paper analyzed the spatial and temporal changing characteristics of wetland vegetation carbon storage in Nansihu lake wetland, mapped the vegetation carbon pattem figure, and calculated the area of various vegetation types and vegetation carbon storage in the three periods. The results of the study show that： in the early period of the study （1987）, vegetation carbon storage pattern has obviously banded characters and its carbon storage increased from the center line of the lake to the tow edges of the lake, while in the later period （1997-2008）, the carbon storage pattern is of fragmentation and eventually disappear. Throughout the whole study period, the patch area with high carbon storage levels constantly decreases, and the patch area with high carbon storage levels increased. The vegetation carbon storage kept stability in early phase and significantly reduces later; the mean wetland vegetation carbon storage in 1987, 1997 and 2008 are 1.07 Tg C, 1.08 Tg C and 0.64 Tg C, respectively. The wetland vegetation carbon storage increased 0.001 Tg C each year in early study period and reduced 0.04 TgC each year in later study period. The natural vegetation carbon storage continued to decline throughout the whole study period, while planted vegetation carbon storage increased firstly and then decreased, with presenting fluctuation. The paper argues that the changing characteristics of the carbon storage in Nansihu wetland are driven by the land use change principally. By analysing carbon dynamic balance of the study area, the decrease of vegetation carbon storage may lead to decline of wetland carbon sequestration capability, even may make wetland become a carbon source.