若尔盖县湿地稳态转换的水文地貌生态阈值

Hydrological and geomorphologic ecological threshold of steady-state transformation of wetland in Zoige County, Sichuan Province

以若尔盖县湿地为研究对象,在Google Earth影像和野外调查基础上获取若尔盖县人工沟渠的空间分布数据,并计算结构特征指数。从地形地貌和水文条件两个方面选择6项指标,利用熵值法筛选出对湿地稳态转换影响最大的指标并厘定生态阈值,包括理想值和临界值,通过1980—2015年土地利用数据识别若尔盖县湿地稳态转换区,最终基于乡镇尺度确定生态阈值调控范围,划分各乡镇湿地恢复优先性。结果表明:(1)若尔盖县存在四类湿地稳态转换区,其中稳态平衡区面积最大,占全县湿地面积的47.56%,退化转化区次之,占全县湿地面积的35.88%。(2)对若尔盖县湿地稳态转换影响最大的两项水文地貌生态指标为网络联通度和沟渠密度,权重分别为0.162和0.161。若尔盖县网络联通度的理想值为0.033、临界值为0.054;沟渠密度的理想值为0.011 km/km^(2)、临界值为0.360 km/km^(2)。(3)在若尔盖县需要进行湿地恢复的10个乡镇中,按湿地恢复优先性划分出3个三级恢复区、4个二级恢复区、3个一级恢复区,其中一级恢复区应优先恢复。

The subject of the research described in this article are the Zoige County wetlands. The spatial distribution of man-made ditches in Zoige County was obtained from Google Earth images and field surveys, and the structural feature index calculated. Six indicators were selected from two aspects of terrain and hydrological conditions. The entropy method was used to screen for the indicators that had the greatest impact on wetland steady-state transition and that determined the ecological threshold. Having identifies wetland steady-state transition zones in Zoige County from 1980—2015 land use data, an ecological threshold control range was finally determined based on township size, and the priority of wetland restoration in each township was allocated. The results show the following:(1) There are four types of wetland steady-state transition zones in Zoige County, of which the stable zone is the largest, accounting for 47.56% of the county′s wetland area. The degradation zone accounts for 35.88% of the county′s wetland area.(2) The two hydrological and geomorphological ecological indicators that have the greatest impact on steady-state conversion of wetland in Zoige County are network connectivity and ditch density, with weights of 0.162 and 0.161, respectively. Ecological thresholds of network connectivity in Zoige County are 0.033 and 0.054, and those of ditch density are 0.011 and 0.360 km/km^(2).(3) In the 10 townships in Zoige County where wetland restoration is needed, three tertiary restoration areas, four secondary restoration areas, and three primary restoration areas are defined according to the priority of wetland restoration. The primary recovery areas should be restored first.