关键词: 根系活力, 秋华柳, 金属元素, 镉胁迫

Abstract: By using GIS and the methods of nearest neighbor index, Ripley’s K function, and kernel density estimation, the spatial distribution of 298 China’s national wetland parks was analyzed. Based on the matrix raster data, the spatial accessibility of China’s national wetland parks at countylevel was calculated by using the cost weighted distance method and ArcGIS as platforms. The spatial differences of countylevel accessibility of the national wetland parks were analyzed by the exploratory spatial data analysis (ESDA). Results show that the national wetland parks generally exhibit an aggregated distribution. There is quite difference of spatial distribution of national wetland parks among both interprovinces and intereconomic regions. The average accessibility is about 144.07 min, and the area with the accessibility of national wetland parks within 120 min reaches 60%, while the area with the accessibility within 30 min accounts for 13.29%, and the longest time needs 1283 min for one park located at central Tibetan Plateau. Moreover, the distribution of the accessibility coincides with that of traffic lines. At county level, the estimated value of Moran’s I is positive. National wetland parks and adjacent areas show a strong positive correlation. The distribution of hot spots regarding the accessibility shows an obvious hot spots-sub-hot spots-sub-cold spots-cold spots distribution pattern from east to west. Service range of each national wetland park is more advanced in western regions than that in eastern and central China.

Key words: metal elements., cadmium stress, Salix variegata, root vigor