岷江上游干旱河谷农林边界影响域的研究

Depth of edge influence on agriculture-forestry boundary in arid valley of upper reaches of Minjiang River,China.

对岷江上游农林边界的影响域进行研究 ,以提高该区管理农田和林地的水平 .共调查 3种类型农林边界 10条样带 ,采用移动窗口法对植物多样性的数据进行分析 ,结果表明 ,当窗口宽度达到 6～ 10时 ,SED曲线的变化趋向稳定 ,并且在曲线上有一或两个峰值出现 .不同类型边界的影响域是不同的 ,但均在距边界 5 0m内 .各类型边界的影响域多在 12～ 30m之间 .6条林地样带只有M 2和M6样带林地的影响域被确定 ,而 4条农田样带的影响域均被确定 .影响域的大小取决于边界两侧斑块类型和地形以及小气候等因子 ,但坡向对其影响不大 ;移动窗口法能有效地刻画边界动态 ,是一种分析边界简单而有力的工具 .这些结果有利于进一步理解干旱河谷区农林间的相互作用 .

By using moving split-window techniques (MSWT),this study estimated how far the edge effects penetrated the forest and agricultural fields in the arid valley of upper reaches of Minjiang River,southwestern China.Its aim was to provide general information on vegetation along edge to interior gradients in order to assist in interpretation and prediction of biological phenomena associated with agriculture-forestry boundary,and to improve current management practices in such areas.Three types of boundaries (10 transects) were investigated and sampled.The results showed that when the window width reached 6～10,the change of the SED curve on the graph tended to become stable,and one or two peaks occurred.The depth of edge influence was clearly different for different types of boundaries,and could be estimated within 50 m from the edge to interior.The depth of edge influence (DEI) on vegetation diversity almost varied between 12～30 m,mainly depending on the patch type,topography and microclimate,but seldom on slope orientation.Of the 6 forest transects in the three types of boundaries,the DEI was detected only in the forest part transects M2 and M6,but almost detectable in the agricultural part of all transects.MSWT was considered to be a useful tool for characterizing edge dynamics if enough data was available,and became a simple and powerful technique for analyzing the boundary.The results will provide further knowledge for understanding the interaction between forestry and agriculture in the arid valley.