岷江上游林农边界网络的生态效应

应用地理信息系统软件从遥感影像中提取出岷江上游的农田边界类型图,结合坡面尺度上林农边界效应的分析结果,对林农边界效应在景观尺度上的影响进行了研究。结果表明:研究区的农田边界共有5种类型,分别是农田与林地、灌木林地、草地、水体、建筑用地之间的边界,其中林农边界长2473.68km,占农田边界的37.57%,广泛分布在岷江干流及其支流的河谷中,在很大范围上影响着农田的土壤水分和生物多样性,对林地的影响相对较小;边界效应使林地边缘和农田边缘的土壤水分低于其内部,研究区有2103hm2的农田和371hm2的林地的土壤水分受到边界网络影响,分别占研究区农田面积和林地面积的2.33%和0.03%。由于土壤水分是制约研究区植物生长的限制性因子,且岷江上游的农田斑块面积较小且分布零散,因此应避免农林复合景观中边界密度进一步增加。

Effects of forestland-farmland boundary network on soil moisture content of forestland and farmland in upper Minjiang River reaches

By using Landsat TM satellite images and combined with field investigation,the information of farmland boundaries in upper Minjiang River reaches was derived,and the edge effect of forestland-farmland boundary at landscape scale was investigated.The results showed that there were 5 types of farmland boundaries,i.e.,forestland-farmland boundary,shrub land-farmland boundary,grassland-farmland boundary,water body-farmland boundary and construction land-farmland boundary,among which,forestland-farmland boundary was 2473.68 km long,accounting for 37.57% of the farmland boundaries and distributed in the valleys of upper Minjiang River reaches,having greater effects on the soil moisture and biodiversity of farmland but less effects on those of forestland.The soil moisture content was lower on the forestland-farmland boundary than on their interiors due to the edge effect.In the upper Minjiang River reaches,there were 2 103 hm2,or 2.33% of the total farmland,and 371 hm2,or 0.03% of the total forestland,whose soil moisture content was affected by the forest-farmland boundary.Since soil moisture content was a limiting factor of the plant growth in the upper Minjiang River reaches and the forestland-farmland landscape in the area was fairly fragmented,the further increase of the forestland-farmland boundary should not be encouraged.