Liu Yuanbo, Nishiyama Soichi, Kusaka Tatsuro
The United Graduate School of Agricultural Sciences, Tottori University, Koyama 4-101, Tottori-Shi 680-8553, Japan.
Environ Manage. 2003 Mar;31(3):365-76. doi: 10.1007/s00267-002-2785-5.
It is usually inappropriate to define rectangular land areas or administrative units as the extent for quantifying landscapes that possess hierarchical structure. As a functional unit established by geophysical relationships, the watershed is one of many natural scales in the hierarchical landscape. We examined the dynamics of the Yashiro watershed of Japan at the landscape level using pattern metrics based on Landsat thematic mapper (TM) imagery from 1985 to 1998. This watershed provides important habitats for the hooded crane (Grus monachus), a vulnerable species. While its world population has remained stable, the number wintering at Yashiro has declined in recent years. Changes in landscape metrics reveal that the spatial pattern within the watershed underwent homogenization due to depopulation of local people and shifts in local energy requirements and forest management policy at Yashiro. Specific changes include: a decrease in bare land area from 6.2% to 1.0% of the landscape, increased forest cover from 69.2% to 76.1%, reduction in patch number from 1194 to 616 and enlarged mean patch size, and a decrease in total edge from 223,740 m to 158,040 m. The rate of change in landscape metrics indicates a rapid change towards homogeneity in the landscape since 1990. The temporal changes in hooded crane populations corresponded to the changes in landscape. An alternative explanation has been proposed that decline of the species is influenced by landscape dynamics affecting both habitat selection and food resources. Conservation at the watershed scale is suggested to be complementary to the current conservation measures of the species.
将矩形的土地面积或行政单位定义为具有层次结构的景观的量化范围通常是不合适的。作为由地球物理关系建立的功能单元，流域是层次景观中众多自然尺度之一。我们利用基于1985年至1998年陆地卫星专题制图仪（TM）图像的格局指标，在景观层面研究了日本八代流域的动态变化。该流域为易危物种白头鹤（Grus monachus）提供了重要栖息地。虽然其全球种群数量保持稳定，但近年来在八代越冬的白头鹤数量有所下降。景观指标的变化表明，由于当地人口减少以及八代当地能源需求和森林管理政策的转变，流域内的空间格局发生了同质化。具体变化包括：裸地面积从景观的6.2%降至1.0%，森林覆盖率从69.2%增至76.1%，斑块数量从1194个减少到616个且平均斑块面积增大，总边缘长度从223740米减少到158040米。景观指标的变化率表明，自1990年以来景观迅速向同质化转变。白头鹤种群的时间变化与景观变化相对应。有人提出了另一种解释，即该物种的数量下降受到影响栖息地选择和食物资源的景观动态变化的影响。建议在流域尺度上进行保护，以补充目前该物种的保护措施。
