Examining Landscape Dynamics at a Watershed Scale Using Landsat TM Imagery for Detection of Wintering Hooded Crane Decline in Yashiro,Japan |
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Authors: | YUANBO LIU SOICHI NISHIYAMA TATSURO KUSAKA |
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Institution: | (1) The United Graduate School of Agricultural Sciences, Tottori University, Koyama 4-101, Tottori-Shi 680-8553, Japan, JP;(2) Department of Biological and Environmental Sciences, Yamaguchi University, 1677-1 Yoshida, Yamaguchi-Shi 753-8515, Japan, JP |
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Abstract: | 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. |
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Keywords: | : Landscape dynamics Watershed scale Landscape pattern metrics Landsat imagery Fragmentation Wintering hooded cranes |
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