Expansion of bamboo forests caused by reduced bamboo-shoot harvest under different natural and artificial conditions |
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Authors: | Shigeo Suzuki Nobukazu Nakagoshi |
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Institution: | (1) Graduate School for International Development and Cooperation, Hiroshima University, 1-5-1 Kagamiyama, Higashi-Hiroshima 739-8529, Japan |
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Abstract: | To elucidate the expansion of bamboo (Phyllostachys pubescens Mazel ex Houzeau de Lehaie) forests, we used multiple linear regression analysis and determined whether there were site differences
for data obtained in Hirasawa, Otaki-machi, Chiba Prefecture, and Kofuki, Takehara City, Hiroshima Prefecture, Japan. Vegetation
maps from 1984 and 2001 for Hirasawa, and from 1986, 1996, 2000, and 2006 for Kofuki, were compared, and the annual expansion
rate of each P. pubescens forest was calculated. We evaluated nine indices, including original bamboo forest area, neighbouring vegetation, slope inclination
and aspect, distance from roads, and shipment of bamboo shoots. Shipment of bamboo shoots was a positive factor for P. pubescens forest expansion, whereas the proportion of adjacent short vegetation, northness (the cosine of slope aspect), and area negatively
affected the expansion in Hirasawa (R
2 = 0.683). On the other hand, distance from roads and eastness (the sine of slope aspect) positively affected expansion, while
slope inclination was a negative factor in Kofuki (R
2 = 0.942). We calculated that P. pubescens forests expanded at about 2% per year in regions of reduced shipments of bamboo-shoot harvest. We showed that not only natural
conditions but also management factors affect P. pubescens forest expansion. Regional differences in natural and anthropogenic effects on expansion were also found. |
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Keywords: | Aging of agricultural workers Bamboo forest expansion Invasive plants Multiple linear regression analysis Topography |
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