| Co-Investigator(Kenkyū-buntansha) |
TANAKA Sota Kochi University, Faculty of Agriculture, Assistant Professor, 農学部, 助手 (10304669)
NINOMIYA Ikuo Ehime University, Faculty of Agriculture, Professor, 農学部, 教授 (80172732)
HARADA Ko Ehime University, Faculty of Agriculture, Professor, 農学部, 教授 (40150396)
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| Research Abstract |
1.Experimentalr Shifting Cultivation and its Effects on Soil Ecosystems
At four experimental plots, we carried out experimental sifting cultivation in 2001-2003, we surveyed there and analyzed the soil samples after the cultivation of upland rice. In Balai Ringin and Niah where clayey soil distributes, the organic matter and nutrients in the soils were maintained, and vegetations recovered well after harvesting. In Sabal where sandy soil distributes, both of them decreased significantly, vegetation recovery was poor. On the other hands, in Bakam where small amount of biomass burned, soil fertility was low before harvesting, and vegetations in the secondary forest was extremely poor. In previous time, Iban people used to burn a primary forest and a secondary forest well-recovered, and to cultivate the upland rice continuously. This farming method was essential to amend soil acidity and add nutrients into the soil in this area where strongly-weathered soils predominate. Hence, in order to
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develop the alternative farming methods from sifting cultivation, we have to consider not only the soil erosion, but also the soil texture and acidity. On the other hands, sandy soil areas are not possible to be utilized for farming, and therefore, should be conserved as forests.
2.Vegetational Recovery after Shifting Cultivation and their Response to the Degraded Environment
We investigated the vegetation recovery and the ecophysiology of planted trees at the plots after 2 years of sifting cultivation. The growths of stem diameter, height, and biomass of recovering vegetation in the burned plots increased with the increments of fire intensities. Thus, the appropriate burning facilitated the vegetation recovery.
3.Construction of Gene-Data Bank in Sarawak and the Study of Genetic Variation in Tropical Trees
The 5000 individuals of tree samples, mainly Dipterocarpaceae, were collected to extract DNA analysis at 8 National Parks, five man-made forests, and Forest Reserves in Sarawak, and the gene-data bank was built. The population genetic structures were analyzed for Dryobalanops aromatica, D.lanceolata, Shorea beccariana, and S.macrophylla by using AFLP, micrpsatellite and chlorophyll variation. Less
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