Sediment Discharge through Buffer Zones in a Tropical Rainforest of Peninsular Malaysia

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概要

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• To prevent soil runoff from logging roads and skid trails, buffer zones are commonly established along both sides of streams. These buffers range in width from 10 to 100 m from the center of the stream, depending on stream width, (from 1 to › 40 m) as dictated by the Reduced-Impact Logging Guidelines for Lowland and Hill Dipterocarp Forests in Indonesia. In the Bukit Tarek Experimental Watershed in Malaysia, sediment accumulations were observed along narrow streams after logging despite the presence of 20-m-wide buffer zones, double the width set out in the guidelines. Thus, we examined erosion-accumulation depths on different slopes in 20-m-wide buffer zones to clarify the spatial effects on sediment discharge, particularly as it relates to the microtopography and the vegetation cover, including fallen trees. Some of the accumulation depths at lower elevations and along streams were small, whereas on steep concave slopes and hollows that extend to streams, large accumulations were observed 1 year after logging. These findings indicated that, although a 20-m-wide buffer zone may be partly effective at preventing sediment discharge, it is not adequate on concave slopes (lower side-hollows and channel walls) where surface flows often converge. We compared several physical properties of the surface soil in accumulated areas relative to undisturbed areas and demonstrated that bulk density was larger and total porosity and coarse porosity were smaller in the accumulated soils, especially on lower side-hollows. These results indicate that soils accumulated on concave slopes would accelerate the occurrence of surface flow. Tree distribution was not dense in the buffer zones, but fallen trees and the relatively dense understory vegetation including rattans and palms partly prevented the discharge of sediment into streams. Our findings suggested that 20-mwide buffer zones with dense fallen trees and understory vegetation are partly sufficient to prevent sediment discharge; however, along steep concave slopes and hollows where rain water converges, wider and thicker buffer zones are needed.

著者

• Noguchi Shoji

  Forestry and Forest Products Research Institute

• Nik Abdul

  Forest Research Institute Malaysia

• NIK Abdul

  Forest Research Institute of Malaysia

• OHNUKI Yasuhiro

  Department of Forest Site Environment, Forestry and Forest Products Research Institute

• SASAKI Shozo

  Forestry Division, Japan International Research Center for Agricultural Sciences

関連論文

• Spatially Distributed Morphological Characteristics of Macropores in Forest Soils of Hitachi Ohta Experimental Watershed, Japan
• Rainfall-runoff Responses and Roles of Soil Moisture Variations to the Response in Tropical Rain Forest, Bukit Tarek, Peninsular Malaysia
• Soil Physical Properties and Preferential Flow Pathways in Tropical Rain Forest, Bukit Tarek, Peninsular Malaysia
• Distribution and Physical Properties of Colluvium and Saprolite in Unchannelized Valleys in Tsukuba Experimental Basin, Japan
• Effect of inter-annual climate variability on evapotranspiration and canopy CO_2 exchange of a tropical rainforest in Peninsular Malaysia
• Sediment Discharge through Buffer Zones in a Tropical Rainforest of Peninsular Malaysia

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