Effect of land use changes on ecosystems in Khlong U-Taphao Basin
ผลกระทบของการใช้ที่ดินที่มีต่อระบบนิเวศในลุ่มน้ำคลองอู่ตะเภา
Charlchai Tanavud, Asst. Prof., D. of Earth Sci., F. of Natural Resources, PSU.
Pramoth Kheowvongsri, D. of Earth Sci., F. of Natural Resources, PSU.
Chao Yongchalermchai, D. of Earth Sci., F. of Natural Resources, PSU.
Omthip Densrisereekul, D. of Earth Sci., F. of Natural Resources, PSU.
Abdollah Bennui, Researcher, Office of Research and Development, PSU.
Jun Murase, F. of Environmental Sci., U. of Shiga Prefecture, Japan
Ken-ichi Kakuda, F. of Agriculture, Yamagata U., Japan
Makoto Kimura, Graduate School of Bioagricultural Sciences, Nagoya U., Japan
Grant : Prince of Songkla University
Published : Research Report
Key words : land use changes, soil erosion, soil and water quality, conservation and manage-ment strategies, Khlong U-Taphao Basin
Amidst the growing concern about land use change, this article examines pattern of land use, investigates effects of land use changes on soil and water components of ecosystems with specific reference to the Khlong U-Taphao Basin, Southern Thailand. During the period from 1967 to 1996, erstwhile existing forests in the basin declined by 77% contributing to a 60% increase in rubber plantation area. The rapid depletion of natural forests was largely attributed to the expansion of rubber plantation area and illegal logging. Results obtained from runoff plot experiments established in
rubber plantation areas showed that soil losses in plots where traditional farming practices were used were seven times greater than in the natural forest areas. Rates of soil loss in farmers' plots could be reduced by 73%, 42% and 45% by the application of straw mulch, legume cover and vetiver grass, respectively. Mulching with rice straw was more effective than cover crops or grass strips in reducing runoff and soil erosion. Findings also revealed that erosion in the farmed plots significantly decreased soil organic matter content, concentration of total nitrogen and plant available water resulting in a reduction in soil quality. Generally, the values of electrical conductivity, total suspended solids, tur-bidity, nitrate nitrogen and orthophosphate were initially low in the river draining the forest and pro-gressively increased in a downstream direction. In contrast, the highest concentration of dissolved oxygen was recorded in the upstream forest part of the river and progressively decreased in a down-stream direction. Increases in total suspended solid and turbidity, and high nutrient loading in the
river lead to the degradation of river water quality. A strategy which would support sustainable use
of land resources and maintain environmental quality is discussed.
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