Vegetation Structure and Floristic Composition along the Edge of Montane Forest and Agricultural land in Um Phang Wildlife Santuary, Western Thailand

Abstract

The impacts of agricultural practices on vegetation changes along forest edges were studied by the selection of appropriate native species for reforestation in degraded lower montane forest (LMF) in the Um Phang Wildlife Sanctuary, Western Thailand. Three different land use practices, abandoned area (AB), annual cropping (AC) and shifting cultivation (SC), were selected for studying the changes in vegetation structure and species composition along a gradient from the interior of LMF into adjacent agricultural lands. At each land use site, three belt transects of 20 × 150 m were established perpendicular to the forest-agriculture edge. The vegetation transect census recorded the living numbers of seedlings, saplings and trees, excluding lianas, and the stem diameter and height were measured for saplings and trees. The light and soil conditions in every belt transect were also investigated. In total, 78 tree species in 73 genera and 40 families were found across all sites. The ShannonWeiner diversity index (H/) values were significantly higher in the remnant forest (RF) than near-to-edge (nAL) and distant-from-edge (dAL) and the species composition at the forest edge consisted mainly of secondary shrubs and tree species. From the RF toward the edge, numbers of seedlings, saplings and secondary trees increased, while numbers of mature forest trees declined. Environmental factors—namely, relative light intensity (RLI), soil moisture content (SMC) and soil bulk density (SDb)—were significantly (P < 0.05) different along the forest edge. The plant species, Shima wallichii, Eurya accuminata, and Collona elobata, had a high correlation that was intermediate between the RLI and SMC gradients, especially in nAL. Thus, these species should be strongly supported in programs associated with the ecological restoration of LMF.