Drivers of Native Species Regeneration in the Process of Restoring a Dry Evergreen Forest from Exotic Tree Plantations in Northeastern Thailand

Abstract

Establishment of exotic plantations is one of the most effective ways to induce natural regeneration for the restoration of degraded lands, as it has the potential to improve soil properties and creates favorable microclimates. This study aims to determine the effects of stand structure and composition as well as environmental factors under the canopies of three exotic plantations in northeastern Thailand on the regeneration of native species. For each plantation, we conducted three 10 m × 150 m transect lines with fifteen 10 m × 10 m subplots along a forest remnant gradient. The canonical correspondence analysis (CCA) was used to identify the environmental factors responsible for the differences in natural regeneration among these stands. Three exotic plantations had different stand structure in terms of number of tree species, basal area, and tree density but similar dominant native tree species. Across all stands, 74 native tree species, 60 genera, and 30 families were observed. Some physical and chemical properties in the topsoil were significantly different between species but similar among stands within a species. On the other hand, differences in environmental factors such as RLI were significant among species and stands within a species. The CCA ordination identified that the soil particles, soil pH, and light intensity were key factors influencing the native species composition, which could be categorized into three groups: drought-tolerant pioneer species; light-demanding pioneer species; and shade-tolerant climax species. However, most of the climax species were incapable of regenerating and maturing along the forest edge gradient to plantation stands. To accelerate the restoration process by converting these old exotic plantations to a dry evergreen forest, further research is required to determine the appropriate canopy management and/or dominant climax species for planting beneath their canopies.

Effect of Thinning on Growth and Wood Production of Naturally Regenerated 8-Year-Old Acacia Mangium Willd. Plantation on Abandoned Mining Area, Southern Thailand

“…Leaf production of A. mangium is not the main objective of a commercial plantation. However, the contributions of leaf biomass and leaf litter were reported to be the most significant in terms of nutrient return to the forest floor (Nambiar & Hardwood 2014;Wongprom et al 2022), as A. mangium leaf is rich in nutrient concentration, especially nitrogen. It therefore plays an important role in increasing the soil nutrients, improving the soil properties (Wongprom et al 2020), and promoting nutrient supply for stand growth (Hardiyanto & Nambiar 2014).…”

“…The reclamation of mining area was undertaken by planting A. mangium, given its growth and high aboveground biomass compared to other fastgrowing or native tree species (Martpalakorn 1990). Additionally, A. mangium has reportedly been recommended to rehabilitate degraded lands with a high survival rate (Majid et al 1998) to restore the soil properties, forest structure, and nutrient cycling (Wongprom et al 2020;Wongprom et al 2022;Staporn et al 2022).…”

Teak (Tectona grandis Linn. f) and Edaphic Factors Affecting the Regeneration of Woody Species and Their Functional Traits in Economic Forest Plantation, Northern Thailand

“…However, commercial plantations are usually planted in monocultures that are expected to have lasting efects on forest structure, diversity, and functioning [6]. Terefore, promoting the natural regeneration of other native plants in plantations could enhance plant diversity and promote forest structures and functions that are closer to those of the natural forests [7][8][9].…”