Environmental Factors Influencing Tree Species Regeneration in Different Forest Stands Growing on a Limestone Hill in Phrae Province, Northern Thailand

Abstract

Improved knowledge of the environmental factors affecting the natural regeneration of tree species in limestone forest is urgently required for species conservation. We examined the environmental factors and tree species characteristics that are important for colonization in diverse forest stands growing on a limestone hill in northern Thailand. Our analysis estimated the relative influence of forest structure and environmental factors on the regeneration traits of tree species. We established sixty-four 100-m 2 plots in four forest stands on the limestone hill. We determined the species composition of canopy trees, regenerating seedlings, and saplings in relation to the physical environment. The relationships between environmental variables and tree species abundance were assessed by canonical correspondence analysis (CCA), and we used generalized linear mixed models to examine data on seedling/sapling abundances. The CCA ordination indicated that the abundance of tree species within the mixed deciduous forest was closely related to soil depth. The abundances of tree species growing within the sink-hole and hill-slope stands were positively related to the extent of rocky outcropping; light and soil moisture positively influenced the abundance of tree species in the hill-cliff stand. Physical factors had a greater effect on tree regeneration than did factors related to forest structure.Tree species, such as Ficus macleilandii, Dracaena cochinchinensis, and Phyllanthus mirabilis within the hill-cliff or sink-hole stand, colonized well on large rocky outcroppings that were well illuminated and had soft soils. These species regenerated well under conditions prevailing on the limestone hill. The colonization of several species in other stands was negatively influenced by environmental conditions at these sites. We found that natural regeneration of tree species on the limestone hill was difficult because of the prevailing combination of physical and biological factors. The influence of these factors was species dependent, and the magnitude of effects varied across forest stands.

Review: Biodiversity of forests over limestone in Southeast Asia with emphasis on the Philippines

“…Limestone landscapes are comprised of several diverse plant communities and are floristically unique compared to other forest types. The varied ecological niches and intricate terrains that can be found within the limestone landscapes result in high species diversity of the area (Asanok and Marod 2016;Clements et al 2006;Saw et al 2010). The surface rock layer of limestone landscapes has innumerable perforations and hollow areas that allow rainwater to drain fast underground.…”

Edaphic Influences on Tree Species Composition and Community Structure in a Secondary-Lowland Dipterocarp Forest of Kota Damansara Forest Reserve, Selangor

“…The variations of floristic composition have been correlated with habitat variables and this correlation has created certain trends in the distribution and abundance of organisms. The abundance of tree species is primarily due to their favorable environmental condition where the same dominant species would be found under similar environmental conditions while different dominants are likely to be present at sites with varying environmental conditions (Asanok & Marod, 2016). Climate and edaphic factors are among the important environmental factors and drivers for the distribution of tree species (Walthert & Meier, 2017).…”

The influence of environmental factors on species composition and distribution in a community forest in Northern Thailand

“…For example, higher soil sand ratio lessens water-holding capacity that can lead to water stress on trees (Aranguren et al 1982;Toledo et al 2012;Zhang et al 2013), and acidity levels affect the distribution of species and is linked to slope and elevation in lowland tropical forests (Nguyen et al 2015;Vahdati et al 2017). Soil moisture also significantly changes the growth patterns of trees in drought areas (Fu et al 2004;Yoshifuji et al 2006;Asanok and Marod 2016;Tilk et al 2017).…”