Species Diversity and Tree Seedling Dynamics in Moist Evergreen Rain Forest at Khlong Naka Wildlife Sanctuary, Ranong Province.

Abstract

Background and Objectives: Recently, the current climate change, the reproduction of seedlings that respond relatively quickly to changes in environmental factors may be affected. This study aimed to clarify the impact of micro-climate on the establishment of seedlings in moist evergreen forest at Khlong Nakha Wildlife Sanctuary.

Methodology: Fifty seedling quadrats; The plot of 2 ´ 2 m, were established and all tree seedling were tagged and identified. Seedling monitoring was done every month from February 2023 to January 2024. In addition, the data logger with automated recorded for temperature and light intensity was also set up. Data analysis includes the importance value index (IVI), diversity index, recruitment rate, mortality rate, and climate change. 

Main Results: The total seedlings species of 128 species 83 genera and 39 families was found the seedling density is 47,100 individual. ha-1 and which had high species diversity based on Shannon-Weiner index (H/= 4.33). The dominance species based on importance value index (IVI) was Ixora javanica, Cinnamomum altissimum, Rinorea sclerocarpa, Syzygium attenuatum, and Diospyros wallichii, with values of 8.81, 8.68, 7.84, 7.31, and 6.17 percentage, respectively. Seedling dynamics during one year showed that the recruitment rate had higher than mortality rate, almost five times (5.57 ± 3.79 and 0.27 ± 0.42 %.m-1). Especially, the mortality rate is very high during the dry season (December-February), which corresponds with low rainfall, high temperatures, and high light intensity throughout the year. Although mortality and recruitment rate vary between species, the species with the highest recruitment rate are Hopea montana, Hopea subpeltata, Hopea griffithii, Parashorea stellata, and Diospyros ranongensis. These species are mostly dominant trees in Thailand's tropical rainforests. In contrast, species with high mortality rates include Gaertnera vaginans, Greenea corymbosa, and Mischocarpus pentapetalus which are secondary trees in the rainforest. However, Dipterocarpus kerrii and Mesua ferrea which are also dominant species, exhibit high mortality rates during the dry season.

Conclusion: Micro-climate changes obviously showed high impacted on seedling regeneration, in particular increased drought event. This knowledge on seedling adaptation is useful for species conservation planning, in particular, susceptible species to maintain their species in the forest ecosystem.

Keywords: Seedling dynamics, species diversity, regeneration, micro climate change