STRUCTURE AND REGENERATION CHARACTERISTICS OF DECIDUOUS BROADLEAF POORFOREST IN NINH SON WARD, KHANH HOA PROVINCE

Abstract

This results of a study on the forest structure and tree species diversity of poor forest in the deciduous forest, Ninh Son ward, Khanh Hoa province, Vietnam. The objective of the study was to identify the structural characteristics and species diversity of woody plants to support forest management and biodiversity conservation. The data were collected from 15 plots, 0.1 ha each. Information recorded in these plots included tree species composition, forest density, diameter at breast height (DBH), tree height of all woody individuals. The results identified 20 species belonging to 18 genera and 11 families. The most species-rich families were Rubiaceae, Anacardiaceae, Dipterocarpaceae, Ebenaceae, Fabaceae; among these, Dipterocarpaceae was the dominant family. The dominant and co-dominant species included Shorea siamensis, Dipterocarpus intricatus, Parinari annamensis. Tree composition, density, volume were mainly concentrated in the DBH class ≤ 20 cm and height class 10 < H ≤ 15 m. The average volume was 85.4 m³/ha, with an average density of 755 trees/ha; mean DBH and height were 15.8 cm and 9.9 m, respectively. The diameter and height class distributions exhibited left-skewed of curve and fitting on Weibull distribution. A total of 19 regenerating tree species were recorded, with high similarity to the adult (91% at the family and 92% at the species). Natural regeneration density was relatively high (4,245 trees/ha), with regeneration occurring continuously under the forest canopy; more than 90% of regenerating individuals were of good quality and showed adequate numbers for future succession. Species and family diversity indices were relatively low (H’_family = 1.02; H’_species = 1.50). A total of seven rare and valuable tree species listed in the IUCN Red List (2024) were recorded, including one species listed in the Vietnam Red Data Book and one species protected under Decree No. 84/2021/ND-CP: Vitex pinnata, Dalbergia oliveri, Shorea siamensis, Dipterocarpus intricatus, Randia tomentosa, Nauclea orientalis, Shorea roxburghii. Three species were based on rarity index (RI), including Vitex pinnata, Morinda tomentosa, Canarium album.