4. Water storage in plant biomass Fresh samples of leaf, branch and stem of dipterocarps were taken in December 2015 from four stem-gbh classes: <25 cm, 25-50 cm, 50-75 cm and >75 cm, oven-dried at 75oC until attaining constant weights, and later determined for water contents. The water amount i n biomass was measured by multiplying water content with its biomass. Average water contents of dipterocarps were used for calculating biomass water amounts of other species. III. RESULTS AND DISCUSSION 1. Changes in plant species richness and composition, and community structure A total of 60 species (51 genera, 31 families) existed in the forest in 2010 and decreased to 53 species (44 genera, 27 families) in 2015. This indicated that 7 species, 7 genera and 4 families including 1,084 tree ha-1 disappeared by 2015. Death of many tree individuals happened during this period caused mainly by competition for environmental factors such as space, light, moisture and nutrients. Tree cutting and forest fires were strongly protected in the Center, and were not the cause of tree death. The decrease of species richness resulted in a little change of species composition. In 2010, 7 species including Semecarpus albescens, Giniothalamus laoticus, Stereospermum neuranthum, Casearia grewiifolia, Bredelia retusa, Pterospermum semisagittatum and Ulmus labcaefolia, existed as only one individual within the 12 plots, and had disappeared by 2015. 1.1 Plant community structure Death of many individuals of dominant species resulted in a large change of densities and population structure (Fig.1). Hiang had the highest number of dead individuals, 279 tree per ha-1, followed by Teng (135), Memecylonscutellatum (109), Dalbergia oliverli (76), Gluta usitata (66), Tristaniopsis burmanica (65), Pluang (62), Rang (60), Aporosa villosa (30), Canarium subulatum and Anneslea fragrans (29), Wendlandia tinctoria (23), Garcinia cowa (20), Catuanregum stellatum (18), and Buchanania lanzan (13). Most dead individuals were small trees. 2. Changes in plant species diversity and forest condition 2.1 Plant species diversity Shannon-Wiener Index (SWI) indicates species diversity according the combined concepts of species richness and heterogeneity (Krebs, 1985). Average SWI value was 3.17± 0.32 in 2010 and 3.05±0.29 in 2015; net. change of -0.11. This implied that a small decrease of plant species diversity in the forest had taken place. Tree density in the Hiang stand was 4,763 tree /ha-1 in 2010 and 3,405 tree/ ha-1 in 2015 (net-1, 359 tree/ ha-1). The net. decreases of tree density for the Rang, Pluang and Teng stands were -403 tree/ ha-1, -288 tree/ ha-1 and -1,063 tree/ ha-1, respectively. The net. increase of importance value index (IVI) was the highest for G. usitata, 0.67%, followed by Hiang (+0.48%), Rang (+0.38%), A. villosa (0.11%), and M. scutellatum (0.06), while a net. decrease was found for Teng (-0.06) and Pluang (-0.17). 2.2 Forest condition: Average FCI values in 2010 and 2015 were 1.94±1.98 and 2.27±1.36, respectively; with net. change of +0.33. The DDF had a small FCI increase between the year 2010 and 2015. However, there were some differences among the stands. The net. increase was observed in the Hiang, Rang, and Pluang stands (+0.43, +0.65 and +0.27, respectively), but the Teng stand had net. decrease (-0.97). Proceedings of the International Conference on Climate Change, Biodiversity and Ecosystem Services for the 25 Sustainable Development Goals (SDGs): Policy and Practice 27-29 June 2016, Cha-am, Phetchaburi, Thailand
Proceedings of International Conference on Climate Change, Biodiversity and Ecosystem Services for the Sustainable Development Goals : Policy and Practice 27-29 June 2016 at the Sirindhorn International Environmental Park, Cha-am, Phetchaburi, Thailand
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