Stand structure of a seasonal dry evergreen forest at Huai Kha Khaeng Wildlife Sanctuary, western Thailand

We describe the structure of a stand of seasonal dry evergreen forest located in the Huai Kha Khaeng Wildlife Sanctuary (HKK), Uthai Thani Province based on a census of all trees ~l cm dbh in a 50-ha plot. Mean densities were 1,613 trees ha-l (~l cm dbh), 439 trees ha-l (~10 cm), and 3.74 trees ha-l (~100 cm). Mean basal area was 30.45 m2 ha-l (~1 cm dbh), 28.69 m2 ha-l (~10 cm dbh), 5.57 m2 ha-l (~100 cm dbh). The stand structure (density and basal area) of the seasonal dry evergreen forest at HKK is comparable to published reports of stand structure for other seasonal evergreen forests in Thailand and would appear to be gen- erally representative of the forest type. The HKK plot was much less dense (1,613 trees ha-l ~1 cm dbh) than similar plots in Malaysia (6,769 trees ha-l ~1 cm dbh) and Panama (4,882 trees ha-l ~1 cm dbh), although had similar values for total basal area. The major difference between the forest types was in the density of the saplings. For trees ~10 cm dbh the seasonal dry evergreen forest plot was as dense or denser than the lowland tropical forest plots. Individual tree species' diameter distributions exhibited a variety of forms, from negative exponential to unimodal to irregular; however, among the 20 most common species unimodal and irregular diameter distributions were twice as frequent as negative exponential distribu- tions. The diameter distribution of Hopea odorata Roxb., the species with the greatest basal area on the plot, was unimodal and approximately normal. These results suggest that the area in and around the HKK plot may have been subject to a large-scale catastrophic disturbance.