Upper montane forest (UMF) within Doi Inthanon National Park, Northern Thailand, was investigated by means of fifty, 40 × 40 m stratified random plots situated between 2080 and 2565 m altitude. The aim was to address a number of community ecological questions concerning woody species composition and structural heterogeneity of the forest. A total of 7474 individuals of trees and woody climbers ≥ 15 cm gbh (girth at breast height) were included in the study and these were identified to 47 species, 39 genera and 26 families. The average density was 934 individuals/ha and the average stem basal area was 71.8 m2/ha. The most important species were: Quercus eumorpha, Sjzygium angkae, Litsea martabanica, Helicia nilagirica, Lindera caudata, Schima wallichii, Osmanthus fiagrans, Eurya acuminata, Myrsine semiserrata and Ilex umbellulata and the most important families were Fagaceae, Lauraceae, Theaceae and Myrtaceae. Altitude was the most important environmental variable explaining species composition and vegetation structure. Most of the calculated vegetation variables showed significant correlation with altitude: species richness, family richness, diversity, density and crown cover declined with altitude, average tree height was uncorrelated with altitude and basal area increased with altitude. An analysis of size class distributions indicated good forest conditions and reverse‐J‐shaped age class distribution of most species.

This study aims to evaluate the roles of community forests managed for different purposes on water storages in plants and soils as the basic information for watershed management. Community forests of Karen people in Chiang Mai province, northern Thailand, were divided to conservation (CF) and utilization (UF) forests. These community forests were classified as pinemontane and montane forests. The number of tree species in the CF and the UF was 256 and 132, respectively. Shannon-Wiener Index in the CF (4.5±0.6) was higher than in the UF (3.4±1.0). Forest biomass was higher in the CF (252.4±72. , respectively. More than 90 % of water was stored in soil. The maximum capacities of water storage within 2 m soil depths of the CF and the UF were 9584 ±934 and 9463 ±233 m 3 ha -1 , respectively. The water storage amounts in soils in rainy season were 73.8 % and 79.2 % of maximum capacities in the CF and the UF, respectively. In winter, the storages changed to 80.5 % and 74.6 %, and in dry season they decreased to be 39.5 % and 23.7 %. Timber harvest in the UF was the main cause of forest degradation and decrease in biomass water storage. The water storage by these community forests can reduce flash flooding and water supply from them is greatly beneficial to the villagers＇ livelihood and also to the lower land communities.

The research assessed water storage in a dry dipterocarp forest (DDF) with enriched 34-year-old pine planting and the role of pine. Plant surveys were carried out using 10, 40×40 m2 plots, and data were obtained by measuring tree stem girths and heights. Plant features, biomass, and stored water amounts were measured. Fresh plant samples of abundant species were taken one time per month from January to December 2018. Three soil pits were made in three plots, and soil samples along 100 cm depth were taken on the same days of collecting plant samples for studying fied capacity, water content and water amount. The DDF was divided into three stands based on the most dominant tree species; Shorea obtusa, Dipterocarpus tuberculatus, and Dipterocarpus obtusifolius. The forest was composed of 86 species with biomass at 101.62 Mg/ha and contained an average water amount of 88.01 m3/ha. The water amount in biomass varied with sampling times from 58.74 to 111.83 m3/ha. The average MWHC of 100 cm soil was estimated to be 5,113.74 m3/ha. The water amount in soil also varied with sampling times from 3,651.50 to 4,481.06 m3/ha. As a result, the total water amount in plant biomass and soil (ecosystem) of the DDF varied in a range from 3,735.0 to 4,558.67 m3/ha. The pine contributed to 30.87 m3/ha (35.07% of the total) and could increase by 64.92% the water storage potential of the forest, and thus these results support the concept of pine enrichment planting in the poor DDF.