Vegetation Dynamics Over a 10-Year Period in a Dry Dipterocarp Forest in Mae-Huad Sector, Ngao Demonstration Forest, Lampang Province

Abstract

The objective of this research was to study the dynamics of vegetation in a Dry Dipterocarp Forest (DDF) in Mae-Huad Sector, Ngao Demonstration Forest, Lampang Province. The research samples consisted of remeasured vegetation in 14 permanent plots established in 2001, as part of an International Tropical Timber Organization (ITTO) study. The remeasured vegetation data were collected in February, 2012 to compare with past data. They consisted of tree species, DBH, status (live, mortality, cut), number of trees, saplings and seedlings. Data were analyzed density, importance value index, diversity index, stand volume growth and diameter class distribution.

            The result was demonstrated that, from 2001-2012, the density of trees increased from 177±38.56 tree/rai to 199±37.46 tree/rai; sapling decreased from 9±2.62 tree/rai to 8±1.66 tree/rai; seedlings decreased from 213±68.78 tree/rai to 30±10.22 tree/rai. The importance value index ranking changed over time for some species. The average tree diversity index decreased from 2.19±0.16 to 2.06±0.20, with no statistically significant difference (p ≤ .05). In terms of stand volume growth, the gross growth increased by 4.40 m³/rai. The net growth decreased by 0.16 m³/rai. This mean that mean mortality rate was higher than the increment. The average mortality rate was 4.57±0.57 m³/rai, the average of wood cutting was 0.27±0.16 m³/rai, while the average ingrowth was 1.26±0.21 m³/rai, and average volume increased by 0.83±0.27 m³/rai, with no statistically significant difference (p ≤ .05). Diameter class distribution at each time was an inversed J - shape curve, which indicates that dry dipterocarp forest in Mae-Huad sector, Ngao demonstration forest, Lampang province resembled a natural forest.

Keywords:  Vegetation dynamics, Dry dipterocarp forest, ingrowth, Ngao Demonstration Forest