A Comparison of Ground Flora Diversity between Forest and Plantations in Doi Suthep-Pui National Park.

ABSTRACT: Ground flora diversity was compared among old-growth forest and tree plantations in Doi Suthep-Pui National Park from March to December 1994. Five study sites, viz. evergreen forest, a forest regenerating gap, a eucalyptus plantation and a mature and a young pine plantation were selected. An extensive qualitative survey and an intensive quantitative survey were carried out. One hundred permanent quadrats (2m x 2m) were used for the intensive ground flora surveys. All plants rooted in each quadrat were identified and scored for percent cover and Domin score every month. Soil samples were also collected and analyzed for texture, % organic matter, soil moisture at field capacity, pH, nutrients, etc. at the Faculty of Agriculture, Chiang Mai University. Soil moisture content was determined monthly.

The total number of species recorded in the extensive qualitative survey was higher than that in the intensive quantitative survey. In the extensive qualitative survey, the numbers of species, recorded in evergreen forest, regeneration gap, eucalyptus, mature and young pine plantations, were 174, 105, 86, 102,and 138 respectively. Herbaceous plant species dominated the ground flora in all five sites for both surveys. The highest species diversity (Hill's number, N1 and N2) and Evenness (Modified Hill's ratio) occurred in evergreen forest (55.91, 35.69 and 0.63; respectively) and the lowest was in the mature pine plantation (16.46, 6.88 and 0.38; respectively). The similarity (Sorensen's index) of mature and young pine plantations was 0.66, while between regenerating gap and mature pine plantation it was 0.46. The highest relative growth rate (RGR) of tree seedlings was 0.234 cm growth/cm of original height/year in the regenerating gap, whilst the lowest was 0.017 cm growth/cm of original height/year in the mature pine plantation. The highest percent mortality of tree seedling was 15.60% in the mature pine plantation, while the lowest was 3.27% in the forest.

Cluster analysis and ordination, using percent cover and soil characteristics, had more or less the same result. Cluster analysis, using the average percent cover from 100 quadrats (20 quadrats of each site), clearly distinguished three main groups. The first cluster included quadrats from the mature pine plantation and regenerating gap. The second group clustered together quadrats from the eucalyptus plantation and the forest. The third group included quadrats from the mature pine site and the young pine plantation. Ordination showed significant differentiation amongst five sites. Mature pine and young pine were very similar, whilst the regenerating gap was similar to both the forest and eucalyptus sites.

The use of indigenous species was recommended to conserve biological diversity within Doi Suthep-Pui National Park. It can be concluded that to preserve maximum biodiversity in either pine or eucalyptus plantation, young pine trees are better than eucalyptus. To allow best regeneration of forest trees, a pine plantation can be used for the early stages of regeneration, but after that, the pines should be selectively cut down to allow other tree seedlings and saplings to grow naturally.