Forest fires have increasingly become a frequent and problematic hazard in Thailand. Fires are a major element of risk particularly on national parks – areas marked for protecting and preserving the flora and fauna and their habitats. Therefore, studies on vulnerabilities to forest fires are essential in properly managing the biodiversity of a place.

Thailand has suffered a rapid decline in forest cover over the past three decades, loosing more than half of its forested area. With a total forest cover of 60% in 1953, Thailand has only about 25% cover remaining now. Recent satellite images show even less cover. This rampant destruction of forest cover is due to logging concessions, encroachment and development of infrastructure such as roads, hydropower plants and mining. The practices of shift-cultivation and slash and burn are still prevalent in northern Thailand, where forests are estimated to cover more than 40% of the land area. A strong link has been established between forest cover and plant diversity. In order to find the changes in plant diversity, and the level of vulnerabilities to forest fires a comparative study of two locations: a two-hectare plot of a deciduous dipterocarp-oak forest, in Doi Suthep-Pui national park of northern Thailand, protected against fire for 28 years and a similar, but frequently burnt forest nearby was undertaken.

A total of 130 plant species, with 29 trees and 101 ground flora species was recorded from the sampled area. The protected area supported a richer ground flora community compared to the burnt area although the species richness of tree community was very similar in both areas. The protected area contained slightly more unique and exclusive species, in comparison to that of the burnt area. It was found that the greater the density of tree population in the protected area the direct consequence of fire protection was more. The protected area contained 25% more individual trees than the burnt area. Also, it has more young trees of DBH (diameter at breast height) 10-20 cm category than in the burnt area. This suggests that forest fire protection decreased the killing or damaging of trees, which ultimately leads to increased productivity and organic matter in soil, thus more favorable conditions for growing. This result also supports the facts that young plants are more badly affected by fires than mature ones. Fire protection seemed to have more impact on the herbaceous community than trees. Almost half of the ground flora species recorded was specific to each site. The majority of herbaceous species in the protected areas were typically of moist condition and some species found in the burnt area were fire resistant. 

The greater influence of evergreen or tropophyllous trees and the presence of some shade-loving herbaceous flora in the protected area suggest that the forest environment in the protected area was favored by plant associated with a mixed evergreen and deciduous forest. However, no distinct differentiation was observed. The higher tree density and more young trees of 10-20 cm DBH category in the protected area adds support to the idea that the fire protection decreased mortality and damage to trees which ultimately leads to more favorable conditions for different species to grow.

This article is extracted from a paper presented at the International Symposium on Remote Sensing of Environment held in Cape Town, South Africa. 

Shesh Kanta Kafle is Environmental Risk Analyst and Planner and is currently Training Manager, Partnerships for Disaster Reduction for South East Asia Project Phase-3 at ADPC. He can be contacted at skkafle@adpc.net