FOREST RESOURCES AND ECOLOGICAL FACTORS IN NAM NGUM WATERSHED

Abstract

Rapid determination of forest resources and ecological factors in Nam Ngum watershed was carried out to provide estimates of volume of submerged trees in the reservior and to collect related ecological data in area surrounding the reservoir.

Aerial survey photograph prior to the construction of the dam were used to develop forest area map. Direct observation from helicopter were useful both for vegetation surveys and marking sample plots location.

Climatic condition of the Nam Ngum area are favorable for a dry evergreen forest. Lithosols underlain by sandstone occupy much of the area. Major piece of forest occur on sandstone. The forest is dominated by Dipterocarpaceae (200 to 400 per hectare) in the upper story, with a sub-story of various species (400 to 900 per hectare) and various lianas (350 to 450 per hectare). Biomass estimates of the vegetation is approximately 1600 tons/hectare.

The submerged vegetation has been proved to be the same types of forest as found on shore. The submerged trees at depths greater than 6 m. will remain intact as long as anaerobic condition persist since anoxic retard decay. Tree of economic value estimatedly 2.7 million m³ and fuel wood of 2 million m³ remained underwater for 12 years will be harvested by Thai firm. This huge underwater logging project has received approval from the Government of the two countries (see Annex).