Site requirements for re-establishment of Hopea odorata Roxb. on degraded lands

Site-species matching is vital for successful reforestation. This study examined the site conditions for seedling growth and development of Hopea odorata Roxb. in a secondary natural evergreen dipterocarp forest in South Vietnam and in artificial gaps in an Acacia hybrid plantation on degraded land in Central Vietnam. The per cent transmitted incident daily photosynthetically active radiation (PAR) near the forest floor of around 11% was necessary for active seedling development in the natural forest. In the plantation, a positive response of seedling growth and photosynthetic rate up to a transmitted PAR level of around 60% was observed. This suggests that while H. odorata is shade-adapted, higher light levels are required to maximise its potential growth rate. Soils with low nutrient concentration associated with low clay and high sand contents appeared not to constrain the growth of H. odorata seedlings given adequate light conditions. Vigorous growth of seedlings in soils ranging from slightly acidic in the natural forest to very acidic in the plantation indicates that this species can adapt to a wide range of soil acidity. Successful re-establishment of H. odorata on degraded sites using nurse crops should be possible provided that high levels of shading are avoided.