SEEDLING ESTABLISHMENT OF CLIMAX SPECIES UNDER THE EUCALYPTUS PLANTATIONS AND OPEN AREAS

Abstract

Reforestation is one of the good methods for sere shortening and rehabitation in the disturbed forest areas. Fast growing pioneer species are commonly recommended at the first stage of the plantation process, however, the final target is how to mix the native climax species into the successional process. To support this concept, the studies were conducted in the disturbed dry evergreen forest, DEF, areas at the Forestry Training Station, Amphoe Wang Nam Khiew, Changwat Nakhon Ratchasima during March 2001 to February 2002. Nine tree species, Hopea odorata, Shorea henryana, S. roxburghii, S. siamensis, Dipterocarpus alatus, Dialium cochinchinense, Pterocarpus marcrocarpus, Xylia xylocarpa, and Peltophorum dasyrachis, were selected to test for seedling survival in the three difrent habitat conditions under the gap of 4 and 20 years old Eucalyptus plantations and the open areas. The results showed that the soil moisture had minor variation among the three sites but in 20-year old Eucalyptus plantation of the top layer had much higher soil moisture nearly all year round. There was no difference among the middle soil layers. The standard sky overcast distribution was lowest under the 20-year old plantation and highest under the open areas. The seedling survival reflected that the seedling of dominant tree species in the DEF performed well under the 20-year old plantation. In contrast, the dominant tree seedlings in the deciduous dipterocarp forest, DDF, and the mixed deciduous forest, MDF, had very high survival and height growth rate under the 4-year old plantation and the open areas. The allocations of root and stem biomass indicated that tree seedlings from the DEF were balanced, around 1, while the ratio of tree seedlings from the other two forest types, DDF and MDF, had over than 1. It is recommended that suitable seedlings for rehabitation in the old plantation such as in the 20-year old Eucalyptus plantation should be the dominant tree from DEF, such as Shorea henryana, Hopea odorata, Dipterocarpus alatus and Dialium cochinchinense and for the young plantations or new disturbed areas should be planted such as, Shorea siamensis, Pterocarpus marcrocarpus, Xylia xylocarpa and Peltophorum dasyrachis. While, Shorea roxburghii can be planted both under the open and close canopy.