GROWTH OF NATIVE FOREST SPECIES PLANTED ON ABANDONED PASTURE LAND IN COSTA-RICA

Many forest plantations in the humid neo-tropics are established on de graded soils in abandoned pasture land and, with some exceptions, the species planted have not grown successfully. Studies of adaptability a nd growth under these conditions are scarce, particularly for native s pecies. In this paper we present data on growth and tree form at 3 yea rs of age for 11 species planted in abandoned pastures. The research p lantation was established at La Selva Biological Station, in the Atlan tic lowlands of Costa Rica (10 degrees 26'N, 83 degrees 59'W). Surviva l, diameter at breast height (DBH),total height, basal area, volume in dex and tree form were used to evaluate the species performance. After 3 years, Vochysia guatemalensis displayed a survival significantly hi gher (98%) than that of the other species. The lowest survival was 75% for Pinus tecunumanii. There were significant differences in growth m easures among species. Acacia mangium exhibited significantly higher g rowth rates than the other species. Although this species grew rapidly , it did not develop straight single stems. About 14% of trees of A. m angium had bifurcation below DBH and more than 50% showed multiple axe s or branches as large in diameter as the principal axis. The native s pecies with the highest growth rate was Vochysia guatemalensis (DBH 12 .7 cm, total height 7.5 m, volume index 55 m(3) ha(-1) at 3 years of a ge). Vochysia ferruginea exhibited a slightly lower growth rate. Both Vochysia species were ranked highly with regard to tree form, with mor e than 80% straight single stemmed trees. The lowest growth rates were exhibited by Pentaclethra macraloba, Pirhecellobium macradenium and V irola koschnyi; however, the latter two species formed straight single stems. Pentaclethra macroloba and Inga edulis failed to form straight single stems. In general, the growth rates of the species studied wer e high in comparison with results reported from other tree plantations in the tropics. In spite of this, it is not prudent to draw final con clusions on the basis of these 3 year measurements.