Amelioration of Degraded Rain Forest Soils by Plantations of Native Trees

Abstract

AbstractEmpirical evidence from temperate Europe and North America indicates that old‐field succession, resulting in reforestation and a protracted period of forest fallow, can improve soil condition on lands once badly degraded. However, the ability of trees to ameliorate degraded sites in the tropics is widely debated. In 1988 eight native tree species: Hyeronima alchorneoides Allemao, Inga edulis Mart., Pentaclethra macroloba (Willd.) Ktze, Pithecellobium macradenium Pittier, Stryphnodendron microstachyum Poepp. et Endl., Virola koschnyi Warb., Vochysia guatemalensis J.D. Smith, and Vochysia ferruginea Mart. and three exotic tree species: Acacia mangium Willd., Gmelina arborea L., and Pinus tecunumanii (Schw.) Equiluz et Perry were planted on abandoned pasture land in northeastern Costa Rica cleared of rain forest 25 yr earlier. Four replicates of 0.25‐ha plots of the 11 species and a control were established in a randomized complete block design. All species survived fairly well, but some grew much better than others. The soil was thoroughly sampled before trees were planted and again 4 yr after trees were established. Although bulk density decreased significantly beneath eight of the 11 species, organic C increased significantly under only three species. Significant increases in base cations also occurred beneath the majority of species. Nitrogen did not increase as much as expected beneath the N2‐fixing legumes; however, the availability of P was significantly enhanced beneath both species of Vochysia. The changes in soil properties were dramatic, and significant amelioration of these degraded soils occurred in a short time beneath the majority of species.