The potential of plantations to foster woody regeneration within a deforested landscape in lowland Costa Rica

Reforestation of degraded pastures in the Atlantic lowlands of Costa Rica since 1988 has created a patchwork of small plantations that may have the potential to capture and conserve the remnant biodiversity in this largely deforested landscape. Studies of woody regeneration in 6 year old experimental plantations and on-farm plantations on abandoned pasture were conducted at the La Selva Biological Station and surrounding region. The experimental plantations include seven native and four exotic tree species, together with an abandoned pasture control. The impact of plantations on woody regeneration varied according to the plantation tree species. Some species fostered greater abundance of woody regeneration, some greater species richness, other species both abundance and richness, while another group had no effect significantly different from abandoned pasture. Abundance of woody regeneration did not appear to be related to canopy cover at the time of sampling, Nevertheless, plantation trees that established rapidly and had high growth rates did in general stimulate higher levels of woody regeneration. A comparison of this study with one conducted in the same plantations Is months later indicates that the effect of some trees promoting greater density of regeneration may decline over time, while differences in species richness may persist or strengthen. Observations in a range of 6 year old plantations on farms showed a wide range of densities of woody regeneration. Part of this variation could be explained by the presence or absence of grazing within the plantation. Abundance and species richness of woody regeneration under plantation stands can be substantial. Nevertheless, the incidence of mature forest species was low and their ability to invade in the future will probably depend on subsequent stand management. It must not be forgotten that the motivation for reforestation is primarily economic; increased biodiversity is a by-product that, if it is to be promoted, will require adaptation of management practices. (C) 1997 Elsevier Science B.V.