Ecology and use of old-growth and recovering montane oak forests in the Cordillera de Talamanca, Costa Rica

Abstract

During the last century, substantial parts of old-growth forest (OGF) in the Cordillera de Talamanca, Costa Rica, were clear-cut. However, in many areas, secondary forests (SEC) have become established on abandoned agricultural land. Based on new and published data, this chapter compares upper montane OGF and SEC stands on the Pacific slope of the Cordillera in terms of differences in plant diversity, stand structure, biogeochemical cycles, and forest use. Furthermore, an attempt is made to assess the potential for, and timescale of, recovery of various forest characteristics during regrowth. Oak species (Quercus spp.) are present in all successional stages. Alpha-diversity of terrestrial, vascular plant species is significantly higher in early- and mid-successional stands than in OGF, probably due to downslope migration of sub-alpine and alpine terrestrial herb species to cleared and abandoned sites. Beta-diversity is seen to decline during succession. Values of stand leaf area in early-successional stages were similar to those observed in OGF, but biomass of epiphytes was significantly lower in SEC (160–520 kg ha−1) compared to OGF (3400 kg ha−1). Rainfall interception was much higher in OGF (25% of gross precipitation) than in SEC (9% and 15% for early- and mid-successional SEC, respectively), despite similar leaf area for OGF and SEC. A combined experimental and modeling study suggested that the epiphyte layer contributed little (6%) to overall rainfall interception in the OGF and could, therefore, not explain the observed hydrological differences between the various successional stages. Instead, these are thought rather to reflect differences in canopy roughness