Tropical Montane Cloud Forests (TMCF) maintain critical hydrological services to downstream regions and also contribute to other strategic ecosystem functions such as the accumulation of high amounts of carbon and the protection of endemic species. In accordance with IPCC predictions, longer and more severe dry seasons are expected for Central America; as result, major shifts in the productivity of these communities and in the rate of accumulation of organic carbon in the soil are likely to occur. The goal of this ongoing project is to determine how the productivity of these communities varies from one year to another as a function of changes in precipitation and the duration of the dry season. We summarize an eight years study to determine the variation in litter production in two patches of TMCF in old grove forests at Cerro de la Muerte Biological Station (elevations ranging 3000 to 3300 m) located in the Talamanca mountain range in Costa Rica. In particular, we focus on the productivity of the dominant oak species, Quercus costaricensis, which account for over 80% of the basal area in these forests. To this end, we used fifteen 0.25 m2 litter traps distributed in three 60 m transects 20 m apart, with traps placed every 10 m along each transect in each patch. Litter was collected monthly, dried at 40oC for 48 hours and separated by species, type of material and weighed.
Results/Conclusions
We found significant variation in the leaf litter production among forest patch and years. Our data revealed lower leaf litter production in 2008, 2009 and 2011 than in 2007, 2010 and 2012. Overall, annual litter production was significantly explained by annual precipitation measured the previous year (Pearson Correlation = 0.56, p-value < 0.05). In addition, litter production was negatively correlated with the duration of the dry season (Pearson Correlation = 0.62, p-value < 0.05). These results indicate that plant productivity is significantly affected by dry season duration and the previous year’s precipitation. In addition, there were also significant differences in leaf litter production during the year, with higher production during the rainy season when trees replace their old leaves. Overall, litter production in these patches exhibited a declining trend from 2007 to 2012 (Pearson Correlation = -0.59, p-value < 0.04). We discussed the potential consequences of climate change predictions for this area on the primary productivity of TMCF in the light of these findings.