EFFECT OF LAND-USE CHANGES ON CARBON AND NITROGEN STORAGE IN CLOUD FOREST SOILS, MONTEVERDE AREA, COSTA RICA

Cloud forests are tropical montane evergreen forests that obtain significant moisture from fog drip. In Costa Rica, they occur on the leeward (Pacific-facing) slopes of the Cordillera de Tilarán where trade winds are forced above the lifting condensation point. Most of Costa Rica's primary forest has been cleared, primarily for agricultural use, although much of this land has been reforested in recent decades. We investigated the effects of these land-use changes on soil carbon and nitrogen storage by comparing soils from primary cloud forest and 30-year secondary forest, both in the Santa Elena Reserve, a state-owned reserve near Monteverde at an altitude of 1700 m, and a clear-cut pasture just outside the reserve. Although soils in the primary forest exhibit the strongest horizonation of the three sites, they also consistently yield the highest carbon and nitrogen contents, 14.8% and 0.8% respectively, in the upper 25 cm. Secondary forest and pasture soils both display similar levels of both carbon, 9.6% and 10.2% respectively, and nitrogen, 0.6% and 0.7%. The pasture soils typically contain a well-defined coarse sandy layer 10 to 20 cm below the surface. We interpret this as a sediment layer deposited across much of the landscape following widespread erosion, likely a consequence of the deforestation. Our preliminary results suggest that reforestation is ineffective at returning soil carbon levels to pre-land use levels on a decadal time scale.