Land-use change in the Atlantic rainforest region: Consequences for the hydrology of small catchments

- Predominance of vertical flowpath in pasture, eucalyptus and forest.
- Forest and eucalyptus convert a similar proportion of precipitation to streamflow.
- Cloud forest conversion to pasture presents no significant increase in streamflow.

SummaryThe Atlantic forest of Brazil is one of the most endangered ecosystems in the world. Despite approximately 500 years of intense land-use change in this biome, the influence of land-use changes on hydrological processes have yet to be investigated in-depth. To bridge this gap, we studied various features of three small catchments covered by pristine original montane cloud forest, pasture, and eucalyptus for 2 years (January 2008-December 2009), including the hydraulic properties of soils, throughfall, overland flow and streamflow processes. The forest saturated hydraulic conductivity (Ksat) was higher near the soil surface (0.15 m depth) compared to eucalyptus and pasture. As a consequence, higher overland flow generation in terms of volume was observed in pasture and eucalyptus. Despite this increase in overland flow generation, overland flow coefficients (overland flow: precipitation ratio) were substantially low throughout the study period with slightly higher values in 2009. These low overland flow coefficients were attributed to the large predominance of low rainfall intensities (<10 mm h−1) as well as high Ksat spatial variability. These overland flow results and the absence of perched water table showed that catchments seem still to be dominated by vertical flowpaths irrespective of land-use. In this sense, the annual streamflow is still dominated by baseflow in all of the catchments. Therefore, despite reductions regarding interception and saturated hydraulic conductivity when converting forest to eucalyptus and pasture, the prevailing rainfall intensities do not cause runoff generation processes to be substantially different among land-uses. Forest and eucalyptus convert a similar proportion of annual precipitation to annual streamflow, with the more likely factors for these results being the high interception under forest and high transpiration under eucalyptus. Finally, cloud forest conversion to pasture does not promote significant monthly streamflow change.