IMPACT OF AFFORESTATION ON HYDROLOGICAL RESPONSE AND SEDIMENT PRODUCTION IN A SMALL CALABRIAN CATCHMENT

Extensive afforestation using Pinus and Eucalyptus has taken place in Calabria since the early 1960's to control expansion of calanchi and b iancane. In 1978 three small catchments were established near Crotone to monitor the effect of afforestation on hydrological response and se diment yield. In 1992, rainfall simulation experiments were carried ou t on plots in these catchments to determine more precisely the effect of tree and ground vegetation on surface runoff and erosional response . Most experiments were carried out in a logged catchment with slopes ranging from 20 to 30 degrees and aspects from SW to NE. Results showe d complex runoff generation and sediment production, reflecting the ef fect of microclimate and subtle variations in vegetation on infiltrati on characteristics. On south-facing slopes with little ground vegetati on runoff generation was rapid with runoff coefficients from 27 to 37% and peak sediment concentrations reaching 83.7 g . 1(-1). On north-fa cing slopes with good tree cover, little grass, but continuous leaf li tter, runoff coefficients reached 21%, but peak sediment concentration was only 3.6 g . 1(-1), while on recently logged north-facing slopes with dense grass cover the highest runoff coefficient was only 5.5% ru noff coefficient, and there was virtually no sediment production. Impl ications of results for forest management and soil conservation are di scussed.