MAJOR, MINOR AND TRACE-ELEMENT BUDGETS IN THE PLYNLIMON AFFORESTED CATCHMENTS (WALES) - GENERAL TRENDS, AND EFFECTS OF FELLING AND CLIMATE VARIATIONS

Annual and monthly input-output budgets for 6-7 years were calculated for more than 30 elements in three upland catchments. The annual budgets show relatively high losses of base cations, sulphate and many trace elements. The budgets are balanced for NO3, Cu and Cr. A net accumulation of Cd and I is observed. Pb is lost from two catchments with bedrock rich in lead-zinc-CaCO3 mineralisation and is accumulated in the other catchment. The monthly variations in flux illustrate the importance of climatic variations: for most of the elements, except Al, Cu and Cr, unevenly distributed rainfall enhanced the solute losses more than heavy rainfall. The felling of the forest in one catchment resulted in increased element losses, especially of NO3, K, Mn, B and Cd.