Quantity and Chemistry of Throughfall as Influenced by Forest-Type and Season

SUMMARY A comparison of nitrogen, phosphorus, potassium, calcium and magnesium transfer in throughfall was conducted for two years in four forest-types (Pinus, Liriodendron tulipifera, Quercusprinus, Quercus-Carya) within Walker Branch Watershed in eastern Tennessee, U.S.A. No differences were found in the amount of throughfall collected under the four forest-types. In addition, this amount was found to be predicted effectively by the equations of Helvey & Patric (1965). Pinus stands cycled significantly more of the cations in throughfall during the dormant season than did the other forest-types; Quercus-Carya tended to cycle more nutrients than other forest types during the growing season. These differences appeared to be due to element leachability (K> Ca> Mg> P> N), occurrence of precipitation within an annual cycle and, to a lesser degree, nutrient composition of the species in each forest-type. The importance of throughfall in comparison to litterfall as a nutrient return mechanism decreases in the order K> Ca = Mg > P = N.