Seasonal nutrient transfers by foliar resorption, leaching, and litter fall in a northern hardwood forest at Lake Clair Watershed, Quebec, Canada

A descriptive temporal model was used to evaluate the flow of macronutrients (N, P, K, Ca, and Mg) between the forest canopy and incident precipitation for the Lake Clair Watershed (LCW) located in the northern hardwood forest region of Quebec, Canada. The model also quantified the resorption mechanism. Wet precipitation, throughfall, foliage, and litter fall data for 1997 were used to quantify the following: (1) dry deposition intercepted by forest cover (0.38, 0.07, 0.07, and 0.03 kg.ha(-1) for Ca, K, Mg, and P, respectively); (2) leaching from foliage (1.81, 6.46, 0.48, and 0.13 kg.ha(-1) for Ca, K, Mg, and P, respectively); and (3) foliar resorption (N = 65%, P = 65%, K = 42%, Mg = 30%, and Ca = 10%). Foliar N, P, and K pools increased after bud break and remained constant until mid-September when they decreased rapidly. The foliar Ca pool increased until leaf fall, while the foliar Mg pool reached a maximum in early July and decreased slowly until leaf senescence. Phosphorus, K, Ca, and Mg were leached from the canopy whereas N from wet precipitation was retained by the canopy. The relatively high Mg and Ca resorption rates are consistent with the low soil Ca and Mg availability reported at the LCW. Consideration of leaching and dry deposition, as well as the temporal dimension, demonstrated the importance of each of these parameters for increasing the accuracy of the foliar nutrient resorption estimates.