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 macronutrient s (N, P, K, Ca, and Mg) between the forest canopy and incident precipitatio n for the Lake Clair Watershed (LCW) located in the northern hardwood fores t region of Quebec, Canada. The model also quantified the resorption mechan ism. Wet precipitation, throughfall, foliage, and litter fall data for 1997 were used to quantify the following: (1) dry deposition intercepted by for est cover (0.38, 0.07, 0.07, and 0.03 kg.ha(-1) for Ca, K, Mg, and P, respe ctively); (2) leaching from foliage (1.81, 6.46, 0.48, and 0.13 kg.ha(-1) f or 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 decreas ed 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 sen escence. Phosphorus, K, Ca, and Mg were leached from the canopy whereas N f rom wet precipitation was retained by the canopy. The relatively high Mg an d Ca resorption rates are consistent with the low soil Ca and Mg availabili ty reported at the LCW. Consideration of leaching and dry deposition, as we ll as the temporal dimension, demonstrated the importance of each of these parameters for increasing the accuracy of the foliar nutrient resorption es timates.