The importance of leaching from litter collected in litterfall traps.

Litterfall (LF) is usually collected by means of open traps. However, this litter will be subject to leaching by the throughfall which passes through the accumulated litter in the traps. The nutrients lost during this leaching are not taken into account in the calculation of LF nutrient fluxes. We report the results from a 2-month (August-September) study carried out in 8 northern coniferous forest stands to assess the possible importance of leaching from litter in LF traps. Compared to throughfall (TF), the litterfall leachate (LFLgross), which includes a throughfall component, had significantly (p < 0.05) higher concentrations and fluxes of Ca, Mg, Na and S. The average net LFL (i.e., LFLnet = LFLgross - TF) fluxes were 21 (Ca), 7 (Mg), 57 (K), 10 (Na), 10 (N), and 19 (S) mg m-2 mo-1. LFLnet accounted for 42%, 37% and 50% of the LFLgross flux, and for 91%, 51% and 49% of the total litterfall flux (i.e., LF + LFLnet) of Na, S and K, respectively. For Ca, Mg and N, the LFLnet flux accounted for 64%, 58% and 29% of the LFLgross flux, and for < 14% of the total litterfall flux. Compared to TF, LF was the dominant return pathway for Ca, Mg and N to the forest floor regardless of whether LFLnet was included or not. However, for K and S, taking LFLnet into account determined whether TF or LF was the dominant pathway. TF remained the dominant pathway for Na even when LFLnet was included.