Throughfall volume and chemistry as affected by precipitation volume, sapling size, and defoliation intensity

Throughfall and stemflow are important components of hydrologic processes i n forests, but relative contributions of multiple factors, including precip itation volume, plant size, and folivory (leaf removal by defoliators), on throughfall/stemflow have not been reported. This paper reports the relativ e influences of precipitation volume (0-230 L m(-2)), sapling size (1.4-6.7 cm diameter at root collar; 0.07-0.45 kg calculated dry foliage mass), and manipulated folivory (0-20% foliage removal) on throughfall volume and N, K, and Ca fluxes as evaluated with stepwise multiple regression in a young Douglas-fir (Pseudotsuga menziesii [Mirb.] France) ecosystem. Precipitation volume explained most variation in throughfall volume (R-2 = 0.81). Folivory and sapling size each had significant but minor effects on throughfall volume and nutrient fluxes. These data indicate that folivore e ffects, while significant, are masked by precipitation in this wee ecosyste m. Wider ranges in sapling size and folivory and/or drier conditions likely would improve interpretation of their influence on throughfall volume and chemistry.