Responses of soil respiration, soil nutrients, and litter decomposition to inputs from canopy herbivores

We tested whether inputs from canopy herbivores would affect soil processes such as respiration, nutrient cycling, and decomposition along an elevation gradient. The five treatments we used were frass additions, throughfall additions, removal of all litter that fell during the study, removal of greenfall that fell during the study, and controls. Soil respiration was significantly reduced on low and mid elevation sites in litter exclusion, greenfall exclusion and throughfall addition treatments (from 0.846 g CO2/m2/h for controls to 0.618, 0.667, and 0.708 g CO2/m2/h, respectively, for the three treatments). Throughfall additions containing PO4 and NH4 contributed to significant increases in PO4 (as much as 0.737 mg/l in 100 ml KCl extract greater then controls), but decreases in NO3, (0.306 mg/l in 100 ml KCl extract less than con trols), in soil solution samples compared to controls. We observed no significant treatment effects on litter decomposition. Precipitation and temperature influenced soil respiration, but both factors showed a significant interaction with elevation. Phosphate concentrations in soil solutions differed significantly with elevation (low elevation mean 0.097 mg/l, mid elevation mean 0.192 mg/l). Elevation had no significant effect on decomposition.