Nutrient fluxes in a snow-dominated, semi-arid forest: Spatial and temporal patterns

We tested five hypotheses regarding the potential effects of precipitation change on spatial and temporal patterns of water flux, ion flux, and ion co ncentration in a semiarid, snowmelt-dominated forest in Little Valley, Neva da. Variations in data collected from 1995 to 1999 were used to examine the potential effects of snowpack amount and duration on ion concentrations an d fluxes. Soil solution NO3-, NH4+, and ortho-phosphate concentrations and fluxes were uniformly low, and the variations in concentration bore no rela tionship to snowmelt water flux inputs of these ions. Weathering and cation exchange largely controlled the concentrations and fluxes of base cations from soils in these systems; however, soil solution base cation concentrati ons were affected by cation concentrations during snowmelt episodes. Soil s olution Cl- and SO42- concentrations closely followed the patterns in snowm elt water, suggesting minimal buffering of either ion by soils. In contrast to other studies, the highest concentration and the majority of ion flux f rom the snowpack in Little Valley occurred in the later phases of snowmelt. Possible reasons for this include sublimation of the snowpack and dry depo sition of organic matter during the later stages of snowmelt. Our compariso n of interannual and spatial patterns revealed that variation in ion concen tration rather than water flux is the most important driver of variation in ion flux. Thus, it is not safe to assume that changes in total precipitati on amount will cause concomitant changes in ion inputs to this system.