We simulated twenty 1m x 1m plots spaced 5m apart on a 100m transect running parallel to the water flow path down a uniform hill slope covered with tussock tundra. We assumed the hill slope had a uniform aspect and slope so that there were not convergent or divergent water flow paths. Water was therefore assumed to run from one plot, through the intervening 4m of tundra, to the next plot down hill. Precipitation inputs and evapotranspiration losses for the intervening 4m were assumed to be the same as those for the uphill plot. The inorganic N concentration in the soil water moving down slope was also assumed to be the same as that leaving the uphill plot, thus the amount of N moving down slope increased in proportion to the amount of water flow. Simulations used a yearly time step for 180 years, from 1921 to 2100 based on the historical reconstruction of climate and CO2 (1921-2000) and the predicted future climate scenarios (2001-2100). Two scenarios enabled the investigation of the effects of two contrasting moisture response curves for microbial activity (Flanagan and Veum 1974 and Sarah Hobbie pers. com.). Because Soil moisture in these soils is almost always high (> 80 mm water), the important distinctions between these two response curves is the decline in decomposition rate as soil moisture increases above the optimum moisture level; the Flanagan and Veum curve declines more strongly as moisture increases above the optimum than does the Hobbie curve. The data file contain all simulation results for each scenario for individual cells along the transect. See Rastetter, E.B., B. L. Kwiatkowski, S. Le Dizès, and J.E. Hobbie. 2004. The Role of Down-Slope Water and Nutrient Fluxes in the Response of Arctic Hill Slopes to Climate Change. Biogeochemistry 69:37-62.

Citations:

Flanagan, P.W. and Veum, A.K. 1974. Relations between respiration, weight loss, temperature, and moisture in organic residues on tundra. Pages 249-277 in Holding, A.J. et al. (eds.) Soil organisms and decomposition in tundra. Tundra Bione Steering committee, Stockholm, Sweden.

Cell naming convention: YYYCellXt where YYY = FaV (Flanagan and Veum response curve) or Hob (Sarah Hobbie moisture response curve) and X = 1-20 is cell number for locations 5 m apart with cell 1 at the top of the hill slope and cell 20 at the bottom.

ACKNOWLEDGEMENTS: This research was supported by funds from the National Science Foundation (NSF-LTER 0221000# and NSF-OPP 9732281).