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At the macro-scale (upper elevation vs. lower elevation), large differences exist in climatic regimes. The two upper elevation plots receive 24% more precipitation than the lower elevation plots. At the plot level, macro-climatic inputs are moderated by site factors such as topography, soil water-holding capacity, and vegetation factors such as leaf area index (LAI) and water use efficiency, which regulate water use. Hence, at the plot level, micro-climatic and macro-climatic gradients differ. At the watershed scale, there are large differences in the water and sulfur budgets of high and low elevation watersheds. Streamflow is markdly greater on the high elevation watersheds, reflecting greater precipitation inputs and lower evapotranspiration losses resulting from cooler temperatures and lower LAI. Less S is retained in the high elevation watersheds because of less absorption and lower rates of microbial incorporation at the watershed scale. Stream water sulfate concentrations are greatest at elevations over the past decade in response to acid deposition. Vegetation biomass ranges from 150 to 236 Mg ha-1, with the xeric site lowest and the cove site highest. Litterfall ranges from 2653 to 3822 kg ha-1 yr-1 with lowest in cove hardwood and highest in low elevation mixed oak. The variation is not related to elevation, basal area, or productivity. Maximum LAI generally follows litter fall patterns and ranges from 3.3 (xeric oak-pine) to 9.0 (low elevation mixed oak). This high LAI value reflects the contribution of Rhododendron maximum -- a major component of the low and high elevation mixed oak stands. Total root biomass in the summer ranges from 13 to 21 Mg ha-1, with the lowest value on the cove hardwood site and the highest on the high elevation mixed oak site. Root:shoot rations generally decline with increasing average annual soil moisture across the gradient plots. We are following the dynamics of roots and the rhizosphere community using root boxes in which dissecting microscope is used to photograph the below-ground community. Decomposition rate varies at least two-fold, although this variation is unrelated to the macro-climatic gradient. Variation in k values may be related to micro-climatic gradients which affect either the activities or population sizes for the decomposer community. Microarthropod abundance was generally lowest on the northern hardwood site and highest on the high elevation mixed oak site. Interestingly, the oribatid mite species richness in the northern hardwood site is among the highest ever recorded with over 160 species. New research projects will allow to assess the diversity of small mammals and amphibians on these plots as well. Soil C ranges from 3.3 to 9.9%. Soil C:N ratios range from 39 on the xeric oak/pine site to 14 on the northern hardwood site. Soil pH is less variable and ranges from 3.9 to 4.2. The lower sites and the upper elevation oak hardwood site are on Ultisols, and the northern hardwood is an Inceptisol. In summary, macro-scale climatic data indicate a strong gradient in precipitation and temperature among the plots with the elevation plots receiving more precipitation and experiencing lower air temperatures. Topography, soil, and vegetation mediate these macro-climatic factors such that plot-level microcliamtic gradients differ from macro-climatic gradients. Watershed-scale nutrient budgets and plot-level responses do not necessarily agree. For example, at the watershed scale N budgets indicate very similar N fluxes on high versus low elevation watersheds. However, N mineralization rates are much greater at the high elevation northern hardwoods site, and this increase N availability is not stored in the vegetation. At the watershed scale, these plot-level responses are being dampened.
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and disturbance. Plots were established in
five locations (