PARENT SESSION
Poster Session #26: Soil Ecology I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

The effects of trees on soil nutrients in the alpine forest-tundra ecotone.

Liptzin, Daniel^*,1, Seastedt, Timothy¹, ¹ University of Colorado, Boulder, CO

ABSTRACT- Although ecosystem structure and function have been well studied in the alpine and subalpine, little is known about the forest-tundra ecotone connecting these two ecosystems. The size and density of trees often decrease with altitude until treeline when trees can no longer survive. Because of the high winds and lack of trees in the alpine tundra, snow, plant debris, and dust are redistributed based on topographic features. Some of these inputs are also transported into the ecotone, but here the trees play the dominant role in determining the spatial pattern of redeposition. These inputs would subsidize the biota in the ecotone because they provide additional moisture, carbon, nitrogen, and base cations to the soil. These subsidies would be expected to be greatest at higher altitudes, because of the proximity to the alpine, and near individual trees, because the tree-wind interaction drives the deposition patterns. Trees are expected to create spatial heterogeneity in nutrient status in the ecotone because of their effects on deposition patterns, litter quality and quantity, and snow cover. One of their most important effects may be that snow cover prevents soils from freezing during the winter. Results presented are the total pools of carbon, nitrogen, and base cations in the soils across the ecotone and around individual trees. This ecotone is also predicted to be heterogeneous in rates of nutrient cycling and loss. Other ecosystems have both woody and herbaceous components and spatial heterogeneity in soil resources, but these systems lack the unidirectional flux of subsidies that the ecotone receives from the alpine and the large differences in snow distribution patterns.

KEY WORDS: treeline, ecotone, soil nutrients, tree effects