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Dan Binkley

The age structure of aspen in Rocky Mountain National Park was characterized to determine if the number of aspen established in recent decades was substantially lower than would be expected from long-term trends. At lower elevations on the eastside of the Park, aspen density averaged 1250 trees/km2, compared with 550 trees/km2 at higher elevations and on the westside. Most aspen in the Park were relatively young, with trees less than 80 years old accounting for 90% of aspen trees and 50% of aspen basal area. The number of trees in each decadal age class increased exponentially from 1855 through 1965, with no decade showing significantly higher or lower aspen numbers than expected from the long-term trend. The number...
Nutrient availability strongly affects the species composition and productivity of most upland ecosystems, but the importance of nutrient availability is largely undefined for riparian ecosystems in semiarid regions of the western United States. The establishment and persistence of riparian cottonwood (Populus spp.) seedlings depends largely on water availability, but this does not preclude an important role for nutrient availability. To investigate how nitrogen availability may influence the composition and productivity of riparian communities, we tested the hypothesis that the growth and survival of first-year Fremont cottonwood seedlings is limited by the availability of both water and nitrogen. Plots of naturally...
Do relationships between species and environmental gradients strengthen or weaken with tree life-stage (i.e., small seedlings, large seedlings, saplings, and mature trees)? Strengthened relationships may lead to distinct forest type boundaries, or weakening connections could lead to gradual ecotones and heterogeneous forest landscapes. We quantified the changes in forest dominance (basal area of tree species by life-stage) and environmental factors (elevation, slope, aspect, intercepted photosynthetically active radiation (PAR), summer soil moisture, and soil depth and texture) across 14 forest ecotones (n = 584, 10 m #x00D7; 10 m plots) in Rocky Mountain National Park, Colorado, U.S.A. Local, ecotone-specific species-environment...
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