Influence of fire regimes on lodgepole pine stand age and density across the Yellowstone National Park (USA) landscape |
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Authors: | Tania Schoennagel Monica G Turner Daniel M Kashian Andrew Fall |
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Institution: | (1) Department of Zoology, University of Wisconsin, Madison, WI, USA;(2) School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC, Canada;(3) Department of Geography, University of Colorado, 260 UCB, Boulder, CO 80309, USA |
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Abstract: | A probabilistic spatial model was created based on empirical data to examine the influence of different fire regimes on stand
structure of lodgepole pine (Pinus contorta var. latifolia) forests across a >500,000-ha landscape in Yellowstone National Park, Wyoming, USA. We asked how variation in the frequency
of large fire events affects (1) the mean and annual variability of age and tree density (defined by postfire sapling density
and subsequent stand density) of lodgepole pine stands and (2) the spatial pattern of stand age and density across the landscape.
The model incorporates spatial and temporal variation in fire and serotiny in predicting postfire sapling densities of lodgepole
pine. Empirical self-thinning and in-filling curves alter initital postfire sapling densities over decades to centuries. In
response to a six-fold increase in the probability of large fires (0.003 to 0.018 year−1), mean stand age declined from 291 to 121 years. Mean stand density did not increase appreciably at high elevations (1,029
to 1,249 stems ha−1) where serotiny was low and postfire sapling density was relatively low (1,252 to 2,203 stems ha−1). At low elevations, where prefire serotiny and postfire lodgepole pine density are high, mean stand densities increased
from 2,807 to 7,664 stems ha−1. Spatially, the patterns of stand age became more simplified across the landscape, yet patterns of stand density became more
complex. In response to more frequent stand replacing fires, very high annual variability in postfire sapling density is expected,
with higher means and greater variation in stand density across lodgepole pine landscapes, especially in the few decades following
large fires. |
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Keywords: | Landscape modeling Pinus contorta var latifolia Postfire regeneration Stand density Succession Yellowstone National Park |
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