DOI: 10.6073/pasta/b454299cd6b61ab707b420bbd62e0b14
title: Looking beyond the mean: Drivers of variability in postfire stand development of conifers in Greater Yellowstone

description: High-severity, infrequent fires in forests shape landscape mosaics of
  stand age and structure for decades to centuries, and forest structure
  can vary substantially even among same-aged stands. This variability
  among stand structures can affect landscape-scale carbon and nitrogen
  cycling, wildlife habitat availability, and vulnerability to
  subsequent disturbances. We used an individual-based forest process
  model (iLand) to ask: Over 300 years of postfire stand development,
  how does variation in early regeneration densities versus abiotic
  conditions influence among-stand structural variability for four
  conifer species widespread in western North America? We parameterized
  iLand for lodgepole pine (Pinus contorta var. latifolia), Douglas-fir
  (Pseudotsuga menziesii var. glauca), Engelmann spruce (Picea
  engelmannii), and subalpine fir (Abies lasiocarpa) in Greater
  Yellowstone (USA). Simulations were initialized with field data on
  regeneration following stand-replacing fires, and stand development
  was simulated under historical climatic conditions without further
  disturbance. Stand structure was characterized by stand density and
  basal area. Stands became more similar in structure as time since fire
  increased. Basal area converged more rapidly among stands than tree
  density for Douglas-fir and lodgepole pine, but not for subalpine fir
  and Engelmann spruce. For all species, regeneration-driven variation
  in stand density persisted for at least 99 years postfire, and for
  lodgepole pine, early regeneration densities dictated among-stand
  variation for 217 years. Over time, stands shifted from
  competition-driven convergence to environment-driven divergence, in
  which variability among stands was maintained or increased. The
  relative importance of drivers of stand structural variability
  differed between density and basal area and among species due to
  differential species traits, growth rates, and sensitivity to
  intraspecific competition versus abiotic conditions. Understanding
  dynamics of postfire stand development is increasingly important for
  anticipating future landscape patterns as fire activity
  increases.High-severity, infrequent fires in forests shape landscape
  mosaics of stand age and structure for decades to centuries, and
  forest structure can vary substantially even among same-aged stands.
  This variability among stand structures can affect landscape-scale
  carbon and nitrogen cycling, wildlife habitat availability, and
  vulnerability to subsequent disturbances. We used an individual-based
  forest process model (iLand) to ask: Over 300 years of postfire stand
  development, how does variation in early regeneration densities versus
  abiotic conditions influence among-stand structural variability for
  four conifer species widespread in western North America? We
  parameterized iLand for lodgepole pine (Pinus contorta var.
  latifolia), Douglas-fir (Pseudotsuga menziesii var. glauca), Engelmann
  spruce (Picea engelmannii), and subalpine fir (Abies lasiocarpa) in
  Greater Yellowstone (USA). Simulations were initialized with field
  data on regeneration following stand-replacing fires, and stand
  development was simulated under historical climatic conditions without
  further disturbance. Stand structure was characterized by stand
  density and basal area. Stands became more similar in structure as
  time since fire increased. Basal area converged more rapidly among
  stands than tree density for Douglas-fir and lodgepole pine, but not
  for subalpine fir and Engelmann spruce. For all species,
  regeneration-driven variation in stand density persisted for at least
  99 years postfire, and for lodgepole pine, early regeneration
  densities dictated among-stand variation for 217 years. Over time,
  stands shifted from competition-driven convergence to
  environment-driven divergence, in which variability among stands was
  maintained or increased. The relative importance of drivers of stand
  structural variability differed between density and basal area and
  among species due to differential species traits, growth rates, and
  sensitivity to intraspecific competition versus abiotic conditions.
  Understanding dynamics of postfire stand development is increasingly
  important for anticipating future landscape patterns as fire activity
  increases.