Populus tremuloides stands continue to deteriorate after drought-incited sudden aspen decline

Abstract

Reports of forest damage have increased with the frequency of climatic extremes, but longer term impacts of such events on population dynamics of forest trees are generally unknown. Incited by the turn-of-the-century drought, sudden aspen decline (SAD) damaged 535 000 ha of Populus tremuloides Michx. in the Southern Rockies ecoregion of western North America. Although spread of the disease stopped in about 2009, most of the affected stands continued to deteriorate. Remeasurement of plots in southwestern Colorado showed that, since the peak of the epidemic, live basal area in sick plots decreased by an additional 28% to only 38% of that in healthy plots. Sick plots had much more recent damage than healthy plots, with almost three times as much recently dead basal area, over twice the density of recently dead trees, and almost four times as much recent crown loss. The important contributing agents in SAD were still active in sick stands in 2013. Density of small regeneration showed opposite trends, increasing in healthy plots and decreasing in sick plots. Timely regeneration treatments may be needed in some such stands to facilitate recovery. In addition to acute damage from climatic extremes, long-term decline diseases like SAD will likely be a common signature of forest damage from climate change.

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

“…The competitive exclusion of aspen in aspen–spruce–fir stands was delayed in both the present study and when blowdown was followed by wildfire (Kulakowski et al ), suggesting that aspen forest cover may increase with expected increases in the area affected by spruce beetle outbreaks (Temperli et al ) and fires in subalpine forests as climate warms. However, this finding must be considered in the context of recent, extensive mortality of aspen in Colorado (Worrall et al ) and a predicted reduction in suitable climate space for aspen (Rehfeldt et al ). Projecting future forest conditions and susceptibility to subsequent disturbances under a warmer climate needs to consider the long‐lasting effects of these shifts in species composition and stand structure.…”

Sudden Aspen Decline: A Review of Pattern and Process in a Changing Climate

“…This type of hydraulic damage may not lead to complete mortality of SAD-affected stands during or immediately after the drought, but losses can be substantial. For example, SAD stricken forests in southwestern Colorado lost approximately 28% of their basal area after the drought in the early 2000s [64].…”

Rapid regeneration offsets losses from warming-induced tree mortality in an aspen-dominated broad-leaved forest in northern China

“…Previous studies have primarily concentrated on the drivers of tree mortality and have linked it to climate change, pest outbreaks, and fire regimes [ 2 – 4 ]. Recently, however, tree regeneration following episodes of mortality—knowledge that is necessary for predicting forest dynamics under future climate change—has become a topic of interest [ 5 ].…”

“…Among the forest types suffering dieback, trembling aspen ( Populus tremuloides ) ranks among the most biologically diverse vegetation communities across the Intermountain Region of western North America, and this type has been well-studied [ 5 – 9 ]. Trembling aspen mortality and overstory dieback have occurred at unusually high levels throughout Colorado and western North America over the past 15 years [ 7 ].…”