Effects and etiology of sudden aspen decline in southwestern Colorado, USA

Worrall, James J.; Marchetti, Suzanne B.; Egeland, Leanne; Mask, Roy A.; Eager, Thomas J.; Howell, B.

doi:10.1016/j.foreco.2010.05.020

Cited by 153 publications

(189 citation statements)

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“…Biological agents that may be affecting survivorship of stands include Cytospora canker, the poplar borer, the bronze poplar borer, and two aspen bark beetle species (Worrall, et al, 2008). Though these agents are generally considered to be of secondary importance to stand health, stands which are already stressed may experience increased mortality from these disease and damage agents (Worrall, et al, 2008(Worrall, et al, , 2010.…”

Section: Aspen Dieback and Sudden Aspen Declinementioning

confidence: 99%

“…This is indicated by the increased rates of adult stem mortality among stands east of the continental divide (which tends to be drier than the west) and the increased presence of such stress-related organisms as Cytospora canker aspen bark beetles, and poplar borers among damaged stands. Other recent studies of aspen mortality throughout western North America have attributed the observed mortality to acute drought conditions (Worrall, et al, 2008(Worrall, et al, & 2010Fairweather, 2008;Hogg, et al, 2008). Acute drought is most likely the main inciting factor, though further analysis is required to definitively link the marked increase in select damage agents with moisture deficit.…”

Section: Prevalence Of Cytospora Canker Was Greater Among Stands Eastmentioning

confidence: 99%

“…Biological agents that may affect survivorship of stands include Cytospora canker (Cytospora spp), poplar borer (Saperda calcarata), the bronze poplar borer (Agrilus liragus), and two aspen bark beetle species (Trypophloeus populi and Procryphalus mucronatus) (Worrall, et al, 2008; Jacobi, W.R., personal communication). Though these agents are generally considered to be of secondary importance to stand health (primary disease and damage agents include sooty bark (Encoelia pruinosa) and Cryptosphaeria (Cryptosphaeria lignyota) cankers and forest tent caterpillar (Melacosoma disstria), stands which are already stressed may experience increased mortality from these disease and damage agents (Worrall, et al, 2008(Worrall, et al, , 2010. The area where Sudden Aspen Decline has been documented includes the national forests of southwestern Colorado (i.e., the Gunnison, Grand Mesa, and Uncompahgre National Forests).…”

Section: Introductionmentioning

confidence: 99%

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Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

Dudley

Burns

Jacobi

2015

Forest Ecology and Management

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We established 573 random roadside survey plots in stands that contained at least 50% aspen cover type. From these random plots, we found average standing aspen tree mortality ranged from 3.3 to 23.7 % on the four national forests and 11% on the east side of the continental divide and 4 % on the west side. Low elevation stands had significantly less mortality (7%) vs. high elevation (8%). The roadside plot data suggests that Colorado's aspen on these four national forests overall were healthy; mortality rates iii among aspen were fairly low (~3 -8%) among all stems, and average percent live crown among adults was high (~85 -90%), in spite of nearly ubiquitous presence of disease (~97 -99%) and high incidence of insect damage (~50 -75%).We also established 98 aspen stand assessment plots with half of the plots in damaged stands, as defined by U.S.D.A. Forest Service aerial detection surveys (ADS), and half in healthy aspen stands. Damaged stands were defined as those stands with (1) thinning crowns among at least 25% of adult aspen, (2) stands with moderate (<50% of stems) levels of overstory mortality, or (3) stands with high (>50% of stems) levels of overstory mortality. Healthy aspen stands were defined as having (1) a maximum mortality rate of 5 -7% among all aspen, and/or (2) more than 75% of adult aspen with full crowns.Adult aspen in damaged stands tended to be less vigorous, based a health score index from 1 to 5, with higher scores indicating less healthy conditions (where 1=0-25% damage; 2 = 25-50% damage; 3 = >50% damage; 4 = recent dead; 5 = >5 years dead).Health scores averaged 1.7 in healthy stands, compared to 2.3 in damaged stands.Saplings in damaged stands tended to be healthier with a score of 1.7, compared to 2.2 in healthy stands. Further, there was no difference in the proportion live or total numbers of saplings per hectare between healthy and damaged stands. The prevalence of damaging organisms, such as Cytospora canker (20% in damaged, 13% in healthy), wood-boring insects (27% in damaged, 10% in healthy), and aspen bark beetles (16% in damaged, 7% in healthy) was considerably greater among damaged stands. Site conditions also influenced the prevalence of some of these damage agents: bark beetles were most common among stands at low elevations (18%, compared to 11% and 6% at moderate iv and high elevations, respectively); Cytospora canker was most common among stands on south-or west-facing aspects (20% and 19%, respectively); both aspen bark beetles and Cytospora canker were also most common among stands in the southernmost section of the survey area, the Pike-San Isabel national forest (41% and 36%). There was no difference in the severity of canker or decay fungal infection between healthy and damaged stands. Cytospora canker infestations were more severe on the Medicine Bow NF compared to the other three national forests, and Marssonina foliar blight infection appeared to be most severe on slope summits, concave sites, and sites with either no to low percent slope or moderately steep sl...

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Section: Aspen Dieback and Sudden Aspen Declinementioning

confidence: 99%

Section: Prevalence Of Cytospora Canker Was Greater Among Stands Eastmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

Dudley

Burns

Jacobi

2015

Forest Ecology and Management

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“…A complex known as sudden aspen decline (SAD) is causing damage and mortality in stands of trembling aspen across the Rocky Mountains, especially in Colorado. Sudden aspen decline is characterized by rapid branch dieback, crown thinning, and mortality without the involvement of primary pathogens and insects (Worrall et al 2010). This complex has not affected much of the aspen population in South Dakota, although it has been recorded as occurring in the State by aerial detection surveys (Fig.…”

Section: What We Foundmentioning

confidence: 99%

South Dakota's Forests 2010

Piva¹,

Walters²,

Haugan³

et al. 2013

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The second full annual inventory of South Dakota's forests reports 1.88 million acres of forest land with an average volume more than 1,200 cubic feet per acre for all live trees. Forest land is dominated by the ponderosa pine forest type, which occupies 60 percent of the forest land area. Sixty-three percent of the forest land consists of large diameter stands, 15 percent medium diameter stands, 15 percent small diameter stands, and 7 percent is nonstocked. The average annual net growth of live trees on forest land from 2006 to 2010 is 40.2 million cubic feet per year while average annual removal is 25.8 million cubic feet per year. This report includes additional information on forest attributes, land use change, carbon, timber products, and forest health. Detailed information on forest inventory methods, data quality estimates, tables, and raw data can be found in the Statistics, Methods, and Quality Assurance section found on the DVD on the inside back cover of this report. AcknowledgmentsThe authors thank the individuals who contributed both to the inventory and analysis of South Dakota's forest resources. Staff with key responsibility for data management, processing, and estimation included Carol Alerich, Manuscript received for publication November 2012Printed on recycled paper

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“…In the central Rocky Mountains, rapid and widespread mortality, referred to as ''Sudden Aspen Decline'' (SAD), is occurring as a result of moisture stress and hydraulic impairment (Worrall et al 2010, Anderegg et al 2012). Mortality such as this is projected to continue as the climate envelope for aspen diminishes in the next century (Rehfeldt et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Evolving paradigms of aspen ecology and management: impacts of stand condition and fire severity on vegetation dynamics

Krasnow

Stephens

2015

Ecosphere

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Abstract. Quaking aspen (Populus tremuloides Michx.) comprises only a small fraction of western USAforests, yet contributes significant biological diversity and is considered by many to be the most important deciduous forest type in western North America. There is currently a high level of concern in the western United States as many seral aspen populations are declining in vigor due to drought, ungulate browsing, and lack of disturbance. It is also highly uncertain if aspen will successfully accommodate future climate warming via migration through seedling establishment, which has been assumed to be extremely rare. In recent years, fundamental assumptions concerning aspen clonal age, regeneration, and genetic diversity have been challenged, and these findings have important implications for management and persistence of aspen in western USA forests. In this study, we compared regeneration dynamics of aspen revitalization strategies (conifer removal and prescribed fire) to unplanned wildfires of low, moderate, and high severity in the Sierra Nevada, and related multiple components of pre-fire stand composition to post-fire aspen regeneration. To better understand the viability of aspen migration to accommodate future climate warming, we examined recent events of aspen seedling establishment. We found substantial evidence that greater disturbance severity yields increased aspen sprout density and growth rates, and that live conifer and/or dead aspen basal area in a stand before a fire reduces post fire sprout density. Additionally, we found evidence that aspen seedling establishment is more common than has been assumed, and represents a viable means for aspen migration. Future climate changes will present both challenges and opportunities for aspen. Increased temperatures and drought will stress existing populations, but increased high severity fire in forested areas, may provide opportunity for successful aspen migration and genet establishment. In addition to revitalizing existing aspen stands, future management goals should include the establishment of new stands in more suitable habitat.

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Effects and etiology of sudden aspen decline in southwestern Colorado, USA

Cited by 153 publications

References 16 publications

Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

South Dakota's Forests 2010

Evolving paradigms of aspen ecology and management: impacts of stand condition and fire severity on vegetation dynamics

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