76-year decline and recovery of aspen mediated by contrasting fire regimes: Long-unburned, infrequent and frequent mixed-severity wildfire

Quaking aspen (Populus tremuloides) is a valued, minor component on northeastern California landscapes. It provides a wide range of ecosystem services and has been in decline throughout the region for the last century. This decline may be explained partially by the lack of fire on the landscape due to heavier fire suppression, as aspen benefit from fire that eliminates conifer competition and stimulates reproduction through root suckering. However, there is little known about how aspen stand area changes in response to overlapping fire. Our study area in northeastern California on the Lassen, Modoc and Plumas National Forests has experienced recent large mixed-severity wildfires where aspen was present, providing an opportunity to study the re-introduction of fire. We observed two time periods; a 52-year absence of fire from 1941 to 1993 preceding a 24-year period of wildfire activity from 1993 to 2017. We utilized aerial photos and satellite imagery to delineate aspen stands and assess conifer cover percent. We chose aspen stands in areas where wildfires overlapped (twice-burned), where only a single wildfire burned, and areas that did not burn within the recent 24-year period. We observed these same stands within the first period of fire exclusion for comparison (i.e., 1941–1993). In the absence of fire, all aspen stand areas declined and all stands experienced increases in conifer composition. After wildfire, stands that burned experienced a release from conifer competition and increased in stand area. Stands that burned twice or at high severity experienced a larger removal of conifer competition than stands that burned once at low severity, promoting expansion of aspen stand area. Stands with less edge:area ratio also expanded in area more with fire present. Across both time periods, stand movement, where aspen stand footprints were mostly in new areas compared to footprints of previous years, was highest in smaller stands. In the fire exclusion period, smaller stands exhibited greater loss of area and changes in location (movement) than in the return of fire period, highlighting their vulnerability to loss via succession to conifers in the absence of disturbances that provide adequate growing space for aspen over time.

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Multidecadal decline and recovery of aspen experiencing contrasting fire regimes: long-unburned, infrequent and frequent mixed-severity wildfire

10.1101/2020.04.28.065896 ◽

2020 ◽

Author(s):

Cerena J. Brewen ◽

John-Pascal Berrill ◽

Martin W. Ritchie ◽

Kevin Boston ◽

Christa M. Dagley ◽

...

Keyword(s):

Populus Tremuloides ◽

Spatial Dynamics ◽

Minor Component ◽

Fire Regimes ◽

Quaking Aspen ◽

Aerial Photos ◽

Wide Range ◽

Fire Exclusion ◽

Time Periods ◽

Root Suckering

AbstractQuaking aspen (Populus tremuloides) is a valued, minor component on western landscapes. It provides a wide range of ecosystem services and has been in decline throughout the arid west for the last century. This decline may be explained partially by the lack of fire on the landscape as aspen benefit from fire that eliminates conifer competition and stimulates reproduction through root suckering. Managers are interested in aspen restoration but there is a lack of knowledge about their spatial dynamics in response to fire. Our study area in northeastern California on the Lassen, Modoc and Plumas National Forests has experienced recent large mixed-severity wildfires where aspen was present, providing an opportunity to study the re-introduction of fire. We observed two time periods; a 54-year absence of fire from 1941 to 1993 preceding a 24-year period of wildfire activity from 1993 to 2017. We utilized aerial photos to delineate aspen stand size, location and succession to conifers. We chose aspen stands in areas where wildfires overlapped (twice-burned), where only a single wildfire burned, and areas that did not burn within the recent 24-year period. We looked at these same stands within the first period of fire exclusion for comparison (i.e., 1941-1993). In the absence of fire, all aspen stand areas declined and all stands experienced increases in conifer composition. After wildfire, stands that burned experienced a release from conifer competition and increased in stand area. Stands that burned twice or at high severity experienced a larger removal of conifer competition than stands that burned once at low severity, promoting aspen recovery and expansion. Stands with less edge:area ratio also expanded more with fire present. Across both time periods, stand movement, where aspen stand footprints were mostly in new areas compared to footprints of previous years, was highest in smaller stands. In the fire exclusion period, smaller stands exhibited greater changes in area and location (movement), highlighting their vulnerability to loss in the absence of disturbances that provide adequate growing space for aspen over time.

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A Landscape Approach to Aspen Restoration: Understanding the Role of Biophysical Setting in Aspen Community Dynamics

The UW National Parks Service Research Station Annual Reports ◽

10.13001/uwnpsrc.2002.3515 ◽

2002 ◽

Vol 26 ◽

pp. 97-102

Author(s):

Kathryn Brown ◽

Andrew Hansen ◽

Robert Keane ◽

Lisa Graumlich

Keyword(s):

Populus Tremuloides ◽

Community Dynamics ◽

Rocky Mountain ◽

Small Sample ◽

Quaking Aspen ◽

Climatic Fluctuations ◽

Conifer Encroachment ◽

Considerable Debate ◽

Fire Exclusion

Considerable debate surrounds the persistence of quaking aspen (Populus tremuloides) communities in western North America. Loss of aspen cover has been documented in several studies in various Rocky Mountain ecosystems (Loope and Gruel 1973; Romme et al. 1995; Renkin and Despain 1996; Wirth et al. 1996; Baker et al. 1997; Kay 1997; Bartos and Campbell 1998; White et al. 1998; Gallant et al. 2003). Explanations for loss of aspen include conifer encroachment, fire exclusion, herbivory, and climatic fluctuations (Loope and Gruell 1973; Mueggler 1985; Bartos et al. 1994; Romme et al. 1995; Kay 1997; White et al. 1998). However, many studies documenting aspen decline have been geographically limited or based on a small sample of subjectively chosen stands (Barnett and Stohlgren 2001; Hessl 2002; Kaye et al. 2003).

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Short-Term Responses of Aspen to Fire and Mechanical Treatments in Interior Alaska

Northern Journal of Applied Forestry ◽

10.1093/njaf/24.2.153 ◽

2007 ◽

Vol 24 (2) ◽

pp. 153-157 ◽

Cited By ~ 6

Author(s):

Thomas F. Paragi ◽

Dale A. Haggstrom

Keyword(s):

Populus Tremuloides ◽

Prescribed Burning ◽

Sandy Loam ◽

Fire Suppression ◽

Fire Behavior ◽

Wildlife Habitat ◽

Quaking Aspen ◽

Prescribed Burns ◽

Loess Hills ◽

Interior Alaska

Abstract Fire suppression and limited timber markets presently hinder maintenance of the early successional broad-leaved forest for wildlife habitat near settlements in interior Alaska. During 1999ߝ2003, we evaluated the efficacy of prescribed burning, felling, and shearblading (with and without debris removal) to regenerate quaking aspen (Populus tremuloides). Treatments were conducted largely during the dormant period for aspen: prescribed burns in mid-May and mechanical treatments in late August through early April. Prescribed burns on loess hills produced 40,900ߝ233,000 stems/ha by the second growing season. Low relative humidity, slope of more than 10°, southerly aspect, and juxtaposition to open areas produced fire behavior adequate to ensure top killing and vigorous sprouting response. Felling by chainsaw on loess hills produced 34,800ߝ89,800 stems/ha, whereas dozer shearblading on glacial outwash (loam over gravel) produced 74,200ߝ209,200 stems/ha (cleared portions and windrows combined) and a sandy loam floodplain produced 31,400ߝ64,800 stems/ha. Pushing debris into windrows or scraping thick moss allowed warmer soils and produced greater sprouting on cleared sites relative to sections where debris or moss remained. Mechanical treatments were 25ߝ75% of current prescribed fire costs, but debris accumulation may hinder access by browsing species and attract terrestrial predators of gallinaceous birds.

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Surface Fire to Crown Fire: Fire History in the Taos Valley Watersheds, New Mexico, USA

Fire ◽

10.3390/fire2010014 ◽

2019 ◽

Vol 2 (1) ◽

pp. 14

Author(s):

Lane Johnson ◽

Ellis Margolis

Keyword(s):

Populus Tremuloides ◽

Fire History ◽

Historical Context ◽

Fire Regimes ◽

High Elevation ◽

Severe Drought ◽

Quaking Aspen ◽

Conifer Forests ◽

High Severity ◽

Historical Photographs

Tree-ring fire scars, tree ages, historical photographs, and historical surveys indicate that, for centuries, fire played different ecological roles across gradients of elevation, forest, and fire regimes in the Taos Valley Watersheds. Historical fire regimes collapsed across the three watersheds by 1899, leaving all sites without fire for at least 119 years. Historical photographs and quaking aspen (Populus tremuloides Michx.) ages indicate that a high-severity fire historically burned at multiple high-elevation subalpine plots in today’s Village of Taos Ski Valley, with large high-severity patches (>640 ha). Low-severity, frequent (9–29-year median interval) surface fires burned on the south aspects in nearby lower elevation dry conifer forests in all watersheds. Fires were associated with drought during the fire year. Widespread fires commonly burned synchronously in multiple watersheds during more severe drought years, preceded by wet years, including fire in all three watersheds in 1664, 1715, and 1842. In contrast, recent local “large” wildfires have only burned within single watersheds and may not be considered large in a historical context. Management to promote repeated low-severity fires and the associated open stand structures is within the historical range of variability in the dry conifer forests of these watersheds. In the high-elevation, subalpine forests, different management approaches are needed, which balance ecological and socioeconomic values while providing public safety.

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Many shades of green: the dynamic tropical forest–savannah transition zones

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0308 ◽

2016 ◽

Vol 371 (1703) ◽

pp. 20150308 ◽

Cited By ~ 59

Author(s):

Immaculada Oliveras ◽

Yadvinder Malhi

Keyword(s):

Fire Suppression ◽

Alternative Stable States ◽

Terrestrial Ecosystems ◽

Fire Regimes ◽

Stable States ◽

Ecological Processes ◽

Wide Range ◽

History Of ◽

Tropical Areas ◽

Global And Local

The forest–savannah transition is the most widespread ecotone in tropical areas, separating two of the most productive terrestrial ecosystems. Here, we review current understanding of the factors that shape this transition, and how it may change under various drivers of local or global change. At broadest scales, the location of the transition is shaped by water availability, mediated strongly at local scales by fire regimes, herbivory pressure and spatial variation in soil properties. The frequently dynamic nature of this transition suggests that forest and savannah can exist as alternative stable states, maintained and separated by fire–grass feedbacks and tree shade–fire suppression feedback. However, this theory is still contested and the relative contributions of the main biotic and abiotic drivers and their interactions are yet not fully understood. These drivers interplay with a wide range of ecological processes and attributes at the global, continental, regional and local scales. The evolutionary history of the biotic and abiotic drivers and processes plays an important role in the current distributions of these transitions as well as in their species composition and ecosystem functioning. This ecotone can be sensitive to shifts in climate and other driving factors, but is also potentially stabilized by negative feedback processes. There is abundant evidence that these transitions are shifting under contemporary global and local changes, but the direction of shift varies according to region. However, it still remains uncertain how these transitions will respond to rapid and multi-faceted ongoing current changes, and how increasing human influence will interact with these shifts. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’.

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

Forests ◽

10.3390/f10080671 ◽

2019 ◽

Vol 10 (8) ◽

pp. 671 ◽

Cited By ~ 2

Author(s):

Jack Singer ◽

Rob Turnbull ◽

Mark Foster ◽

Charles Bettigole ◽

Brent Frey ◽

...

Keyword(s):

Land Use ◽

North America ◽

Populus Tremuloides ◽

Tree Species ◽

Close Relative ◽

Rapid Decline ◽

Land Use History ◽

Quaking Aspen ◽

Fire Exclusion ◽

Sudden Aspen Decline

The American quaking aspen (Populus tremuloides Michx.) and its close relative, the Eurasian quaking aspen (Populus tremula L.), cover a realm that is perhaps the most expansive of all tree species in the world. In North America, sudden aspen decline (SAD) is a growing concern that marks the rapid decline of quaking aspen trees leading to mortality at the stand and landscape scale. Research suggests that drought and water stress are the primary causes of SAD. Predisposing factors (age, structure, and landscape position), as well as associated stressors (i.e., pests and pathogens), have been linked to mortality in affected stands. The conflation of multiple interacting factors across the aspen’s broad geographic range in North America has produced significant debate over the classification of SAD as a disease and the proper management of affected stands. Interestingly, no such effects have been reported for the Eurasian aspen. We here review and synthesize the growing body of literature for North America and suggest that SAD is a novel decline disease resulting from multiple inciting and interacting factors related to climate, land-use history, and successional dynamics. We suggest that the range of aspen observed at the onset of the 21st Century was bolstered by a wet period in western North America that coincided with widespread regional cutting and clearing of late-successional forests for timber and grazing. No comparable land-use history, successional status, or age-class structure is apparent or linked for Eurasian forests. Eurasian aspen is either absent or young in managed forests, or old and decadent in parks in Fenno-Scandinavia, or it grows more intimately with a more diverse mixture of tree species that have arisen from a longer period of frequent timber cutting in Russia. Based on these insights we provide recommendations for practical management techniques that can promote stand resilience and recovery across a range of stand conditions in North America. Managers should attempt to identify SAD-prone stands using the presence of predisposing conditions and focus treatments such as coppice or prescribed fire on stands with suitable topographies, elevations, and climates. We conclude that SAD will persist throughout the coming decades, given the enormity of past cutting history, fire exclusion, and current changes in climate until a more active restoration agenda is implemented.

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Short-Term Flooding Effects on Root Suckering of Quaking Aspen

Northern Journal of Applied Forestry ◽

10.1093/njaf/15.4.169 ◽

1998 ◽

Vol 15 (4) ◽

pp. 169-173 ◽

Cited By ~ 3

Author(s):

P. C. Bates ◽

E. Sucoff ◽

C. R. Blinn

Keyword(s):

Populus Tremuloides ◽

Soil Conditions ◽

Quaking Aspen ◽

Short Term ◽

Soil Material ◽

Root Segments ◽

Temperature Regimes ◽

Flooding Duration ◽

Controlled Environments ◽

Root Suckering

Abstract Unexpectedly few root suckers may develop following summer clearcuts of quaking aspen (Populus tremuloides Michx.) on sites with fine-textured soils and level terrain. We hypothesized that the poor regeneration is partially a result of the flooded soil conditions that follow such harvests, and that the damage would increase with duration of flooding and temperature. Root segments from ca. 45-yr-old aspen trees were planted in saturated mixtures of O and A horizon soil material for 2, 6, 10, and 14 days at relatively warm and cool temperatures (12 hr day/night temperature regimes of 28/20°C and 20/12°C, respectively). The root segments were then transplanted into moist soil at ambient O2 for an additional 14 to 38 days. Suckering was significantly reduced by increased flooding duration and by flooding at warmer temperatures. The percentage of segments that suckered decreased exponentially with accumulated growing degree days during flooding. Saturated soil conditions can inhibit aspen suckering in controlled environments and may have the potential for precluding successful regeneration following clearcutting. North. J. Appl. For. 15(4):169-173.

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A century of transformation: Fire regime transitions from 1919 to 2019 in southeastern British Columbia, Canada

10.31219/osf.io/qhtcj ◽

2021 ◽

Author(s):

Jennifer N Baron ◽

Sarah E. Gergel ◽

Paul F. Hessburg ◽

Lori D. Daniels

Keyword(s):

British Columbia ◽

Fire Regime ◽

Fire Suppression ◽

Fire Regimes ◽

Fire Frequency ◽

Burned Area ◽

Annual Number ◽

Fire Size ◽

Climatic Period ◽

Fire Exclusion

The past 100 years marks a transition between pre-colonial and modern era fire regimes, which provides crucial context for understanding future wildfire behavior. Using the greatest depth of digitized fire events in Canada, we identify distinct phases of wildfire regimes from 1919 to 2019 by evaluating changes in mapped fire perimeters (>20-ha) across the East Kootenay forest region (including the southern Rocky Mountain Trench), British Columbia (BC). We detect transitions in annual number of fires, burned area, and fire size; explore the roles of lightning- and human-caused fires in driving these transitions; and quantify departures from historical fire frequency at the regional level. We found that, relative to historical fire frequency, fire exclusion created a significant fire deficit across 89% of the flammable landscape. Fire was active from 1919 to 1940 with frequent and large fire events, but the regime was already altered by a century of colonization. Fire activity decreased after 1940, coinciding with effective fire suppression influenced by a mild climatic period. After 2003, the combined effects of fire exclusion and accelerated climate change fueled a shift in fire regimes of various forest types, with increases in area burned and mean fire size driven by lightning.

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Understanding Distressed Residential Transaction Discounts Across Price Segments and Market Conditions

Journal of Real Estate Research ◽

10.22300/0896-5803.42.1.151 ◽

2020 ◽

Vol 42 (1) ◽

pp. 151-182

Author(s):

Ramya Rajajagadeesan Aroul ◽

J. Andrew Hansz ◽

Mauricio Rodriguez

Keyword(s):

Transaction Costs ◽

Time Varying ◽

Market Segment ◽

Market Conditions ◽

Large Market ◽

Space And Time ◽

Wide Range ◽

Time Periods ◽

Market Areas

In the literature, there is a wide range of discounts associated with foreclosures. Comparisons across studies are difficult as they use different methodologies across large areas over different time periods. We employ a consistent methodology across space and time. We find modest discounts, within the range of typical transaction costs, in all but the highest priced market segment. Higher priced segments could explain prior findings of substantial discounts. We find that discounts are time-varying, with discounts increasing with market distress. A one-size-fits-all approach is not appropriate when estimating distressed transaction discounts across large market areas or under changing market conditions.

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