Wildfire activity and land use drove 20th‐century changes in forest cover in the Colorado front range

Rodman, Kyle C.; Veblen, Thomas T.; Saraceni, Sara; Chapman, Teresa B.

doi:10.1002/ecs2.2594

Cited by 34 publications

(19 citation statements)

References 105 publications

(270 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, postfire planting of spruce is already occurring in some locations within the West Fork Complex (USFS 2019). However, the slow nature of subalpine forest recovery following disturbance (Rodman et al 2019 b ) and shifting climate space for subalpine species as climate warms (Bell et al 2014) implies that management action to support postfire compositional recovery of spruce may be a short‐term fix, particularly in marginal sites (e.g., lower elevation, drier sites). If the goal is to maintain forest cover, strategies that facilitate movement of species (e.g., assisted migration) suitable to current and future climate and disturbance regimes may be preferred (Millar et al 2007).…”

Section: Discussionmentioning

confidence: 99%

Future dominance by quaking aspen expected following short‐interval, compounded disturbance interaction

et al. 2021

Self Cite

View full text Add to dashboard Cite

The spatial overlap of multiple ecological disturbances in close succession has the capacity to alter trajectories of ecosystem recovery. Widespread bark beetle outbreaks and wildfire have affected many forests in western North America in the past two decades in areas of important habitat for native ungulates. Bark beetle outbreaks prior to fire may deplete seed supply of the host species, and differences in fire-related regeneration strategies among species may shift the species composition and structure of the initial forest trajectory. Subsequent browsing of postfire tree regeneration by large ungulates, such as elk (Cervus canadensis), may limit the capacity for regeneration to grow above the browse zone to form the next forest canopy. Five stand-replacing wildfires burned~60,000 ha of subalpine forest that had previously been affected by severe (>90% mortality) outbreaks of spruce beetle (SB, Dendroctonus rufipennis) in Engelmann spruce (Picea engelmannii) in 2012-2013 in southwestern Colorado. Here we examine the drivers of variability in abundance of newly established conifer tree seedlings [spruce and subalpine fir (Abies lasiocarpa)] and resprouts of quaking aspen (Populus tremuloides) following the short-interval sequence of SB outbreaks and wildfire (2-8 yr between SB outbreak and fire) at sites where we previously reconstructed severities of SB and fire. We then examine the implications of ungulate browsing for forest recovery. We found that abundances of postfire spruce seedling establishment decreased substantially in areas of severe SB outbreak. Prolific aspen resprouting in stands with live aspen prior to fire will favor an initial postfire forest trajectory dominated by aspen. However, preferential browsing of postfire aspen resprouts by ungulates will likely slow the rate of canopy recovery but browsing is unlikely to alter the species composition of the future forest canopy. Collectively, our results show that SB outbreak prior to fire increases the vulnerability of spruce-fir forests to shifts in forest type (conifer to aspen) and physiognomic community type (conifer forest to non-forest). By identifying where compounded disturbance interactions are likely to limit recovery of forests or tree species, our findings are useful for developing adaptive management strategies in the context of warming climate and shifting disturbance regimes.

show abstract

Section: Discussionmentioning

confidence: 99%

Future dominance by quaking aspen expected following short‐interval, compounded disturbance interaction

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…As an alternative to field‐derived distances to mature conifers that could be characterized throughout each fire perimeter, we quantified postfire canopy cover of mature conifers using image processing (following Rodman et al. ) and classification of 1‐m aerial imagery from the National Agriculture Imagery Progam (USFS ; Appendix ). Overall accuracy of this classification was 90.2% at the level of a 1‐m pixel (Appendix : Table S1).…”

Section: Methodsmentioning

confidence: 99%

Limitations to recovery following wildfire in dry forests of southern Colorado and northern New Mexico, USA

Rodman

Veblen

Chapman

et al. 2019

Ecological Applications

Self Cite

View full text Add to dashboard Cite

Climate warming is contributing to increases in wildfire activity throughout the western United States, leading to potentially long‐lasting shifts in vegetation. The response of forest ecosystems to wildfire is thus a crucial indicator of future vegetation trajectories, and these responses are contingent upon factors such as seed availability, interannual climate variability, average climate, and other components of the physical environment. To better understand variation in resilience to wildfire across vulnerable dry forests, we surveyed conifer seedling densities in 15 recent (1988–2010) wildfires and characterized temporal variation in seed cone production and seedling establishment. We then predicted postfire seedling densities at a 30‐m resolution within each fire perimeter using downscaled climate data, monthly water balance models, and maps of surviving forest cover. Widespread ponderosa pine (Pinus ponderosa) seed cone production occurred at least twice following each fire surveyed, and pulses of conifer seedling establishment coincided with years of above‐average moisture availability. Ponderosa pine and Douglas‐fir (Pseudotsuga menziesii) seedling densities were higher on more mesic sites and adjacent to surviving trees, though there were also important interspecific differences, likely attributable to drought and shade tolerance. We estimated that postfire seedling densities in 42% (for ponderosa pine) and 69% (for Douglas‐fir) of the total burned area were below the lowest reported historical tree densities in these forests. Spatial models demonstrated that an absence of mature conifers (particularly in the interior of large, high‐severity patches) limited seedling densities in many areas, but 30‐yr average actual evapotranspiration and climatic water deficit limited densities on marginal sites. A better understanding of the limitations to postfire forest recovery will refine models of vegetation dynamics and will help to improve strategies of adaptation to a warming climate and shifting fire activity.

show abstract

“…MTBS thresholds for Low, Moderate, and High burn severity are subjective, based on analyst interpretation, and do not necessarily reflect these mortality thresholds for burn severity classes. Modern forests of the CFR reflect complex spatio-temporal patterns of human impacts through episodes of intentional burning during severe droughts in the 19 th century, 20 th century fire exclusion, grazing, and logging [56][57][58]. In the lower montane zone, the exclusion of frequent low-severity fires has resulted in increased stand densities [6,[9][10][11]59].…”

Section: Study Areamentioning

confidence: 99%

“…The importance and decline of small meadows in ponderosa pine has been documented in Colorado [102]. Between 1938 and 2015 fire-excluded areas with a historic low-severity fire regime in the lower montane of the CFR experienced an almost 16% net increase in forest cover and fire-excluded mixed-severity stands showed an almost 12% net increase [58]. While mixed-and high-severity fire has been an integral part of ponderosa pine forests in the Southern Rockies in higher elevations [6,7,54], the presence of small patches of surviving trees within and bordering savannas may have been a critical aspect of ecosystem recovery, particularly at lower elevations with low-severity fire regimes [11,53,59].…”

Section: Predictability Of Conifer Refugia Using Landscape Variables:mentioning

confidence: 99%

Still standing: Recent patterns of post-fire conifer refugia in ponderosa pine-dominated forests of the Colorado Front Range

et al. 2020

Self Cite

View full text Add to dashboard Cite

Forested fire refugia (trees that survive fires) are important disturbance legacies that provide seed sources for post-fire regeneration. Conifer regeneration has been limited following some recent western fires, particularly in ponderosa pine (Pinus ponderosa) forests. However, the extent, characteristics, and predictability of ponderosa pine fire refugia are largely unknown. Within 23 fires in ponderosa pine-dominated forests of the Colorado Front Range (1996-2013), we evaluated the spatial characteristics and predictability of refugia: first using Monitoring Trends in Burn Severity (MTBS) burn severity metrics, then using landscape variables (topography, weather, anthropogenic factors, and pre-fire forest cover). Using 1-m resolution aerial imagery, we created a binary variable of post-fire conifer presence ('Conifer Refugia') and absence ('Conifer Absence') within 30-m grid cells. We found that maximum patch size of Conifer Absence was positively correlated with fire size, and 38% of the burned area was � 50m from a conifer seed source, revealing a management challenge as fire sizes increase with warming further limiting conifer recovery. In predicting Conifer Refugia with two MTBS-produced databases, thematic burn severity classes (TBSC) and continuous Relative differenced Normalized Burn Ratio (RdNBR) values, Conifer Absence was high in previously forested areas of Low and Moderate burn severity classes in TBSC. RdNBR more accurately identified post-fire conifer survivorship. In predicting Conifer Refugia with landscape variables, Conifer Refugia were less likely during burn days with high maximum temperatures: while Conifer Refugia were more likely on moister soils and closer to higher order streams, homes, and roads; and on less rugged, valley topography. Importantly, pre-fire forest canopy cover was not strongly associated with Conifer Refugia. This study further informs forest management by mapping post-fire patches lacking conifer seed sources, validating the use of RdNBR for fire refugia, and detecting abiotic and topographic variables that may promote conifer refugia.

show abstract

Wildfire activity and land use drove 20th‐century changes in forest cover in the Colorado front range

Cited by 34 publications

References 105 publications

Future dominance by quaking aspen expected following short‐interval, compounded disturbance interaction

Future dominance by quaking aspen expected following short‐interval, compounded disturbance interaction

Limitations to recovery following wildfire in dry forests of southern Colorado and northern New Mexico, USA

Still standing: Recent patterns of post-fire conifer refugia in ponderosa pine-dominated forests of the Colorado Front Range

Contact Info

Product

Resources

About