Changes in forest structure since 1860 in ponderosa pine dominated forests in the Colorado and Wyoming Front Range, USA

Battaglia, Michael A.; Gannon, Benjamin M.; Brown, Peter M.; Fornwalt, Paula J.; Cheng, Antony S.; Huckaby, Laurie S.

doi:10.1016/j.foreco.2018.04.010

Cited by 56 publications

(62 citation statements)

References 107 publications

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“…Our findings suggest that management activities that reduce fire severity could contribute to the conservation of plant diversity in dry conifer forests. Many such forests are increasingly experiencing uncharacteristically extensive high‐severity fire (Singleton et al., ; Stevens et al., ), due at least in part to increased forest density and homogeneity following a century of fire suppression, livestock grazing, and logging (Battaglia et al., ; Safford & Stevens, ). Restoration and fuels reduction treatments that create more open and heterogeneous forest conditions have been shown to reduce fire‐caused tree mortality, even under extreme weather conditions (Fulé, Crouse, Roccaforte, & Kalies, ; Safford, Stevens, Merriam, Meyer, & Latimer, ).…”

Section: Discussionmentioning

confidence: 99%

Fire severity and changing composition of forest understory plant communities

Stevens

Miller

Fornwalt

2019

J Vegetation Science

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Questions Gradients of fire severity in dry conifer forests can be associated with variation in understory floristic composition. Recent work in dry conifer forests in California, USA, has suggested that more severely burned stands contain more thermophilic taxa (those associated with warmer and drier conditions), and that forest disturbance may therefore accelerate floristic shifts already underway due to climate change. However, it remains unknown how rapidly thermophilic taxa shifts occur following disturbance, how long such shifts are likely to persist, and how different thermophilic post‐disturbance communities are from pre‐disturbance communities. Location Colorado Front Range, USA. Methods We investigated these questions using a unique 15‐year vegetation plot dataset that captures pre‐ and post‐fire understory community composition across a gradient of fire severity in dry conifer forests, classifying taxa using the biogeographic affinity concept. Results Thermophilization (defined here as a decrease in the ratio of cool‐mesic taxa to warm‐xeric taxa, based on biogeographic affinity of paleobotanical lineages) was observed as early as one year post‐fire for all fire severity classes, but was stronger at sites that burned at higher severity. The ratio of cool‐mesic to warm‐xeric taxa recovered to pre‐fire levels within 10 years in stands that burned at low severity, but not in stands that burned at moderate or high severity. The process of thermophilization after high‐severity fire appears to be driven primarily by the gain of warm‐xeric taxa that were absent before the fire, but losses of cool‐mesic taxa, which did not return during the duration of the study, also played a role. Conclusions Decreases in canopy cover appear to be a main contributor to understory thermophilization. Fine‐scale heterogeneity in post‐fire forest structure is likely an important driver of floristic diversity, creating the microclimatic variation necessary to maintain floristic refugia for species mal‐adapted to increasingly warm and dry conditions.

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Section: Discussionmentioning

confidence: 99%

Fire severity and changing composition of forest understory plant communities

Stevens

Miller

Fornwalt

2019

J Vegetation Science

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“…Stand age data indicate that abundant tree establishment occurred during the early 1900s throughout the lower montane zone (Sherriff and Veblen , Battaglia et al. ). Because it may take several years for tree crowns to expand to a size that could be classified in the 1938 imagery (i.e., >2 m crown diameter), some of this early 1900s establishment likely appeared to be forest cover increase during the 1938–2015 period of our study.…”

Section: Discussionmentioning

confidence: 99%

“…), historical stand densities (Battaglia et al. ), climate and tree growth (Villalba et al. , Veblen et al.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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Recent shifts in global forest area highlight the importance of understanding the causes and consequences of forest change. To examine the influence of several potential drivers of forest cover change, we used supervised classifications of historical (1938–1940) and contemporary (2015) aerial imagery covering a 2932‐km2 study area in the northern Front Range (NFR) of Colorado and we linked observed changes in forest cover with abiotic factors, land use, and fire history. Forest cover in the NFR demonstrated broad‐scale changes 1938–2015 and overall cover increased 7.8%, but there was notable spatial variability and many sites also experienced Forest Loss. Recent (1978–2015) wildfire was the largest single driver of Forest Loss, with fires burning 14.3% of the total study area. Recently burned areas showed net losses of 36.9% forest cover. Reasons for Forest Gain were more complex, with elevation, past mining density, fire history, and topographic heat load index being the strongest predictors of increases in forest cover. Historical mining activity is one of the dominant anthropogenic impacts in ecosystems in the NFR and it had a complex, non‐linear relationship with 20th‐century changes in forest cover. Subalpine stands originating after stand‐replacing fires circa mid‐1800s to early 1900s showed some of the greatest gains in forest cover, indicative of slow and continuous post‐fire recovery through the 20th century. We also investigated factors such as land ownership, road density, forest management activities, and development intensity, which played detectable, but more minor roles in observed change. Twentieth‐century changes in forest cover throughout the NFR are a result of ecological disturbances and anthropogenic influences operating at varying timescales and overlaid upon variability in the abiotic environment.

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“…Restoration objectives for a given area are usually informed by the range of conditions that occurred there historically (i.e., the historical range of variability (HRV)), as they represent the fire-resilient conditions that existed prior to post-settlement land-use practices like fire suppression, logging, and grazing [34,57,58]. Regarding live overstory structure, Battaglia et al [7] estimated that historical density in dry conifer forests of the Front Range ranged from about 62 to 214 stems ha −1 and that historical basal area ranged from about 5 to 11 m 2 ha −1 .…”

Section: Live Overstory Structurementioning

confidence: 99%

“…While wildfire activity for these forests was diminished relative to historical levels for most of the 20th century due to fire suppression, logging, grazing, and other land-use practices [1][2][3], in recent decades it has increased markedly [4][5][6]. The recent increase has likewise been borne out of past land-use practices, which allowed forests to become denser and more homogeneous [1,3,7], as well as out of a changing climate [4][5][6]. The resurgence of wildfires in western dry conifer forests thus makes it important that managers, researchers, and others thoroughly understand how forests are directly affected by fire and how they subsequently develop through time.…”

Section: Introductionmentioning

confidence: 99%

Overstory Structure and Surface Cover Dynamics in the Decade Following the Hayman Fire, Colorado

Fornwalt

Stevens‐Rumann

Collins

2018

Forests

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Abstract:The 2002 Hayman Fire burned with mixed-severity across a 400-ha dry conifer study site in Colorado, USA, where overstory tree and surface cover attributes had been recently measured on 20 0.1-ha permanent plots. We remeasured these plots repeatedly during the first post-fire decade to examine how the attributes changed through time and whether changes were influenced by fire severity. We found that most attributes were temporally dynamic and that fire severity shaped their dynamics. For example, low-severity plots experienced a modest reduction in live overstory density due to both immediate and delayed tree mortality, and no change in live overstory basal area through time; in contrast, high-severity plots experienced an immediate and total loss of live overstory density and basal area. Large snag density in low-severity plots did not vary temporally because snag recruitment balanced snag loss; however, in high-severity plots large snag density increased markedly immediately post-fire and then declined by about half by post-fire year ten as snags fell. Mineral soil cover increased modestly immediately post-fire in low-severity plots and substantially immediately post-fire in high-severity plots, but changed little in ensuing years for either severity class. By incorporating pre-fire and repeatedly-measured post-fire data for a range of severities, our study uniquely contributes to the current understanding of wildfire effects in dry conifer forests and should be of interest to managers, researchers, and others.

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Changes in forest structure since 1860 in ponderosa pine dominated forests in the Colorado and Wyoming Front Range, USA

Cited by 56 publications

References 107 publications

Fire severity and changing composition of forest understory plant communities

Fire severity and changing composition of forest understory plant communities

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

Overstory Structure and Surface Cover Dynamics in the Decade Following the Hayman Fire, Colorado

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