Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado

Calder, W. John; Shuman, Bryan N.

doi:10.1002/ecy.1959

Cited by 38 publications

(65 citation statements)

References 84 publications

(229 reference statements)

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“…We hypothesized that warming facilitated larger fires, but that the fires drove changes in vegetation structure that limited the spread of additional fires (Calder et al., ). Consistent with this hypothesis, we also found that the fires at one of our study sites accelerated the local development of ‘ribbon forests’, a discontinuous mix of linear alpine meadows and ribbons of conifer forest (Calder & Shuman, ). Fossil pollen indicates that ribbon forests only developed there after the fires, but were maintained throughout the last millennium by climatic cooling, which culminated in the Little Ice Age (LIA), a period of cool conditions beginning about ad 1300 or 650 bp (years before ad 1950) (Calder & Shuman, ).…”

Section: Introductionsupporting

confidence: 83%

“…We hypothesized that warming facilitated larger fires, but that the fires drove changes in vegetation structure that limited the spread of additional fires (Calder et al, 2015). Consistent with this hypothesis, we also found that the fires at one of our study sites accelerated the local development of 'ribbon forests', a discontinuous mix of linear alpine meadows and ribbons of conifer forest (Calder & Shuman, 2017).…”

Section: Introductionsupporting

confidence: 78%

“…Climate trends, such as cooling that culminated in the LIA after ca. 650 bp (Figure a), played a large role shaping forest composition, with an oxygen isotopic record (interpreted as a climate proxy for temperature and ratio of snow to precipitation) explaining 30% of the variation in conifer pollen percentages (Calder & Shuman, ). Ribbon forests, for example, became most extensive during the LIA (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…The work presented here builds on previous analyses of sediment cores within and around the Mount Zirkel Wilderness Area (Calder & Shuman, 2017;Calder et al, 2015). The six sites described above were used for pollen and charcoal analysis and an additional six sites were added for charcoal analysis (pollen was not analysed in these additional sediment cores).…”

Section: Materials S and Me Thodsmentioning

confidence: 99%

“…Fossil pollen indicates that ribbon forests only developed there after the fires, but were maintained throughout the last millennium by climatic cooling, which culminated in the Little Ice Age (LIA), a period of cool conditions beginning about ad 1300 or 650 bp (years before ad 1950) (Calder & Shuman, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Climate–fire–vegetation interactions and the rise of novel landscape patterns in subalpine ecosystems, Colorado

2019

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Interactions at multiple scales can shape how forest ecosystems respond to both climate change and disturbance. At landscape scales, feedbacks cause vegetation and wildfire regimes to alter one another, while forest patterns at local scales can result from feedbacks between plants and their abiotic environment. Consequently, disturbances and abiotic changes may give rise to forest patterns that further affect processes like wildfire. Examples may exist in the history of subalpine ribbon forests, which are alternating areas of forest and meadow where snow drifting and linear bands of trees depend upon each other. Just as ongoing climate changes may change snow levels and the dynamics in these forests, past climate changes and wildfires may have generated the conditions suitable for ribbon forests. To examine feedbacks in subalpine forests and the potential that climate changes and fires gave rise to ribbon forests, we obtained six fossil pollen records from a subalpine landscape in Colorado. Forests there may have responded to climate change and widespread wildfires ˜1,000 years ago when >80% of sites on the landscape burned within a century. The fires coincided with regional warming, but the extent of burning declined before the climate cooled, possibly driven by changes in fuel structure and composition. The pollen records indicate that large vegetation changes coincided with the widespread wildfires at five of the six sites. Pollen assemblages consistent with ribbon forests first became important at this time as sagebrush (Artemisia) and other meadow taxa increased and conifers, especially spruce (Picea) declined. The ribbon forests emerged as novel fuel breaks at the time when temperatures rose ˜0.5°C but the number of sites burned per century declined. Cooling during the Little Ice Age then expanded the openings and extent of ribbon forests, probably helping to reduce the frequency of fires across our sites to its minimum. Synthesis. The rise of ribbon forests in northern Colorado illustrates how climate and fire can interact to rapidly transform landscapes and disturbance regimes. The interactions can produce forest patterns with unexpected consequences such as reduced wildfire despite regional warming.

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Section: Introductionsupporting

confidence: 83%

Section: Introductionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Materials S and Me Thodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Climate–fire–vegetation interactions and the rise of novel landscape patterns in subalpine ecosystems, Colorado

2019

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Disturbance theory for ecosystem ecologists: A primer

Gough,

Buma,

Jentsch

et al. 2024

Ecology and Evolution

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Understanding what regulates ecosystem functional responses to disturbance is essential in this era of global change. However, many pioneering and still influential disturbance‐related theorie proposed by ecosystem ecologists were developed prior to rapid global change, and before tools and metrics were available to test them. In light of new knowledge and conceptual advances across biological disciplines, we present four disturbance ecology concepts that are particularly relevant to ecosystem ecologists new to the field: (a) the directionality of ecosystem functional response to disturbance; (b) functional thresholds; (c) disturbance–succession interactions; and (d) diversity‐functional stability relationships. We discuss how knowledge, theory, and terminology developed by several biological disciplines, when integrated, can enhance how ecosystem ecologists analyze and interpret functional responses to disturbance. For example, when interpreting thresholds and disturbance–succession interactions, ecosystem ecologists should consider concurrent biotic regime change, non‐linearity, and multiple response pathways, typically the theoretical and analytical domain of population and community ecologists. Similarly, the interpretation of ecosystem functional responses to disturbance requires analytical approaches that recognize disturbance can promote, inhibit, or fundamentally change ecosystem functions. We suggest that truly integrative approaches and knowledge are essential to advancing ecosystem functional responses to disturbance.

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The magnitude, direction, and tempo of forest change in Greater Yellowstone in a warmer world with more fire

Turner

Braziunas

Hansen

et al. 2021

Ecological Monographs

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As temperatures continue rising, the direction, magnitude, and tempo of change in disturbance-prone forests remain unresolved. Even forests long resilient to stand-replacing fire face uncertain futures, and efforts to project changes in forest structure and composition are sorely needed to anticipate future forest trajectories. We simulated fire (incorporating fuels feedbacks) and forest dynamics on five landscapes spanning the Greater Yellowstone Ecosystem (GYE) to ask: (1) How and where are forest landscapes likely to change with 21 st -century warming and fire activity? (2) Are future forest changes gradual or abrupt, and do forest attributes change synchronously or sequentially? (3) Can forest declines be averted by mid-21 stcentury stabilization of atmospheric greenhouse gas (GHG) concentrations? We used the spatially explicit individual-based forest model iLand to track multiple attributes (forest extent, stand age, tree density, basal area, aboveground carbon stocks, dominant forest types, species occupancy) through 2100 for six climate scenarios. Hot-dry climate scenarios led to more fire, but stand-replacing fire peaked in mid-century and then declined even as annual area burned continued to rise. Where forest cover persisted, previously dense forests were converted to sparse young woodlands. Increased aridity and fire drove a ratchet of successive abrupt declines (i.e., multiple annual landscape-level changes ≥ 20%) in tree density, basal area and extent of older (>150 yr) forests, whereas declines in carbon stocks and mean stand age were always gradual.Forest changes were asynchronous across landscapes, but declines in stand structure always preceded reductions in forest extent and carbon stocks. Forest decline was most likely in less topographically complex landscapes dominated by fire-sensitive tree species (Picea engelmannii, Abies lasiocarpa, Pinus contorta var. latifolia) and where fire resisters (Pseudotsuga menziesii var. glauca) were not already prevalent. If current GHG emissions continue unabated (RCP 8.5) and aridity increases, a suite of forest changes would transform the GYE, with cascading effects on biodiversity and myriad ecosystem services. However, stabilizing GHG concentrations by mid-century (RCP 4.5) would slow the ratchet, moderating fire activity and dampening the magnitude and rate of forest change. Monitoring changes in forest structure may serve as an operational early warning indicator of impending forest decline.

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Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado

Cited by 38 publications

References 84 publications

Climate–fire–vegetation interactions and the rise of novel landscape patterns in subalpine ecosystems, Colorado

Climate–fire–vegetation interactions and the rise of novel landscape patterns in subalpine ecosystems, Colorado

Disturbance theory for ecosystem ecologists: A primer

The magnitude, direction, and tempo of forest change in Greater Yellowstone in a warmer world with more fire

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