Spatial dynamics of tree group and gap structure in an old-growth ponderosa pine-California black oak forest burned by repeated wildfires

Pawlikowski, Natalie C.; Coppoletta, Michelle; Knapp, Eric E.; Taylor, Alan H.

doi:10.1016/j.foreco.2018.12.016

Cited by 20 publications

(10 citation statements)

References 89 publications

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“…Second, our results suggest that fire burning under these conditions can convert larger tree groups to isolated individuals and small groups that dominate historic forest structure. The role of prescribed fires and wildfires burning under moderate conditions in reducing fuel loading is well understood, and our results lend further support that they can also restore the structures and complex spatial patterns that existed in these forests historically (Holden et al 2007, Battaglia et al 2008, Larson et al 2013, Lydersen et al 2013, Kane et al 2019, Brown et al 2019, Pawlikowski et al 2019, Walker et al 2018). Forest restoration through the use of fire is an important management tool given the reality that mechanical treatments alone cannot achieve forest restoration goals across the vast areas in need of treatment (North et al 2012, 2015, Schoennagel et al 2017).…”

Section: Discussionsupporting

confidence: 66%

Fine‐scale fire patterns mediate forest structure in frequent‐fire ecosystems

et al. 2020

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In frequent‐fire forests, wildland fire acts as a self‐regulating process creating forest structures that consist of a fine‐grained mosaic of isolated trees, tree groups of various sizes, and non‐treed openings. Though the self‐regulation of forest structure through repeated fires is acknowledged, few studies have investigated the role that fine‐scale pattern‐process linkages play in determining fire behavior and effects. To better understand the physical mechanisms driving these pattern‐process linkages, we used a three‐dimensional, physics‐based fire behavior model to investigate how the local arrangement of canopy fuels influences heat transfer from a surface fire to tree crowns and subsequent crown ignition and consumption. In particular, we were interested in the impacts of tree group size and crown separation distance on heat transfer. We found increased convective cooling for isolated individual trees and 3‐tree groups as compared to larger 7‐ and 19‐tree groups which resulted in a reduction of the net energy transferred from the surface fire to the tree crowns. Because isolated individuals and 3‐tree groups are exposed to less thermal energy, they require a greater surface fireline intensity to initiate torching and have less crown consumption than trees within larger groups. Similarly, we found that increased crown separation distance also reduced heat transfer and crown ignition. However, differences in crown ignition and consumption among various sized groups and separation distances depended upon the surface fireline intensity, suggesting that any change in crown consumption or tree mortality due to pattern‐process linkages may be best viewed as a conditional in nature. These findings identify the potential physical mechanisms responsible for supporting the complex forest structures typical of high‐frequency fire regimes, and the results may be useful for managers designing fuel hazard reduction and ecological restoration treatments.

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Section: Discussionsupporting

confidence: 66%

Fine‐scale fire patterns mediate forest structure in frequent‐fire ecosystems

et al. 2020

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“…Stands and landscapes with relatively intact or restored fire regimes (i.e., active fire regimes) provide insight into how historical forests and landscapes operate under contemporary climate and disturbance regimes (Cortés Montaño et al 2012, Yocom Kent et al 2017, Arizpe et al 2021, Dewar et al 2021, Murphy et al 2021 press: Table 2). Contemporary forests with relatively intact fire regimes experienced the climate variations of the 19th and 20th centuries, but do not exhibit changes in structure and composition comparable to fire-excluded forests (Stephens and Fulé 2005, Lydersen and North 2012, Pawlikowski et al 2019. Similarly, forests with relatively intact fire regimes have not experienced the increased severity of disturbance events observed on comparable areas affected by fire exclusion (Rivera-Huerta et al 2016, Murphy et al 2021.…”

Section: Fire Regimes Are Significantly Departedmentioning

confidence: 99%

Evidence for widespread changes in the structure, composition, and fire regimes of western North American forests

Hagmann

Hessburg

Prichard

et al. 2021

Ecological Applications

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Implementation of wildfire-and climate-adaptation strategies in seasonally dry forests of western North America is impeded by numerous constraints and uncertainties. After more than a century of resource and land use change, some question the need for proactive management, particularly given novel social, ecological, and climatic conditions. To address this question, we first provide a framework for assessing changes in landscape conditions and fire regimes. Using this framework, we then evaluate evidence of change and lack of change in contemporary conditions relative to those maintained by active fire regimes, i.e., those uninterrupted by a century or more of human-induced fire exclusion. The cumulative results of more than a century of research document a persistent and substantial fire deficit and widespread alterations to ecological structures and functions. These changes are not necessarily apparent at all spatial scales or in all dimensions of fire regimes and forest and nonforest conditions. Nonetheless, loss of the once abundant influence of low-and moderate-KEYWORDS

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“…Clump and gap sizes varied predictably with species-level traits including seed dispersal distances and in-filling rates, and with patchy tree mortality driven by surface and ladder fuels ( Figure 5C). Restoring more typical tree clump and gap size variation is key to restoring patch-level resistance to severe wildfires, and to adapting patches to coming climatic changes (Pawlikowski et al, 2019), particularly in dry and moist mixed conifer forests.…”

Section: Species Traits and Adaptations Drive Patch Structure Composmentioning

confidence: 99%

Climate, Environment, and Disturbance History Govern Resilience of Western North American Forests

et al. 2019

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Before the advent of intensive forest management and fire suppression, western North American forests exhibited a naturally occurring resistance and resilience to wildfires and other disturbances. Resilience, which encompasses resistance, reflects the amount of disruption an ecosystem can withstand before its structure or organization qualitatively shift to a different basin of attraction. In fire-maintained forests, resilience to disturbance events arose primarily from vegetation pattern-disturbance process interactions at several levels of organization. Using evidence from 15 ecoregions, spanning forests from Canada to Mexico, we review the properties of forests that reinforced qualities of resilience and resistance. We show examples of multi-level landscape resilience, of feedbacks within and among levels, and how conditions have changed under climatic and management influences. We highlight geographic similarities and important differences in the structure and organization of historical landscapes, their forest types, and in the conditions that have changed resilience and resistance to abrupt or large-scale Hessburg et al. Resilience in North American Forests disruptions. We discuss the role of the regional climate in episodically or abruptly reorganizing plant and animal biogeography and forest resilience and resistance to disturbances. We give clear examples of these changes and suggest that managing for resilient forests is a construct that strongly depends on scale and human social values. It involves human communities actively working with the ecosystems they depend on, and the processes that shape them, to adapt landscapes, species, and human communities to climate change while maintaining core ecosystem processes and services. Finally, it compels us to embrace management approaches that incorporate ongoing disturbances and anticipated effects of climatic changes, and to support dynamically shifting patchworks of forest and non-forest. Doing so could make these shifting forest conditions and wildfire regimes less disruptive to individuals and society.

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Spatial dynamics of tree group and gap structure in an old-growth ponderosa pine-California black oak forest burned by repeated wildfires

Cited by 20 publications

References 89 publications

Fine‐scale fire patterns mediate forest structure in frequent‐fire ecosystems

Fine‐scale fire patterns mediate forest structure in frequent‐fire ecosystems

Evidence for widespread changes in the structure, composition, and fire regimes of western North American forests

Climate, Environment, and Disturbance History Govern Resilience of Western North American Forests

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