Tree spatial patterns in fire-frequent forests of western North America, including mechanisms of pattern formation and implications for designing fuel reduction and restoration treatments

Larson, Andrew J.; Churchill, Derek J.

doi:10.1016/j.foreco.2011.11.038

Cited by 263 publications

(290 citation statements)

References 138 publications

(312 reference statements)

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“…The majority of the variability in structure in frequent-fire forests has been observed at spatial scales smaller than 0.4 ha Churchill 2012, Fry et al 2014), and topographic characteristics that influence forest structure may also be observed at a smaller scale (Lydersen and North 2012). The scale at which the 1911 inventory data were recorded homogenizes this patchiness, which has been shown to include widely spaced individuals, clusters of large trees, dense patches of regeneration, and small openings (North et al 2002, Franklin and Van Pelt 2004, Larson and Churchill 2012, Lydersen et al 2013, Fry et al 2014. This fine-scale patchiness, and the scale at v www.esajournals.org which topography affects forest patterns, are important characteristics that warrant further investigation.…”

Section: Discussionmentioning

confidence: 99%

Historical and current landscape‐scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

et al. 2015

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Abstract. Many managers today are tasked with restoring forests to mitigate the potential for uncharacteristically severe fire. One challenge to this mandate is the lack of large-scale reference information on forest structure prior to impacts from Euro-American settlement. We used a robust 1911 historical dataset that covers a large geographic extent (.10,000 ha) and has unbiased sampling locations to compare past and current forest conditions for ponderosa pine and mixed conifer forests in the southern Sierra Nevada. The 1911 dataset contained records from 18,052 trees in 378 sampled transects, totaling just over 300 ha in transect area. Forest structure was highly variable in 1911 and shrubs were found in 54% of transects. Total tree basal area ranged from 1 to 60 m 2 ha À1 and tree density from 2 to 170 ha À1 (based on trees .30 cm dbh). K-means cluster analysis divided transects into four groups: mixed conifer-high basal area (MC High BA), mixed conifer-average basal area (MC Ave BA), mixed conifer-average basal area-high shrubs (MC Ave BA Shrubs), and ponderosa pine (Pond Pine). The percentage of this 1911 landscape that experienced high severity fire was low and varied from 1-3% in mixed conifer forests and 4-6% in ponderosa pine forests. Comparing forest inventory data from 1911 to the present indicates that current forests have changed drastically, particularly in tree density, canopy cover, the density of large trees, dominance of white fir in mixed conifer forests, and the similarity of tree basal area in contemporary ponderosa pine and mixed conifer forests. Average forest canopy cover increased from 25-49% in mixed conifer forests, and from 12-49% in ponderosa pine forests from 1911 to the present; canopy cover in current forest types is similar but in 1911 mixed conifer forests had twice the canopy cover as ponderosa pine forests. Current forest restoration goals in the southern Sierra Nevada are often skewed toward the higher range of these historical values, which will limit the effectiveness of these treatments if the objective is to produce resilient forest ecosystems into the future.

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Section: Discussionmentioning

confidence: 99%

Historical and current landscape‐scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

et al. 2015

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“…Forest structure has two principal dimensions: the types, number and sizes of individual structural elements (e.g., individual trees); and their arrangement in space [7,41]. Here, residual forest structure refers to remnant surviving trees and does not include dead standing or downed trees.…”

Section: Residual Forest Structurementioning

confidence: 99%

“…These fires also acted as a control on tree recruitment [4,5], thereby resulting in a variety of tree densities and tree size and age distributions [5,6]. The clustered spatial pattern commonly associated with historical dry conifer stands-where well-defined groups of trees and individual trees were interspersed in a matrix of treeless openings is further attributed to the relatively frequent historical fire regime [7][8][9]. This heterogeneity in historical forest structure is thought to be more resilient to drought and subsequent wildfires [1], yet little is known regarding the process responsible for this spatial structure.…”

Section: Introductionmentioning

confidence: 99%

Mixed-Severity Fire Fosters Heterogeneous Spatial Patterns of Conifer Regeneration in a Dry Conifer Forest

Malone

Fornwalt

Battaglia

et al. 2018

Forests

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Abstract:We examined spatial patterns of post-fire regenerating conifers in a Colorado, USA, dry conifer forest 11-12 years following the reintroduction of mixed-severity fire. We mapped and measured all post-fire regenerating conifers, as well as all other post-fire regenerating trees and all residual (i.e., surviving) trees, in three 4-ha plots following the 2002 Hayman Fire. Residual tree density ranged from 167 to 197 trees ha −1 (TPH), and these trees were clustered at distances up to 30 m. Post-fire regenerating conifers, which ranged in density from 241 to 1036 TPH, were also clustered at distances up to at least 30 m. Moreover, residual tree locations drove post-fire regenerating conifer locations, with the two showing a pattern of repulsion. Topography and post-fire sprouting tree species locations further drove post-fire conifer regeneration locations. These results provide a foundation for anticipating how the reintroduction of mixed-severity fire may affect long-term forest structure, and also yield insights into how historical mixed-severity fire may have regulated the spatially heterogeneous conditions commonly described for pre-settlement dry conifer forests of Colorado and elsewhere.

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“…Reference conditions are also used as a source of information for identifying restoration goals and the types of treatment that might be used in places where contemporary forest conditions are approaching a bounded range of variation (Moritz et al 2013) or have moved outside their historical range of variability (Morgan et al 1994, White and Walker 1997, Swetnam et al 1999, Taylor 2004, Larson and Churchill 2012, Wiens et al 2012. Presumably, moving highly altered forests towards conditions within the historical range of variability should increase their resilience to wildfire and reduce the risk of unexpected outcomes such as vegetation type conversions caused by unusually severe wildfire related to high fuel loads from logging and or fire exclusion (Weatherspoon and Skinner 1996, Landres et al 1999, Savage and Mast 2005, Odion et al 2010.…”

Section: Introductionmentioning

confidence: 99%

“…Estimates of basal area, species composition, and diameter-class distributions required pooling data across even larger areas (.7.8 km 2 ) with the least accurate estimates for forest size structure (Williams and Baker 2011). Spatial heterogeneity in structural attributes (density, size, age, basal area), which is a hallmark of many ponderosa pine and dry mixed conifer forests (Cooper 1960, White 1985, Youngblood et al 2004, Beaty and Taylor 2007, Scholl and Taylor 2010, Larson and Churchill 2012 occurs mainly at small spatial scales (,0.4 ha; Larson and Churchill 2012) and is not well captured by small point samples from aggregated samples (Bouldin 2008, Hanberry et al 2011). This could lead to misguided goals and objectives for restoration of forest structural conditions typical of forests with an intact fire regime.…”

Section: Introductionmentioning

confidence: 99%

Landscape‐scale modeling of reference period forest conditions and fire behavior on heavily logged lands

et al. 2014

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Landscape-scale modeling of reference period forest conditions and fire behavior on heavily logged lands. Ecosphere 5(3):32. http://dx.doi.org/10.1890/ES13-00294.1Abstract. Forest conditions prior to extensive land clearing are often used as a point-of-reference by ecologists and resource managers for characterizing the historical range of variability in forest conditions shaped by intact disturbance regimes. Quantitative data on forest reference conditions can be developed from forest surveys and reconstructions using dendroecology; however, these methods lack the spatial resolution needed for landscape management. In this paper, we combine predictive vegetation mapping methods with reference forest conditions inferred from early forest surveys, dendroecology, and fire simulation models to develop landscape-scale reference conditions for forest structure, forest fuels, fire frequency, and fire behavior using the Lake Tahoe Basin, California as an example.The dendroecological reconstruction method used for the Lake Tahoe Basin forests was not sensitive to variation in decomposition rates suggesting that our method provided robust estimates of reference period forest characteristics. The cluster analysis procedure identified five forest structure types (white fir, Jeffrey pine, red fir, lodgepole pine, and subalpine) and 15 subtypes. Each forest type had a characteristic composition, density, and basal area. Our random forests approach to classifying and mapping the spatial distribution of the five dominant reference forest structure types resulted in 51.5% classification accuracy using 14 physiographic and climatic variables. The random forests model to identify subtypes within each forest group had an average percent correct classification of 47.8%. The random forests model for fire intervals explained 67% of the variance in the point fire return interval estimates from fire-scarred trees. Estimates of reference period fuels modeled from stand structure suggested moderate fuel loads for reference forests. The predicted potential fire type for forest subtypes under extreme weather was surface fire except for red fir and the lodgepole pine subtypes with potential for crown fire. By characterizing the reference forest composition, structure, and disturbance frequency with a range of variability, managers can develop a forested landscape more resilient to changes in disturbance regime and climate. Although our approach was developed for the Lake Tahoe Basin, California, it could be applied to a wide range of forest landscapes to identify forest reference conditions.

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Tree spatial patterns in fire-frequent forests of western North America, including mechanisms of pattern formation and implications for designing fuel reduction and restoration treatments

Cited by 263 publications

References 138 publications

Historical and current landscape‐scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

Historical and current landscape‐scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

Mixed-Severity Fire Fosters Heterogeneous Spatial Patterns of Conifer Regeneration in a Dry Conifer Forest

Landscape‐scale modeling of reference period forest conditions and fire behavior on heavily logged lands

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