Coarse woody debris and canopy cover in an old-growth Jeffrey pine-mixed conifer forest from the Sierra San Pedro Martir, Mexico

Stephens, Scott L.; Fry, Danny L.; Franco-Vizcaı́no, Ernesto; Collins, Brandon M.; Moghaddas, Jason M.

doi:10.1016/j.foreco.2006.12.012

Cited by 39 publications

(46 citation statements)

References 28 publications

(56 reference statements)

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“…IV). NNVM values were similar to those reported by Stephens et al (2007) for an unmanaged xeric forest in northwestern Mexico (Tab. IV), but comparisons with other studies are complicated because researchers define CWD differently.…”

Section: Fuel Loads and Snag Densitiessupporting

confidence: 87%

“…Obtaining accurate fuel load data can be difficult (Westfall and Woodall, 2007) and current methods for estimating fuel loads tend to be general, focusing on patterns in fuel loads while ignoring the processes that govern fuel load dynamics. Several authors note the need for fuel treatments with an ecosystem management approach that considers both patterns and process at multiple spatial scales (Lehmkuhl et al, 2007;McKenzie et al, 2007;Reinhardt et al, 2008;Stephens et al, 2007;Weatherspoon and McIver, 2000), but it remains difficult to assess multiple aspects of stand dynamics such as tree density, insect outbreaks, and species diversity across multiple spatial and temporal scales. If the management goal is to maintain or restore healthy and resilient forests, variation and heterogeneity in fuel composition must be considered along with stand history and the ecosystem processes that led to the observed patterns in forest and fuel composition.…”

Section: Discussionmentioning

confidence: 99%

“…Redundancy analysis separated the plots into five groups (I) pure lodgepole pine, (II) large and mature white fir, (III) pure (2005a) Sierra Nevada Managed n/a n /a n /a 3 5 2 8 Ganey (1999) N Arizona Managed n/a n /a n /a n /a 5 Barbour et al (2002) Lake Tahoe Basin Unmanaged n/a n /a n /a n /a 109 Stephens et al (2007) NW Mexico Unmanaged n/a n /a n /a 1 6 n /a Robertson and Bowser (1999) Front Range Colorado Managed n/a n /a n /a 3 n /a Robertson and Bowser (1999) SW Colorado Managed n/a n /a n /a 5 n /a ponderosa pine, (IV) smaller ponderosa pine with a fir and lodgepole pine component , and (V) smaller and younger fir) based on relative age and dominance of the three tree species (Fig. 3).…”

Section: Environmental Variables and Stand Typementioning

confidence: 99%

“…Stephens et al (2007) investigated CWD in unmanaged, old-growth Jeffrey pine (Pinus jeffreyi) stands in northwestern Mexico that experience frequent, low-moderate severity fires and found greater amounts of CWD compared to xeric, managed ponderosa pine forests in the western United States. Spies et al (1988) evaluated log and snag volume and biomass in old-growth Douglas-fir forests (Pseudotsuga menziesii) in the Pacific Northwest.…”

Section: Introductionmentioning

confidence: 99%

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Fuel and stand conditions in an isolated, unmanaged forest landscape in central Oregon

Stanton

Arabas

2009

Ann. For. Sci.

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Abstract• Mature, unmanaged forests in western North America provide important reference conditions for managers, yet little is known about fuel composition and the factors that influence fuel accumulation in such stands. Our objectives were to characterize fuels in a passively managed landscape of dry forests in central Oregon and identify environmental factors influencing fuel accumulation.• Ordination techniques and analysis of variance revealed no statistical differences in total fuel loads across a wide range of environmental conditions.• Individual fuel size classes, however, did vary by stand location and composition. Interior stands had more 1-to 100-h fuels and snags than stands at or near the edge, stands dominated by ponderosa pine had fewer small-diameter fuels and snags, lodgepole pine stands had more 1-h fuels and snags, and white fir stands had more 10-h fuels, duff, and snag basal area.• Tree species, density and age, and years since last fire were the most important environmental variables, explaining 23% of the variation in fuels.• Our results present further evidence that fuel composition is highly variable at many spatial and temporal scales. They also provide useful baseline information for managers of fire-prone western forests.

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Section: Fuel Loads and Snag Densitiessupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Section: Environmental Variables and Stand Typementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fuel and stand conditions in an isolated, unmanaged forest landscape in central Oregon

Stanton

Arabas

2009

Ann. For. Sci.

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“…What is more surprising is just how open these forests were in 1911, with average canopy cover being 25% and 12% in mixed-conifer and ponderosa pine types, respectively (Table 6). Fornwalt et al (2002) modeled ponderosa pine reference canopy cover conditions of 13-22% on the Colorado Front Range and canopy cover in unmanaged Jeffrey pine-mixed conifer forests in northern Baja California, Mexico, was 27% (Stephens et al 2007b). In addition, other canopy cover studies including White (1985), Covington and Sackett (1986), and Covington et al (1997) reported 21.9%, 19.0%, and 17.3% canopy cover for ponderosa pine reference conditions on the Fort Valley Experimental Forest, Arizona, respectively (Reynolds et al 2013); these values are similar to canopy cover estimates from southern Sierra Nevada ponderosa pine forests in 1911 (Table 1).…”

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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Climate and fire impacts on tree recruitment in mixed conifer forests in northwestern Mexico and California

Stephens

Steel

Collins

et al. 2023

Ecological Applications

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Frequent-fire forests were once heterogeneous at multiple spatial scales, which contributed to their resilience to severe fire. While many studies have characterized historical spatial patterns in frequent-fire forests, fewer studies have investigated their temporal dynamics. We investigated the influences of fire and climate on the timing of conifer recruitment in old-growth Jeffrey pinemixed conifer forests in the Sierra San Pedro Martir (SSPM) and the eastern slope of the Sierra Nevada. Additionally, we evaluated the impacts of fire exclusion and recent climate change on recruitment levels using statistical models with realized as well as fire suppression and climate change-free counterfactual scenarios. Excessive soil drying from anthropogenic climate change resulted in diminished recruitment in the SSPM but not in the Sierra Nevada. Longer fire-free intervals attributable to fire suppression and exclusion resulted in greater rates of recruitment across all sites but was particularly pronounced in the Sierra Nevada, where suppression began >100 years ago and recruitment was 28 times higher than the historical fire return interval scenario. This demonstrates the profound impact of fire's removal on tree recruitment in Sierra Nevada forests even in the context of recent climate change.Tree recruitment at the SSPM coincided with the early-20th-century North American pluvial, as well as a fire-quiescent period in the late 18th and early 19th centuries. Episodic recruitment occurred in the SSPM with no "average" recruitment over the last three centuries. We found that temporal heterogeneity, in conjunction with spatial heterogeneity, are critical components of frequent-fire-adapted forests. Episodic recruitment could be a desirable characteristic of frequent-fire-adapted forests, and this might be more amenable to climate change impacts that forecast more variable precipitation patterns in the future. One key to this outcome would be for frequent fire to continue to shape these forests versus continued emphasis on fire suppression in California.

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Coarse woody debris and canopy cover in an old-growth Jeffrey pine-mixed conifer forest from the Sierra San Pedro Martir, Mexico

Cited by 39 publications

References 28 publications

Fuel and stand conditions in an isolated, unmanaged forest landscape in central Oregon

Fuel and stand conditions in an isolated, unmanaged forest landscape in central Oregon

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

Climate and fire impacts on tree recruitment in mixed conifer forests in northwestern Mexico and California

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