Stand structure in eastside old-growth ponderosa pine forests of Oregon and northern California

Youngblood, Andrew; Max, Timothy A.; Coe, Kent

doi:10.1016/j.foreco.2004.05.056

Cited by 131 publications

(156 citation statements)

References 50 publications

(42 reference statements)

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“…Current ponderosa pine density for Arizona averages 300 trees ha −1 , double the GLO reconstruction value (O'Brien, 2002). Many ponderosa pine landscapes in the west support stand densities of many hundreds to thousands of trees per hectare (Cooper, 1960;Youngblood et al, 2004;Ritchie et al, 2007). Although the present paper is not focused on the accuracy of W&B's forest reconstructions, it is worth noting that recently published empirical data from Oregon showed that the GLO-based estimates of historical forest density were 2.5 times higher than historical plot measurements on the former Klamath Indian Reservation (Hagmann et al, 2013).…”

Section: Comparisons With Other Studiesmentioning

confidence: 86%

“…Tree size and age are poorly correlated in ponderosa pine (e.g. Ehle & Baker, 2003), with variability from site to site and among age classes even at the same site, requiring site-specific empirical data from cored trees to develop a relationship (Youngblood et al, 2004). Age and size are even less correlated in more shade-tolerant taxa such as Douglas-fir (Pseudotsuga menziesii) and true fir species (e.g.…”

Section: Inferences About Fire Severitymentioning

confidence: 99%

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Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Fulé

Swetnam

Brown

et al. 2013

Global Ecology and Biogeography

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Reconstructions of dry western US forests in the late 19th century in Arizona, Colorado and Oregon based on General Land Office records were used by Williams & Baker (2012; Global Ecology and Biogeography, 21, 1042-1052; hereafter W&B) to infer past fire regimes with substantial moderate and high-severity burning. The authors concluded that present-day large, high-severity fires are not distinguishable from historical patterns. We present evidence of important errors in their study. First, the use of tree size distributions to reconstruct past fire severity and extent is not supported by empirical age-size relationships nor by studies that directly quantified disturbance history in these forests. Second, the fire severity classification of W&B is qualitatively different from most modern classification schemes, and is based on different types of data, leading to an inappropriate comparison. Third, we note that while W&B asserted 'surprising' heterogeneity in their reconstructions of stand density and species composition, their data are not substantially different from many previous studies which reached very different conclusions about subsequent forest and fire behaviour changes. Contrary to the conclusions of W&B, the preponderance of scientific evidence indicates that conservation of dry forest ecosystems in the western United States and their ecological, social and economic value is not consistent with a present-day disturbance regime of large, high-severity fires, especially under changing climate. KeywordsFire regime, fire severity, General Land Office survey, historical range of variability, ponderosa pine, wildfire. INTRODUCTIONA recent study in Global Ecology and Biogeography (Williams & Baker, 2012, hereafter W&B) applied historical data from General Land Office (GLO) surveys c. 1880 to reconstruct historical dry forests on four large landscapes in Arizona, Colorado and Oregon (USA). W&B described forest composition as characterized by 'abundant ponderosa pine (Pinus ponderosa C. Lawson), with lesser amounts of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), white fir (Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.), grand fir (Abies grandis (Douglas ex D. Don) Lindl.), juniper (Juniperus L.), western larch (Larix occidentalis Nutt.) and lodgepole pine (Pinus contorta Douglas ex Louden)' . W&B infer that the presence of a certain proportion of trees below a site-specific diameter threshold is evidence of 'higher'-severity fire, a term they use to indicate a combination of 'mixed-plus high-severity fire' . They then compare the proportion of plots with evidence of 'higher'-severity fire to the distribution of fire severities estimated from satellite imagery of recent large wildfires in the western United States, concluding that modern fires are within the historical range of variability (HRV) of fire severity. They also found it 'surprising' that dry forests 'commonly thought to have been open and parklike' were heterogeneous and relatively dense. W&B conclude that current management pr...

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Section: Comparisons With Other Studiesmentioning

confidence: 86%

Section: Inferences About Fire Severitymentioning

confidence: 99%

Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Fulé

Swetnam

Brown

et al. 2013

Global Ecology and Biogeography

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show abstract

“…Large trees shade their smaller neighbors, dominate the rooting zone, and harbor large populations of pathogens, herbivores and mutualists (e.g., mycorrhizae) (Laliberte et al 2015). Individual trees often live for centuries, and although age-size relationships can be highly variable (Youngblood et al 2004, Fulé et al 2014, larger individuals usually tend to be older than smaller conspecifics in forests that are in stable conditions (Leak 1985). Thus, we used the size of focal trees (diameter at 1.3 m above ground, DBH) as an integrator of the strength and duration of interactions with neighbors and asked whether the phylogenetic composition of neighbors surrounding focal trees shifted with focal tree size.…”

Section: Accepted Ar Ticlementioning

confidence: 99%

Forest tree neighborhoods are structured more by negative conspecific density dependence than by interactions among closely related species

et al. 2017

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Interactions among neighbors influence the structure of communities of sessile organisms. Closely related species tend to share habitat and resource requirements and to interact with the same mutualists and natural enemies so that the strength of interspecific interactions tends to decrease with evolutionary divergence time. Nevertheless, the degree to which such phylogenetically related ecological interactions structure plant communities remains unclear. Using data from five large mapped forest plots combined with a DNA barcode mega‐phylogeny, we employed an individual‐based approach to assess the collective effects of focal tree size on neighborhood phylogenetic relatedness. Abundance‐weighted average divergence time for all neighbors (ADT_all) and for heterospecific neighbors only (ADT_hetero) were calculated for each individual of canopy tree species. Within local neighborhoods, we found phylogenetic composition changed with focal tree size. Specifically, significant increases in ADT_all with focal tree size were evident at all sites. In contrast, there was no significant change in ADT_hetero with tree size in four of the five sites for both sapling‐sized and all neighbors, even at the smallest neighbourhood scale (0–5 m), suggesting a limited role for phylogeny‐dependent interactions. However, there were inverse relationships between focal tree size and the proportion of heterospecific neighbors belonging to closely related species at some sites, providing evidence for negative phylogenetic density dependence. Overall, our results indicate that negative interaction with conspecifics had a much greater impact on neighborhood assemblages than interactions among closely related species and could contribute to community structure and diversity maintenance in different forest communities.

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“…Although there are some exceptions, such as a random distribution found in an Oregon ponderosa pine stand (Youngblood et al 2004), presettlement and current live old-growth trees often exhibit a clumped distribution within sites (Harrod et al 1999). Thus, openings alternating with tree clumps typify within-forest patterns in many frequent-fire conifer forests.…”

Section: Tree Structure and Patternmentioning

confidence: 99%

Past, Present, and Future Old Growth in Frequent-fire Conifer Forests of the Western United States

Abella¹,

Covington²,

Fulé³

et al. 2007

E&S

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Stand structure in eastside old-growth ponderosa pine forests of Oregon and northern California

Cited by 131 publications

References 50 publications

Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Forest tree neighborhoods are structured more by negative conspecific density dependence than by interactions among closely related species

Past, Present, and Future Old Growth in Frequent-fire Conifer Forests of the Western United States

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