Technical Commentary: A Structural Classification for Inland Northwest Forest Vegetation

O’Hara, Kevin L.; Latham, Penelope; Hessburg, Paul F.; Smith, Bradley G.

doi:10.1093/wjaf/11.3.97

Cited by 65 publications

(29 citation statements)

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“…Refined definitions based on regional inventories incorporating the full range of potential structural conditions have the potential to avoid confusion that has occurred in the past regarding policy and management (Parker et al 2000, Spies 2004). Our results also clearly show that the relationship between stand age and structural development does not apply to all ''old'' forests, especially those in low productivity or frequently disturbed environments (O'Hara et al 1996). The general model of stand development from the western hemlock zone that emphasizes development of high live and dead biomass and canopy layering is not necessarily a good basis for assessment and conservation of ''older'' forest in other vegetation zones.…”

Section: Implications For Conservation and Managementmentioning

confidence: 71%

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Reilly

Spies

2015

Ecosphere

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Despite its importance to biodiversity and ecosystem function, patterns and drivers of regional scale variation in forest structure and development are poorly understood. We characterize structural variation, create a hierarchical classification of forest structure, and develop an empirically based framework for conceptualizing structural development from 11,091 plots across 25 million ha of all ownerships in Oregon, Washington, and inland Northern California, USA. A single component related to live tree biomass accounted for almost half of the variation in a principal components analysis of structural attributes, but components related to live tree density and size, dead wood, and understory vegetation together accounted for as much additional variation. These results indicate that structural development is more complex than a monotonic accumulation of live biomass as other components may act independently or emerge at multiple points during development. The classification revealed the diversity of structural conditions expressed at all levels of live biomass depending on the timing and relative importance of a variety of ecological processes (e.g., mortality) in different vegetation zones. Low live biomass structural types (<25 Mg/ha) illustrated the diversity of early‐seral conditions and differed primarily in density of live trees and abundance of snags and dead wood. Moderate live biomass structural types (25–99 Mg/ha) differed in tree size and density and generally lacked dead wood, but some structurally diverse types associated with partial stand‐replacing disturbance had abundant live and dead legacies. High live biomass structural types (>100 Mg/ha) substantiated the diversity of later developmental stages and exhibited considerable variation in the abundance of dead wood and density of big trees. Most structural types corresponded with previously described stages of development, but others associated with protracted early development, woodland/savannah transitions, and partial stand‐replacing disturbance lacked analogs and indicated alternative pathways of development. We propose a conceptual framework that distinguishes among families of pathways depending on the range of variation along different components of structure, the relative importance of different disturbances, and complexity of pathways. Our framework is a starting point for developing more comprehensive models of structural development that apply to a wider variety of vegetation zones differing in environment and disturbance regimes.

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Section: Implications For Conservation and Managementmentioning

confidence: 71%

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Reilly

Spies

2015

Ecosphere

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“…Oliver's stages were as follows: stand initiation (si), closed canopy-stem exclusion (secc), understory re-initiation (ur), and old growth. We expanded their classification to seven classes, in order to include conditions characteristic of stand development in Interior Northwest forests with their frequent disturbance (see O'Hara et al 1996). Additional structural classes (SCs) were: open canopy-stem exclusion (seoc), young forest multistory (yfms), and old forest-single story (ofss).…”

Section: Classifying Forest Composition Structure and Potential Vegmentioning

confidence: 99%

Detecting Change in Forest Spatial Patterns from Reference Conditions

Hessburg¹,

Smith²,

Salter³

1999

Ecological Applications

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109

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Timber harvest, fire suppression, road construction, and domestic livestock grazing have transformed spatial patterns of Interior Northwest forests. As a consequence, parameters of current disturbance regimes differ radically from historical regimes; presentday wildlife habitat distributions differ from historical distributions; and long-term survival of some native terrestrial species is uncertain. Public land managers are under increasing scientific and social pressure to mold existing forest spatial patterns to reflect those resulting from natural disturbance regimes and patterns of biophysical environments. However, knowledge of the characteristics of natural spatial patterns is unavailable.Using a dichotomized ordination procedure, we grouped the 343 forested subwatersheds (mean area, 8000 ha) on the eastern slope of the Cascade Mountains in Washington State into ecological subregions by similarity of area in potential vegetation and climate attributes. We built spatially continuous ''historical' ' (1938-1956) and ''current'' (1985-1993) vegetation maps for 48 randomly selected subwatersheds from aerial photo interpretations. From remotely sensed attributes, we classified cover types, structural classes, and potential vegetation types and attributed them to individual patches. We then estimated a reference variation (RV) in spatial patterns of patch types (cover type and structural class), by subwatersheds and five forested ecological subregions, using the 48 historical vegetation maps stratified by subregion and a spatial pattern analysis program. Finally, we compared the current pattern of an example subwatershed (MET11) with the RV estimates of its corresponding subregion to illustrate how reference conditions can be used to evaluate the importance of spatial pattern change. By evaluating pattern changes in light of RV estimates (nominally, the sample median 80% range of a metric) and the full range of class and landscape metrics, we could identify both current and historical conditions of MET11 that fell outside the RV. This approach gives land managers a tool to compare characteristics of present-day managed landscapes with reference conditions to reveal significant pattern departures, as well as to identify specific pattern characteristics that might be modified through management. It also provides a means to identify ''outlier'' conditions, relative to subregion RV estimates, that may occasionally be the object of pattern restoration activities.

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“…However, as climate change progresses and summers in the boreal region become drier and warmer, the wildfire season is predicted to become even longer and more severe (Balshi et al., ; Fauria & Johnson, ; Littell et al., ), with more frequent fires burning larger areas at higher severity (Hessburg et al., ). Not only will this ongoing regime shift cause more lynx habitat to revert to the open stand‐initiation stages (O'Hara, Latham, Hessburg, & Smith, ) that snowshoe hares and lynx generally avoid, but also higher severity burns may homogenize areas within a burn perimeter so that the residual trees and fire skips lynx select are less abundant (Cansler & McKenzie, ). Additionally, climate change may also degrade regenerating lynx habitat in burns as warmer and drier summers will likely hinder the regeneration of dense forest stands (Littell et al., ).…”

Section: Discussionmentioning

confidence: 99%

Canada lynx use of burned areas: Conservation implications of changing fire regimes

Vanbianchi

Murphy

Hodges

2017

Ecology and Evolution

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A fundamental problem in ecology is forecasting how species will react to major disturbances. As the climate warms, large, frequent, and severe fires are restructuring forested landscapes at large spatial scales, with unknown impacts on imperilled predators. We use the United States federally Threatened Canada lynx as a case study to examine how predators navigate recent large burns, with particular focus on habitat features and the spatial configuration (e.g., distance to edge) that enabled lynx use of these transformed landscapes. We coupled GPS location data of lynx in Washington in an area with several recent large fires and a number of GIS layers of habitat data to develop models of lynx habitat selection in recent burns. Random Forest habitat models showed lynx‐selected islands of forest skipped by large fires, residual vegetation, and areas where some trees survived to use newly burned areas. Lynx used burned areas as early as 1 year postfire, which is much earlier than the 2–4 decades postfire previously thought for this predator. These findings are encouraging for predator persistence in the face of fires, but increasingly severe fires or management that reduces postfire residual trees or slow regeneration will likely jeopardize lynx and other predators. Fire management should change to ensure heterogeneity is retained within the footprint of large fires to enable viable predator populations as fire regimes worsen with climate change.

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Technical Commentary: A Structural Classification for Inland Northwest Forest Vegetation

Cited by 65 publications

References 0 publications

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Detecting Change in Forest Spatial Patterns from Reference Conditions

Canada lynx use of burned areas: Conservation implications of changing fire regimes

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