Ecological Processes Linking Forest Structure and Avian Diversity in Western Oregon

Hansen, Andrew J.; Vega, Robyn M.; McKee, Arthur; Moldenke, Andrew R.

doi:10.1007/978-3-642-78972-4_13

Cited by 6 publications

(5 citation statements)

References 15 publications

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“…Vega (1993) found that the Lazuli Bunting showed a similar pattern, although the sample size was too small to allow inclusion of this species in our analysis. These species may avoid open stands with canopy trees either because nest predation rates are elevated in such stands, or because overs tory cover may reduce primary productivity and food availability for these species (Vega 1993, Hansen et al 1994. These findings are important in suggesting that not all opencanopy bird species benefit from canopy tree retention.…”

Section: Habitat Use and Natural History Of Bird Speciesmentioning

confidence: 99%

“…The first objective is to compare the abundance of individual bird species among five stand types: recent clearcuts, canopy-retention units, closed-canopy plantations, mature stands, and old-growth stands. The consequences of these patterns of habitat use for bird survival and reproduction are not examined in this study (see Vega 1993 andHansen et al 1994 for initial work). The second objective is to develop statistical functions relating bird abundance to stand-level habitat characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon

Hansen¹,

McComb²,

Vega³

et al. 1995

Ecological Applications

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136

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Ecologists have advocated retaining various densities of canopy trees in harvest units in Pacific Northwest forests. In contrast to clear‐cutting, this practice may better emulate the patterns of disturbance and structural complexity typical of natural forests in the region. Several ecological attributes, including vertebrate habitat diversity, are thought to be associated with stands of complex structure. The goal of this study was to determine bird abundance in canopy retention sites relative to other common stand types in the Pacific Northwest and to develop habitat functions for extrapolating bird abundance across current and future landscapes. We used data from five previous studies in the west central Cascades of Oregon to compare bird abundance and to develop habitat functions for forest birds across a wide range of natural and managed stand structures and ages. The 67 stands included clearcuts, retention sites, young closed‐canopy plantations, mature stands, and old‐growth stands. ANOVA revealed that 18 of the 23 species included in the analysis differed significantly in abundance among the stand types, with some species being primarily associated with each of the stand types. The habitat variables used to build habitat functions included tree density by size class, mean tree diameter, and variation in tree diameter. Linear, polynomial, and various nonlinear regression models were evaluated for each bird species. Significant habitat functions were generated for 17 of the 23 bird species. The analyses identified four habitat‐use guilds among the 17 bird species: open‐canopy; open‐canopy with dispersed large trees; structurally complex closed‐canopy; and structurally simple closed‐canopy guilds. This study is the first in the Pacific Northwest to compare bird abundances across natural stands, traditionally managed plantations, and stands managed under ecological forestry approaches. The results suggested that canopy tree retention benefits many, but not all, of the bird species we studied, Moreover, the nonlinear responses of bird abundance revealed thresholds in tree density at which bird abundance changed dramatically. Knowledge of these thresholds allow managers to design stands for specific biodiversity objectives. The habitat functions presented here can be used to predict bird abundance based on habitat measurements derived from field data, remotely sensed data, or output from computer models of forest dynamics.

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Section: Habitat Use and Natural History Of Bird Speciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon

Hansen¹,

McComb²,

Vega³

et al. 1995

Ecological Applications

Self Cite

136

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show abstract

“…Many bird species showed nonlinear relationships with canopy tree density, suggesting thresholds in tree density where habitat quality changes abruptly. At least three ecological factors may link canopy tree density and bird communities: pathways of net primary productivity, habitat niche diversity, and nest predation rates (Hansen et a!. 1994).…”

mentioning

confidence: 99%

Alternative Silvicultural Regimes in the Pacific Northwest: Simulations of Ecological and Economic Effects

Hansen¹,

Garman²,

Weigand³

et al. 1995

Ecological Applications

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125

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New silivicultural strategies to sustain both ecological and human communities are being developed and implemented on federal forest lands in the Pacific Northwest (PNW) United States. Two important stand‐level components of the new silviculture regimes are rotation age and retention level of live trees in harvest units. Ecologists have suggested that canopy tree retention and longer rotations will create patterns of stand structure in managed forest that are similar to those in natural forests, and promote long‐term ecological productivity and biodiversity. Forest economists, however, are concerned that canopy tree retention and long rotations may reduce wood production, although the high value of large logs produced by these new silvicultural regime may compensate for reduced growth rates. We used the forest model ZELIG to perform a factorial simulation experiment on long‐term responses of ecological and economic variables to nine retention levels and four rotation lengths. ZELIG output on forest structure and composition was input to a forest economics model that calculated net value of wood products in 1989 dollars. The simulated stand data were also linked with regression equations to predict the densities of 17 bird species as a function of tree size class distribution. Five replicates of each treatment were run for the 240‐yr simulation period. Results indicated that stand structure under each of the canopy tree retention levels was more similar to the pre‐treatment natural forest than following clear‐cutting. Variation in tree size under intermediate levels of retention, however, did not reach the level of the natural forest during the simulation period. Tree species composition was strongly related to retention level and rotation age. Shade‐intolerant Douglas‐fir (Pseudotsuga menziesii) lost dominance to shade‐tolerant species under intermediate retention levels and longer rotations. Wood production decreased significantly with increasing retention level and rotation age, with a notable threshold between retention levels of 0 and 5 trees per hectare. Net wood products value did not decrease as rapidly with retention level, and did not differ much among rotation ages, because of the high value of large logs. Bird species responded individualistically to retention level and rotation age. Some had peak densities under short‐rotation clear‐cutting, but most were associated with structurally complex, closed‐canopy forest. Consequently, bird species richness increased significantly with retention level and rotation age. Within the assumptions and limitations of our models, this application provided knowledge on trends and thresholds that can help land managers to choose silvicultural regimes that best balance their management objectives. We concluded that retention level and rotation age strongly influence ecological and economic responses in PNW forests; efforts are needed to reduce uncertainty about these effects.

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“…More diverse forests, it follows, may have more growth forms represented and thus have more building blocks with which to construct structural complexity (Gough 2020). At the same time, structural complexity also tends to facilitate biodiversity by increasing available niche space for other flora and fauna species (Hansen et al 1994, Hyde et al 2006, Torresani et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Vegetation structural complexity and biodiversity in the Great Smoky Mountains

2021

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Vegetation structural complexity and biodiversity tend to be positively correlated, but understanding of this relationship is limited in part by structural metrics tending to quantify only horizontal or vertical variation, and that do not reflect internal structure. We developed new metrics for quantifying internal vegetation structural complexity using terrestrial LiDAR scanning and applied them to 12 NEON forest plots across an elevational gradient in Great Smoky Mountains National Park, USA. We asked (1) How do our newly developed structure metrics compare to traditional metrics? (2) How does forest structure vary with elevation in a high-biodiversity, high topographic complexity region? (3) How do forest structural metrics vary in the strength of their relationships with vascular plant biodiversity? Our new measures of canopy density (Depth) and structural complexity (σDepth), and their canopy height-normalized counterparts, were sensitive to structural variations and effectively summarized horizontal and vertical dimensions of structural complexity. Forest structure varied widely across plots spanning the elevational range of GRSM, with taller, more structurally complex forests at lower elevation. Vascular plant biodiversity was negatively correlated with elevation and more strongly positively correlated with vegetation structure variables. The strong correlations we observed between canopy structural complexity and biodiversity suggest that structural complexity metrics could be used to assay plant biodiversity over large areas in concert with airborne and spaceborne platforms.

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Ecological Processes Linking Forest Structure and Avian Diversity in Western Oregon

Cited by 6 publications

References 15 publications

Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon

Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon

Alternative Silvicultural Regimes in the Pacific Northwest: Simulations of Ecological and Economic Effects

Vegetation structural complexity and biodiversity in the Great Smoky Mountains

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