Northwest Forest Plan—the first 20 years (1994-2013): status and trends of northern spotted owl habitats

Davis, Raymond J.; Hollen, Bruce; Hobson, Jeremy; Gower, Julia E.; Keenum, David

doi:10.2737/pnw-gtr-929

Cited by 41 publications

(18 citation statements)

References 34 publications

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“…Species’ distributions may also be strongly influenced by less-apparent factors such as interspecific interactions with predators or competitors ( Siren, 2020 ). As an example, spotted owls ( Strix occidentalis ) closely align with old-growth forest conditions which have been characterized with relatively high accuracy ( Davis et al, 2016 ), yet spotted owl population viability is dramatically decreased with presence of barred owls ( S. varia ) due to interspecific competition and predation ( Wiens, Anthony & Forsman, 2014 ; Diller et al, 2016 ; Dugger et al, 2016 ). Although few examples exist for carnivores, a recent evaluation suggests that while lynx ( Lynx lynx ) distributions are closely-tied to deep snow, the influence of reducing bobcat ( L. rufus ) competition was stronger than the influence of snow itself ( Siren, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

“…We projected our model to available vegetation data from Gradient Nearest Neighbor (GNN) data supplied by the Landscape Ecology, Modeling, Mapping and Analysis lab ( Bell, Gregory & Davis, 2020 ; Bell et al, 2021 ), which included the coastal and Klamath level-3 eco-provinces ( U.S. Environmental Protection Agency, 2013 ). We removed urban areas and water from the background data ( Davis et al, 2016 ). We summarized the range, average, and standard deviation for each variable within the modeling region and study area ( Table 1 , Fig.…”

Section: Methodsmentioning

confidence: 99%

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Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis)

Moriarty

Thompson

Delheimer

et al. 2021

PeerJ

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Background Many mammalian species have experienced range contractions. Following a reduction in distribution that has resulted in apparently small and disjunct populations, the Humboldt marten (Martes caurina humboldtensis) was recently designated as federally Threatened and state Endangered. This subspecies of Pacific marten occurring in coastal Oregon and northern California, also known as coastal martens, appear unlike martens that occur in snow-associated regions in that vegetation associations appear to differ widely between Humboldt marten populations. We expected current distributions represent realized niches, but estimating factors associated with long-term occurrence was challenging for this rare and little-known species. Here, we assessed the predicted contemporary distribution of Humboldt martens and interpret our findings as hypotheses correlated with the subspecies’ niche to inform strategic conservation actions. Methods We modeled Humboldt marten distribution using a maximum entropy (Maxent) approach. We spatially-thinned 10,229 marten locations collected from 1996–2020 by applying a minimum distance of 500-m between locations, resulting in 384 locations used to assess correlations of marten occurrence with biotic and abiotic variables. We independently optimized the spatial scale of each variable and focused development of model variables on biotic associations (e.g., hypothesized relationships with forest conditions), given that abiotic factors such as precipitation are largely static and not alterable within a management context. Results Humboldt marten locations were positively associated with increased shrub cover (salal (Gautheria shallon)), mast producing trees (e.g., tanoak, Notholithocarpus densiflorus), increased pine (Pinus sp.) proportion of total basal area, annual precipitation at home-range spatial scales, low and high amounts of canopy cover and slope, and cooler August temperatures. Unlike other recent literature, we found little evidence that Humboldt martens were associated with old-growth structural indices. This case study provides an example of how limited information on rare or lesser-known species can lead to differing interpretations, emphasizing the need for study-level replication in ecology. Humboldt marten conservation would benefit from continued survey effort to clarify range extent, population sizes, and fine-scale habitat use.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis)

Moriarty

Thompson

Delheimer

et al. 2021

PeerJ

View full text Add to dashboard Cite

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“… †† Davis et al. ( 2011 , 2016 ). ‡‡ Tested and moved forward with one of three structures for territory experience based on stage 1 model rankings: n yr of territory tenure (EXP_yrs; continuous variable), territory experience (EXP_any; binary variable), and territory experience class (none, 1–4 yr [EXP_low], or ≥5 yr [EXP_high]).…”

Section: Methodsmentioning

confidence: 99%

Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls

Jenkins

Lesmeister

Forsman

et al. 2021

Ecological Applications

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Breeding dispersal, the movement from one breeding territory to another, is rare for philopatric species that evolved within relatively stable environments, such as the old-growth coniferous forests of the Pacific Northwest. While dispersal is not inherently maladaptive, the consequences of increased dispersal on population dynamics in populations whose historical dispersal rates are low could be significant, particularly for a declining species. We examined rates and possible causes of breeding dispersal based on a sample of 4,118 northern spotted owls (Strix occidentalis caurina) monitored in seven study areas over 28 years, 1990 to 2017, in Oregon and Washington, USA. Using a multistate mark-resight analysis, we investigated the potential impacts of an emergent congeneric competitor (barred owl Strix varia) and forest alteration (extrinsic factors), and social and individual conditions (intrinsic factors) on 408 successive and 1372 non-successive dispersal events between years. The annual probability of breeding dispersal increased for individual owls that had also dispersed in the previous year and decreased for owls on territories with historically high levels of reproduction.Intrinsic factors including pair status, prior reproductive success, and experience at a site, were also associated with breeding dispersal movements. The percent of monitored owls dispersing each year increased from ~7% early in the study to ~25% at the end of the study, which coincided with a rapid increase in numbers of invasive and competitively dominant barred owls. We suggest that the results presented here can inform spotted owl conservation efforts as we identify factors contributing to changing rates of demographic parameters including site fidelity and breeding dispersal. Our study further shows that increasing rates of breeding dispersal associated with population declines contribute to population instability and vulnerability of northern spotted owls to extinction, and the prognosis is unlikely to change unless active management interventions are undertaken.

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“…We used the Maxent regularization multiplier parameter [ 41 ] from 0.1 to 2.0 with steps of 0.1 to calibrate the Maxent model [ 13 , 14 ]. We contrasted the owl locations (pixels) used for model training against a random sample of 10,000 background forest-capable pixels, drawn from the area labeled “forestland” in Fig 1 , for each replicate [ 42 ].…”

Section: Methodsmentioning

confidence: 99%

“…The recent application of time series analysis allows researchers to identify and use the central tendency of Landsat reflectance over time to minimize the effect of such issues [ 5 , 12 ]. Emerging applications for temporally stable, accurate landscape-scale habitat maps include long-term wildlife habitat monitoring programs [ 13 , 14 ] and species recovery efforts [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

Linking robust spatiotemporal datasets to assess and monitor habitat attributes of a threatened species

et al. 2022

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Accessibility of multispectral, multitemporal imagery combined with recent advances in cloud computing and machine learning approaches have enhanced our ability to model habitat characteristics across broad spatial and temporal scales. We integrated a large dataset of known nest and roost sites of a threatened species, the Mexican spotted owl (Strix occidentalis lucida), in the southwestern USA with Landsat imagery processed using the Continuous Change Detection and Classification (CCDC) time series algorithm on Google Earth Engine. We then used maximum entropy modeling (Maxent) to classify the landscape into four ‘spectral similarity’ classes that reflected the degree to which 30-m pixels contained a multispectral signature similar to that found at known owl nest/roost sites and mapped spectral similarity classes from 1986–2020. For map interpretation, we used nationally consistent forest inventory data to evaluate the structural and compositional characteristics of each spectral similarity class. We found a monotonic increase of structural characteristics typically associated with owl nesting and roosting over classes of increasing similarity, with the ‘very similar’ class meeting or exceeding published minimum desired management conditions for owl nesting and roosting. We also found an increased rate of loss of forest vegetation typical of owl nesting and roosting since the beginning of the 21st century that can be partly attributed to increased frequency and extent of large (≥400 ha) wildfires. This loss resulted in a 38% reduction over the 35-year study period in forest vegetation most similar to that used for owl nesting and roosting. Our modelling approach using cloud computing with time series of Landsat imagery provided a cost-effective tool for landscape-scale, multidecadal monitoring of vegetative components of a threatened species’ habitat. Our approach could be used to monitor trends in the vegetation favored by any other species, provided that high-quality location data such as we presented here are available.

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Northwest Forest Plan—the first 20 years (1994-2013): status and trends of northern spotted owl habitats

Cited by 41 publications

References 34 publications

Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis)

Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis)

Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls

Linking robust spatiotemporal datasets to assess and monitor habitat attributes of a threatened species

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