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Describing vegetation characteristics used by two rare forest-dwelling species: Will established reserves provide for coastal marten in Oregon?

ABSTRACT: Forest management guidelines for rare or declining species in the Pacific Northwest, USA, include both late successional reserves and specific vegetation management criteria. However, whether current management practices for well-studied species such as northern spotted owls (Strix occidentallis caurina) can aid in conserving a lesser known subspecies-Humboldt martens (Martes caurina humboldtensis)-is unclear. To address the lack of information for martens in coastal Oregon, USA, we quantified vegetation characteristics at locations used by Humboldt martens and spotted owls in two regions (central and southern coast) and at two spatial scales (the site level summarizing extensive vegetation surveys and regionally using remotely sensed vegetation and estimated habitat models). We estimated amount of predicted habitat for both species in established reserves. If predicted overlap in established reserves was low, then we reported vegetation characteristics to inform potential locations for reserves or management opportunities. In the Central Coast, very little overlap existed in vegetation characteristics between Humboldt martens and spotted owls at either the site or regional level. Humboldt martens occurred in young forests composed of small diameter trees with few snags or downed logs. Humboldt martens were also found in areas with very dense vegetation when overstory canopy and shrub cover percentages were combined. In the South Coast, Humboldt martens occurred in forests with smaller diameter trees than spotted owl sites on average. Coastal Humboldt martens may use stands of predicted high quality spotted owl habitat in the Pacific Northwest. Nonetheless, our observations suggest that coastal Humboldt martens exist in areas that include a much higher diversity of conifer size classes as long as extensive dense shrub cover, predominantly in the form of high salal and evergreen huckleberry, are available. We suggest that managers consider how structural characteristics (e.g., downed logs, shrub cover, patch size), are associated with long-term species persistence rather than relying on reserves based on broad cover types. Describing vegetation may partially describe suitability, but available prey or predation risk ultimately influence likelihood of individual Humboldt marten use. Guidelines for diversifying vegetation management, and retaining or restoring appropriate habitat conditions at both the stand level and regionally, may increase management flexibility and identify forest conditions that support both spotted owls and Humboldt martens.

SUBMITTER: Moriarty KM

PROVIDER: S-EPMC6354973 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Urban park managers are tasked with maintaining ecological function and quality of parks while also meeting visitor preferences. The purpose of this study was to better understand how managers currently manage vegetation in parks of Portland, Oregon. Twenty-one urban park manager interviews were completed regarding 15 parks, which included natural-passive use, recreational-active use, and multi-use park types. Responses were coded for themes and patterns of meaning. Mixed methods were used to evaluate the urban park manager interview data in the context of visitor interview and plant community composition data collected at the same parks. Nonmetric multidimensional scaling ordinations were used to identify urban park manager and visitor perspectives correlated with different park types and their vegetation. Across park types, managers discussed maintenance as a favorite aspect of plant management, while ecosystem management was often described by managers of natural-passive use parks. Some managers indicated that they would make no changes to plant management, but the majority provided detailed recommendations such as enhancing maintenance, increasing staffing, adding plants, updating infrastructure, and improving plant species selection. There are opportunities to better meet the preferences of both managers and visitors by continuing to maintain large trees and trail/path vegetation for accessibility, removing invasive/harmful plants, and improving plant selection to include those that are heartier, more colorful, produce flowers, and are disease resistant, climate adapted, and provide habitat for a variety of species. While urban park managers discussed how they incorporated visitor preferences and accessibility in plant management, they also described limitations such as funding, staff resources, and undesirable visitor behaviors. Increased communication and collaboration among governmental agencies, non-profit organizations, and community members, as well as continued investment in park management and interdisciplinary mixed methods research have the potential to enhance the many ecological and social benefits of urban parks.

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Project description:BackgroundMany 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.MethodsWe 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.ResultsHumboldt 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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Describing vegetation characteristics used by two rare forest-dwelling species: Will established reserves provide for coastal marten in Oregon?

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