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

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

10.1101/2021.02.05.429381 ◽

2021 ◽

Author(s):

Katie Moriarty ◽

Joel Thompson ◽

Matthew Delheimer ◽

Brent Barry ◽

Mark Linnell ◽

...

Keyword(s):

North American ◽

Species Distribution Model ◽

Spatial Scales ◽

Abiotic Factors ◽

Mammalian Species ◽

Distribution Model ◽

Shrub Cover ◽

Limited Information ◽

Distribution Models ◽

Management Actions

AbstractBackgroundA suite of mammalian species have experienced range contractions following European settlement and post-settlement development of the North American continent. For example, while North American martens (American marten, Martes americana; Pacific marten, M. caurina) generally have a broad range across northern latitudes, local populations have experienced substantial reductions in distribution and some extant populations are small and geographically isolated. The Humboldt marten (M. c. humboldtensis), a subspecies of Pacific marten that occurs in coastal Oregon and northern California, was recently designated as federally threatened in part due to its reduced distribution. To inform strategic conservation actions, we assessed Humboldt marten occurrence by compiling all known records from their range.MethodsWe compiled Humboldt marten locations since their rediscover to present (1,692 marten locations, 1996-2020). We spatially-thinned locations to 500-m to assess correlations with variables across contemporary Humboldt marten distribution (n=384). Using maximum entropy modeling (Maxent), we created distribution models with variables optimized for spatial scale; pre-selected scales were associated with marten ecology (50 to 1170 m radius). Marten locations were most correlated with abiotic factors (e.g., precipitation), which are unalterable and therefore uninformative within the context of restoration or management actions. Thus, we created variables to focus on hypothesized marten habitat relationships, including understory conditions such as predicted suitability of shrub species.ResultsHumboldt marten locations were positively associated with increased shrub cover (salal (Gautheria shallon), mast producing trees), increased pine (Pinus sp) overstory cover and precipitation at home-range spatial scales, areas with low and high amounts of canopy cover and slope, and cooler August temperatures. Unlike other recent literature on the species, we found little evidence that Humboldt marten locations were associated with old growth structural indices, perhaps because of a potential mismatch in the association between this index and shrub cover. As with any species distribution model, there were gaps in predicted distribution where Humboldt martens have been located during more recent surveys, for instance the southeastern portion of Oregon’s coast range. Conservation efforts and our assessment of potential risks to Humboldt marten populations would benefit from additional information on range extent, population sizes, and fine-scale habitat use. Like many rare and lesser-known species, this case study provides an example of how limited information can provide differing interpretations, emphasizing the need for study-level replication in ecology.

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Structure and composition of unmanaged riparian forests in the coastal mountains of Oregon, U.S.A.

Canadian Journal of Forest Research ◽

10.1139/x99-133 ◽

1999 ◽

Vol 29 (10) ◽

pp. 1557-1573 ◽

Cited By ~ 53

Author(s):

Robert J Pabst ◽

Thomas A Spies

Keyword(s):

Spatial Scales ◽

Canopy Cover ◽

Basal Area ◽

Tree Regeneration ◽

Riparian Forests ◽

Stream Order ◽

Third Order ◽

First Order ◽

Hardwood Tree ◽

Stand Attributes

We characterized the structure and composition of unmanaged riparian forests in three river basins in Oregon's coastal mountains. Our objective was to evaluate stand attributes at three spatial scales: streamside (site), drainage network (stream order), and basin (subregion). Data on basal area, species composition, snag density, canopy cover, and tree regeneration were collected along transects at 124 sites. Conifer basal area increased with distance from stream, a trend similar among subregions, and was highest at sites along first-order streams. Hardwood basal area was relatively constant with distance from stream and was proportionally higher at sites along second- and third-order streams than at sites along first-order streams. Conifer and hardwood tree regeneration occurred infrequently and varied by topographic position, stream order, and subregion. Conifer regeneration was associated with basal area of shade-tolerant conifers and appeared to be limited by shrub competition. The unmanaged forests we studied were characterized by a patchy mosaic of structure and composition. Hardwoods and shrubs were major components of the near-stream environment in these forests, whereas dominance of conifers was limited to hillslopes. It appears that fine-scale patterns associated with proximity to the stream are influenced by coarser scale factors such as valley-floor width and climate.

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Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries

Marine Ecology Progress Series ◽

10.3354/meps13530 ◽

2020 ◽

Vol 655 ◽

pp. 123-137

Author(s):

TM Grimes ◽

MT Tinker ◽

BB Hughes ◽

KE Boyer ◽

L Needles ◽

...

Keyword(s):

Abiotic Factors ◽

Sea Otter ◽

Dungeness Crab ◽

Sea Otters ◽

Elkhorn Slough ◽

Enhydra Lutris Nereis ◽

Crab Abundance ◽

Population Sizes ◽

Commercially Important ◽

The Impact

Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

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Deriving Tree Size Distributions of Tropical Forests from Lidar

Remote Sensing ◽

10.3390/rs13010131 ◽

2021 ◽

Vol 13 (1) ◽

pp. 131

Author(s):

Franziska Taubert ◽

Rico Fischer ◽

Nikolai Knapp ◽

Andreas Huth

Keyword(s):

Size Distribution ◽

Spatial Scales ◽

Basal Area ◽

Tree Height ◽

Tree Size ◽

Diameter Distribution ◽

Forest Inventories ◽

Allometric Relations ◽

Lidar Measurements ◽

Derived Data

Remote sensing is an important tool to monitor forests to rapidly detect changes due to global change and other threats. Here, we present a novel methodology to infer the tree size distribution from light detection and ranging (lidar) measurements. Our approach is based on a theoretical leaf–tree matrix derived from allometric relations of trees. Using the leaf–tree matrix, we compute the tree size distribution that fit to the observed leaf area density profile via lidar. To validate our approach, we analyzed the stem diameter distribution of a tropical forest in Panama and compared lidar-derived data with data from forest inventories at different spatial scales (0.04 ha to 50 ha). Our estimates had a high accuracy at scales above 1 ha (1 ha: root mean square error (RMSE) 67.6 trees ha−1/normalized RMSE 18.8%/R² 0.76; 50 ha: 22.8 trees ha−1/6.2%/0.89). Estimates for smaller scales (1-ha to 0.04-ha) were reliably for forests with low height, dense canopy or low tree height heterogeneity. Estimates for the basal area were accurate at the 1-ha scale (RMSE 4.7 tree ha−1, bias 0.8 m² ha−1) but less accurate at smaller scales. Our methodology, further tested at additional sites, provides a useful approach to determine the tree size distribution of forests by integrating information on tree allometries.

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Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity

Scientific Reports ◽

10.1038/s41598-020-80077-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Mulalo M. Muluvhahothe ◽

Grant S. Joseph ◽

Colleen L. Seymour ◽

Thinandavha C. Munyai ◽

Stefan H. Foord

Keyword(s):

Climate Change ◽

Species Composition ◽

High Altitude ◽

Functional Diversity ◽

Large Scale ◽

Climate Models ◽

Spatial Scales ◽

Abiotic Factors ◽

Composition Analysis ◽

Fine Scale

AbstractHigh-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.

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Adjudicating Perspectives on Forest Structure: How Do Airborne, Terrestrial, and Mobile Lidar-Derived Estimates Compare?

Remote Sensing ◽

10.3390/rs13122297 ◽

2021 ◽

Vol 13 (12) ◽

pp. 2297

Author(s):

Jonathon J. Donager ◽

Andrew J. Sánchez Meador ◽

Ryan C. Blackburn

Keyword(s):

Ponderosa Pine ◽

Laser Scanning ◽

Canopy Cover ◽

Basal Area ◽

Tree Height ◽

Absolute Error ◽

Forest Monitoring ◽

Individual Tree ◽

Structural Configurations ◽

Individual Trees

Applications of lidar in ecosystem conservation and management continue to expand as technology has rapidly evolved. An accounting of relative accuracy and errors among lidar platforms within a range of forest types and structural configurations was needed. Within a ponderosa pine forest in northern Arizona, we compare vegetation attributes at the tree-, plot-, and stand-scales derived from three lidar platforms: fixed-wing airborne (ALS), fixed-location terrestrial (TLS), and hand-held mobile laser scanning (MLS). We present a methodology to segment individual trees from TLS and MLS datasets, incorporating eigen-value and density metrics to locate trees, then assigning point returns to trees using a graph-theory shortest-path approach. Overall, we found MLS consistently provided more accurate structural metrics at the tree- (e.g., mean absolute error for DBH in cm was 4.8, 5.0, and 9.1 for MLS, TLS and ALS, respectively) and plot-scale (e.g., R2 for field observed and lidar-derived basal area, m2 ha−1, was 0.986, 0.974, and 0.851 for MLS, TLS, and ALS, respectively) as compared to ALS and TLS. While TLS data produced estimates similar to MLS, attributes derived from TLS often underpredicted structural values due to occlusion. Additionally, ALS data provided accurate estimates of tree height for larger trees, yet consistently missed and underpredicted small trees (≤35 cm). MLS produced accurate estimates of canopy cover and landscape metrics up to 50 m from plot center. TLS tended to underpredict both canopy cover and patch metrics with constant bias due to occlusion. Taking full advantage of minimal occlusion effects, MLS data consistently provided the best individual tree and plot-based metrics, with ALS providing the best estimates for volume, biomass, and canopy cover. Overall, we found MLS data logistically simple, quickly acquirable, and accurate for small area inventories, assessments, and monitoring activities. We suggest further work exploring the active use of MLS for forest monitoring and inventory.

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How many bird extinctions have we prevented?

Oryx ◽

10.1017/s0030605306000950 ◽

2006 ◽

Vol 40 (3) ◽

pp. 266-278 ◽

Cited By ~ 101

Author(s):

Stuart H.M. Butchart ◽

Alison J. Stattersfield ◽

Nigel J. Collar

Keyword(s):

Invasive Species ◽

Captive Breeding ◽

Extinction Risk ◽

Bird Species ◽

Iucn Red List ◽

Additional Species ◽

Conservation Actions ◽

Declining Populations ◽

Population Sizes ◽

Principal Actions

Considerable resources and efforts have been directed at biodiversity conservation in recent years, but measures of the success of conservation programmes have been limited. Based on information on population sizes, trends, threatening processes and the nature and intensity of conservation actions implemented during 1994–2004, we assessed that 16 bird species would have probably become extinct during this period if conservation programmes for them had not been undertaken. The mean minimum population size of these 16 species increased from 34 to 147 breeding individuals during 1994–2004. In 1994, 63% of them had declining populations but by 2004, 81% were increasing. Most of these species (63%) are found on islands. The principal threats that led to their decline were habitat loss and degradation (88%), invasive species (50%) and exploitation (38%), a pattern similar to that for other threatened species, but with exploitation and invasive species being relatively more important. The principal actions carried out were habitat protection and management (75% of species), control of invasive species (50%), and captive breeding and release (33%). The 16 species represent only 8.9% of those currently classified as Critically Endangered, and 1.3% of those threatened with extinction. Many of these additional species slipped closer to extinction during 1994–2004, including 164 that deteriorated in status sufficiently to be uplisted to higher categories of extinction risk on the IUCN Red List (IUCN, 2006). Efforts need to be considerably scaled up to prevent many more extinctions in the coming decades. The knowledge and tools to achieve this are available, but we need to mobilize the resources and political will to apply them.

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Plant-Herbivore Interactions

Structure and Function of an Alpine Ecosystem ◽

10.1093/oso/9780195117288.003.0021 ◽

2001 ◽

Author(s):

Denise Dealing

Keyword(s):

Community Dynamics ◽

Spatial Scales ◽

Abiotic Factors ◽

Secondary Compounds ◽

Nutritional Composition ◽

Secondary Chemistry ◽

Niwot Ridge ◽

Herbivore Interactions ◽

Ultimate Objective ◽

Plant Herbivore

The alpine provides a tremendous opportunity for studying plant-herbivore interactions at the population, community, and ecosystem levels. For herbivores, variations in topography and microclimate result in a relatively large amount of spatial variation in plant communities within short distances (chapter 6). A large community of herbivores, from nematodes to grasshoppers to elk, occurs on Niwot Ridge. Furthermore, given the low rates of nutrient availability in alpine soils (Fisk and Schmidt 1995; chapter 12) combined with the slow-growing perennial habit of the vegetation, alpine plants should, in theory, invest heavily in defense against herbivores (Coley et al. 1985). The goal of this chapter is to provide: (1) a summary of the feeding behaviors of the herbivores on Niwot Ridge, (2) information on the nutritional and secondary chemistry of plants on Niwot Ridge as it relates to herbivory, and (3) a review of hypotheses on community dynamics of herbivores and plants relevant to the alpine. The ultimate objective is to provide a synthesis of information that will stimulate interest in alpine tundra as a system for studying the dynamics of plant-herbivore interactions at all levels of ecological organization. The flora of Niwot Ridge has been divided into six communities (May and Webber 1982; chapter 6). Regardless of community association, nearly all of the plant species occurring on the ridge are perennials and several are very long lived (May and Webber 1982). Communities can change across small spatial scales (meters), and community origin and maintenance are believed to be largely determined by abiotic factors (Walker et al. 1994; chapter 6). However, several studies suggest that biotic factors such as herbivory may have a significant impact on plant community dynamics (Huntly et al. 1986; Davies 1994). There is significant variation in the nutritional composition of plants on Niwot Ridge. Generally, and in the absence of plant secondary compounds, species that are high in nitrogen and low in fiber are presumed to be the most desirable as forage. Based solely on these nutritional variables, the clover Trifolium parryi is hypothesized to be one of the more-preferred forages, whereas alpine sandwort, Minuartia obtusiloba, should be one of the less-preferred food items.

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Scales of Food Availability for an Endangered Insectivore, The Hawaii Akepa

The Auk ◽

10.1093/auk/119.1.166 ◽

2002 ◽

Vol 119 (1) ◽

pp. 166-174 ◽

Cited By ~ 3

Author(s):

J. Scott Fretz

Keyword(s):

Food Availability ◽

Prey Availability ◽

Spatial Scales ◽

Canopy Cover ◽

Distribution Patterns ◽

Prey Population ◽

Suitable Habitat ◽

Population Declines ◽

Loxops Coccineus ◽

A Site

Abstract The Hawaii Akepa (Loxops coccineus coccineus) is an endangered bird that has declined dramatically in the last 100 years, and is now rare or absent from many areas that appear to support suitable habitat. Food availability may play a role in these distribution patterns, but differences in food between sites may arise from different sources. I compared prey availability between a site supporting a large, stable Hawaii Akepa population, and a site from which Hawaii Akepa have declined in the last 100 years for unknown reasons. I used three spatial scales to compare food between sites to explore the basis of differences in food between sites. At a scale appropriate for comparing prey population dynamics (scale 1), I found that prey population densities are similar between sites, suggesting that introduced (or native) predators or parasitoids have not affected prey populations differently between sites. At two larger scales incorporating habitat structure, I found that food availability is much lower at the site of Hawaii Akepa declines. Differences in canopy density per square meter (scale 2), and in canopy cover per square kilometer (scale 3), result in lower food availability that may have effects on individual foraging birds as well as on potential Hawaii Akepa population density. These findings illustrate the importance of explicitly incorporating spatial scale into inquiries about food for Hawaii Akepa, and suggest that the site of population declines may not be suitable habitat with respect to food for this species.

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Forest transformation resulting from an exotic pathogen: regeneration and tanoak mortality in coast redwood stands affected by sudden oak death

Canadian Journal of Forest Research ◽

10.1139/x11-020 ◽

2011 ◽

Vol 41 (4) ◽

pp. 763-772 ◽

Cited By ~ 18

Author(s):

Benjamin S. Ramage ◽

Kevin L. O’Hara ◽

Alison B. Forrestel

Keyword(s):

Canopy Cover ◽

Phytophthora Ramorum ◽

Sudden Oak Death ◽

Coast Redwood ◽

Marin County ◽

Wildlife Species ◽

Management Interventions ◽

Redwood Forests ◽

Exotic Pathogen ◽

Notholithocarpus Densiflorus

Sudden oak death is dramatically altering forests throughout coastal California, but little is known about the communities that are assembling in affected areas. This emerging disease, caused by the exotic pathogen Phytophthora ramorum (S. Werres, A.W.A.M. de Cock), has had especially severe effects on tanoak ( Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh), a broadleaf evergreen that is abundant in forests dominated by coast redwood ( Sequoia sempervirens (D.Don) Endl.). Tanoak, a valuable food source to numerous wildlife species, is unlikely to successfully regenerate in diseased areas, and thus, affected redwood forests are transitioning to a novel state. In this study, to predict which species might replace tanoak, we investigated regeneration patterns in heavily impacted stands in Marin County, California. Our main findings were as follows: (i) despite reductions in canopy cover, there is no evidence that any species other than tanoak has exhibited a regenerative response to tanoak mortality, (ii) the regeneration stratum was dominated by redwood and tanoak (other tree species were patchy and (or) scarce), and (iii) some severely affected areas lacked sufficient regeneration to fully re-occupy available growing space. Our results indicate that redwood is likely to initially re-occupy the majority of the ground relinquished by tanoak, but also provide evidence that longer-term trajectories are unresolved, and may be highly responsive to management interventions.

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