Hartwell H Welsh

• Ph.D. University of California
• Researcher at US Forest Service

Disturbances are part of the natural dynamics of Earth's ecosystems, with these events more common now in the Anthropocene. Yet metrics for calibrating these impacts and measuring an ecosystem's capacity to recover are lacking. Highway construction in 1989 to bypass Prairie Creek Redwoods State Park in California resulted in storm‐driven infusion o...

Species that breed in stream environments with unpredictable interannual variability in hydrological regimes may exhibit plasticity in the timing of their breeding activities. Breeding phenology should coincide with conditions and habitats that maximize a species' reproductive success. For the lotic-breeding frog Rana boylii, the timing of breeding...

This chapter focuses mostly on terrestrial conditions of species and biodiversity associated with late-successional and old-growth forests in the area of the Northwest Forest Plan (NWFP).

Studies of resource selection at multiple scales are critical to understanding ecological and evolutionary attributes of a species. We analyzed relative abundance, habitat use, and oviposition site selection of Foothill Yellow-Legged Frogs (Rana boylii) at 11 localities across two geographic regions in California (northern Coast Range and Sierra Ne...

Many riverine organisms are well adapted to seasonally dynamic environments, but extreme changes in flow and thermal regimes can threaten sustainability of their populations in regulated rivers. Altered thermal regimes may limit recruitment to populations by shifting the timing of breeding activities and affecting the growth and development of earl...

This figure, compiled by my co-author of the California conservation strategy for this species Don T. Ashton, depicts the ecological, habitat, and conservation needs of the key life stages of the western pond turtle (Actinemys marmorata).

Management of regulated rivers for yellow-legged frogs (Rana boylii) and salmonids exemplifies potential conflicts among species adapted to different parts of the natural flow and temperature regimes. Yellow-legged frogs oviposit in rivers in spring and depend on declining flows and warming temperatures for egg and tadpole survival and growth, wher...

Water diversions can disrupt flows and alter thermal regimes changing seasonal patterns that signal the onset of life-history functions of native organisms and compromise the fitness of their populations. We compared size, growth,relative mass, volumetric body condition, and reproductive status of Western Pond Turtles (Actinemys marmorata) across a...

Counter‐gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human‐altered habitats and changing climat...

Woodland (Plethodontid) salamanders are the most abundant vertebrates in North American forests, functioning as predators on invertebrates and prey for higher trophic levels. We investigated the role of Ensatina (Ensatina eschscholtzii ) in regulating invertebrate numbers and leaf litter retention in a northern California forest. Our objective was...

Woodland (Plethodontid) salamanders occur in huge numbers in healthy forests in North America where the abundances of many species vary along successional gradients. Their high numbersand trophic role as predators on shredder and decomposer arthropods influence nutrient and carbonpathways at the leaf litter/soil interface. Their extreme niche conse...

We examined seasonal reproductive patterns of the Del Norte Salamander, Plethodon elongatus, in mixed conifer and hardwood forests of northwestern California and southwestern Oregon. Seasonal size differences in reproductive structures suggested that maximum spermatogenic activity occurred during the late summer, with spermatozoa transfer to the va...

Western pond turtle biology, conservation, and management

Successfully addressing the multitude of stresses influencing forest catchments, their native biota, and the vital ecological services they provide humanity will require adapting an integrated view that incorporates the full range of natural and anthropogenic disturbances acting on these landscapes and their embedded fluvial networks. The concepts...

Extensive modifications of river systems have left floodplains some of the most endangered ecosystems in the world and made restoration of these systems a priority. Modified river ecosystems frequently support invasive species to the detriment of native species. Rana catesbeiana (American bullfrog) is an invasive amphibian that thrives in modified...

We investigated the aquatic and riparian herpetofauna in a 789 km2 river catchment in northwest California to examine competing theories of biotic community structuring in catchment stream networks. Research in fluvial geomorphology has resulted in multi-scale models of dynamic processes that cyclically create, maintain, and destroy environments in...

Los límites ecológicos han sido de interés para los naturalistas desde los tiempos de Darwin y Wallace debido a que son zonas de transición en el paisaje donde ocurren cambios en la estructura de comunidades de plantas y animales. Los oasis de palma de abanico (Erythea armata y Washingtonia robusta) presentes en los ambientes xéricos de la región c...

.— Headwaters can represent 80% of stream kilometers in a watershed, and they also have unique physical and biological properties that have only recently been recognized for their importance in sustaining healthy functioning stream networks and their ecological services. We sampled 60 headwater tributaries in the South Fork Trinity River, a 2,430 k...

Spatial patterns of animals have Important Implications for population dynamics and can reveal other key aspects of a species' ecology. Movements and the resulting spatial arrangements have fitness and genetic consequences for both Individuals and populations. We studied the spatial and dispersal patterns of the Oregon Gartersnake, Thamnophis atrat...

Kroll et al. [Kroll, A.J., Runge, J.P., MacCracken, J.G., 2009. Unreliable amphibian population metrics may obfuscate more than they reveal. Biological Conservation] criticized our recent advocacy for combining readily attainable metrics of population status to gain insight about relationships between terrestrial plethodontid salamanders and forest...

1. Kroll, Hayes & MacCracken (in press) Concerns regarding the use of amphibians as metrics of critical biological thresholds: a comment on Welsh and Hodgson 2008 . Freshwater Biology , criticised our paper [ Welsh & Hodgson (2008) Amphibians as metrics of critical biological thresholds in forested headwater streams of the Pacific Northwest. Freshw...

We provide a framework for developing predictive species habitat models using preexisting vegetation, physical, and spatial data in association with animal sampling data. The resulting models are used to evaluate questions relevant to species conservation, in particular, comparing occurrence estimates in reserved and unreserved lands. We used an in...

Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984–86 and from 1993–95) to address the question of whether evidence ex...

Tri-agency Conservation Strategy for the Northern Population of Plethodon stormi in Oregon; Habitat model: Risk assessment; Fire-management recommendations around at-risk human communities; Survey protocols, Version 3.0, 1999 for the federal Northwest Forest Plan Survey and Management Program, for species detection

The Foothill Yellow-legged Frog (Rana boylii) has declined across much of its native range in California. Improper stream management may lower egg mass survival and reduce the availability of suitable breeding habitats. We collected data during six breeding-seasons (2002-2007) along an unregulated stream in northwestern California. We monitored tem...

1. Amphibians are recognized both for their sensitivity to environmental perturbations and for their usefulness as cost‐effective biometrics of ecosystem integrity (=system health). 2. Twenty‐three years of research in headwater streams in the Klamath‐Siskiyou and North Coast Bioregions of the Pacific Northwest, U.S.A., showed distinct patterns in...

Hyperpredation occurs when non-native prey facilitate invasive predators, which then suppress native prey. Direct impacts of introduced fish on amphibians are well studied, but the role of fish in supporting shared predators has not been considered. We present evidence for indirect effects of trout on amphibians through snake predation. Analyses of...

Investigations to determine stable or source-sink animal population dynamics are challenging and often infeasible for most species due to the time and expense of mark-recapture studies and the challenge of life histories attributes that result in low detectability and low recapture probabilities. Often, managers rely solely on occupancy or relative...

Monitoring the distribution, population size, and trends of declining species is necessary to evaluate their vulnerability to extinction. It is the responsibility of scientists to alert management professionals of the need for preemptive action if a species approaches imminent, regional extirpation. This is the case with Rana cascadae (Cascades Fro...

We analyzed environmental relationships of the Siskiyou Mountains salamander, comparing attributes at the landscape, macro-and micro-environmental scales, and the three scales combined, to determine which attributes best predicted salamander presence. Separate analyses were conducted for sites on the north and south sides of the Siskiyou Mountains...

Monitoring the distribution, population size, and trends of declining species is necessary to evaluate their vulnerability to extinction. It is the responsibility of scientists to alert management professionals of the need for preemptive action if a species approaches imminent, regional extirpation. This is the case with Rana cascadae (Cascades Fro...

Terrestrial salamanders are integral components of forest ecosystems and the examination of their feeding habits may provide useful information regarding various ecosystem processes. We studied the diet of the Del Norte Salamander (Plethodon elongatus) and assessed diet differences between age classes, genders, and seasons. The stomachs of 309 suba...

Stream–riparian areas represent a nexus of biodiversity, with disproportionate numbers of species tied to and interacting within this key habitat. New research in Pacific Northwest headwater forests, especially the characterization of microclimates and amphibian distributions, is expanding our perspective of riparian zones, and suggests the need fo...

Abstract.—We investigated habitat use and movements of the wandering salamander, Aneides vagrans, in an old-growth forestcanopy. We conducted a mark-recapture study of salamanders in the crowns of five large redwoods (Sequoia sempervirens) inPrairie Creek Redwoods State Park, California. This represented a first attempt to document the residency an...

Conservation needs for amphibians in managed timberlands may differ based upon the species present and the timber harvesting methods employed. Clearcuts have been documented to be detrimental to amphibians but the impacts of associated silvicultural edges and alternative harvesting treatments are not well understood. The primary objective of this s...

The Klamath-Siskiyou forests of northern California and southern Oregon are recognized as an area of globally outstanding biological distinctiveness. When evaluated at a national or global level, this region is often, necessarily, considered to be uniformly diverse. Due to large variation in biotic and abiotic variables throughout this region, howe...

The goal of this study was to examine how introduced trout influence the distributions and abundances of a sub-alpine amphibian assemblage whose members display a variety of different life-history and defence strategies. Our study was conducted in the sub-alpine lentic habitats of three wilderness areas that form the core of the Klamath-Siskiyou Bi...

We compared species richness and relative abundance of stream-associated amphibians in late-seral redwood forests with those in mid-seral, second-growth forests to examine the continued (as opposed to immediate) effects of timber harvest on amphibian populations. Lacking pre-harvest data on amphibian abundances for streams in the second-growth stan...

Ecosystems are rapidly being altered and destabilized on a global scale, threatening native biota and compromising vital services provided to human society. We need to better understand the processes that can undermine ecosystem integrity (resistance-resilience) in order to devise strategies to ameliorate this trend. We used a herpetofaunal assembl...

We examined differences in riparian and aquatic environments within the three dominant vegetation patch types of the Mattole River watershed, a 789-km2 mixed conifer-deciduous (hardwood) forest and grassland-dominated landscape in northwestern California, USA. Riparian and aquatic environments, and particularly microclimates therein, influence the...

Snakes have recently been proposed as model organisms for addressing both evolutionary and ecological questions. Because of their middle position in many food webs they may be useful indicators of trophic complexity and dynamics. However, reliable data on snake populations are rare due to the challenges of sampling these patchily distributed, crypt...

Salamanders are cryptic and, though largely unrecognized as such, extremely abundant vertebrates in a variety of primarily forest and grassland environ-ments, where they regulate food webs and contribute to ecosystem resilience-resistance (= stability) in several ways: (a) As mid-level vertebrate predators, they provide direct and indirect biotic c...

Life stage determination for many western plethodontids often requires dissec- tion of the specimen. Availability of reliable external measures that could be applied under field conditions would enhance future studies of the genus Plethodon. We examined preserved spec- imens of the Del Norte Salamander, Plethodon elongatus, taken from 11 sites in n...

Regional amphibian distribution patterns can vary greatly depending on species and the spatial scale of inquiry (e.g., landscape to microenvironment). These differences appear to be related both to habitat selection among species as well as availability of suitable habitats across scales. M7e sampled amphibians in 39 second- and third-order streams...

Our goal was to describe and evaluate patterns of association between stream size and abundances of amphibians and small mammals in a northwestern California watershed. We sampled populations at 42 stream sites and eight upland sites within a 100-km(2) watershed in 1995 and 1996. Stream leaches sampled ranged from poorly defined channels that rarel...

In an attempt to define the upper thermal tolerance of coho salmon Oncorhynchus kisutch, we examined the relationship between the presence of this species and the summer tem- perature regime in 21 tributaries of the Mattole River of northwestern California. We characterized the temperature regime of each tributary by determining the highest average...

Terrestrial salamanders of the family Plethodontidae have unique attributes that make them excellent indicators of biodiversity and ecosystem integrity in forested habitats. Their longevity, small territory size, site fidelity, sensitivity to natural and anthropogenic perturbations, tendency to occur in high densities, and low sampling costs mean t...

Previous chapters have made a variety of points relevant to the management of redwood forests. Four general lessons stand out: First, primary old-growth red-wood forests are immensely valuable for biological, aesthetic, and other reasons and have become rare in the region after a century and a half of logging. As these forests have declined by more...

We describe and quantify the components of an unusual snake behavior used to attract fish prey: lingual-luring. Our earlier research on the foraging behavior of the Pacific Coast aquatic garter snake (Thamnophis atratus) indicated that adults are active foragers, feeding primarily on aquatic Pacific giant salamanders (Dicamptodon tenebrosus) in str...

The primary purpose of this chapter is to describe aquatic ecosystems within the redwood region and discuss related management and conservation issues. Although scientists from many disciplines have conducted research in the red-wood region, few comprehensive interdisciplinary studies exist (but see Ziemer 1998b) and no regionwide overview or synth...

This report describes the logic and design of an effectiveness monitoring program for the Northwest Forest Plan. The program is prospective, providing an early warning of environmental change before irreversible loss has occurred. Monitoring is focused at two resource levels: individual species and specific ecosystem types. Selection of prospective...

Western pond turtle (Clemmys marmorata) populations were examined on two forks of the Trinity River in northern California, one of which is subject to the impacts of damming and one of which is free-flowing. Mark-recapture was conducted over a three-year period for each population, and the Jolly-Seber model was used to estimate population size. Siz...

Road construction of the Redwood National Park highway bypass resulted in a large accidental infusion of fine sediments into pristine streams in Prairie Creek State Park, California, during an October 1989 storm event. This incident provided a natural experiment where we could measure, compare, and evaluate native stream amphibian den- sities as in...

Habitat associations of western pond turtles (Clemmys marmorata) were examined in a dammed and undammed tributary of the Trinity River in northwestern California to clarify the relations between habitat use and damming. The dammed tributary had more sedimentation, decreased water temperatures, increased canopy cover, and higher mater velocities, al...

Road construction of the Redwood National Park highway bypass resulted in a large accidental infusion of fine sediments into pristine streams in Prairie Creek State Park, California, during an October 1989 storm event. This incident provided a natural experiment where we could measure, compare, and evaluate native stream amphibian densities as indi...

We present a sampling method for use in small to medium-sized streams that is rigorous and repeatable, and contains the necessary flexibility to be species- or habitat-specific. Our habitat-based method generates large sample sizes for reliable statistical analyses yet remains cost effective. Streams are mapped, "habitat typed", and cross-stream sa...

The advantages of amphibians and reptiles (herpetofauna) as vertebrate indicators of environmental change is increasingly recognized, and their use for this purpose is becoming more common. However, herpetofauna consists of a broad range of species with very diverse natural histories, making the design of a strategy for sampling entire assemblages...

Despite its extensive range, the western pond turtle, Clemmys marmorata, is currently a can- didate for federal listing. Understanding its use of the landscape has become increasingly important to the development of appropriate management plans. Using radiotelemetry, we examined movements of turtles in a two-mile stretch of the Trinity River (Trini...

A systematic stratified sampling design was used to quantify the habitat relationships of the southern torrent salamander, Rhyacotriton variegatus, in northwestern California. We sampled 53 first to third order streams, each surrounded by at least 5-7 ha of relatively homogeneous forest or harvested forest habitat. Measurements of 121 attributes of...

Although the debate continues on the relative roles of natural fluctuations and anthropogenic influences in recently observed amphibian population declines (Blaustein 1994; McCoy 1994; Pechman et al. 1991; Pechman and Wilbur 1994; Travis 1994), many species are clearly demonstrating local extinctions and large-scale declines (Blaustein and Wake 199...

A stratified systematic sampling design was used to quantify the habitat relationships of the Del Norte salamander (Plethodon elongatus) in northwestern California. We sampled 57 sites, each within at least 5-7 ha of relatively homogeneous forest or post-forest habitat, where we measured 83 characteristics of the environment. Salamander sampling co...

Foraging behaviour, stream habitat use and food habits of a population of the aquatic, Oregon garter snake were studied in the field during the spring and summer of 1987 and 1988. Continuous records of behaviour and habitat use were obtained for each snake. Adults foraged more actively and in a wider variety of stream habitats than juveniles or neo...

Bioregions are natural assemblages of plants and animals with discernible but dynamic boundaries existing simultaneously along both spatial and temporal trajectories. I argue that the designation of bioregions should be based on the study of biogeography and must adhere to the tenets of this discipline; they are not spatial designations of politica...

Thesis (Ph. D.)--University of California, Berkeley, 1993. Includes bibliographical references (leaves 183-199). Photocopy.

We investigated the population ecology of the southern Olympic salamander (Rhyacotriton variegatus) and the Del Norte salamander (Plethodon elongatus) in the Klamath Mountains of northwestern California. A random stratified sampling design was used to investigate the distribution and relative abundance of subpopulations (metapopulation structure) o...

Terrestrial and aquatic herpetofauna were sampled by pitfall traps, time-constrained searches, and area-constrained searches (stream sites only) over a three-year period to examine the importance of forest age to amphibians and reptiles. Fifty-four terrestrial and 39 aquatic sites in Douglas-fir—dominated, mixed evergreen forests were located in so...

Noted 25 species of terrestrial herpetofauna in stands of Douglas-fir Pseudotsuga menziesii hardwood forest in SW Oregon and NW California. Stands ranged in age from 40-450 years. Species diversity was greater in older forest stands. Amphibians were significantly more abundant in old stands and significantly less abundant in dry stands. Changes in...

Thesis (M.S.)--Humboldt State University, 1976. Includes bibliographical references (leaves [89]-96). Photocopy of typescript.

Abstract—Basking activity of western pond turtles (Clemmys marmorata) was studied on two forks of the Trinity River in northern California, the dammed Mainstem Trinity River and the undammed,South Fork Trinity River. The thermal regime between these two riverine systems is extreme due to the hypolimnetic release from the Lewiston Dam on the Mainste...