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Matthew Johnson

Publications and source records attributed to Matthew Johnson.

9 recordsLinked to original sources
USGS2024

Wildfire burn severity and stream chemistry influence aquatic invertebrate and riparian avian mercury exposure in forested ecosystems

Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of terrestrial-bound Hg via reemission to the atmosphere or mobilization in watersheds where it may become available for methylation and uptake into food webs. Using data associated with the 2007 Moonlight and Antelope Fires in California, we examined the long-term direct effects of wildfire burn severity on the distribution and magnitude of Hg concentrations in riparian food webs. Additionally, we quantified the cross-ecosystem transfer of Hg from aquatic invertebrate to riparian bird communities; and assessed the influence of biogeochemical, landscape variables, and ecological factors on Hg concentrations in aquatic and terrestrial food webs. Benthic macroinvertebrate methylmercury (MeHg) and riparian bird blood total mercury (THg) concentrations varied by 710- and 760-fold, respectively, and Hg concentrations were highest in predators. We found inconsistent relationships between Hg concentrations across and within taxa and guilds in response to stream chemical parameters and burn severity. Macroinvertebrate scraper MeHg concentrations were influenced by dissolved organic carbon (DOC); however, that relationship was moderated by burn severity (as burn severity increased the effect of DOC declined). Omnivorous bird Hg concentrations declined with increasing burn severity. Overall, taxa more linked to in situ energetic pathways may be more responsive to the biogeochemical processes that influence MeHg cycling. Remarkably, 8 years post-fire, we still observed evidence of burn severity influencing Hg concentrations within riparian food webs, illustrating its overarching role in altering the storage and redistribution of Hg and influencing biogeochemical processes.

Ecotoxicology↗
USGS2021

Extent, configuration and diversity of burned and forested areas predict bat richness in a fire-maintained forest

Context Fire transforms, fragments and sometimes maintains forests, creating mosaics of burned and unburned patches. Highly mobile animals respond to resources in the landscape at a variety of spatial scales, yet we know little about their landscape-scale relationships with fire. Objectives We aimed to identify drivers of bat richness in a landscape mosaic of forested and burned areas while identifying spatial scales at which bat richness was most strongly related to extent, configuration, and diversity measures of landscape-level habitat. Methods We used multi-species hierarchical occupancy modelling to relate bat richness to landscape variables at 10 spatial scales, based on acoustic data collected in the Sierra Nevada, United States. We also assessed redundancy among landscape variable type (extent, configuration, and diversity) and between focal patch types (forested and burned). Results Bat richness was positively associated with heterogenous landscapes, shown by positive associations with pyrodiversity, extent and mean area of burned patches, burned and forested edge density and patch density and relationships were generally consistent across scales. Extent of forest cover and burned areas were highly correlated, but configuration and diversity of these patch types diverged. Conclusions Bat communities of our study area appear to be largely resilient to wildfire and adapted to more heterogenous forests and shorter-interval fire regimes that likely predominated before the fire suppression era.

California↗
USGS2021

Fish habitat use and food web structure following pond and plug restoration of a Montane Meadow in the Sierra Nevada, California

Montane meadows are areas of high biodiversity and provide many important ecosystem services; however, degradation of 40–60% of these habitats in the Sierra Nevada region of California has left many of these areas impaired. The “pond-and-plug” meadow-restoration technique is 1 type of treatment implemented to restore montane meadows. The objectives of this technique are to re-water the meadow and promote downstream flow by increasing the water-table elevation and providing additional water storage that will promote the growth of mesic and hydric vegetation that maintains and stabilizes stream channels. However, aquatic habitat and the composition and functioning of aquatic communities in these systems post-treatment are poorly documented or understood. We evaluated: (1) fish habitat, community composition, and relative abundance among recently created ponds spanning the range of pond habitats; (2) seasonal movement and survival of fish within and among ponds; and (3) food web structure in ponds. We documented over-summer and winter survival in the fish community and short-distance movement by 1 species occupying the ponds. Mark-recapture data suggest that all fish species present are capable of surviving both summer and winter conditions when pond conditions could be most limiting. Food web structure among intensively sampled ponds was similar, with overlapping isotopic niche width for dominant taxa. However, basal resource diversity (BRD) varied among ponds, with those having higher macrophyte cover also showing greater BRD. Our findings suggest that pond-and-plug techniques can provide habitat for native fishes that are able to tolerate departures from the species thermal and dissolved oxygen optima. Future meadow treatments could benefit from short-term restoration techniques such as pond-and-plug to allow for longer-term processes to influence meadow condition over time.

California↗
USGS2020

Multi-scale habitat selection by Northern Goshawks (Accipiter gentilis) in a fire-prone forest

Increasing frequency and severity of wildfire may jeopardize persistence of large tracts of late seral forest, raising concerns over population viability of forest-dependent species like the Northern Goshawk ( Accipiter gentilis ). We tracked 20 adult Northern Goshawks with GPS loggers over 4 years to investigate roosting (nocturnal) and foraging (diurnal) habitat selection in a heterogeneously burned forest landscape of the Sierra Nevada mountains of California, United States. Goshawks selected late seral forest attributes for both roosting and foraging at multiple spatio-temporal scales, although at the finest (daily) scale, goshawks selected more diverse forest structure that included small trees and medium canopy cover. Less than 6% of roosts were in areas burned in the last 50 years and goshawks avoided areas burned at high severity when roosting and when foraging across spatial scales. Four goshawks (3 males, 1 female) undertook forays >5 km from their nest location, two of which forayed into burned areas during at least one season. High severity fire is likely to make forests unsuitable foraging or roosting habitat for Northern Goshawks, although lower severity fire may provide foraging opportunities for this generalist predator. Eighty percent of foraging space use and 87% of roost locations were considered high fire hazard potential, suggesting that goshawk habitat in western North America is likely to be reduced by predicted increases in fire frequency and severity in the region.

California↗
USGS2012

Patterns of mortality in free-ranging California condors (Gymnogyps californianus)

We document causes of death in free-ranging California Condors (Gymnogyps californianus) from the inception of the reintroduction program in 1992 through December 2009 to identify current and historic mortality factors that might interfere with establishment of self-sustaining populations in the wild. A total of 135 deaths occurred from October 1992 (the first post-release death) through December 2009, from a maximum population-at-risk of 352 birds, for a cumulative crude mortality rate of 38%. A definitive cause of death was determined for 76 of the 98 submitted cases, 70% (53/76) of which were attributed to anthropogenic causes. Trash ingestion was the most important mortality factor in nestlings (proportional mortality rate [PMR] 73%; 8/11), while lead toxicosis was the most important factor in juveniles (PMR 26%; 13/50) and adults (PMR 67%; 10/15). These results demonstrate that the leading causes of death at all California Condor release sites are anthropogenic. The mortality factors thought to be important in the decline of the historic California Condor population, particularly lead poisoning, remain the most important documented mortality factors today. Without effective mitigation, these factors can be expected to have the same effects on the sustainability of the wild populations as they have in the past.

Journal of Wildlife Diseases↗
USGS2010

Life history and demographics of the endangered birdwing pearlymussel ( Lemiox rimosus ) (Bivalvia: Unionidae)

The life history and population demography of the endangered birdwing pearlymussel ( Lemiox rimosus ) were studied in the Clinch and Duck rivers, Tennessee. Reproducing populations of L. rimosus now occur only in the Clinch, Duck and Powell rivers, as the species is considered extirpated from the remaining portions of its range in the Tennessee River drainage. Females are long-term winter brooders, typically gravid from Oct. to May. Glochidia are contained in the outer gills and are released in association with a mantle-lure that resembles a small freshwater snail. Estimated fecundity, based on 8 gravid females collected from the Clinch and Duck rivers, ranged from 4132 to 58,700 glochidia/mussel. Seven fish species were tested for suitability as hosts for glochidia, and five darter species were confirmed through induced infestations: Etheostoma blennioides , E. camurum , E. rufilineatum , E. simoterum and E. zonale . Ages of L. rimosus shells were determined by thin-sectioning and ranged from 3 to 15 y in both rivers. Shell growth was higher and maximum size greater in males than females in both rivers. Shell growth was greatest in the Duck River. Densities of L. rimosus in the Clinch River were maintained at seemingly stable but low levels ranging from 0.07 to 0.27 m −2 from 2004–2007, and in the Duck River at similar but higher levels ranging from 0.6 to 1.0 m −2 from 2004–2006. In the latter river, abundance has increased since 1988, likely due to improved minimum flows and dissolved oxygen levels in water releases from a reservoir upstream.

Tennessee↗
USGS2010

Analysis of California Condor (Gymnogyps californianus) use of six management units using location data from global positioning system transmitters, southern California, 2004-09-Initial report

This report provides an analysis of California Condor (Gymnogyps californianus) space use of six management units in southern California (Hopper Mountain and Bitter Creek National Wildlife Refuges, Wildlands Conservancy-Wind Wolves Preserve, Tejon Mountain Village Specific Plan, California Condor Study Area, and the Tejon Ranch excluding Tejon Mountain Village Specific Plan and California Condor Study Area). Space use was analyzed to address urgent management needs using location data from Global Positioning System transmitters. The U.S. Fish and Wildlife Service provided the U.S. Geological Survey with location data (2004-09) for California Condors from Global Positioning System transmitters and Geographic Information System data for the six management units in southern California. We calculated relative concentration of use estimates for each management unit for each California Condor (n = 21) on an annual basis (n = 39 annual home ranges) and evaluated resource selection for the population each year using the individual as our sampling unit. The most striking result from our analysis was the recolonization of the Tejon Mountain Village Specific Plan, California Condor Study Area, and Tejon Ranch management units during 2008. During 2004-07, the home range estimate for two (25 percent) California Condors overlapped the Tejon Mountain Village Specific Plan, California Condor Study Area, and Tejon Ranch management units (n = 8), and use within the annual home range generally was bimodal and was concentrated on the Bitter Creek and Hopper Mountain National Wildlife Refuges. However, 10 (77 percent) California Condor home ranges overlapped the Tejon Mountain Village Specific Plan, California Condor Study Area, and Tejon Ranch management units during 2008 (n = 13), and by 2009, the home range of every condor carrying a Global Positioning System transmitter (n = 14) overlapped these management units. Space use was multimodal within the home range during 2008-09 and was concentrated on Hopper Mountain Refuge in the south, Bittercreek Refuge and the Wind Wolves Preserve in the northwest, and the Tejon Mountain Village Specific Plan, California Condor Study Area, and Tejon Ranch management units in the northeast. Recolonization of the Tejon Mountain Village Specific Plan, California Condor Study Area, and Tejon Ranch management units reestablished traditional condor movement and foraging patterns in southern California and provides the travel corridor (approximately 20 kilometers wide) for recolonization of the northeastern part of the species historical range.

Open-File Report↗
USGS2010

Seasonal movements, winter range use, and migratory connectivity of the Black Oystercatcher

The Black Oystercatcher ( Haematopus bachmani ) is an intertidal obligate along North America's Pacific coast and a species of high conservation concern (population size 8900–11 000 individuals). Understanding birds' movements and space use throughout the annual cycle has become paramount in the face of changing environmental conditions, and intertidal species may be particularly vulnerable to habitat change due to anticipated sea-level rise associated with climate change and increasing coastal development. Conservation of the Black Oystercatcher is hindered by a lack of information on the species' nonbreeding distribution, seasonal movements, and habitat connectivity. Using satellite ( n = 19) and VHF ( n = 19) radio transmitters, we tracked Black Oystercatchers from five breeding sites (Vancouver Island, British Columbia; Kodiak Island, Prince William Sound, Middleton Island, and Juneau, Alaska) through one and one half annual cycles (May 2007–Dec 2008). We documented medium- to long-distance migration (range of migration distance 130–1667 km) in three populations (Prince William Sound, Middleton Island, and Juneau) and year-round residency in two others (Kodiak and Vancouver Island). We observed variation in the timing and length of migration by study site, and individual birds demonstrated fidelity to breeding and nonbreeding sites. We did not observe strong migratory connectivity. Migratory oystercatchers distributed themselves widely along the coasts of British Columbia and southeast Alaska during winter. Results provide baseline information on the Black Oystercatcher's movements and space use throughout the annual cycle.

Alaska↗