Influences of high severity fire and postfire logging on avian and small mammal communities of the Siskiyou Mountains, Oregon, USA

High severity fire is a historical and integral disturbance process in coniferous forest types. Compounded disturbances such as multiple fires or post-disturbance management activities are increasingly common, but ecological responses are not well understood and may represent novel types of disturbances. I studied bird and small mammal communities in the mixed severity fire regime of the Siskiyou Mountains of southwestern Oregon, USA, at various points in time after one or two high severity fires in and around the historic 200,000-ha Biscuit Fire. Post-disturbance time intervals included 2-4 years after a single fire, 17-18 years after a single fire, 2-3 years after a repeat fire (15 year interval between fires), and >100 years since stand-replacement fire (mature/old-growth forest). Additionally, I examined the response of these communities to postfire salvage logging of the Biscuit Fire. Avian species richness did not differ significantly among habitats. Among the recently burned habitats, bird density was highest 17-18-years after fire and lowest 2 years after a single fire. Sites 17-18 years postfire were dominated by broad-leaved shrubs. Ordination of community data revealed two distinct gradients in avian species composition, one relating to tree structure (live, dead-sound, dead-decayed) and another relating to shrub volume and height. Bird density was positively related to shrub height and volume; increases in broad-leaved plants following fire were associated with significant increases in bird density. Immediately after a single high severity fire event, small mammal communities transitioned from low abundance and high species richness to high abundance and low species richness dominated by deer mice. Partial recovery to a pre-burn state was evident 17 years after fire with wood rats being present but vole species still absent relative to unburned mature forest. Repeat fire was associated with heightened abundance of deer mice and herbaceous cover. Postfire salvage logging created a significant pulse of woody debris but no significant changes in densities or biomass of small mammals were observed. Fire effects on small mammal communities were much larger than those of postfire salvage logging in the short term. Longer term studies of changes in small mammal communities following salvage logging are needed over decades and greater time scales to fully evaluate the impacts of the management activity. To examine bird response to postfire salvage logging, we used point counts to measure changes in densities and occurrence for 17 common bird species. Response was measured at two spatial scales (20 ha and 2 ha) relative to two measures of salvage logging: proportion of surrounding area logged and logging intensity (basal area removed). The 20-ha scale comprised the logging unit as well as unit edges and surrounding unlogged areas, while the 2-ha scale comprised only the logging unit and not surrounding edges. At the 20-ha scale, we found a positive response in the density of shrub-associated species (house wren, lazuli bunting, black-headed grosbeak [scientific names given in Appendix A]) and edge-associated species (olive-sided flycatcher, yellow-rumped warbler) and little evidence of negative responses, save for a reduction in density of Hammond’s flycatcher. At the 2-ha scale, shrub-associates again responded positively but not edge-associates. Brown creeper responded negatively at the 2-ha scale and five species had suggestive negative trends but they were not significant suggesting that, except for shrub nesting species, bird use of salvage units is associated with edges and not interior portions of salvage units. The lack of a strong negative response to salvage logging of the Biscuit Fire suggests that the small logging unit sizes relative to the burn area, as well as extensive snag retention in riparian buffers, tended to retain many bird species in the burn landscape

Ultrasonic Deterrents Reduce Nuisance Cat (Felis Catus) Activity on Suburban Properties

Urban environments are increasingly important for biodiversity conservation, but pet cats threaten wildlife therein, displaying nuisance behaviour such as hunting, fighting, fouling and urine spraying. In an attempt to empower landholders wishing to reduce cat incursions humanely, we tested the effectiveness of two ultrasonic cat deterrents (CatStop© and On-Guard Mega-Sonic Cat Repeller©). After confirming in arena trials that cats detect and respond negatively to an ultrasonic device, we tested both deterrents in 18 suburban gardens in Perth, Western Australia. Camera monitoring at foci of cat activity (e.g. fish ponds, property entry/exit points) occurred for two weeks before (Period 1: device off), during (Period 2: device on) and after (Period 3: device off) the activation of deterrents. Data included individual cat demographics and behaviours, number of cat detections per site per day per sampling period, the duration of cat activity, and detection of non-target species. Seventy-eight unique cats were detected at 17 of 18 garden sites (2e9 cats/garden). Over half the cats could be sexed (56.4%, with 65.1% males). Nearly 53.0% of cats were confirmed to be pets living nearby. Cats that were most active in period 1 (100 s total activity duration) were classified as ‘residents’; all others were ‘peripherals’. Overall, the ultrasonic deterrents reduced the frequency of incursions into gardens by resident cats by 46%, while the duration of incursions was reduced by 78%. Cat activity declined significantly from period 1 (baseline) to period 2 for resident cats but not peripheral cats (50% reduction; p . 0.001), and remained depressed in period 3 for resident cats but not peripheral cats (p \u3c 0.001). Peripheral cat activity remained at an unchanging low level across all three periods. Males were slightly more active than females over the experiment (p . 0.04), but sexes did not vary in response to deterrents (p \u3e 0.05). Cats confirmed as owned (53% of cats) generated more activity than cats of unknown ownership status (p . 0.03), probably reflecting proximity of their residences to trial gardens. Both deterrent models had similar effects (p . 0.89). By allowing pets to roam, cat owners are complicit in cat nuisance. This requires public education. Ultrasonic deterrents offer a cost-effective, humane option to reduce incursions by unwanted cats. Ultrasonic deterrents will not prevent all incursions, but they reduce their frequency and duration. Reduced cat activity has flow-on benefits to wildlife across a variety of urban-suburban settings, including gardens and parks

Carbon emissions from decomposition of fire-killed trees following a large wildfire in Oregon, United States

A key uncertainty concerning the effect of wildfire on carbon dynamics is the rate at which fire-killed biomass (e.g., dead trees) decays and emits carbon to the atmosphere. We used a ground-based approach to compute decomposition of forest biomass killed, but not combusted, in the Biscuit Fire of 2002, an exceptionally large wildfire that burned over 200,000 ha of mixed conifer forest in southwestern Oregon, USA. A combination of federal inventory data and supplementary ground measurements afforded the estimation of fire-caused mortality and subsequent 10 year decomposition for several functionally distinct carbon pools at 180 independent locations in the burn area. Decomposition was highest for fire-killed leaves and fine roots and lowest for large-diameter wood. Decomposition rates varied somewhat among tree species and were only 35% lower for trees still standing than for trees fallen at the time of the fire. We estimate a total of 4.7 Tg C was killed but not combusted in the Biscuit Fire, 85% of which remains 10 years after. Biogenic carbon emissions from fire-killed necromass were estimated to be 1.0, 0.6, and 0.4 Mg C ha⁻¹ yr⁻¹ at 1, 10, and 50 years after the fire, respectively; compared to the one-time pyrogenic emission of nearly 17 Mg C ha⁻¹.Keywords: necromass, carbon emissions, forest decomposition, dead wood, wildlif

Burning the legacy? Influence of wildfire reburn on dead wood dynamics in a temperate conifer forest

Dynamics of dead wood, a key component of forest structure, are not well described for mixed-severity fire regimes with widely varying fire intervals. A prominent form of such variation is when two stand-replacing fires occur in rapid succession, commonly termed an early-seral “reburn.” These events are thought to strongly influence dead wood abundance in a regenerating forest, but this hypothesis has scarcely been tested. We measured dead wood following two overlapping wildfires in conifer-dominated forests of the Klamath Mountains, Oregon (USA), to assess whether reburning (15-yr interval, with >90% vegetation mortality) resulted in lower dead wood abundance and altered character relative to once-burned stands, and how any differences may project through succession. Total dead wood mass (standing + down) following the reburn (169 ± 83 Mg/ha [95%CI]) was 45% lower than after a single fire (309 ± 87 Mg/ha). Lower levels in reburn stands were due to, in roughly equal parts, additional combustion and greater time for decay. Although a single fire in mature forest both consumed and created dead wood (by killing large live trees), a reburn only consumed dead wood (few large live trees to kill). Charred biomass (black carbon generation) was higher in reburned stands by a factor of 2 for logs and 8 for snags. Projecting these stands forward (notwithstanding future disturbances) suggests: (1) the near-halving of dead-wood mass in reburn stands will persist for ~50 yr until the recruitment of new material begins, and (2) the reburn signature on dead wood abundance will remain apparent for over a century. These findings demonstrate how a single stochastic variation in disturbance interval can impart lasting influence on dead-wood succession, reinforcing the notion that many temperate forests exist in a state of dead-wood disequilibrium governed by site-specific disturbance history. Accounting for such variation in disturbance impacts is crucial to better understanding forests with complex mixed-severity disturbance regimes and with increasing stochasticity under climatic change

Synthesis of knowledge on the effects of fire and fire surrogates on wildlife in U.S. dry forests

"Dry forests throughout the United States are fire-dependent ecosystems, and much attention has been given to restoring their ecological function.Published September 2009. Reviewed December 2013. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalogKeywords: forest fires, fire surrogate

Bat Response to Differing Fire Severity in Mixed-Conifer Forest California, USA

Abstract Wildlife response to natural disturbances such as fire is of conservation concern to managers, policy makers, and scientists, yet information is scant beyond a few well-studied groups (e.g., birds, small mammals). We examined the effects of wildfire severity on bats, a taxon of high conservation concern, at both the stand (,1 ha) and landscape scale in response to the 2002 McNally fire in the Sierra Nevada region of California, USA. One year after fire, we conducted surveys of echolocation activity at 14 survey locations, stratified in riparian and upland habitat, in mixed-conifer forest habitats spanning three levels of burn severity: unburned, moderate, and high. Bat activity in burned areas was either equivalent or higher than in unburned stands for all six phonic groups measured, with four groups having significantly greater activity in at least one burn severity level. Evidence of differentiation between fire severities was observed with some Myotis species having higher levels of activity in stands of high-severity burn. Larger-bodied bats, typically adapted to more open habitat, showed no response to fire. We found differential use of riparian and upland habitats among the phonic groups, yet no interaction of habitat type by fire severity was found. Extent of high-severity fire damage in the landscape had no effect on activity of bats in unburned sites suggesting no landscape effect of fire on foraging site selection and emphasizing stand-scale conditions driving bat activity. Results from this fire in mixed-conifer forests of California suggest that bats are resilient to landscapescale fire and that some species are preferentially selecting burned areas for foraging, perhaps facilitated by reduced clutter and increased post-fire availability of prey and roosts

The Proximal Drivers of Large Fires: A Pyrogeographic Study

Variations in global patterns of burning and fire regimes are relatively well measured, however, the degree of influence of the complex suite of biophysical and human drivers of fire remains controversial and incompletely understood. Such an understanding is required in order to support current fire management and to predict the future trajectory of global fire patterns in response to changes in these determinants. In this study we explore and compare the effects of four fundamental controls on fire, namely the production of biomass, its drying, the influence of weather on the spread of fire and sources of ignition. Our study area is southern Australia, where fire is currently limited by either fuel production or fuel dryness. As in most fire-prone environments, the majority of annual burned area is due to a raelatively small number of large fires. We train and test an Artificial Neural Networks ability to predict spatial patterns in the probability of large fires (>1,250 ha) in forests and grasslands as a function of proxies of the four major controls on fire activity. Fuel load is represented by predicted forested biomass and remotely sensed grass biomass, drying is represented by fraction of the time monthly potential evapotranspiration exceeds precipitation, weather is represented by the frequency of severe fire weather conditions and ignitions are represented by the average annual density of reported ignitions. The response of fire to these drivers is often non-linear. Our results suggest that fuel management will have limited capacity to alter future fire occurrence unless it yields landscape-scale changes in fuel amount, and that shifts between, rather than within, vegetation community types may be more important. We also find that increased frequency of severe fire weather could increase the likelihood of large fires in forests but decrease it in grasslands. These results have the potential to support long-term strategic planning and risk assessment by fire management agencies.OP’s salary was provided by the NSW Rural Fire Service. MB was partly financially supported by the Bushfires and Natural Hazards Cooperative Research Centre

Subcontinental heat wave triggers terrestrial and marine, multi-taxa responses

Heat waves have profoundly impacted biota globally over the past decade, especially where their ecological impacts are rapid, diverse, and broad-scale. Although usually considered in isolation for either terrestrial or marine ecosystems, heat waves can straddle ecosystems of both types at subcontinental scales, potentially impacting larger areas and taxonomic breadth than previously envisioned. Using climatic and multi-species demographic data collected in Western Australia, we show that a massive heat wave event straddling terrestrial and maritime ecosystems triggered abrupt, synchronous, and multi-trophic ecological disruptions, including mortality, demographic shifts and altered species distributions. Tree die-off and coral bleaching occurred concurrently in response to the heat wave, and were accompanied by terrestrial plant mortality, seagrass and kelp loss, population crash of an endangered terrestrial bird species, plummeting breeding success in marine penguins, and outbreaks of terrestrial wood-boring insects. These multiple taxa and trophic-level impacts spanned \u3e300,000 km2—comparable to the size of California—encompassing one terrestrial Global Biodiversity Hotspot and two marine World Heritage Areas. The subcontinental multi-taxa context documented here reveals that terrestrial and marine biotic responses to heat waves do not occur in isolation, implying that the extent of ecological vulnerability to projected increases in heat waves is underestimated

The Effects of Forest Fuel-Reduction Treatments in the United States

The current conditions of many seasonally dry forests in the western and southern United States, especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Both prescribed fire and its mechanical surrogates are generally successful in meeting short-term fuel-reduction objectives such that treated stands are more resilient to high-intensity wildfire. Most available evidence suggests that these objectives are typically accomplished with few unintended consequences, since most ecosystem components (vegetation, soils, wildlife, bark beetles, carbon sequestration) exhibit very subtle effects or no measurable effects at all. Although mechanical treatments do not serve as complete surrogates for fire, their application can help mitigate costs and liability in some areas. Desired treatment effects on fire hazards are transient, which indicates that after fuel-reduction management starts, managers need to be persistent with repeated treatment, especially in the faster-growing forests in the southern United States.Keywords: wildfire, forest conservation, forest management, fire surrogates, fire ecolog