We detected Heartland virus (HRTV) in lone star nymphs collected in 2018 in northern Alabama, USA. Real-time reverse transcription PCR selective for the small segment of the HRTV genome and ...confirmatory sequencing of positive samples showed high identity with HRTV strains sequenced from Tennessee and Missouri.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Strong white oak sawtimber markets, partially attributed to the stave and cooperage industries, are encouraging forest managers to re-examine silvicultural practices for white oak (Quercus ...alba). We examined recruitment and retention of white oak in mixed oak–pine stands on the William B. Bankhead National Forest in northcentral Alabama. Stands were subjected to three thinning levels (residual basal areas of 75 ft2/ac, 50 ft2/ac, and no thinning) and three fire frequencies (dormant season burns of none, one, three fires) in a factorial design. Both thinning treatments reduced overstory white oak tree densities, and fire had no effect on densities. For all reproduction height classes, regardless of thinning treatment, three prescribed burns increased white oak densities; thinned and burned stands had larger white oak seedling sprouts than those thinned with no burn. However, white oak reproduction height was primarily less than 2 ft tall, and seedlings larger than 4 ft tall were reduced. Thinning with one fire resulted in the highest densities of large white oak reproduction (4 ft tall up to 1.5 in. dbh). Red maple reproduction was the dominant competitor in all treatments and is positioned to dominate the reproduction cohort without additional tending treatments.
Variability in historic fire regimes in eastern North America resulted in an array of oak natural communities that were dominant across the region. In the past century, savannas and woodlands have ...become scarce because of conversion to agriculture or development of forest structure in the absence of fire. Their restoration is a primary goal for public agencies and conservation organizations. Although they can be restored with a long-term regimen of prescribed burning, a combination of fire, timber harvesting, and forest thinning produces the desired structure and composition more efficiently. Prescribed fire is useful for sustaining oak savannas and woodlands, but it must be used judiciously to minimize timber damage and decreases in value. Integrating fire within a modified shelterwood approach promotes competitive oak reproduction and is flexible enough to produce savannas or woodlands. Sustaining these communities requires the replacement of the overstory during periods of no fire.
For millennia, natural disturbance regimes, including anthropogenic fire and hunting practices, have led to forest regeneration patterns that created a diversity of forest lands across the USA. But ...dramatic changes in climates, invasive species, and human population, and land use have created novel disturbance regimes that are causing challenges to securing desired natural regeneration. Climate is an ever-present background disturbance and determinant of species distribution. Changes in certain other factors such as large herbivore populations, wildfire, and pests modify forest composition and structure, and are common barriers to natural regeneration of desired species. Changes in long-standing disturbance regimes have led to the homogenization of forest landscape composition and structure. Today, forests have low regeneration potential and are low in resilience. They have reduced productivity and are prone to widespread health issues including severe forest mortality. In addition to epidemics of native invasive species due to climate change and availability of habitat at landscape scales, the continued introduction and spread of non-native pests and diseases are causing large-scale forest mortality. These ecological changes have cascading ecological consequences such as increases in severe wildfire, which pose new barriers to natural regeneration. Equally challenging are the barriers to natural regeneration that arise from social, political and economic factors. To address many of these issues requires active management that links all critical stages in the regeneration niche necessary for achieving desired regeneration to sustain forest development and production in a socially acceptable manner and economically viable market system.
► Lizards displayed species-specific responses to forest management. ► Some large-bodied snake species increased in thinned forest stands. ► Salamander declines were related either to rainfall ...patterns or population cycling. ► Pond-breeding amphibian captures were linked to the hydroperiod of aquatic habitats. ► Herpetofaunal responses were exacerbated by Southern Pine Beetle disturbances.
We evaluated the response of amphibians and reptiles to two levels of prescribed burning and three levels of thinning using a field experiment consisting of a before–after, control-impact, and factorial complete block design over a four year period in the William B. Bankhead National Forest located in northwestern Alabama. We captured 2643 individuals representing 47 species (20 amphibians and 27 reptiles) during 3132 trap nights. Pre-treatment captures varied widely for both amphibians and reptiles among the stands designated for management, which was likely due to forest structural changes caused by tree mortality resulting from Southern Pine Beetle (Dendroctonus frontalis) infestations. Within each amphibian and reptile species assemblage, we observed species-specific associations with specific treatments and environmental characteristics. In regards to individual species responses, Eastern Fence Lizards (Sceloporus undulatus) increased in thin-with-burn treatments and Green Anoles (Anolis carolinensis) tended to increase in all thinned stands. North American Racers (Coluber constrictor) increased in thin-only plots primarily during the second post-treatment year. Mississippi Slimy Salamander (Plethodon mississippi) captures tended to decrease in all treatment stands throughout the study period, which may been due to either drier environmental conditions during post-treatment sampling or natural population cycling. Pool-breeding amphibian captures were more likely related to the hydroperiod of aquatic breeding environments within 290m of survey locations rather than forest treatments. Our results illustrate that forest restoration through tree thinning can positively influence certain reptile species with limited impacts on amphibians in upland, pine-dominated forests of northern Alabama. However, as our forest stands are scheduled to be burned every 3–5years, continued monitoring is necessary to understand the impacts of repeated disturbances.
•Oaks became dominant through an intensive disturbance regime 100years ago.•A disturbance occurred every 3 years across six 10-ha stands.•A woodland restoration treatment favored trees with larger ...tree-ring growth.•The treatment favored trees with larger growth during recent drought events.•Silviculture can simultaneously meet ecological and utilitarian objectives.
Woodland restoration has been conducted in many countries, primarily in Mediterranean regions, but has only recently been attempted on publically and privately owned lands in the eastern United States. We reconstructed historical stand dynamics and tested the immediate effects of an oak (Quercus) woodland restoration treatment on forest health, inferred from tree-ring widths (TRW). The stands were upland white oak (Q. alba) and chestnut oak (Q. prinus) dominated and were located on the Cumberland Plateau of eastern Kentucky, USA. The stands regenerated primarily under a severe disturbance regime concurrent with peak industrial logging approximately 100years ago. A relatively high percentage of trees (38 percent) recruited under large canopy gaps or clearings, indicative of a severe disturbance; however, gap-phase dynamics was also an important process in oak recruitment to the canopy. Primarily small (<31cmDBH) and young (<110years old) trees were removed during the restoration treatment, and mean DBH of residual trees was 13cm larger than harvested trees. Residual trees were 22years older than harvested trees, but this difference was not significant. The largest and oldest trees represented important legacy trees that could provide desirable forest biodiversity attributes. Residual trees had larger TRWs than harvested trees, beginning in the 1930s, and these differences increased over time. Residual trees also had larger TRW during two recent drought events (1986 and 1999), but recovery following drought was similar between residual and harvested trees. Managers can use well established silvicultural techniques to obtain desired stand structural conditions, while selecting healthy trees that have better response to stress factors such as drought. The oak woodland restoration treatment may help to maintain residual overstory trees until oak regeneration can be recruited to provide sustainability towards the next generation.
Prescribed fires are increasingly implemented throughout eastern deciduous forests to accomplish various management objectives, including maintenance of oak-dominated (Quercus spp.) forests. Despite ...a regional research-based understanding of prehistoric and historic fire regimes, a parallel understanding of contemporary fire use to preserve oak forests is only emerging, and with somewhat inconsistent results. For prescribed fires to be effective, they must positively influence oak regeneration at one or more critical life stages: pollination, flowering, seed set, germination, establishment, seedling development, and release into the canopy. We posit that a simplistic view of the relationship between fire and oak forests has led to a departure from an ecologically based management approach with prescribed fire. Here, we call for a refinement in our thinking to improve the match between management tools and objectives and provide some guidelines for thinking more ecologically about when and where to apply fire on the landscape to sustain oak-dominated forests.
•Probability of stem mortality increased with increasing diameter.•Composition was similar across all disturbance severity classes.•Ostrya virginiana was less likely to be killed by wind in the light ...disturbance.•Species intermingling was relatively high in all disturbance classes.
Natural forest disturbances, which drive succession and development, differ in extent, severity, and return interval and range from frequent, gap-scale disturbances, to infrequent stand-replacing events. Most studies have focused on natural disturbances near the ends of the disturbance severity gradient and relatively little quantitative information is available on intermediate-severity disturbance. On 20 April 2011, an EF1 tornado tracked 5kmthrough the Sipsey Wilderness in Alabama and resulted in a patchwork mosaic of disturbed areas. To analyze the effects of the intermediate-severity wind event on composition, structure, and intra-stand spatial patterns, we established a 100×200m (2ha) rectangular plot perpendicular to the path of the storm within an affected Quercus alba stand. Based on the basal area removed (i.e. basal area of snags, snapped stems, or uprooted stems in decay class 1) by the wind event, we divided the plot into disturbance classes (minimal, light, and moderate) to compare compositional and structural attributes along a disturbance severity gradient. Composition varied little across the disturbance gradient, but diversity was highest in the moderately disturbed neighborhoods. Stems were relatively intermingled by species (i.e. each tree neighbored by trees of different species) in each disturbance severity class. However, some species, such as Fagus grandifolia and Ostrya virginiana exhibited less intermingling than Quercus spp. and stems classed in the “other spp.” taxonomic group. Large stems were disproportionately removed by the storm in the light and moderate disturbance categories. In the light disturbance class, O. virginiana was significantly less likely to experience mortality from the storm, which may in part explain the relatively high density of O. virginiana stems in the plot.
•PAR statistically differed along the disturbance intensity gradient.•Significant differences in diversity were restricted to the sapling layer.•The disturbance released advanced reproduction in ...subcanopy strata.•Our results may guide silvicultural systems patterned after natural processes.
Forest disturbances are discrete events in space and time that disrupt the biophysical environment and impart lasting legacies on forest composition and structure. Disturbances are often classified along a gradient of spatial extent and magnitude that ranges from catastrophic events where most of the overstory is removed to gap-scale events that modify local environmental conditions only. Without question, a paucity of data is available on disturbance events of the intermediate scale (i.e. those events too localized to be classed as catastrophic and too widespread to be considered gap scale). The specific objectives of this study were to quantify and compare canopy structure, understory light regimes, woody species composition, and tree species diversity along a gradient of canopy disturbance caused by an EF1 tornado and to analyze the influence of intermediate-scale disturbance on the successional trajectory of an upland Quercus forest. Statistically significant differences in diversity measures between control (no storm damage), light, or moderate damage class plots were only found in the sapling layer. We documented significant differences (P<0.01) in percent of intercepted PAR between the control and moderate damage classes and between moderate and light classes. Three growing seasons post-disturbance, the understory light regime had largely returned to pre-disturbance conditions. The disturbance event acted primarily as a release mechanism for advanced reproduction in the understory and for stems in the midstory. Our results provide quantitative information on disturbances of this extent and magnitude and can be used to guide silvicultural systems designed to emulate natural disturbance processes, which is an increasingly popular management approach especially on public lands.
Drag sampling and flagging are two of the most effective and widely applied techniques to monitor tick populations. Despite the importance of this sampling strategy, there is a lack of standardized ...protocols for the construction of an inexpensive tick drag/flag. To this end, we provide a step-by-step protocol that details the construction of a tick drag/flag. We provide evidence of efficacy by comparing results obtained over 3-months at 108 locations within the William B. Bankhead National Forest, Alabama, USA. Overall, our drag/flag sampling approach yielded 1127 larvae, 460 nymphs, and 53 adults for a total of 1640 ticks representing three species. We detected significant patterns in
Amblyomma americanum
abundance for nymphs and adults with greater counts in June (β = 0.91 ± 0.36, 95% CI 0.55–1.27; β = 2.44 ± 0.63, 95% CI 1.81–3.07, respectively) and July (β = 0.73 ± 0.36, 95% CI 0.37–1.09; β = 1.65 ± 0.66, 95% CI 0.99–2.31, respectively) as compared to August. We also detected a significant difference in tick captures by tick drag/flag fabric type with greater captures when muslin was used as compared to flannel (β = 1.07 ± 0.06, 95% CI 1.01–1.13). Our goal is to provide instructions to assemble a highly effective tick drag/flag using minimal supplies. Evaluation and improvements of sampling techniques is essential to understand impacts of landscape management and larger stressors, such as climate change on tick populations but also for enhancing detection of invasive non-native species.
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