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The black-footed ferret (Mustela nigripes), once extinct in the wild, remains one of the most critically endangered mammals in North America despite 18 years of reintroduction attempts. Because black-footed ferrets are specialized predators of prairie dogs (Cynomys sp.), a better understanding of how black-footed ferrets select resources might provide insight into how best to identify and manage reintroduction sites. We monitored ferret resource selection at two reintroduction sites with different densities of prairie dog populations-one that contained a high density of prairie dogs (Conata Basin, South Dakota) and one that was lower (UL Bend, Montana). We evaluated support for hypotheses about ferret resource selection as related to the distribution of active burrows used by black-tailed prairie dogs (Cynomys ludovicianus), interactions between ferrets, and habitat edge effects. We found support for all three factors within both populations; however, they affected ferret resource selection differently at each site. Ferrets at Conata Basin tended to select areas with high prairie dog burrow density, closer to the colony edge, and that overlapped other ferret ranges. In contrast, ferrets at UL Bend tended not to select areas of high active prairie dog burrow density, avoided areas close to edge habitat, and females avoided areas occupied by other ferrets. The differences observed between the two sites might be best explained by prairie dog densities, which were higher at Conata Basin (119.3 active burrows per ha) than at UL Bend (44.4 active burrows per ha). Given the positive growth of ferret populations at Conata Basin, management that increases the density of prairie dogs might enhance ferret success within natural areas. To achieve long-term recovery of ferrets in the wild, conservationists should increasingly work across and outside natural area boundaries to increase prairie dog populations.
The Blackland Prairie of east-central Texas, the southernmost tip of the once vast North American Tallgrass Prairie, now covers only 1% of its original 6.8 million hectares. Thus, there is considerable interest in restoration and re-establishment of this endangered ecosystem. In a randomized complete block field experiment conducted near San Marcos, Texas, we tested the effectiveness of the post-emergent herbicide imazapic on weed control, establishment, and growth of four C4 warm-season grasses native to the Blackland Prairie (Andropogon gerardii, Sorghastrum nutans, Schizachyrium scoparium, and Bouteloua curtipendula). Treatment with three different levels of imazapic (0.07, 0.092, and 0.138 kg ai/ha) all significantly increased seedling density of native grasses, and low-to-medium levels of imazapic increased seedling shoot growth and flowering relative to water controls. End-of-season aboveground biomass of native grasses also increased with imazapic treatment while that of broadleaf species decreased. However, shoot biomass of exotic C4 grasses (principally Bothriochloa ischaemum and Dichanthium sericeum), the dominant species of this site prior to study, was not significantly affected by imazapic treatment. Despite vigorous site preparation and pretreatment with a broad-spectrum herbicide (Roundup®), these exotic C4 bluestem grasses continued to dominate all treatment plots. These findings indicate that while imazapic is beneficial for native warm season grass establishment, it is inadequate to effectively control these exotic bluestems, which are abundant on many sites once occupied by Blackland Prairie. Successful restoration of native grasses in the Blackland Prairie will, therefore, require more effective means of controlling or eliminating these aggressive exotic species.
Landscape connectivity is vital to the ecological health of many landscapes, and identification of linkages in working landscapes that are somewhat, but not irreversibly, degraded is needed. Assessment of the current ecological condition of habitat linkages can be used to determine appropriate management activities, including restoration. Forecasting the future ecological condition of identified linkages under multiple human-use scenarios can identify future patterns of vulnerability and degradation, and thus aid in prioritization of conservation and restoration actions. We forecast the ecological condition of a modeled conservation network of cores and habitat linkages in the San Joaquin Valley, California, a highly developed agricultural area. We assessed current and projected future impacts from modeled urban growth representing seven regional urban growth policy scenarios to determine conservation and restoration priorities. We characterized current ecological condition of the linkages using a clustering algorithm that compared vegetation type, length, and major road and canal crossings. The modeled urban growth forecasts were overlaid on the ecological network to identify expected impacts. A threat index was calculated for individual network components and for component clusters, and revealed significant impact differences between the various urban growth scenarios. The linkages most threatened by urban conversion were those that are currently the most ecologically degraded, suggesting that a significant future conservation issue in this working landscape will be the loss of restoration opportunities rather than loss of intact wildlife linkages. This study presents an approach for incorporating regional conservation design with urban growth policy analysis for working landscapes.
Invasive species are an increasing threat to native diversity and ecosystem function. Microstegium vimineum (Trin.) A. Camus (Poaceae) is an annual invasive grass threatening native ecosystems of the eastern United States. While information regarding the invasion, spread, and general ecology of M. vimineum is readily available, few studies exist regarding habitat restoration following M. vimineum invasion. Thus, the objectives of this study were to examine the effects of M. vimineum removal on the growth and survival of native planted hardwood seedlings. Two-year-old hardwood seedlings (Acer saccharum, Quercus rubra, and Liriodendron tulipifera) were planted in a split-plot (open vs. closed forest canopy) block design at Crummies Creek Tree Farm, Calhoun County, West Virginia, in an area that was heavily invaded by M. vimineum. Within each block, three treatments were employed: (1) chemical (Sethoxydim) control, (2) mechanical (hand pulling) control, and (3) no removal (experimental control). The growth (height and basal diameter) and survival of planted seedlings were assessed within each treatment over a two-year period. Hardwood seedling height and diameter differed significantly as a function of forest canopy type and among species; however, no significant treatment effects were detected. There were no differences in survival between M. vimineum removal treatments. These data suggest that restoration of forested habitats invaded by M. vimineum can be achieved by a bottom-up approach that utilizes planted native hardwood seedlings with little additional expenditure of resources for control. Restoring a mid-story tree regeneration layer will likely shade out M. vimineum and erode its dominance in forest stands over time.
Redstone Arsenal (RA) is a large federal landholding (15,050 ha) managed by the U.S. Department of the Army located on the Highland Rim of north Alabama. This large landholding provided a unique opportunity to document forest vegetation and development patterns in a region with a paucity of quantitative information. In this study, we quantified land cover types, delineated forest stands on the reserve using a GIS, and assessed forest composition and structural measures. Stands were classed into Pinus, hardwood, mixed Pinus-hardwood, and forested wetland types. The majority of land area in stands ≥ 2 ha was hardwood dominated, while the majority of the land area in stands < 2 ha was Pinus dominated. We used a stratified random scheme to establish sampling points (n = 684) within forest stands through the RA. Pinus taeda, Liquidambar styraciflua, and Quercus phellos were the three most important tree species in the RA forest. Biodiversity for the forest was relatively high with a tree species richness of 56 and diversity (H') of 2.50. Total forest evenness (J) was 0.62, but this value was lowered by the abundance of Pinus in plantation management. Average stand age was 38 years with a range from 7 to 90 years. Basal area was 22.6 m2 ha-1 and we expect this value to increase with forest age. Significant differences were noted between tree age and height across the three surveyed forest types. Our results provide information on forest conditions in an understudied region.
At the broadest spatial scales, the distribution of south Florida slash pine (Pinus elliottii var. densa Little and Dorman) is limited by variation in fire and hydrological regimes, occurring only in relatively dry areas and succeeding to hardwood hammocks when fire is absent. These same forces also appear important in driving smaller-scale variation in the structure and composition of slash-pine forests. Important gaps remain, however, in our understanding of how plants and animals in slash-pine ecosystems respond to variation in fire and hydrological regimes. We addressed this issue for one taxon — landbirds — by estimating density at 285 locations in southwest Florida that differed in fire history and water-table elevation. Bird densities during the breeding season and during the winter did not vary appreciably as a function of either fire history or water-table elevation, and neither did vegetation structure at our survey locations. Birds and plants in this fire-climax forest are both resilient and resistant to changes brought about by frequent, low-intensity fire, and we suspect that significant effects of variation in fire history are only observable under extreme conditions (e.g., complete fire suppression) outside of the range of variation that we sampled. Water-table elevation had a stronger, albeit still small, effect on bird densities and vegetation structure, but the effects were difficult to generalize. Sampling across a broader range of hydrological conditions may yield valuable insight into the structure of pineland bird assemblages, especially given the likelihood that ecosystem restoration efforts in south Florida will produce substantial changes in water-table elevation.
Colorado butterfly plant (Oenothera coloradensis (Rydb.) W.L. Wagner & Hoch ssp. coloradensis [syn. Gaura neomexicana Woot. ssp. coloradensis (Rydb.) Raven & Gregory]) in the Onagraceae; Primrose family) is a Threatened plant whose population declined in a protected area in southeastern Wyoming in 2007–2008, setting record low numbers in 23 years of the annual population census. This trend was accompanied by pervasive flea beetle herbivory (Altica spp.) in 2007. The most frequent flea beetle species collected in 2008–2009 was Altica foliaceae LeConte, a native species. Altica foliaceae favors members of Onagraceae, and A. foliaceae adults were collected on browsed Oenothera plants. The Oenothera population returned to pre-infestation numbers in 2009–2010, evidence that it survived by vegetative plants and seed bank. Results point to the importance of repeated long-term monitoring, without which this event could have been interpreted as a disaster or have gone unnoticed. It also documents an event that can inform population viability analysis.
Clones of mature aspen (Populus grandidentata, P. tremuloides) can rapidly spread and become invasive in the absence of regular fire. Aspen trees resprout vigorously when top-killed by fire in globally rare inland pitch pine (Pinus rigida)/scrub oak (Quercus ilicifolia, Q. prinoides) barrens; thus, complete aspen kill (all trees in a clone) is desirable before introducing fire into barrens. Manual girdling may achieve complete kill but the scale of invasion can easily exceed the capacity to girdle. We evaluated dormant-season herbicide treatments by measuring aspen diameters and kill rates in an urban pine barrens preserve in east-central New York State. Chainsaw frill and drill/fill applications of glyphosate clearly outperformed stem injection of glyphosate capsules and basal bark spraying of triclopyr. Chainsaw frill was 95% likely to kill aspen smaller than 18.3 cm diameter whereas drill/fill was 95% likely to kill aspen smaller than 23.6 cm diameter. A single-cut chainsaw frill approach was fastest and incurred the lowest chemical cost, but mortality was limited to smaller trees. Drill and fill was effective regardless of tree size and drill effort, and a 20-cm drill-hole interval may provide the most cost-effective complete kill of mature aspen clones in barrens historically dominated by pitch pine and scrub oak.
In the southeastern United States, private landowners manage a majority of the forests, and despite their widespread pursuit of longleaf pine (Pinus palustris) restoration, little is known about their motivation, the challenges they face, and their expected outcomes. In 2009, in order to increase understanding of how landowners perceive, practice, and afford longleaf pine restoration, we conducted a written survey of managers in nine southeastern states. Motivations for longleaf pine restoration included both profit, as at least 50% of the respondents emphasized longleaf pine's economic value, and non-profit (wildlife habitat, natural heritage, biological diversity) goals. Our results also show that time and effort are not limiting factors, while availability of financial support and the cost of restoration are. Over 80% of respondents relied on some form of financial support for their restoration projects. The vast majority (78%) of restoration practitioners identified single-species dominance of longleaf pine as the targeted “reference state.” We suggest landowners consider expanding their desired targets to include a mixed-dominance stand component, thereby reducing costs associated with regeneration and time-to-rotation, since mature loblolly (P. taeda), shortleaf (P. echinata), and slash (P. elliottii) pines are often already present. Mixed-stand inclusion would still meet the reported objectives of restoration, but would decrease the specific challenges associated with solely rearing longleaf pine and thereby ease the financial burden of restoring forests to include a significant longleaf pine component.
Worldwide, old-growth forest loss and fragmentation resulting from logging are considered major threats to biodiversity. In many regions of the boreal zone, remaining patches of old-growth forests left following logging are restricted to small areas exposed to edge effects. Our objectives were to evaluate, from a literature review, the distance of edge influence (DEI) induced by sharp logginginduced edges on adjacent old-growth residual forests and to compare, in order to exemplify edge effect influence, two contrasting scenarios of residual stand configurations (linear vs. agglomerated). Synthesis from studies conducted in boreal forests of Canada and Fennoscandia indicates a DEI of ∼50 meters for residual old-growth forests located along recently (≤ 20 years) cutover areas. Based on the comparison of two contrasted scenarios, we demonstrate the strong relationship between residual forest configuration and area under edge influence. For a similar area of residual old-growth forest, linear strips scenario was > 2.5 times more affected by edge compared to agglomerated scenario. We thus recommend considering various types of dispersion strategies that result in large forest residual stands interconnected with remnants > 100 m wide in order to reduce edge influence on the remnant old-growth stands, to mimic forest fire patterns, and to conserve associated biodiversity. To our knowledge, this study is the first meta-analysis to review and assess the DEI in boreal forest of North America and Fennoscandia. In addition, it quantifies, using a spatially explicit model, the impacts of logging-induced edges on the amount of interior forest for two common strategies of residual forest configuration that are well established in eastern Canada.
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