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Application of glyphosate to cut stumps is broadly viewed as an effective way to control invasive woody shrubs like the buckthorn species (Rhamnus cathartica L. and Frangula alnus Mill.). Since the primary cost associated with this control method is labor, identifying factors that improve efficacy is important. The objective of this research was to determine the effect of glyphosate concentration and soil moisture on the control of buckthorn using the cut-stump method. More than 600 mature buckthorn plants were cut and treated with glyphosate at concentrations between 0 and 41% active ingredient during October in soils varying from dry to moist. While increased glyphosate concentration improved control rates, soil moisture played a dominant role. In moist soils, the impact of glyphosate concentration was insignificant (z=-1.723, p=0.085), and between 40% and 60% of treated buckthorn plants escaped control at all glyphosate concentrations. In dry soils, however, control rates increased significantly with higher concentrations of glyphosate (z=-8.84, p < 10–15), achieving up to 98% control with 41 % glyphosate. Root exudates of two three-year old field-grown buckthorn seedlings that were treated with high glyphosate concentrations in dry soils using cut-stump treatments contained detectable glyphosate comparable to control rates of mature plants. These results suggest that using the highest labeled concentration of herbicide in relatively dry soil conditions will provide optimum effectiveness with control rates up to 98%.
Managers of natural areas often employ controlled disturbances as a tool to manage plant and animal populations. This approach assumes that disturbances are responsible for the structure of biological communities and that appropriate application of the disturbance will ensure the persistence of native plants and animals. If species in a community do not respond predictably to variation in disturbance regime, then management strategies based on emulating disturbance may fail to ensure the persistence of all species. In this study, we examined the efficacy of using prescribed fire as a tool for managing populations of breeding and wintering birds in the pine rocklands of southern Florida. We found that variation in fire history had little effect on vegetation structure and no effect on bird abundance. Instead, vegetation structure was more closely associated with water-table elevation and soil type, whereas most of the observed variation in the structure of bird assemblages appeared to be a function of degree of urbanization in the landscape. That the structure and composition of bird assemblages was independent of variation in fire history suggests that manipulating the fire regime, at least within the range of variability observed in this study, is unlikely to prove effective as a means to manage bird populations. In general, our results argue for caution in assuming that a single process can be used to control the structure of biological communities, especially in systems where landscapes have been substantially altered by human activity.
Tsuga canadensis (L.) Carrière (eastern hemlock), a long-lived, coniferous tree species native to the southern Appalachian Mountains, is currently experiencing rapid defoliation and mortality resulting from recent invasions of hemlock woolly adelgid (Adelges tsugae Annand, HWA), an exotic, invasive insect. Prior to HWA infestation, T. canadensis often developed unique microclimates and exerted a strong functional influence upon the landscape. Therefore, its loss will likely impact forest structure, composition, and future successional trends throughout the Region. Research has shown that overstory T. canadensis trees are currently experiencing severe decline. However, the early effects of this decline on understory vegetation have received little study. We investigated the impacts of HWA upon T. canadensis-associated understory vegetation in Great Smoky Mountains National Park (GSMNP) by resampling understory vegetation on 29 permanent plots established 5 – 6 years previously across five forest communities in GSMNP: hemlock, montane cove, montane oak/hickory (Quercus spp.(Carya spp.)), acid hardwood, and northern hardwood. We found that understory composition has not yet been drastically altered by overstory decline and mortality caused by HWA, likely due to the heavy dominance of Rhododendron maximum (L.) (rosebay rhododendron) in many forests. This ericaceous shrub forms a buffer between the increased light passing through the declining overstory and the low light environment of the forest floor.
Old-growth northern white-cedar (Thuja occidentalis L.) stands were examined in the Mid-Boreal Lowlands of west-central Manitoba. These stands represent the NW distribution limit of the species, which occurs disjunct from its continuous range limit in North America. The objectives involved characterizing the vegetation-environmental relationships, forest structure, and old-growth attributes of these stands. The environmental control exerted on these communities was explored with both cluster analysis and canonical correspondence analysis. Three T. occidentalis stand types were identified: xeric, mesic, and hydric — each representing a specific moisture regime and successional pathway. In the xeric sites, T. occidentalis co-occurred with jack pine (Pinus banksiana Lamb.), whereas in the mesic sites it co-occurred with white spruce (Picea glauca (Moench) Voss) and balsam fir (Abies balsamea (L.) Mill.). In the hydric sites, tamarack (Larix lancina (Du Roi) K. Koch) was the companion species. All stand types also had a significant component of black spruce (Picea mariana (Mill.) B.S.P.). The existence of these stands, containing trees upwards of 250 years of age, suggests a long return interval between stand replacing disturbances allowing T. occidentalis to subsist in the landscape. These old-growth T. occidentalis stands differed from one another in composition, tree size distribution, amounts and sizes of coarse woody debris, and snags. The uniqueness of these stands (in space, age, and composition) in central Canada stresses their need for conservation.
We evaluated the efficacy of a mixture of ground hot mustard and water as a sampling method for earthworms (Lumbricina) in research projects involving citizen scientists. To do so we conducted a field experiment to determine if sampling earthworms using mustard-powder would reveal similar patterns of earthworm abundance and community composition as relying on the more difficult to prepare, and possibly hazardous, allyl isothiocyanate (AITC) solution. Earthworms were sampled using either mustard or AITC in four pairs of 0.25-m2 plots located in each of four woodland sites that were predicted to exhibit a range of earthworm densities. Soil gravimetric water content (GWC) of each plot was quantified as a covariate. For analyses of changes in abundance and community structure, earthworms were classified as belonging to one of five groups based on where they occur in the soil profile, developmental stage, and level of taxonomic identification. The two sampling techniques revealed similar earthworm abundances and community composition across the four sites (all Ps > 0.16) and across the range in GWC (all Ps > 0.36). We conclude that using the mustard-water mixture to sample earthworms at our study site appears to be just as effective and reliable as using AITC. The mustard-water mixture, which is easier to prepare and is less hazardous than AITC solution, should, therefore, be considered as an appropriate tool to be utilized by researchers who collaborate with citizen scientists to help collect the large datasets needed to reveal how woodland management and restoration programs affect earthworms.
Species inventory is considered an important component of natural resource management in National Park System units. We trapped small mammals in forested patches in the Grand Sable Dunes, Pictured Rocks National Lakeshore, Michigan, during 2007 and 2009 to inventory species occurrences and test predictions of island biogeography theory in a terrestrial landscape. We captured 538 individuals representing nine small mammal species. Fewer species were present in isolated patches than those closer to the mainland or another patch (F1,11 = 5.752, P = 0.035), as predicted. Contrary to predictions, there was no relationship between species richness and patch area, proportion of patch edge, or other isolation metrics. We documented range expansion of a southern species, the white-footed mouse (Peromyscus leucopus Rafinesque), into the Grand Sable Dunes. White-footed mice were more likely to be captured in less isolated patches (Omnibus χ21 = 9.684, Nagelkerke R2 = 0.605, P = 0.002). Our results provide the first small mammal inventory for the Grand Sable Dunes and will serve as a baseline for future monitoring of small mammal species in this perched-dune system.
Eradicating the invasive species cheatgrass (Bromus tectorum) presents a significant challenge to land managers across the western United States and can require integrated and adaptive management, including biological, chemical, and prescribed fire control strategies. Resource managers in the Larimer County Open Space Program in Northern Colorado began a cheatgrass reduction program at the Devil's Backbone Open Space preserve that consisted of prescribed burns in fall 2007 and spring 2008, followed by post-emergent imazapic treatments at 0.44 L/ha. The fire was characterized as a slow-moving, highly consumptive burn, and managers monitored results intermittently following the integrated treatments. Post treatment, average cheatgrass cover was reduced from 82% to 9% from 2007 to 2009 based on six permanent monitoring transects. While quantitative data was not taken for the emergence of native grasses and forbs, incidence of bare ground did not increase significantly following treatment. This case study suggests a highly consumptive burn can decrease cheatgrass from the seed bank and create favorable conditions for vegetation other than cheatgrass to return. More research and long-term monitoring building upon this pilot study could help to understand if this combined treatment is a viable long-term reduction strategy.
The eradication of garlic mustard (Alliaria petiolata) from natural populations has proven to be difficult; however, manual removal efforts can be effective at reducing or eliminating small populations when repeated for several years, exhausting the seed bank. We evaluated a variety of manual removal methods for efficacy in reducing viable seed production in garlic mustard. Plants were uprooted and evaluated for subsequent viable seed production based on four variables: (1) height (short, tall), (2) phenological stage (flowering, early-fruiting, late-fruiting), (3) deradication (root removed from uprooted plant), and (4) disposal method (hang, scatter, pile). Uprooting plants at the flowering stage prevented production of any viable seed, while early- and late-fruiting plants were still able to produce viable seed. Fruits initiated on taller plants (≥ 40 cm) produced significantly (P < 0.01) more viable seed than those on short plants (≤ 35 cm). Deradication of uprooted plants did not offer an advantage in reducing viable seed production. There were no significant differences in viable seed production between groups of plants subjected to different disposal methods. Garlic mustard root systems left in the ground after aboveground portions of the plants were removed at four phenological stages (budding, flowering, early-fruiting, and late-fruiting) either did not resprout or produced short-lived sprouts that died without flowering. Our findings suggest that pulling garlic mustard before fruit initiation will reduce seed production, regardless of the disposal method employed or whether roots are left intact.
In 2011, the Government of Ontario, Canada, enacted the “Far North Act, 2010” to protect ecological systems and areas of cultural value in northern Ontario in an interconnected network of protected areas. This law establishes that at least 225,000 square kilometres of northern Ontario, known as the Far North, will be protected through the creation of community-based land-use plans. A central purpose of the “Far North Act, 2010” is to create a significant role for First Nation communities in land-use planning, which is cast as a joint responsibility with the Government of Ontario. The maintenance of biological diversity, ecological processes, and ecological functions — including the storage and sequestration of carbon — are key objectives of this land-use planning initiative. This law sets an ambitious target for protected areas coverage; once implemented, terrestrial protected area coverage will cover 26.5% of the Province of Ontario, greatly exceeding the target of 17% coverage for signatories of the international Convention on Biological Diversity by the year 2020.
Although reliance on ‘focal species’ for conservation planning has been criticized, it is often the most practicable approach available, and its use continues to increase. We, and other researchers, have suggested the chucao tapaculo (Scelorchilus rubecula Kittlitz) as a potentially useful focal species regarding landscape connectivity for a select group of endemic understory birds and mammals in the South American Temperate Rainforest (SATR) biome. Each of these species is a forest understory specialist that is potentially dispersal limited. Because knowledge about dispersal ability for the chucao is better than for any other vertebrate in the biome, it has also been suggested as a focal species for connectivity planning at larger-scales and for a larger suite of species. While we are confident that landscapes designed to meet the connectivity requirements of the chucao would be permeable to movement by most SATR vertebrates, we caution that large-scale applicability of design strategies based on local-scale movement studies for this bird requires close examination. In the context of regional-scale conservation networks, we argue that the connection/corridor, itself, should be designed to sustain a continuous viable (meta)population. In this paper we: (1) review the body of research on landscape connectivity for the chucao and other SATR understory-birds; (2) suggest some possible strategies for scaling-up corridor designs to function at larger spatial scales, by addressing (meta)population viability in addition to habitat permeability; and (3) critically evaluate the degree to which these designs may, and in many cases may not, meet the conservation needs of other vertebrates in the SATR biome.
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