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Eastern box turtles (Terrapene Carolina) inhabit many fire-prone habitats in eastern North America and frequently succumb to natural and anthropogenic fires. However, little is known about the fire ecology of box turtles, and population-level effects of burning have yet to be quantified. We studied the effect of prescribed burns on a population of Florida box turtles (T. Carolina bauri) inhabiting National Key Deer Wildlife Refuge, Big Pine Key, Florida. A total of 27.4 ha were burned during seven prescribed fires (1998 to 2000). We found 14 fire-killed box turtles after four wet season burns (1.04 turtles/ha); no mortality was observed following three dry season burns. Multiple regression analysis indicated that season of burning had a significant effect on the occurrence of box turtle mortality. The effect of char height (used as a surrogate measure of fire intensity in our model) was only marginally significant. Our results suggested that between 10.2% and 21.6% of box turtles per ha perished during wet season fires. Fires appeared to affect male and female turtles equally. No juvenile mortality was observed, perhaps due to their apparent rarity in the study population. If fire mortality is a concern to land managers, we recommend restricting prescribed burns to periods of the year when box turtles are dormant (dry season in south Florida; late fall, winter, and early spring in temperate regions of North America). If prescribed burns must be conducted when turtles are active, survival might be enhanced by using slower moving, less intense backfires, and burning small areas. More frequent burning might reduce fuel loads and thus fire intensity, reducing the likelihood of turtle mortality.
We examined the influence of western dwarf mistletoe (Arceuthobium campylopodum) infestation on fuel loads in mature mixed-conifer forest in Crater Lake National Park and unmanaged ponderosa pine (Pinus ponderosa) stands in Lave Cast Forest, Oregon. We measured biomass of woody surface fuels (1-, 10-, 100-, and 1000-hr), litter and duff, and snag basal area in 29 stands infested with mistletoe and 21 non-infested stands. Univariate tests revealed no significant differences in total surface fuel loads or snag basal area between infested and non-infested plots in either stand type, but there were more fine fuels and litter in infested stands at Lava Cast Forest. Ordination analyses showed that stand level variables other than mistletoe abundance explained more variance in fuel loads. Ponderosa pine basal area and stand age were stronger predictors of fuel loads in pure ponderosa pine stands at Lava Cast Forest, while basal area of non-host fir was a key explanatory variable in the mixed-conifer stands at Crater Lake. Our results indicate that mistletoe has weak direct and indirect effects on fuel loads in mature forests, resulting primarily in greater accumulations of fine woody fuels.
Management of the nature reserve network in Jordan by the Royal Society for the Conservation of Nature (RSCN) requires information on the productivity and diversity of each reserve. Moreover, calculation of biomass is becoming increasingly important, not only for local firewood estimates, but also in a global context of determining carbon management options. Accordingly, we developed a 200-m grid for the systematic random selection of sample sites within the recently established 12 km2 Ajloun Reserve, in the evergreen oak zone of northern Jordan. The method applied can be used in a variety of ecosystems and is in accord with local resources of staffing and training. In order to develop a method to compare these ecosystems across broad areas, we used high resolution satellite imagery to make ocular estimates of tree volume (as a depiction of biomass) for all 167 grid points falling within the reserve. A subset of 57 grid points was randomly selected and field sampled for calibration of the ocular estimates. Diameter and species were recorded for all trees in each sample. Stem counts were made by species for all tree regeneration (stems < 2.0 cm diameter). Following the inventory, a correction coefficient was identified according to the disparity between ocular estimates and volume estimates generated from field data, and then applied to all remaining grid points. Volume averaged 2.5 m3/ha (12.4% sample error using a 95% confidence interval). Using this method, biomass estimates can be extrapolated across landscapes in order to compare them. The permanent sampling network we established is relatively easy to maintain over time, and also provides a monitoring framework for other studies, including wildlife and rare plants. Repeat sampling (n = 12 points) in 2008 showed results similar to those of 2007, except for a decrease in the proportion of oaks in the 2.0 to 4.9 cm class.
The relevance of diversity-biotic resistance studies to conservation of biodiversity could be improved by simultaneously examining the drivers of regional diversity and their effects on local species diversity and invasion. Using path analysis, I examined direct and indirect effects of various abiotic factors (i.e., flooding, treefall gaps, soil texture, proximity to roads, and stand age) on plant species richness, floristic quality (a proxy for regional plant diversity), and the abundance of a non-native invasive grass, Microstegium vimineum, in 117 3.14-m2 plots within four stands of mesic floodplain forests in northern Mississippi. Results of this study showed a significant negative effect of species richness on M. vimineum abundance in year two. However, species richness varied in response to flooding and gaps, and the positive indirect effects of flooding and gaps on M. vimineum abundance mediated through reductions in species richness in fall 2008 were not nearly as great as the positive direct effects of these disturbances on M. vimineum abundance. In contrast to species richness, floristic quality (weighted mean fidelity to mesic forests or wetlands minus fidelity to anthropogenically disturbed areas) responded positively to gaps in flooded areas and was not affected by M. vimineum. Altogether, these results suggest that the same factors that reduce biotic resistance have even greater direct positive effects on the abundance of an invasive grass and native floodplain specialists. Control of M. vimineum in mature floodplain forest ecosystems should be done selectively to avoid collateral damage of native floodplain specialists.
Historically, wetland and grassland ecosystems throughout the Prairie Pothole Region (PPR) of North America were shaped by fire, grazing, and alternating drought and deluge conditions. These historic disturbance patterns of the PPR have been altered by human modifications to the landscape. In recent years, managers have attempted to implement practices that simulate historic disturbance patterns in order to improve the diversity of structure and function in impacted ecosystems. This study evaluated the characteristics of restored and native wetland/grassland plant communities located within two National Wildlife Refuges (NWR) in the PPR of North Dakota. An extensive analysis of plant community composition following an environmental gradient was conducted in order to relate the composition and quality of wetland communities to the condition of adjacent upland grasslands and to compare the composition and quality of native and restored sites. Plant communities were evaluated using quadrat and transect methods and a Floristic Quality Index (FQI). Statistical analyses employed Nonmetric Multidimensional Scaling ordination and Multi-Response Permutation Procedure. We found wide variability in the composition and quality of the plant communities evaluated. Native plant communities were generally of higher quality than restored communities; also, plant communities located at Lostwood NWR generally contained more native components than those located at Tewaukon NWR. The results of this study show that restoration efforts, when properly managed, have the potential to improve the composition and quality of wetland and grassland plant communities. It is likely that the quality of the restored plant communities evaluated in this study will continue to improve with time and sustained management.
The fire history of a rimrock pine forest at the New River Gorge National River, West Virginia, was studied using 21 fire-scarred Pinus virginiana Mill. (Virginia pine) cross-sections. Fire frequency and the goodness-of-fit between the fire interval distribution and the normal and Weibull distributions were evaluated with the FHX2® program. A 107-year fire chronology (1898–2005) was constructed from 53 fire scars. Fire intervals ranged from 1 to 8 years. The Weibull median interval was approximately 3 years using liberal (one or more trees scarred during a single year) or conservative (two or more trees scarred during a single year) criteria. Similar to other mixed forest stands in the Central Hardwood Region, fires in the 20th century were likely ignited from coal mining activities and steam-driven locomotives near the study site. Anthropogenic fires may have caused an artificial increase in rimrock pine forests or allowed pines to persist in greater numbers than would be possible in the absence of disturbance. Restoration (e.g., prescribed burning) is probably not needed to retain P. virginiana as a component of the rimrock forest, but the species' dominance will continue to be restricted on the rim of the gorge.
Invasive, non-native plants threaten forest ecosystems by reducing native plant species richness and potentially altering ecosystem processes. Seed dispersal is critical for successful invasion and range expansion by non-native plants; dispersal is likely to be enhanced if they can successfully compete with native plants for disperser services. Fruit production by non-native plants during winter (or dormant season), when native fruits and arthropods are scarce, might enhance chances of fruit consumption and seed dispersal by vertebrates. We compared the proportion and rate of fruit removal among five invasive, non-native and two native plant species that retain fruit during winter to test whether non-native fruits are readily removed and their seeds dispersed by vertebrates-even where native fruit is available. We also assessed whether the nutritional content of fruit pulp affects fruit removal rates, and collected bird droppings from fecal traps to examine species and rates of seed dispersal. Most (83% to 93%) fruit was removed from all species except native Smilax rotundifolia L. (55%). Most (92%) seeds collected from bird droppings were from non-native plants (six species); only 8% were from native plants (four species). Mean fruit survival time (across species) was positively correlated with total sugar and negatively correlated with lipid. Total fruit consumed was not correlated with nutrient content. Our results indicate most fruits of tested winter-fruiting, non-native invasive plants are removed, and their seeds are dispersed. In the southern Appalachian Mountains, only a few native plant species, notably greenbriar (Smilax spp.), American holly (Ilex opaca Alton), and sumac (Rhus spp.) retain abundant, ripe fruit during winter months, and these species tend to be patchy in their distribution. Therefore, winter fruit availability by non-native invasive plants offers an important opportunity for dispersal and range expansion, and is likely key in their successful invasion of ecosystems.
Although slugs (Mollusca: Gastropoda) are known to be important generalist herbivores, fungivores, and detrivores in a variety of ecosystems, little is known about their abundance and diversity in protected areas. Likewise, the presence of non-native slug species and their impacts on invaded ecosystems have also not been well documented. In this study, the abundance and diversity of native and non-native slugs was investigated in a sensitive protected area comprised of a recently burned black spruce (Picea mariana) - lichen (Cladonia) woodland in Terra Nova National Park, Newfoundland, Canada. To estimate the diversity and abundance of slugs, pitfall traps were established in areas of high-burn intensity, including sites within and at the edge of the burn, low-burn intensity, and a non-burned reference. Of the nine slug taxa known from Newfoundland, five were captured within burned sites; of those five taxa, only one, Deroceras laeve, is native. Almost 90% of captures were of non-native taxa; dominant slug taxa were the introduced Arion subfuscus aggregate (agg.) and A. hortensis agg. The majority of captures occurred at the edge of the burn, and least in the high-intensity open sites. Given that non-native species can dominate the slug fauna in naturally disturbed areas, it is recommended that monitoring for these non-native invasive species and their impact on native vegetation be implemented within protected areas. The invasive nature of non-native slugs and their pivotal role in influencing bio-diversity and plant regeneration suggests that these invertebrates are key elements within a monitoring framework of protected areas.
Though typically considered benign, recreational trails have the potential to both alter vegetation and disturb birds in ways that might influence parental nest attendance rates and other behaviors that ultimately can affect reproductive success. We hypothesized that recreational trails negatively impact avian reproductive success either by (1) reducing nest attendance due to direct human disturbance or (2) modifying vegetation characteristics surrounding nests. From April to August of 2006 and 2007, 263 nests of Northern Cardinals (Cardinalis cardinalis) were monitored in 14 forested riparian sites containing paved and unpaved recreational trails in central Ohio. Vegetation characteristics were measured around 161 nests and 114 random locations. Trail use was estimated using cameras at seven of 14 sites. Nest attendance was not related to distance to trail, nest height, or trail use. We found little evidence that daily nest survival rates were related to distance to trail, nest attendance, trail use, or site. Rather, daily nest survival was best explained by and positively related to nest height. Though vegetation characteristics in randomly-located plots were unrelated to distance from trail, nests closer to trails were surrounded by more small stems (dbh < 8 cm), less native vegetation, and were placed at greater heights and farther from the foliage edge. Thus, birds may modify nest-site selection in relation to recreational trails.
Numerous studies describe the biology of invasive plants and control techniques for addressing site-specific infestations. However, few describe the practical steps and components needed to control invasives at larger, more ecologically-meaningful scales. The Skagit Knotweed Working Group was formed in 2000 to control Japanese knotweed (Polygonum cuspidatum Sieb. & Zucc.) and related congeners (knotweed) throughout the upper Skagit River system. Based on our experience, we present several elements that we consider necessary for a successful landscape-scale weed control program: (1) delineation of a clearly defined project area; (2) setting realistic and attainable program goals; (3) the ability to quantify and report measures of control success; (4) engaged partnerships of major public and private landowners; (5) coordination of partner effort to encompass the entire project area; (6) participation of small private landowners; (7) biologically-based, adaptive, and prioritized control strategy; and (8) conducting continuous and rigorous status surveys. We suggest these elements as a framework to overcome challenges to controlling weeds at the landscape scale, using the knotweed control project in the upper Skagit as a case study.
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