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The North American Waterfowl Management Plan highlights the importance of enhancing waterfowl habitat for productivity and resilience. Many forms of land management are conducted in wetlands to support the diverse communities of waterfowl and other species. Primary burrowing crayfish are also abundant and important in these environments, but little research is available assessing the effects of waterfowl land management on primary burrowers. We examined the response of the digger crayfish, Creaserinus fodiens, to the common vegetation management practices of mowing and disking at waterfowl conservation areas in south-eastern Missouri. Our results demonstrated that at a fine scale, crayfish density was affected by only canopy cover. We also highlighted distributional effects of landscape-level environmental variables and suggested that habitat generalists were tolerant of vegetation management, responding more to vegetation composition and broader landscape effects. We discuss wetlands conservation practices and suggest that burrowing crayfish management would integrate well with some current management strategies for waterfowl.

Soil disturbance threatens native perennial grasslands and savannas worldwide, including pine savannas of the North American Coastal Plain. Disk harrows are used in the region to plow linear features for firebreaks to contain prescribed fires, to manage game and other wildlife, and to reduce wildfire hazard to protect forest resources. However, the long‐term response of vegetation to these disturbances has not been well investigated. Our aim was to compare vegetation changes over time (0–9 years) following repeated disturbance by disking and a single disturbance by disking for firebreaks with undisturbed vegetation within a native pine savanna. We hypothesized that (1) a single disking event has multiyear effects on plant species composition and abundance because of the loss of perennial, dispersal‐limited species, but that partial survival of propagules allows the recovery to be more complete than following repeated disturbance, and (2) post‐disturbance changes are determined by species' life‐history characteristics resulting in a successional trajectory toward the undisturbed community. We established 10 plots within a repeated‐disturbance firebreak and a single‐disturbance firebreak, and in undisturbed vegetation (n = 30). We identified plant species within the plots six times over nine years, categorized plant species by life span, seed bank persistence, and dispersal mechanism, and assessed changes in the plant community using ordination. Changes in species  composition in both repeated and single disturbance treatments showed a pattern consistent with succession toward the undisturbed plant community, but vegetation in neither disturbance treatment matched undisturbed treatment conditions within the nine years of study. Repeated‐disturbance plots progressed from a high occurrence of annuals to species with persistent seed banks and wind‐dispersed species. Single‐disturbance plots were more strongly associated with perennials, species lacking a persistent seed bank, and species dispersed by vertebrate consumption, but not to the same degree as undisturbed plots, although differences decreased slightly over time. Our results relating to narrow mechanical soil disturbances in pine savanna vegetation are consistent with studies concluding that similar but larger scale disturbances have long‐term degradational effects on the plant community. Therefore, conservation management plans should consider the possible negative long‐term effects of soil disturbance on native perennial herbaceous plant communities.

Several approaches can be used to terminate legume cover crops in the spring prior to planting summer crops, but the effect that these methods have on decomposition and nitrogen (N) release dynamics of legume cover-crop roots is poorly understood. The main objectives of this study were to: (i) quantify decomposition and N release of roots from pea (Pisum sativum), clover (Trifolium incarnatum) and vetch (Vicia villosa Roth); (ii) determine if roots decompose and release N faster when cover crops are terminated by disking compared with roller-crimping; and (iii) determine if roots decompose and release N faster under higher soil inorganic N levels. Two field experiments were conducted in Goldsboro and Kinston, North Carolina in the summer of 2012. Cover crops at these sites were terminated in spring by disking or roller-crimping and planted to unirrigated corn. Air-dried roots placed in litterbags were buried in their corresponding cover-crop plots and in plots where cover crops had not been grown that had either synthetic N fertilizer added at burial or had no fertilizer addition. Root litterbags were collected over 16 weeks at both sites. Cover-crop plots terminated by disking had up to 117 and 49% higher soil inorganic N than roller-crimped plots in Goldsboro and Kinston, respectively. However, roots did not appear to contribute significantly to these increases, as measured root decomposition and N release was not affected by termination approach at either site. Roots decomposed rapidly at both sites, losing up to 65% of their original biomass within 4 weeks after burial. Root N release was also rapid at both sites, with vetch generally releasing N fastest and clover slowest. It was estimated that cover-crop roots supplied 47–62 and 19–33 kg N ha−1 during the corn cycle in Goldsboro and Kinston, respectively. Our results indicate that under the warm, humid summer conditions of the Southeastern USA, legume cover-crop roots decompose and release N rapidly.

Managed moist-soil wetlands are important habitats for waterfowl and other waterbirds in the Mississippi Alluvial Valley (MAV) and elsewhere in North America. These wetlands often contain abundant food resources, but they also contain tall and dense (i.e., robust) vegetation that may constrain use and foraging by waterbirds. During winters 2006–2009, we estimated densities of waterbirds, seeds and tubers, and aquatic invertebrates following autumn, preflooding treatments of disking, mowing, and no manipulation (control) of robust vegetation in 26 moist-soil wetlands in and near the MAV. In late autumn, seed and tuber dry mass was greater in control (x̄= 750.7 kg/ha) and mowed (x̄= 709.7 kg/ha) than disked plots (x̄= 509.8 kg/ha). Dabbling ducks (Anatini) accounted for 92% of all waterbirds observed and were 2–3 times more abundant in mowed and disked than control plots during winter. Invertebrates comprised <1% (dry mass) of potential waterbird foods, but were greatest in control plots throughout winter. In mid- and late winter, residual seed and tuber masses were similar among mowed, disked, and control plots within study sites (approx. 260 kg/ha), despite different waterbird use. We recommend 1) active management of moistsoil wetlands, including partial autumn mowing of robust vegetation to increase use by waterbirds; 2) that conservation planners consider increasing foraging thresholds (e.g., giving-up density) in carrying-capacity models for moist-soil wetlands; and 3) additional experiments to describe foraging thresholds in moist-soil and other wetlands targeted by the North American Waterfowl Management Plan.

Animals inhabiting disturbance-prone systems, such as the northern bobwhites (Colinus virginianus) in pine (Pinus spp.) savanna, are adapted to certain intensities of disturbance (e.g., frequency, spatial extent, seasonality). Management practices attempt to mimic these natural conditions. Even though northern bobwhites are known as the firebird, most fire-related management is currently based on tradition and limited peer-reviewed literature. We studied habitat selection of northern bobwhites on private property in Georgetown County, South Carolina, USA, managed with fire, winter disking, and supplemental feeding. We radio-tagged 338 individual bobwhites and monitored them 3–4 times weekly via very high frequency (VHF) telemetry for 2 years. We used hierarchical habitat selection functions in a Bayesian framework to model the data. We considered 2 spatial scales: the study site (second-order) and within home ranges (third-order). Bobwhites selected for small burns during the breeding season but had the highest selection for areas intermediately distant from burn edges during winter (i.e., 67 m). Bobwhites had the strongest selection for fire return intervals of 2–3 years during winter but 1–2 years during the breeding season. Use of supplemental feed was strong across seasons but not selected for by brooding birds within their home range. Use of fallow fields was strongest for brooding birds. Our results are useful for bobwhite managers, especially those in subtropical climates, because they provide scientifically defensible information supporting the use of prescribed fire, winter disking, and supplemental feeding in the context of habitat use.

The phenomenon of core disking is commonly seen in deep drilling of highly stressed regions in the Earth’s crust. Given its close relationship with the in situ stress state, the presence and features of core disking can be used to interpret the stresses when traditional in situ stress measuring techniques are not available. The core disking process was simulated in this paper using the three-dimensional discrete element method software PFC3D (particle flow code). In particular, PFC3D is used to examine the evolution of fracture initiation, propagation and coalescence associated with core disking under various stress states. In this paper, four unresolved problems concerning core disking are investigated with a series of numerical simulations. These simulations also provide some verification of existing results by other researchers: (1) Core disking occurs when the maximum principal stress is about 6.5 times the tensile strength. (2) For most stress situations, core disking occurs from the outer surface, except for the thrust faulting stress regime, where the fractures were found to initiate from the inner part. (3) The anisotropy of the two horizontal principal stresses has an effect on the core disking morphology. (4) The thickness of core disk has a positive relationship with radial stress and a negative relationship with axial stresses.

Created wetlands are increasingly used to mitigate wetland loss. Thus, identifying wetland creation methods that enhance ecosystem development might increase the likelihood of mitigation success. Noting that the microtopographic variation found in natural wetland settings may not commonly be found in created wetlands, this study explores relationships between induced microtopography, hydrology, and plant species richness/diversity in non-tidal freshwater wetlands, comparing results from two created wetland complexes with those from a mature reference wetland complex in northern Virginia. Elevation, steel rod oxidation depth, and species cover were measured along replicate multiscale (0.5 m-, 1 m-, 2 m-, and 4 m-diameter) tangentially conjoined circular transects in each wetland. Microtopography was surveyed using a total station and results used to derive three roughness indices: tortuosity, limiting slope, and limiting elevation difference. Steel rod oxidation depth was used to estimate water table depth, with data collected four times during the growing season for each study site. Plant species cover was estimated visually in 0.2 m2 plots surveyed at peak growth and used to assess species richness, diversity, and wetland prevalence index. Differences in each attribute were examined among disked and non-disked created wetlands and compared to a natural wetland as a reference. Disked and non-disked created wetlands differed in microtopography, both in terms of limiting elevation difference and tortuosity. However, both were within the range of microtopography encompassed by natural wetlands. Disked wetlands supported higher plant diversity and species richness than either natural or non-disked wetlands, as well as greater within-site species assemblage variability than non-disked wetlands. Irrespective of creation method, plant diversity in created wetlands was correlated with tortuosity and limiting elevation difference, similar to correlations observed for natural wetlands. Vegetation was more hydrophytic at disked sites than at non-disked sites, and of equivalent wetland indicator status to natural sites, even though all sites appeared comparable in terms of hydrology. Results suggest that disking may enhance vegetation community development, thus better supporting the goals of wetland mitigation.

The influence of various agrotechnical measures on macrostructural changes in topsoil and subsoil was studied in the course of a four-year experiment. Macrostructure was evaluated according to the ability of soil aggregate to resist degradation. Three variants of soil tillage were established: ploughing to a depth of 0.22 m, reduced tillage (subsoiling to 0.35–0.40 m, and shallow disking of soil to a depth of 0.15 m). For observation, three locations were chosen in various production areas of the Czech Republic with differing soil and climatic conditions. In these locations crops were grown under the same crop rotation: rapeseed (Brassica napus L.), wheat (Triticum aestivum L.), maize (Zea mays), wheat (Triticum aestivum L.), and barley (Hordeum vulgare). After four years of different tillage, a change in the water stability of soil aggregates (WSA) was evident. It was found out that reduced tillage of soil positively influenced both the WSA and the yield of the crops grown. A relationship of positive dependence between WSA, the content of humus substances, and cation exchange capacity of soil was also found. According to the obtained results, for agricultural practice a classification scale of structural quality was proposed on the basis of statistics of one variable (average, its mean error and distribution normality).

Rock is a typical inhomogeneous material with a large number of flaws in different scales; the stress field of the rock in its elastic state consists of two parts: the elastic stress, which distributes uniformly in the entire region; and an additional stress, which only exists around the flaws. Theoretical expressions of the additional stress and local stress are derived based on the Maxwell model. Core disking which takes place under the condition that the axial stress is rapidly reduced while the confining pressure is kept unchanged is explained with a new method. Unloading duration’s effect on core disking is analyzed. A new criterion for core disking is presented based on attributing the core disking to the result of the exceedance of local tensile stress over the tensile strength. Based on our theoretical analysis and the conclusions from published resources, core disking is most likely to occur if the maximum principal stress is more than five to six times the tensile strength.