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Native seed predators, such as mice (Peromyscus spp.) and ground beetles (Carabidae), consume weed seeds and waste grain within agricultural fields and thus provide a potentially important service to farmers. Most previous investigations of agricultural seed predation services have focused on within-field factors that affect rates of seed removal and consumption by field-resident seed predators. However, seasonal migrants from adjacent non-crop habitats may also contribute to removal of weed seed, particularly along field edges. We investigated whether rates of weed seed removal within fields increased during summer crop growth when Peromyscus leucopus noveboracensis (White-Footed Mouse), a ubiquitous forest-dwelling rodent in the eastern US, seasonally migrates into crop fields from adjacent forested woodlots. We used exclosure experiments to quantify the relative number of Setaria faberi (Giant Foxtail) seeds removed from seed trays by vertebrate and invertebrate seed predators within 4 corn fields in central Indiana during 4 different stages of crop growth (emergence [May], vegetative [July], reproductive [August], post-harvest [November]). Seed-removal experiments were coupled with live trapping of rodents and pitfall sampling of invertebrates to identify seed predators. Vertebrates (mice) contributed nearly twice as much (∼50%) to seed removal compared to invertebrates (∼25%), irrespective of season. Rates of invertebrate consumption differed among seasons but were not affected by distance from forest—field edge. Rates of seed removal by mice significantly interacted with season and distance from field edge, with higher rates of seed loss near forest—field edges during July and August even though mouse abundance showed no strong association with distance. Increased seed loss near (within 90 m) forest—field edges was presumably due to consumption by seasonally field-resident White-footed Mice, which constituted the majority (>70%) of mouse captures near field edges. Peromyscus maniculatus bairdii (Prairie Deer Mouse) is a year-round resident in crop fields and most likely contributed to seed loss nearer field interiors, where they comprised >90% of the rodents caught. Although non-crop habitats are often overlooked as a source of seed predation services, our results indicate that forest-dwelling White-footed Mice likely supplement rates of in-field predation on weed seed. Future investigations of seed-predation services should consider the role of resident and seasonally opportunistic seed predators in regulation of weed populations in crop fields.
Natural history information on habitat relationships of Semotilus atromaculatus (Creek Chub) in channelized agricultural headwater streams in the northeastern region of North America is limited. We hypothesized that Creek Chubs within channelized agricultural headwater streams would be more strongly influenced by instream habitat than other physical and chemical habitat variables. We sampled Creek Chubs and measured watershed characteristics, riparian habitat characteristics, geomorphology, instream habitat characteristics, and water chemistry in 14 channelized agricultural headwater streams in central Ohio from 2006 to 2011. We found that the abundance, mean length, and biomass of Creek Chub were most strongly influenced by watershed characteristics (land use, soil type) and geomorphology (channel shape, channel size). Our results indicate that conservation and restoration practices designed to mitigate physical habitat degradation are most likely to benefit Creek Chub within channelized agricultural headwater str eams.
On Nantucket Island, MA, the present range of coastal sandplain grasslands is primarily attributed to intense and prolonged historic sheep grazing following European settlement. The maintenance of this early successional habitat (ranked S-1 or “critically imperiled” in Massachusetts) relies on disturbance-based land-management tools. Habitat management efforts have focused primarily on mechanical and prescribed fire treatments, with limited emphasis on re-introducing sheep. This study examined and compared the impacts of repeated growing-season grazing, repeated growing-season mowing, and no management on vegetation community composition in a previously managed grassland. Sheep grazing effectively controlled and reduced clonal and vining woody plant coverage while increasing available bare ground for grassland species seed recruitment. However, grazing and mowing treatments resulted in an increase in weedy agricultural plant species, which may be an inherent side effect of management that results in soil disturbance. Given the long-term, variable nature of the ecological disturbances that created Nantucket's sandplain grassland vegetation communities, one management technique alone will not likely result in successful habitat restoration over a short period of time. We recommend that sheep grazing be more widely considered as an addition to the existing sandplain grassland management “tool box”.
This study sought to ascertain how different grazing management protocols affect the coupling between soil microbial and vascular plant communities. Changes in microbial and plant communities were observed over a grazing season (Spring 2013–Spring 2014) at 2 previously ungrazed agricultural sites—a moist lowland (Longfield Farm) and a drier upland (Normanskill Farm)—near Albany, NY. Each landscape was divided into 6 fenced enclosures (paddocks). One paddock at each farm was managed by a managementintensive grazing (MIG) protocol, which employs high stock density and frequent rotations. A second paddock was managed by continuous grazing (CG) at lower (conventional) stock density. A third paddock at each site was left ungrazed (U). Three “simulation” paddocks were used to explore the underlying dynamics of grazer-microbe-plant interactions. By spring 2014, plant species richness (S) was significantly higher (t-tests: P < 0.05) in the MIG paddocks at both farms. At Normanskill Farm, S was correlated with both microbial diversity and biomass, while at Longfield Farm, S was independent of microbial diversity and biomass but varied directly with soil moisture. Our findings suggest that while MIG leads to increased S relative to CG, different forcing factors may be responsible for the enhancements in upland and lowland systems.
Grassland breeding bird abundances in New York State mirror a national downward trajectory as land-use changes degrade, destroy, and fragment suitable habitat. We quantified and compared bird abundances on pastures that were subject to continuous grazing, minimal rotation, or holistic resource management. We hypothesized that grassland bird abundance varied systematically with pasture management approaches. We measured grassland bird abundances using 40-m radius point counts performed on 27 pastures. Further, we assessed vegetation and environmental parameters to characterize the available habitat on each pasture. Holistic resource managed pastures had 1.5 and 4.5 times higher average abundances of obligate grassland birds than minimally rotated or continuously grazed pastures, respectively. Overall, our results indicate that farms can employ strategies that promote grassland bird habitat and may therefore have a positive influence on grassland bird metapopulations in New York State.
Biodiversity conservation frequently competes with the needs of society for agricultural production and development. However, properly designed and efficiently implemented conservation programs can be used to integrate wildlife and human needs. We tested the efficacy of multicriteria decision analysis as a tool to select priority areas for conservation in human-dominated landscapes using grassland birds in the northeastern US as a test case. We created detailed GIS layers including landscape- (forest, grassland, development, and roads within a 3000-m buffer around each grassland patch) and patch-level (size, management, and conservation status) criteria important in grassland bird habitat selection and conservation. We developed a set of 36 scenarios in which we varied the relative weights associated with different patch attributes. A sensitivity analysis showed that the habitat quality score for each patch was less sensitive to changes in weights at the landscape level, and more sensitive to changes at the patch level. Integrating the GIS dataset into a multicriteria decision analysis framework, we produced maps in which grassland patches were ranked based on habitat quality and used these maps to identify priority conservation areas. Grassland blocks of >100 ha were mainly concentrated in 2 regions and were identified as priority sites that had the highest quality values for grassland bird conservation. This approach resulted in maps that managers can use to focus conservation efforts. The integration of GIS with multicriteria decision analysis can serve as a model for researchers to help set priorities for land conservation for other species and in other regions.