In south-eastern Australia, low winter temperatures often reduce pasture growth and thus winter herbage supply relative to livestock requirements. Grazing of vegetative grain crops in winter is one ...strategy that might overcome this feed gap. In a study with young sheep over two seasons near Canberra, ACT, we compared pasture-only grazing with three separate crop–livestock systems in which the sheep grazed long-season wheat, winter canola or a combination of these, for intervals over the period May–August. We measured forage biomass, sheep grazing days (SGD) and liveweight accumulated per ha. Crop-grazing treatments resulted in much more winter forage for grazing sheep (tDMha-1): in 2010, one crop 2.5–3.0, two crops 3.5 v. pasture only 1; in 2011, one crop 2, two crops 3 v. pasture only 1.4. In the first season, grazing one crop resulted in ~2000 extra SGD ha-1 and the accumulation of more liveweight per ha than in the pasture-only treatment; grazing of two crops resulted in >3500 extra SGD ha-1. Equivalent values in the second, drier season were: one crop, ~1000 extra SGD ha-1; two crops, 2600 extra SGD ha-1. Spelling of pastures during crop grazing led to extra pasture growth, such that in each of the two seasons, 40% of the total benefit in extra SGD per ha came from the extra pasture. The results indicate that, like grazed wheat, grazed canola can provide valuable winter forage, especially when used together with wheat. The data also provide the first quantification of the effect of crop grazing on pasture spelling and subsequent pasture supply, and suggest value in the incorporation of grazing wheat and canola into grazing systems in the high-rainfall zone.
Human‐mediated dispersal of non‐native earthworms can cause substantial changes to the functioning and composition of ecosystems previously earthworm‐free. Some of these earthworm species have the ...potential to “geoengineer” soils and increase plant nitrogen (N) uptake. Yet the possible consequences of increased plant N concentrations on rodent grazing remains poorly understood. In this study, we present findings from a common garden experiment with two tundra communities, meadow (forb dominated) and heath (shrub dominated), half of them subjected to 4 years of earthworm presence (Lumbricus spp. and Aporrectodea spp.). Within four summers, our earthworm treatment changed plant community composition by increasing graminoid density by, on average, 94% in the heath vegetation and by 49% in the meadow. Rodent winter grazing was more intense on plants growing in soils with earthworms, an effect that coincided with higher N concentrations in plants, indicating a higher palatability. Even though earthworms reduced soil moisture, plant community productivity, as indicated by vegetation greenness (normalized difference vegetation index), was not negatively impacted. We conclude that earthworm‐induced changes in plant composition and trophic interactions may fundamentally alter the functioning of tundra ecosystems.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Coherent X-ray imaging is an active field at synchrotron sources. The images rely on the available coherent flux over a limited field of view. At many synchrotron beamlines a double-crystal ...monochromator (DCM) is employed in a standard nondispersive arrangement. For coherent diffraction imaging it is advantageous to increase the available field of view by increasing the spatial coherence length (SCL) of a beam exiting such a DCM. Here, Talbot interferometry data together with ray-tracing simulations for a (+ - - +) four-reflection experimental arrangement are presented, wherein the first two reflections are in the DCM and the final fourth reflection is asymmetric at grazing exit. Analyses of the interferometry data combined with the simulations show that compared with the beam exiting the DCM a gain of 76% in the SCL was achieved, albeit with a factor of 20 reduction in flux density, which may not be a severe penalty at a synchrotron beamline. Previous efforts reported in the literature to increase the SCL that employed asymmetric crystal diffraction at grazing incidence are also discussed. A much reduced SCL is found presently in simulations wherein the same asymmetric crystal is set for grazing incidence instead of grazing exit. In addition, the present study is compared and contrasted with two other means of increasing the SCL. These are (i) focusing the beam onto an aperture to act as a secondary source, and (ii) allowing the beam to propagate in vacuum an additional distance along the beamline.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Trophic rewilding is a restoration strategy focusing on the restoration of trophic interactions to promote self-regulating, biodiverse ecosystems. It has been proposed as an alternative to ...traditional conservation management in abandoned or defaunated areas. Arthropods constitute the most species-rich group of eukaryotic organisms, but are rarely considered in rewilding. Here, we first present an overview of direct and indirect pathways by which large herbivores and predators affect arthropod communities. We then review the published evidence of the impacts of rewilding with large herbivores on arthropods, including grey literature. We find that systematic monitoring is rare and that a comparison with a relevant control treatment is usually lacking. Nevertheless, the available data suggest that when the important process of top-down control of large-herbivore populations is missing, arthropod diversity tends to decrease. To ensure that rewilding is supportive of biodiversity conservation, we propose that if natural processes can only partially be restored, substitutes for missing processes are applied. We also propose that boundaries of acceptable outcomes of rewilding actions should be defined a priori, particularly concerning biodiversity conservation, and that action is taken when these boundaries are transgressed. To evaluate the success of rewilding for biodiversity, monitoring of arthropod communities should be a key instrument.
This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Habitat selection links individual behavior to population abundance and dynamics, so evaluation of habitat selection is necessary for conservation and management. Land management can potentially ...alter both the structure and composition of habitats, thus influencing habitat selection and population size. Livestock grazing is the dominant land use worldwide and, while overstocking has been linked to the decline of many wildlife species, properly managed grazing could improve habitat quality and maintain native rangeland habitats. We evaluated breeding season habitat selection of female sharp-tailed grouse, an indicator species for grassland ecosystems, in relation to grazing management and landscape features in eastern Montana and western North Dakota. At broad spatial scales, females selected for multiple landscape features, including grassland, but exhibited no selection for either landscape or management variables when selecting habitat at smaller spatial scales. Females selected for pastures managed with rest-rotation grazing when choosing a home range, but selection did not equate to improved fitness. Moreover, we observed strong individual variation in both home range size and third-order habitat selection. While the high variability among individuals makes specific management recommendations difficult, selection for grassland habitats at broad scales suggests that strategies that maintain intact native rangelands are important for the conservation of sharp-tailed grouse.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Grasslands are a major biome on Earth, and their soils play a dominant role in the overall ecosystem functions and dynamics. Though the majority of global grasslands are used for grazing, the impact ...of grazing on soil structure and soil quality remains unclear due to large variations among grasslands. In this study, we assessed soil nutrient content, enzyme activities and soil aggregates at 0–30 cm depth under different grazing intensities, including a treatment of grazing exclusion. Heavy grazing reduced content of soil nitrogen, potassium, and soil urease and sucrase activities. While grazing increased the mechanical stability of soil aggregates, it reduced the water stability of soil aggregates. With increasing grazing intensity, water stability of the aggregates was correspondingly weakened, as was the erosion resistance of the soil. The soil urease activity, available soil nutrients, mean weight diameter by wet sieving (w-MWD), and geometric mean diameter by wet sieving (w-GMD) showed significant high sensitivity to grazing intensity in this Stipa kirschnii dominated grassland in Inner Mongolia. Overall, the soil quality at the heavy grazing site appeared poor compared with that at the light grazing site. For developing grazing management strategies, it is clear that heavy grazing should be avoided in this type of grasslands, albeit continued monitoring of soil structure is needed to explore the potential long-term consequences of the grazing.
•Soil nutrients, enzyme activities and aggregates responded differently to grazing.•Grazing changed both soil nitrogen and potassium level.•Urease activity and water stability of the aggregates were reduced.•Heavy grazing produced detrimental impacts on soil quality and should be avoided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mesozooplankton (copepods and euphausiids) grazing rates and prey preferences were determined during a series of three research cruises to the eastern Bering Sea in spring 2008, 2009, and 2010. ...Chlorophyll was dominated by large cells (>5µm), especially at bloom locations where they usually comprised greater than 90% of the total chlorophyll biomass. The relative importance of microzooplankton to the prey field biomass decreased with increasing chlorophyll concentration, and was less than 10% of the total prey biomass in ice-edge bloom regions. Overall, microzooplankton was the preferred prey of the mesozooplankton, although phytoplankton/ice algae were the dominant component of the diet because of their much greater biomass, especially during blooms. There were differences between mesozooplankton species in their prey preferences: Metridia pacifica, Pseudocalanus spp. and Calanus spp. had the strongest preference for microzooplankton prey, while euphausiids (Thysanoessa spp.) and Neocalanus flemingeri/plumchrus appeared to feed non-selectively on all prey items. Mesozooplankton exhibited a saturating feeding response to chlorophyll concentration (Holling׳s type II) that could be modeled by Michaelis–Menten equations. Taxa-specific maximum ingestion rates generally followed allometric theory, with smaller zooplankton having higher feeding rates than larger zooplankton, and ranged from about 4–30% body carbon day−1. Trophic cascades during grazing experiments could result in a substantial underestimate of chlorophyll ingestion rates, especially for those taxa that had a strong preference for microzooplankton. Grazing impacts by mesozooplankton on the integrated chlorophyll biomass and primary production were 2.7±4.4 and 26±48% day−1, respectively. Impacts increased significantly with increasing mesozooplankton biomass, which increased from early to late spring. However, grazing impacts were extremely low in ice-edge bloom regions. Our findings suggest that even when grazing by microzooplankton is included in our grazing impact estimates, about 50% of the primary production in phytoplankton blooms during spring on the eastern Bering Sea shelf is not grazed and is available for direct export to the benthic community.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial ...vegetation have been identified, there remains substantial uncertainty about how regional‐scale and local‐scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one‐season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional‐scale and local‐scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot‐level variation was contingent on pasture‐level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture‐level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture‐level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot‐level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture‐level and plot‐level favorability interacted: perennial grasses had a higher plot‐level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross‐scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Trophic rewilding is increasingly applied in restoration efforts, with the aim of reintroducing the ecological functions provided by large‐bodied mammals and thereby promote self‐regulating, ...biodiverse ecosystems. However, empirical evidence for the effects of megafauna introductions on the abundance and richness of other organisms such as plants and invertebrates, and the mechanisms involved still need strengthening. In this study, we use environmental DNA (eDNA) metabarcoding of dung from co‐existing feral cattle and horses to assess the seasonal variation in plant diet and dung‐associated arthropods and nematodes. We found consistently high diet richness of horses, with low seasonal variability, while the generally lower dietary diversity of cattle increased substantially during summer. Intriguingly, season‐specific diets differed, with a greater proportion of trees in the horses' diet during winter, where cattle relied more on shrubs. Graminoids were predominantly found in the diet of horses, but were generally underrepresented compared to previous studies, possibly due to the high prevalence of forbs in the study area. Dung‐associated arthropod richness was higher for cattle, largely due to a high richness of flies during summer. Several species of dung‐associated arthropods were found primarily in dung from one of the two herbivores, and our data confirmed known patterns of seasonal activity. Nematode richness was constantly higher for horses, and nematode communities were markedly different between the two species. Our results demonstrate complementary effects of cattle and horses through diet differences and dung‐associated invertebrate communities, enhancing our understanding of large herbivore effects on vegetation and associated biodiversity. These results are directly applicable for decision‐making in rewilding projects, suggesting biodiversity‐benefits by inclusion of functionally different herbivores.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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