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Different Herbivores (different + herbivore)
Selected AbstractsQuantifying the grazing impacts associated with different herbivores on rangelandsJOURNAL OF APPLIED ECOLOGY, Issue 6 2007S. D. ALBON Summary 1Rangelands, produced by grazing herbivores, are important for a variety of agricultural, hunting, recreation and conservation objectives world-wide. Typically, there is little quantitative evidence regarding the magnitude of the grazing impact of different herbivores on rangeland habitats to inform their management. 2We quantified the grazing and trampling impact of sheep, cattle, red deer Cervus elaphus, rabbits Oryctolagus cuniculus, mountain hares Lepus timidus and red grouse Lagopus lagopus on open-hill habitats in 11 areas of upland Scotland. The degradation of heather in upland Scotland Calluna vulgaris -dominated habitats, of conservation significance at a European scale, has been attributed, anecdotally, to increasing sheep and red deer populations. 3Field indicators of habitat condition were used to generate a five-point scale of impact in vegetation polygons of seven habitats. The presence of each herbivore species was attributed on the basis of ,signs' of occupancy. A Bayesian regression model was used to analyse the association of herbivore species with grazing impact on plant communities, controlling for environmental attributes. 4Overall the presence of sheep was associated with the largest increase (7/11 areas) in grazing and trampling impact of all herbivores. Cattle had the second largest impact but generally this was restricted to fewer areas and habitats than sheep. In contrast, impacts associated with wild herbivores tended to be small and only significant locally. 5Although red deer presence was associated with a significantly lower impact than sheep, this impact increased with increasing deer density at both land-ownership and regional scales. For sheep there was little or no evidence of density dependence. 6Synthesis and applications. The higher impact associated with sheep presence probably reflects their greater aggregation because of their limited ranging behaviour, exacerbated by sheep being herded in places convenient for land managers. Consequently, future reductions in sheep numbers as a result of reform of European Union farming policies may limit the extent of their impact, but not necessarily the local magnitude. However, reductions in sheep stocks may lead to increases in deer densities, with greater impact, particularly in heather-dominated habitats. Where habitat conservation is a priority this may well require a reduction in deer numbers. [source] Contrasting effects of cattle and wildlife on the vegetation development of a savanna landscape mosaicJOURNAL OF ECOLOGY, Issue 5 2010Kari E. Veblen Summary 1.,Through their effects on plant communities, herbivores can exert strong direct and indirect effects on savanna ecosystems and have the potential to create and maintain savanna landscape heterogeneity. Throughout much of sub-Saharan Africa, periodic creation and abandonment of livestock corrals leads to landscape mosaics of long-term ecosystem hotspots that attract both cattle and large ungulate wildlife. 2.,The development and maintenance of vegetation in these types of hotspots may be controlled in part by herbivory. Cattle and wildlife may have different, potentially contrasting effects on plant succession and plant,plant interactions. We ask how cattle and wild herbivores affect the maintenance and vegetation development of corral-derived landscape heterogeneity (0.25,1.0 ha treeless ,glades') in Laikipia, Kenya, through their effects on long-term successional and short-term plant,plant dynamics. 3.,We used the Kenya Long-term Exclosure Experiment to exclude from glades different combinations of cattle, large ungulate wildlife (i.e. zebras, gazelles and other antelopes), and mega-herbivore wildlife (i.e. giraffes and elephants). We first assessed long-term changes in cover of the dominant grass species, Cynodon plectostachyus and Pennisetum stramineum (the early- and late-dominant species, respectively). We then used a neighbour removal experiment to test the effects of different herbivores on competition and facilitation between the two glade grass species. 4.,In the long-term experiment, we found that large ungulate wildlife reinforced landscape heterogeneity over time by helping maintain glades in their early C. plectostachyus -dominated form. Cattle and mega-herbivore wildlife, on the other hand, appeared to reduce the positive effects through forage preference for C. plectostachyus. 5.,In the neighbour removal experiment, we found that each grass species benefited from facilitation when it was the preferred forage for the dominant grazer. Facilitation of C. plectostachyus by P. stramineum was strongest when cattle co-occurred with wildlife, whereas facilitation of P. stramineum by C. plectostachyus was strongest when cattle were absent. 6.,Synthesis. Our results demonstrate that different combinations of cattle and wildlife have different effects, largely via contrasting forage preferences, on the persistence of landscape heterogeneity in this savanna landscape. More generally, we provide evidence for contrasting effects of cattle and wildlife on short-term plant interactions (facilitation) and successional processes within the herbaceous plant community. [source] Local and systemic effects of two herbivores with different feeding mechanisms on primary metabolism of cotton leavesPLANT CELL & ENVIRONMENT, Issue 7 2009LILIAN SCHMIDT ABSTRACT Caterpillars and spider mites are herbivores with different feeding mechanisms. Spider mites feed on the cell content via stylets, while caterpillars, as chewing herbivores, remove larger amounts of photosynthetically active tissue. We investigated local and systemic effects of short-term caterpillar and spider mite herbivory on cotton in terms of primary metabolism and growth processes. After short-term caterpillar feeding, leaf growth and water content were decreased in damaged leaves. The glutamate/glutamine ratio increased and other free amino acids were also affected. In contrast, mild spider mite infestation did not affect leaf growth or amino acid composition, but led to an increase in total nitrogen and sucrose concentrations. Both herbivores induced locally increased dark respiration, suggesting an increased mobilization of storage compounds potentially available for synthesis of defensive substances, but did not affect assimilation and transpiration. Systemically induced leaves were not significantly affected by the treatments performed in this study. The results show that cotton plants do not compensate the loss of photosynthetic tissue with higher photosynthetic efficiency of the remaining tissue. However, early plant responses to different herbivores leave their signature in primary metabolism, affecting leaf growth. Changes in amino acid concentrations, total nitrogen and sucrose content may affect subsequent herbivore performance. [source] | ||||||||||