Allocating species in Grime’s strategy space: an alternative to trait-based approaches

Background: The three primary-strategy theory proposed by Grime identifies stress and disturbance as key environmental factors leading to the emergence of distinct plant strategies. These are defined by a combination of stress and disturbance tolerance. Plant strategies are usually inferred from sets of traits, but this may lead to circular reasoning and artificial restrictions to species’ distribution in strategy space. Question: Can measurements of stress and disturbance tolerance be used to estimate the position of different species relative to each other in Grime’s strategy space? Data description: Stress, disturbance, and abundances for 50 species at 25 0.5 ha sites. Study site and dates: Semiarid grassland, Oaxaca, Mexico, 2014. Methods: Species’ tolerance to stress and disturbance were inferred from abundances, and used to allocate species in Grime’s space. We tested if some attributes of our study species changed over the strategy space according to theoretical expectations. Results: Most species were allocated towards high disturbance and low stress intensities. Species attributes were in line with the trends expected from their position in the strategy space. Discussion: Perhaps because of a long grazing history, most species were tolerant to disturbance. The allocation of species in the strategy space using stress and disturbance measurements seemed correct based on their attributes. Thus, our measurements seem to reflect the basic principles proposed by Grime. Our method provides relative positions in the strategy space, and (as previous work) requires defining somewhat arbitrary limits to such space if we wish to label species as ruderals, competitors or stress-tolerant.

Effects of Fire and Large Herbivores on Canopy Nitrogen in a Tallgrass Prairie

This study analyzed the spatial heterogeneity of grassland canopy nitrogen in a tallgrass prairie with different treatments of fire and ungulate grazing (long-term bison grazing vs. recent cattle grazing). Variogram analysis was applied to continuous remotely sensed canopy nitrogen images to examine the spatial variability in grassland canopies. Heterogeneity metrics (e.g., the interspersion/juxtaposition index) were calculated from the categorical canopy nitrogen maps and compared among fire and grazing treatments. Results showed that watersheds burned within one year had higher canopy nitrogen content and lower interspersions of high-nitrogen content patches than watersheds with longer fire intervals, suggesting an immediate and transient fire effect on grassland vegetation. In watersheds burned within one year, high-intensity grazing reduced vegetation density, but promoted grassland heterogeneity, as indicated by lower canopy nitrogen concentrations and greater interspersions of high-nitrogen content patches at the grazed sites than at the ungrazed sites. Variogram analyses across watersheds with different grazing histories showed that long-term bison grazing created greater spatial variability of canopy nitrogen than recent grazing by cattle. This comparison between bison and cattle is novel, as few field experiments have evaluated the role of grazing history in driving grassland heterogeneity. Our analyses extend previous research of effects from pyric herbivory on grassland heterogeneity by highlighting the role of grazing history in modulating the spatial and temporal distribution of aboveground nitrogen content in tallgrass prairie vegetation using a remote sensing approach. The comparison of canopy nitrogen properties and the variogram analysis of canopy nitrogen distribution provided by our study are useful for further mapping grassland canopy features and modeling grassland dynamics involving interplays among fire, large grazers, and vegetation communities.

Impact of Grazing History on Pollinator Communities in Fescue Prairie

Impact of Grazing History on Pollinator Communities in Fescue Prairie

Rev iew on Ovine Fasciolosis in Ethiopia

Fasciolosis is one of the major constraint factors for ovine production development in Ethiopia by inflecting direct and indirect loss at different parts of the country. Ovine fasciolosis is an economically important parasitic disease of sheep caused by tr ematodes species of the genus Fasciola , which migrate in the hepatic parenchyma and establish and develops in the bile ducts. In Ethiopia, both species co - exist at different altitudes. The snails of the genus lymnae are mainly involved as an intermediate host in the life cycle of fasciolosis. Ovine fascioliasis in Ethiopia were losses annually estimated at 48.4 million Ethiopian birr due to mortality, productivity (weight loss and reproductive wastage), and liver condemnation at slaughter. This fasciola di sease has three phases of clinical sign acute, sub - acute and chronic forms. Acute fasciolosis occurs as disease outbreak following a massive, but relatively short - term, intake of metacercariae. Death usually results from blood loss due to hemorrhage and ti ssue destruction caused by the migratory juvenile flukes in the live resulting in traumatic hepatitis. Diagnosis of Fasciolosis is based on clinical sign, grazing history, and seasonal occurrence, examination of feces by laboratory tests and post mortem ex amination. Treatment of infected animals will largely depend on the correct use of appropriate and registered anthelmintic. Triclabendazole is the most effective anthelmintic drug which can be destroys or kills all stage of fasciola. Fasciolosis may be con trolled by reducing the populations of the intermediate snail host, or by appropriate anthelminthic treatment and the population of snail should be destroyed by applying Molluscicide and destroying the environment that suit for snail’s reproduction.