Habitat selection, foraging behavior, and dietary nutrition of elk in burned aspen forest

Prescribed burning is frequently used to enhance regeneration of aspen. The effects of burning aspen on wild ungulates are poorly understood. We used free-ranging tame elk to assess diet composition and quality on a site containing a 40-ha aspen burn, pure unburned aspen, mixtures of aspen and conifers, and other habitats. Foraging preferences of elk among the habitats were also investigated. Overall, no dietary nutritional differences were found between burned and unburned aspen habitats. Diet composition by forage class varied somewhat, due primarily to an abundance of very palatable post-fire forbs on the burn. Time spent feeding was significantly different among habitats. The burn was substantially more attractive for foraging probably because preferred forages were consistently available and greater foraging efficiency was possible than in other habitats.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Densification of Ni and TiAl by SPS: kinetics and microscopic mechanisms

International audienceDensification by spark plasma sintering (SPS) of ductile (Ni) and brittle (TiAl) metallic materials have been studied to elucidate the mechanism of densification in the two cases. Isothermal densification experiments were carried out to determine the activation parameters in Ni. Transmission electron microscopy (TEM) observations of thin foils extracted by focused ion beam (FIB) in the contact regions between particles of TiAl and Ni powders are presented. Macroscopically, the most striking feature observed here is that the densification of Ni takes place in the wide temperature range of 0.2-1.0 Tm, whereas that of TiAl varies in 0.7-0.9 Tm, which is significantly narrower (Tm being the melting temperature of Ni and the peritectic temperature of TiAl). In Ni, the low activation energy (164 ± 30 kJ/mol), the high dislocation density in the inter-particle contact region, and the formation of recovery cells involving dislocation climb, indicate that the rate-controlling mechanism is probably self-diffusion in dislocations. In TiAl, high dislocation densities leading to reorganization into sub-boundaries point to dislocation climb mechanisms, which are kinetically controlled by volume diffusion. The difference in densification kinetics between Ni and TiAl is then accounted for in terms of the difference in their respective rate-controlling mechanisms operative during densification