17 resultados para rainforest
Resumo:
Hominid evolution in the late Miocene has long been hypothesized to be linked to the retreat of the tropical rainforest in Africa. One cause for the climatic and vegetation change often considered was uplift of Africa, but also uplift of the Himalaya and the Tibetan Plateau was suggested to have impacted rainfall distribution over Africa. Recent proxy data suggest that in East Africa open grassland habitats were available to the common ancestors of hominins and apes long before their divergence and do not find evidence for a closed rainforest in the late Miocene. We used the coupled global general circulation model CCSM3 including an interactively coupled dynamic vegetation module to investigate the impact of topography on African hydro-climate and vegetation. We performed sensitivity experiments altering elevations of the Himalaya and the Tibetan Plateau as well as of East and Southern Africa. The simulations confirm the dominant impact of African topography for climate and vegetation development of the African tropics. Only a weak influence of prescribed Asian uplift on African climate could be detected. The model simulations show that rainforest coverage of Central Africa is strongly determined by the presence of elevated African topography. In East Africa, despite wetter conditions with lowered African topography, the conditions were not favorable enough to maintain a closed rainforest. A discussion of the results with respect to other model studies indicates a minor importance of vegetation-atmosphere or ocean-atmosphere feedbacks and a large dependence of the simulated vegetation response on the land surface/vegetation model.
Resumo:
The annual birthrate of female offspring and the intrinsic rate of natural increase (rmax) of populations are key reproductive parameters in models for assessing hunting sustainability or population viability of species. We calculated wild birthrate (pregnancy rate) for ten mammal species, using 180 months (from 2000 to 2015) of reproductive data from 950 hunted female animals collected with the participation of local hunters in the Peruvian Amazon. The methodology assured that no animals were killed outside the hunter's normal activities. The data included shows the reproductive state (pregnant or non-pregnant) of all collected individuals (n=1090), related to the date of collection. Hunters registered required data from genital organs from 950 (87.2%) hunted females, and 140 (12.8%) collected tracts lacked the collection date due to lost or non-legible individual sample codification.