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Using Advanced Very High Resolution Radiometer data spanning 1981–2006 and calibrated for long‐term analyses of vegetation dynamics, we examine whether vegetation cover has increased across Australia and whether there has been a differential response of vegetation functional types in response to changes in climatic growing conditions. Trends in vegetation cover are interpreted within Budyko's energy – water limitation framework. Results from an Australia‐wide analysis indicate that vegetation cover (as described by the fraction of Photosynthetically Active Radiation absorbed by vegetation; fPAR) has increased, on average, by 0.0007 per year – an increase of ∼8% over the 26 years. The majority of this change is due to a 0.0010 per year increase in persistent fPAR (representing nondeciduous perennial vegetation types; up 21%). In contrast, recurrent fPAR (representing deciduous, annual and ephemeral vegetation types) decreased, on average, by 0.0003 per year (down 7%), the trends of which are highly seasonal. Over the same period, Australian average annual precipitation increased by 1.3 mm yr−2 (up 7%). A site‐based analysis using 90 long‐term meteorological stations with minimal localized land‐cover changes showed that energy‐limited sites where total fPAR increased generally experienced decreases in precipitation, and water‐limited sites that experienced decreases in cover were almost always associated with decreases in precipitation. Interestingly, where vegetation cover increased at water‐limited sites, precipitation trends were variable indicating that this is not the only factor driving vegetation response. As Australia is a generally highly water‐limited environment, these findings indicate that the effective availability of water to plants has increased on average over the study period. Results also show that persistent vegetation types have benefited more than recurrent types from recent changes in growing conditions. Regardless of what has been driving these changes, the overall response of vegetation over the past 2–3 decades has resulted in an observable greening of the driest inhabited continent on Earth.  相似文献   

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Elephant mortality in Tsavo National Park, Kenya   总被引:1,自引:0,他引:1  
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Herpetological zoo research published in three journals between 1977 and 1981 was surveyed. Fifty-three of 1,084 published papers involved zoos. Research for 30 papers was conducted in zoos. Just under three fourths of zoo papers involved behavioral research. Sixteen zoos were involved in research in this survey.  相似文献   

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A Danish mire influenced by culture until ca. 100 years ago and since then with incipient growth of Betula pubescens , was analyzed in 1957 and 1981 with regard to height of the Betula trees and cover percentage of plant species in the field layer. In 1957, every m2 along a 110 m transect was examined; in 1981 only 56 m2 representatively selected from the transect were examined. Betula showed considerable changes with a net intake of 10 trees (23%) and a net loss of 23 trees (52%), i.e. a net loss of 13 trees (30%). The mean height of the trees has, however, increased by 80 cm and the sum of the height of the trees per m2 by 29 cm. An increased total cover was found for Em–petrum nigrum, Molinia coerulea , and Erica tetralix , and a decreased total cover for Calluna, Sphagnum magellanicum, S. nemoreum, S. rubellum, Hypnum cupressi–forme, Pleurozium schreberi , and Aulacomnium palustre. An almost unchanged total cover was found for Eriophorum vaginatum, E. angustifolium, Sphagnum recurvum, Andromeda polifolia, Drosera rotundifolia , and Oxycoccus palustris. On the basis of quantitative changes in the individual plots, a specific index of change is calculated, decreasing in the order Empetrum > Sphagnum magellanicum > S. recurvum = Molinia > Calluna > Hypnum cupressiforme > Pleurozium schreberi> Oxycoccus palustre> Sphagnum nemoreum = S. rubellum = Eriophorum vaginatum = E. angustifolium > Aulacomnium palustre > Erica> Drosera > Andromeda. Analyses from 1981 demonstrate that usually the light conditions and/or the water content and rarely the bulk density of the soil is correlated with the change in cover of the individual species. For some species it is also shown that the change is correlated with the strongly increased cover of Empetrum in particular. The changes are finally illustrated by showing the position of the species along ecological gradients in 1981.  相似文献   

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Medical and human genetics 1977: trends and directions   总被引:2,自引:2,他引:0  
Our field is in a rapid state of evolution. The broader concerns of human genetics not of immediate medical interest such as behavioral genetics are often investigated by persons not trained or identified as human geneticists. Both medical genetics and human genetics in general have prospered when various biologic techniques have been applied to genetic concepts. A search for novel biologic methods may provide new insights and may bridge the gulf between Mendelian and biometric approaches in studies of behavior and of common diseases. Medical geneticists need to broaden their fields of interest to encompass other fields than those of pediatric interest alone. We need to attract more basic scientists. Our field is evolving from a largely research oriented science to a service-oriented specialty. This logical development is a sign of increasing maturity and makes available to the public the results of our research. The resulting stresses and strains need careful watching to prevent their slowing the momentum of our science which can contribute continued insights into the many problems of behavior, health, and disease.  相似文献   

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The Tana River forest patches significantly decreased in total area by 1875 ha (34.5%), from 5439 to 3564 ha between 1979 and 2000. The area covered by forests outside the Tana River Primate National Reserve declined by 1246 ha (38%) from 3283 to 2037 ha. This loss was higher than that inside the reserve, where total forest area reduced by 629 ha (29%) from 2156 to 1527 ha. The numbers of Tana River red colobus (Procolobus rufomitratus) and Tana crested mangabey (Cercocebus galeritus galeritus) groups were significantly correlated with forest sizes suggesting that both red colobus and crested mangabeys are likely to be affected by forest loss and fragmentation. However, comparison of the 1974/75 and 2001 census data did not reveal any significant change in the number of groups of either the red colobus or crested mangabey. The two endangered primates may have developed strategies to cope with a shrinking habitat.  相似文献   

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The total of all non-migratory wildlife species in the Masai Mara ecosystem has declined by 58% in the last 20 years. This decline ranges from 49% in small brown antelopes to 72% in medium brown antelopes. In individual wildlife species, the decline ranges from 52% in Grant's gazelle to 88% in the warthog. Declines of over 70% have been recorded in buffalo, giraffe, eland and waterbuck. Only elephant, impala and ostrich have not shown any significant decline or increase. Overall, there has not been any significant difference in decline of all wildlife population sizes inside and outside the reserve, except for Thomson's gazelle and warthog. Livestock have not significantly declined over the entire analysis period. However, livestock and cattle populations significantly declined during the 1983–88 period. Donkey declined by 67%, while shoats (goats and sheep) remained stable. In the case of wildlife, land use and vegetation changes, drought effects and poaching are considered to be among the potential factors that may have been responsible for the decline; the decline in livestock during the 1983–84 period was probably due to drought effects.  相似文献   

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