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The effects of disturbance on the population structure and regeneration potential of five dominant woody species – in Hugumburda‐Gratkhassu National Forest Priority Area,North‐eastern Ethiopia 下载免费PDF全文
Vast areas of forests in North‐eastern Ethiopia have been replaced by cropland, shrub land or grazing areas. Thus, information about how vegetation composition and structure varies with disturbance is fundamental to conservation of such areas. This study aimed to investigate the effects of disturbance on the population structure and regeneration potential of five dominant woody species within forest where local communities harvest wood and graze livestock. Vegetation structure and environmental variables were assessed in 50 quadrats (20 m × 20 m). In most of both disturbed and undisturbed treatments, Juniperus procera was the highest contributor to the basal area of the forest, while that of Olinia rochetiana was the lowest. Analysis of population structure showed high density at lower Diameter at Breast Height (DBH) and low density at higher DBH classes. Undisturbed forest treatments had 84% canopy cover, 22 m mean vegetation height and a density of 1320 trees of dominant species and 1024 seedlings/saplings ha?1. In disturbed habitats, canopy cover (73%), mean vegetation height (18 m) and density of dominant trees and saplings were significantly lower than in undisturbed habitats. Thus, to ensure species, survival and maintain species diversity managed use of the protected area is essential. 相似文献
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Fatty acids and stable isotopes (δ13C and δ15N) reveal temporal changes in narwhal (Monodon monoceros) diet linked to migration patterns 下载免费PDF全文
Narwhals (Monodon monoceros) are sentinel species in the Arctic and to investigate marine food web changes from 1982–2011 we examined diet using fatty acids, δ15N, and δ13C, in narwhals from Baffin Bay (BB) and northern Hudson Bay (NHB). We predicted temporal changes would be greater in NHB due to a significant reduction in summer ice cover. In NHB, δ15N significantly increased, δ13C displayed a parabolic trend, and fatty acids gradually shifted, albeit not significantly, over time. δ15N was stable, δ13C decreased, and fatty acids significantly changed over time in BB. Stable isotope mixing models indicated a dietary reduction in capelin and increase in Greenland halibut from 1994–2000 to 2006–2011 in BB, while capelin was an important dietary component for narwhals in NHB in recent years (2006–2011). These dietary changes may be attributed to changes in sea ice and narwhal migration. Seasonal dietary changes, as evidenced by changes in blubber fatty acids and skin and muscle stable isotopes, were not as apparent in the NHB population, which may be indicative of a reduced migratory distance. Long‐term monitoring of narwhal diet and migratory patterns associated with reduced sea ice provides invaluable information about how the marine ecosystem will redistribute with global warming. 相似文献
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Maria B. Tereshina Anastasiya S. Ivanova Fedor M. Eroshkin Daria D. Korotkova Alexey M. Nesterenko Andrey V. Bayramov Elena A. Solovieva Elena A. Parshina Eugeny E. Orlov Natalia Y. Martynova Andrey G. Zaraisky 《Genesis (New York, N.Y. : 2000)》2019,57(5)
The Agr family genes, Ag1, Agr2, and Agr3, encode for the thioredoxin domain containing secreted proteins and are specific only for vertebrates. These proteins are attracting increasing attention due to their involvement in many physiological and pathological processes, including exocrine secretion, cancer, regeneration of the body appendages, and the early brain development. At the same time, the mode by which Agrs regulate intracellular processes are poorly understood. Despite that the receptor to Agr2, the membrane anchored protein Prod1, has been firstly discovered in Urodeles, and it has been shown to interact with Agr2 in the regenerating limb, no functional homologs of Prod1 were identified in other vertebrates. This raises the question of the mechanisms by which Agrs can regulate regeneration in other lower vertebrates. Recently, we have identified that Tfp4 (three‐fingers Protein 4), the structural and functional homolog of Prod1 in Anurans, interacts with Agr2 in Xenopus laevis embryos. In the present work we show by several methods that the activity of Tfp4 is essential for the tadpole tail regeneration as well as for the early eye and forebrain development during embryogenesis. These data show for the first time the common molecular mechanism of regeneration regulation in amphibians by interaction of Prod1 and Agr2 proteins. 相似文献
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Changing gull diet in a changing world: A 150‐year stable isotope (δ13C, δ15N) record from feathers collected in the Pacific Northwest of North America 下载免费PDF全文
Louise K. Blight Keith A. Hobson T. Kurt Kyser Peter Arcese 《Global Change Biology》2015,21(4):1497-1507
The world's oceans have undergone significant ecological changes following European colonial expansion and associated industrialization. Seabirds are useful indicators of marine food web structure and can be used to track multidecadal environmental change, potentially reflecting long‐term human impacts. We used stable isotope (δ13C, δ15N) analysis of feathers from glaucous‐winged gulls (Larus glaucescens) in a heavily disturbed region of the northeast Pacific to ask whether diets of this generalist forager changed in response to shifts in food availability over 150 years, and whether any detected change might explain long‐term trends in gull abundance. Sampled feathers came from birds collected between 1860 and 2009 at nesting colonies in the Salish Sea, a transboundary marine system adjacent to Washington, USA and British Columbia, Canada. To determine whether temporal trends in stable isotope ratios might simply reflect changes to baseline environmental values, we also analysed muscle tissue from forage fishes collected in the same region over a multidecadal timeframe. Values of δ13C and δ15N declined since 1860 in both subadult and adult gulls (δ13C, ~ 2–6‰; δ15N, ~4–5‰), indicating that their diet has become less marine over time, and that birds now feed at a lower trophic level than previously. Conversely, forage fish δ13C and δ15N values showed no trends, supporting our conclusion that gull feather values were indicative of declines in marine food availability rather than of baseline environmental change. Gradual declines in feather isotope values are consistent with trends predicted had gulls consumed less fish over time, but were equivocal with respect to whether gulls had switched to a more garbage‐based diet, or one comprising marine invertebrates. Nevertheless, our results suggest a long‐term decrease in diet quality linked to declining fish abundance or other anthropogenic influences, and may help to explain regional population declines in this species and other piscivores. 相似文献
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Isotopic perspectives (δ13C, δ15N, δ34S) of diet,social complexity,and animal husbandry during the proto‐shang period (ca. 2000–1600 BC) of China 下载免费PDF全文
Ying Ma Benjamin T. Fuller Dong Wei Lei Shi Xiaozheng Zhang Yaowu Hu Michael P. Richards 《American journal of physical anthropology》2016,160(3):433-445