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71.
72.
Anna Bond Estes Tobias Kuemmerle Hadas Kushnir Volker Christian Radeloff Herman Henry Shugart 《Biological conservation》2012,147(1):255-263
The growth of human populations around protected areas accelerates land conversion and isolation, negatively impacting biodiversity and ecosystem function, and can be exacerbated by immigration. It is often assumed that immigration around protected areas is driven by attraction in the form of economic benefits, but in many cases, people may be pushed from their areas of origin toward protected areas. Mitigating the effects of immigration around protected areas necessitates understanding the actual mechanisms causing it, which can be aided by analysis of patterns of land-cover change. Our goal was to identify the reasons for human population growth and land-cover change around the protected areas in the greater Serengeti ecosystem (henceforth “the park”), and to relate agricultural conversion from 1984–2003 to trends in human demography. We found that conversion of natural habitats to agriculture was greatest closer to the park (up to 2.3% per year), coinciding with the highest rates of human population growth (3.5% per year). Agricultural conversion and population growth were greatest where there was less existing agriculture, and population density was lowest. Lack of unfarmed land farther from the park, coupled with greater poverty near the park, suggest that movement away from areas with high population densities and land scarcity was likely driving immigration near the park, where arable land was available. Our results are essential for conservation planning for one of Africa’s hallmark ecosystems, and should encourage further examination of population growth and land-cover trends near protected areas throughout the developing world. 相似文献
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Teodora Todorcic Vekic Shahid Nadeem Lars Molstad Vegard Martinsen Elisabeth Gautefall Hiis Lars Bakken Tobias Rütting Leif Klemedtsson Peter Dörsch 《Soil Use and Management》2023,39(3):1082-1095
Liming of acidic agricultural soils has been proposed as a strategy to mitigate nitrous oxide (N2O) emissions, as increased soil pH reduces the N2O/N2 product ratio of denitrification. The capacity of different calcareous (calcite and dolomite) and siliceous minerals to increase soil pH and reduce N2O emissions was assessed in a 2-year grassland field experiment. An associated pot experiment was conducted using homogenized field soils for controlling spatial soil variability. Nitrous oxide emissions were highly episodic with emission peaks in response to freezing–thawing and application of NPK fertilizer. Liming with dolomite caused a pH increase from 5.1 to 6.2 and reduced N2O emissions by 30% and 60% after application of NPK fertilizer and freezing–thawing events, respectively. Over the course of the 2-year field trial, N2O emissions were significantly lower in dolomite-limed than non-limed soil (p < .05), although this effect was variable over time. Unexpectedly, no significant reduction of N2O emission was found in the calcite treatment, despite the largest pH increase in all tested minerals. We tentatively attribute this to increased N2O production by overall increase in nitrogen turnover rates (both nitrification and denitrification) following rapid pH increase in the first year after liming. Siliceous materials showed little pH effect and had no significant effect on N2O emissions probably because of their lower buffering capacity and lower cation content. In the pot experiment using soils taken from the field plots 3 years after liming and exposing them to natural freezing–thawing, both calcite (p < .01) and dolomite (p < .05) significantly reduced cumulative N2O emission by 50% and 30%, respectively, relative to the non-limed control. These results demonstrate that the overall effect of liming is to reduce N2O emission, although high lime doses may lead to a transiently enhanced emission. 相似文献
75.
In simple epithelia, such as living epithelial pancreatic cancer cells (Panc-1), unusual amounts of keratin filaments can be found, which makes these cells an ideal model system to study the role of keratin for cell mechanical properties. In this work, the elastic moduli of Panc-1 cells and their extracted in-situ subcellular keratin intermediate filament network are determined and compared with each other. For this, the living adherent cells and their extracted keratin network were probed with local quasistatic indentation testing during large deformations using the Atomic Force Microscope (AFM). We determined the elastic modulus of the skeletonized but structurally intact keratin network to be in the order of 10 Pa, while the living cell elastic modulus ranged from 100 to 500 Pa. By removing microfilaments, microtubules, membranes and soluble cytoplasmic components during keratin network extraction, we excluded effects caused by crosslinking with other filamentous fibers and from the viscosity of the cytoplasm. Thus, the determined elastic modulus equals the actual elastic modulus inherent to such a keratin filamentous network. In our assessment of the effective mechanical contribution of the architecturally intact, skeletonized keratin network to living cell mechanics, we come to the conclusion that it plays only a very limited role. Evidently, the quantitative dominance of keratin in these cells does not reflect a strong influence on determining the cell's elastic modulus. Instead, keratin like other filamentous structures in the cell's scaffolding, e.g., F-actin and microtubuli, is one part of a greater whole. 相似文献
76.
Naaf Tobias Feigs Jannis Till Huang Siyu Brunet Jörg Cousins Sara A. O. Decocq Guillaume De Frenne Pieter Diekmann Martin Govaert Sanne Hedwall Per-Ola Lenoir Jonathan Liira Jaan Meeussen Camille Plue Jan Vangansbeke Pieter Vanneste Thomas Verheyen Kris Holzhauer Stephanie I. J. Kramp Katja 《Landscape Ecology》2022,37(5):1365-1384
Landscape Ecology - Plant populations in agricultural landscapes are mostly fragmented and their functional connectivity often depends on seed and pollen dispersal by animals. However, little is... 相似文献
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Baron MK Boeckers TM Vaida B Faham S Gingery M Sawaya MR Salyer D Gundelfinger ED Bowie JU 《Science (New York, N.Y.)》2006,311(5760):531-535
The postsynaptic density (PSD) is a complex assembly of proteins associated with the postsynaptic membrane that organizes neurotransmitter receptors, signaling pathways, and regulatory elements within a cytoskeletal matrix. Here we show that the sterile alpha motif domain of rat Shank3/ProSAP2, a master scaffolding protein located deep within the PSD, can form large sheets composed of helical fibers stacked side by side. Zn2+, which is found in high concentrations in the PSD, binds tightly to Shank3 and may regulate assembly. Sheets of the Shank protein could form a platform for the construction of the PSD complex. 相似文献
80.
Heo WD Inoue T Park WS Kim ML Park BO Wandless TJ Meyer T 《Science (New York, N.Y.)》2006,314(5804):1458-1461
Many signaling, cytoskeletal, and transport proteins have to be localized to the plasma membrane (PM) in order to carry out their function. We surveyed PM-targeting mechanisms by imaging the subcellular localization of 125 fluorescent protein-conjugated Ras, Rab, Arf, and Rho proteins. Out of 48 proteins that were PM-localized, 37 contained clusters of positively charged amino acids. To test whether these polybasic clusters bind negatively charged phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] lipids, we developed a chemical phosphatase activation method to deplete PM PI(4,5)P2. Unexpectedly, proteins with polybasic clusters dissociated from the PM only when both PI(4,5)P2 and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] were depleted, arguing that both lipid second messengers jointly regulate PM targeting. 相似文献