Incorporating anthropogenic threats into evaluations of regional biodiversity and prioritisation of conservation areas in the Limpopo Province, South Africa     

Belinda Reyers 《Biological conservation》2004,118(4):521-531

Recent attempts to streamline the identification of areas requiring immediate conservation attention have resulted in the development of prioritisation procedures that identify areas of biodiversity importance facing large threats in the near future. This study incorporated biodiversity data on bird and vegetation distribution with an assessment of land use suitability for cultivation and afforestation for the Limpopo Province of South Africa. The low altitude savanna regions in the northeast contain high species diversity, but are unsuitable to alternative forms of land use and are well conserved (by e.g., the Kruger National Park). The central and eastern mountain ranges, sites of high biodiversity, are suitable to dryland cultivation and afforestation and are thus potential conservation priorities. Areas with high biodiversity values, e.g., irreplaceable areas that contain biodiversity features essential for meeting conservation targets, were then investigated for their potential land-use threats in order to prioritise those needing immediate conservation actions. We suggest how losses of biodiversity could be minimised by reaching such decisions more quickly.  相似文献   

Measuring socio-economic position in dietary research: is choice of socio-economic indicator important?     

Turrell G  Hewitt B  Patterson C  Oldenburg B 《Public health nutrition》2003,6(2):191-200

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Performance of new and commercial xylanases for ECF and TCF bleaching of eucalyptus kraft pulp     

Cristina Valls  Óscar Gallardo  Teresa Vidal  F. I. Javier Pastor  Pilar Díaz  M. Blanca Roncero 《Wood Science and Technology》2011,45(3):433-448

Since xylanases can differ widely in their bleaching efficiency, the performance of one new and two commercial xylanases was evaluated in an eucalyptus kraft pulp following XD (X: xylanase; D: chlorine dioxide) and XP (P: hydrogen peroxide) sequences. The new xylanase did not show a significant bleach boosting effect but increased the hexenuronic acid (HexA) removal by 10% after the D stage. The two commercial xylanases behaved in a different way, being one of them (X_C) the most effective in increasing delignification (9%) and brightness (3%ISO). Its effectiveness was related to its greater action on releasing the xylan polymer, thus producing also a strong decrease in the HexA contents during the enzymatic stage (15%). All xylanases produced morphological changes in the fibre surfaces, but only with X_C cracks and holes that improved the diffusion of reactives were observed. Finally, the best bleaching results were obtained with the XD sequence and therefore, a complete bleaching sequence XDEopD₁ (Eop: alkaline extraction with oxygen and peroxide) was carried out with the best enzyme.  相似文献   

Rooting depth explains [CO2] x drought interaction in Eucalyptus saligna     

Duursma RA  Barton CV  Eamus D  Medlyn BE  Ellsworth DS  Forster MA  Tissue DT  Linder S  McMurtrie RE 《Tree physiology》2011,31(9):922-931

Elevated atmospheric [CO(2)] (eC(a)) often decreases stomatal conductance, which may delay the start of drought, as well as alleviate the effect of dry soil on plant water use and carbon uptake. We studied the interaction between drought and eC(a) in a whole-tree chamber experiment with Eucalyptus saligna. Trees were grown for 18 months in their C(a) treatments before a 4-month dry-down. Trees grown in eC(a) were smaller than those grown in ambient C(a) (aC(a)) due to an early growth setback that was maintained throughout the duration of the experiment. Pre-dawn leaf water potentials were not different between C(a) treatments, but were lower in the drought treatment than the irrigated control. Counter to expectations, the drought treatment caused a larger reduction in canopy-average transpiration rates for trees in the eC(a) treatment compared with aC(a). Total tree transpiration over the dry-down was positively correlated with the decrease in soil water storage, measured in the top 1.5 m, over the drying cycle; however, we could not close the water budget especially for the larger trees, suggesting soil water uptake below 1.5 m depth. Using neutron probe soil water measurements, we estimated fractional water uptake to a depth of 4.5 m and found that larger trees were able to extract more water from deep soil layers. These results highlight the interaction between rooting depth and response of tree water use to drought. The responses of tree water use to eC(a) involve interactions between tree size, root distribution and soil moisture availability that may override the expected direct effects of eC(a). It is essential that these interactions be considered when interpreting experimental results.  相似文献   

Paired comparison of water, energy and carbon exchanges over two young maritime pine stands (Pinus pinaster Ait.): effects of thinning and weeding in the early stage of tree growth     

Moreaux V  Lamaud E  Bosc A  Bonnefond JM  Medlyn BE  Loustau D 《Tree physiology》2011,31(9):903-921

The effects of management practices on energy, water and carbon exchanges were investigated in a young pine plantation in south-west France. In 2009-10, carbon dioxide (CO(2)), H(2)O and heat fluxes were monitored using the eddy covariance and sap flow techniques in a control plot (C) with a developed gorse layer, and an adjacent plot that was mechanically weeded and thinned (W). Despite large differences in the total leaf area index and canopy structure, the annual net radiation absorbed was only 4% lower in plot W. We showed that higher albedo in this plot was offset by lower emitted long-wave radiation. Annual evapotranspiration (ET) from plot W was 15% lower, due to lower rainfall interception and transpiration by the tree canopy, partly counterbalanced by the larger evaporation from both soil and regrowing weedy vegetation. The drainage belowground from plot W was larger by 113 mm annually. The seasonal variability of ET was driven by the dynamics of the soil and weed layers, which was more severely affected by drought in plot C. Conversely, the temporal changes in pine transpiration and stem diameter growth were synchronous between sites despite higher soil water content in the weeded plot. At the annual scale, both plots were carbon sinks, but thinning and weeding reduced the carbon uptake by 73%: annual carbon uptake was 243 and 65 g C m(-2) on plots C and W, respectively. Summer drought dramatically impacted the net ecosystem exchange: plot C became a carbon source as the gross primary production (GPP) severely decreased. However, plot W remained a carbon sink during drought, as a result of decreases in both GPP and ecosystem respiration (R(E)). In winter, both plots were carbon sources, plots C and W emitting 67.5 and 32.4 g C m(-2), respectively. Overall, this study highlighted the significant contribution of the gorse layer to mass and energy exchange in young pine plantations.  相似文献   

Evolution of coral pigments recreated     

Ugalde JA  Chang BS  Matz MV 《Science (New York, N.Y.)》2004,305(5689):1433

In proteins homologous to the green fluorescent protein (GFP), formation of red fluorescence requires three autocatalytic steps, whereas only two are needed for green fluorescence. Multiple red/green color diversification events in the GFP superfamily may reflect convergent evolution of the more complex three-step pathway. In the great star coral Montastraea cavernosa, a recreated common ancestor of green and red proteins turned out to be green, indicating that in this case red proteins evolved their color independently from most other homologous red proteins. Furthermore, red color appears to have evolved gradually by small incremental transitions.  相似文献   

Quantitative determinations of chemical compounds with nutritional value from inca crops:Chenopodium quinoa (‘quinoa’)     

J. A. González  A. Roldán  M. Gallardo  T. Escudero  F. E. Prado 《Plant foods for human nutrition (Dordrecht, Netherlands)》1989,39(4):331-337

Quantitative determinations of total and soluble proteins, total and free sugars, starch, total lipids, tanins, ash (Ca, Na, K, Fe, and P), and caloric value were carried out on quinoa flour.Results show that the amount of soluble proteins was higher than the standard value for wheat and maize and was very close to that of barley's. The yield of free sugars like glucose (4.55%), fructose (2.41%) and sucrose (2.39%) were also of importance.Iron and calcium levels were higher than the reported values for maize and barley. The same occurred for the caloric value (435.5 Kcal/100 g).The content of saponins was also examined since its effect on red blood cells of group A and O has been related as a potential problem of the Andes population.From the chemical analysis a more complete view about quinoa as human food was presented.  相似文献   

Gross for kids but good for parents: differing messages in advertisements for the same products     

Jones S  Fabrianesi B 《Public health nutrition》2008,11(6):588-595

OBJECTIVES: There has been surprisingly little research into the effects of food advertising on parents' perception of commonly consumed children's food items, although the available research suggests that parents may find nutritional claims in these advertisements confusing. The purpose of the present study was to investigate parents' perceptions of branded snack foods targeted at children, and the extent to which these perceptions are influenced by advertising messages. DESIGN: Using an intercept survey, participants were shown either adult-targeted or child-targeted advertisements for the same food products. SETTING: Central business district of a major Australian city. SUBJECTS: One hundred adults, mean age 40 years. RESULTS: The study results suggest that: (1) adults' perceptions of advertised food products and, most importantly, purchase intentions for those products differ according to the version of the advertisement seen (for three of the products, 42-54% would buy the product after seeing the child version compared with 82-84% after seeing the adult version); and (2) adults clearly perceive distinctly different messages in advertisements for the same products which are targeting parents vs. those targeting children (e.g. for three of the products, 74-92% perceived that the adult version of the advertisement suggested the food was nutritionally beneficial compared with 2-14% perceiving this for the child version). CONCLUSIONS: It is clear that the messages conveyed to children about specific foods are quite different to the messages conveyed to adults - and importantly parents - about the same foods.  相似文献   

A comparative analysis of simulated and observed photosynthetic CO2 uptake in two coniferous forest canopies     

Ibrom A  Jarvis PG  Clement R  Morgenstern K  Oltchev A  Medlyn BE  Wang YP  Wingate L  Moncrieff JB  Gravenhorst G 《Tree physiology》2006,26(7):845-864

Gross canopy photosynthesis (P(g)) can be simulated with canopy models or retrieved from turbulent carbon dioxide (CO2) flux measurements above the forest canopy. We compare the two estimates and illustrate our findings with two case studies. We used the three-dimensional canopy model MAESTRA to simulate P(g) of two spruce forests differing in age and structure. Model parameter acquisition and model sensitivity to selected model parameters are described, and modeled results are compared with independent flux estimates. Despite higher photon fluxes at the site, an older German Norway spruce (Picea abies L. (Karst.)) canopy took up 25% less CO2 from the atmosphere than a young Scottish Sitka spruce (Picea sitchensis (Bong.) Carr.) plantation. The average magnitudes of P(g) and the differences between the two canopies were satisfactorily represented by the model. The main reasons for the different uptake rates were a slightly smaller quantum yield and lower absorptance of the Norway spruce stand because of a more clumped canopy structure. The model did not represent the scatter in the turbulent CO2 flux densities, which was of the same order of magnitude as the non-photosynthetically-active-radiation-induced biophysical variability in the simulated P(g). Analysis of residuals identified only small systematic differences between the modeled flux estimates and turbulent flux measurements at high vapor pressure saturation deficits. The merits and limitations of comparative analysis for quality evaluation of both methods are discussed. From this analysis, we recommend use of both parameter sets and model structure as a basis for future applications and model development.  相似文献   

Chemical conversion of alpha-amino acids into alpha-keto acids by 4,5-epoxy-2-decenal     

Zamora R  Navarro JL  Gallardo E  Hidalgo FJ 《Journal of agricultural and food chemistry》2006,54(16):6101-6105

The comparative formation of phenylalanine and phenylpyruvic acid in the reaction of 4,5-epoxy-2-decenal with phenylalanine was studied to determine whether epoyalkenals may also degrade amino acids without producing their decarboxylation. Both compounds were produced in the reaction to an extent that depended on the reaction pH, the amount of lipid oxidation product, and the reaction time and temperature. The optimum pH was 3 for producing both carbonyl derivatives, and the amount of both compounds increased linearly with the amount of epoxyalkenal present in the reaction mixture. In addition, phenylpyruvic acid was produced to a higher extent than phenylacetaldehyde at 37 degrees C. However, at 60 degrees C the degradation of phenylpyruvic acid was observed and phenylacetaldehyde was usually found to a higher extent than the alpha-keto acid in the overnight-incubated reaction mixtures. The degradation of phenylpyruvic acid produced benzaldehyde and phenylacetaldehyde. All these results suggest that epoxyalkenals can not only degrade amino acids by a Strecker-type mechanism but convert them into their corresponding alpha-keto acids. This new reaction may be an alternative chemical route for the formation in foods of alpha-keto acids, which can later participate in the generation of important amino acid-derived flavor compounds.  相似文献