A general model for assessment of the carbon sequestration potential of afforestation projects   总被引：1，自引：0，他引：1  

Henrik Meilby  Finn Helles 《New Forests》2011,42(3):383-396

Among the objectives of afforestation projects, carbon sequestration is attracting increasing political attention. Therefore, there is a need for understanding the carbon sequestration ??mechanism?? and for ex-ante assessment of the sequestration potential of afforestation projects. Such assessment must be based on parameter estimates that are inherently uncertain, making the basis for applying an advanced sequestration model weak. This paper presents a transparent, simple and general model for quantification of the carbon sequestration in afforestation projects. The model can easily be modified so as to fit specific conditions, and it is held sufficiently reliable when taking into account the ex-ante character of the decision problem. The use of the model is exemplified by application to a yield table for Sitka spruce. Limitations of the model framework and its application in combination with scenarios of climate change are discussed.  相似文献   

Effects of grassland abandonment, restoration and management on butterflies and vascular plants     

Erik Öckinger  Anna K. Eriksson  Henrik G. Smith 《Biological conservation》2006,133(3):291-300

When semi-natural pastures are abandoned, specialized grassland species are lost as a consequence of succession. As a counter-measure, previously abandoned grasslands may be restored by clearing shrubs and trees and re-introducing grazing livestock. In order to examine the effects of this type of habitat restoration, we compared species richness of plants and of specialized plants thought to be dependent on continuous management and species richness and abundance of butterflies and red-listed butterflies in 12 sets of matched continuously managed, abandoned and restored grassland in southern Sweden. We found no differences in species richness or abundance between the three grassland types. There were, however, some negative effects of abandonment. The number of management-dependent plants decreased with increasing cover of trees and shrubs, and in restored sites species richness of all groups decreased with increasing cover of trees and shrubs before restoration. Also the present management significantly affected both butterflies and plants. Species richness of both groups increased with increasing vegetation height and differed between sites depending on the species of grazers, with negative effects of sheep compared to cattle or horses. Our study indicates that for grassland management to be efficient, the restoration actions should mainly be directed towards sites where the post-abandonment succession has not proceeded too far.  相似文献   

Significance of preslaughter stress and different tissue PUFA levels on the oxidative status and stability of porcine muscle and meat     

Young JF  Rosenvold K  Stagsted J  Steffensen CL  Nielsen JH  Andersen HJ 《Journal of agricultural and food chemistry》2003,51(23):6877-6881

Polyunsaturated fatty acids (PUFAs) and exercise-induced stress are known to increase the oxidative susceptibility of lipids in muscle tissue. In contrast, antioxidative enzymes, e.g., catalase, superoxide dismutase, and glutathione peroxidase, are known to help sustain the delicate oxidative balance in biological tissue upon the application of stressors. The present study investigates the combined effect of different diet-induced muscle PUFA contents and preslaughter stress on the activity of antioxidative muscle enzymes and the oxidative stability of cooked meat. An increased content of unsaturated fatty acids in the tissue led to a decreased activity of lactate dehydrogenase in the plasma, indicating increased cell integrity. Catalase activity in the muscle tissue increased with increasing PUFA levels. However, this upregulation in antioxidative status of the muscle could not counteract the subsequent development of accelerated lipid oxidation in cooked meat as measured in terms of thiobarbituric acid reactive substances. Moreover, preslaughter stress induced increasing oxidative changes with elevated PUFA levels in the muscle tissue.  相似文献   

That's my hand! Activity in premotor cortex reflects feeling of ownership of a limb     

Ehrsson HH  Spence C  Passingham RE 《Science (New York, N.Y.)》2004,305(5685):875-877

When we look at our hands, we immediately know that they are part of our own body. This feeling of ownership of our limbs is a fundamental aspect of self-consciousness. We have studied the neuronal counterparts of this experience. A perceptual illusion was used to manipulate feelings of ownership of a rubber hand presented in front of healthy subjects while brain activity was measured by functional magnetic resonance imaging. The neural activity in the premotor cortex reflected the feeling of ownership of the hand. This suggests that multisensory integration in the premotor cortex provides a mechanism for bodily self-attribution.  相似文献   

Extensive gene traffic on the mammalian X chromosome     

Emerson JJ  Kaessmann H  Betrán E  Long M 《Science (New York, N.Y.)》2004,303(5657):537-540

Mammalian sex chromosomes have undergone profound changes since evolving from ancestral autosomes. By examining retroposed genes in the human and mouse genomes, we demonstrate that, during evolution, the mammalian X chromosome has generated and recruited a disproportionately high number of functional retroposed genes, whereas the autosomes experienced lower gene turnover. Most autosomal copies originating from X-linked genes exhibited testis-biased expression. Such export is incompatible with mutational bias and is likely driven by natural selection to attain male germline function. However, the excess recruitment is consistent with a combination of both natural selection and mutational bias.  相似文献   

Another phocine distemper outbreak in Europe     

Jensen T  van de Bildt M  Dietz HH  Andersen TH  Hammer AS  Kuiken T  Osterhaus A 《Science (New York, N.Y.)》2002,297(5579):209

  相似文献   

An mRNA is capped by a 2', 5' lariat catalyzed by a group I-like ribozyme     

Nielsen H  Westhof E  Johansen S 《Science (New York, N.Y.)》2005,309(5740):1584-1587

  相似文献   

Significance of old aspen (Populus tremula) trees for the occurrence of lichen photobionts     

Henrik Hedenås  Patrik Blomberg  Lars Ericson 《Biological conservation》2007,135(3):380-387

In the boreal forest landscape, aspen has been effectively selected against in favour of conifers. The decrease in aspen is of particular concern, since it has more host-specific species associated with it than any other boreal tree species. Recently, forest management systems have begun to include green-tree retention in order to maintain structural diversity. Earlier studies have focused on the importance of remnant aspen trees for lichen species prevalence. We have focused on the occurrence of free-living photobionts, i.e. cyanobacteria and green-algae, since a successful establishment of sexually dispersed lichens will depend upon the presence of the photobiont. Our study shows that the abundances of Gloeocystis, Nostoc, Scytonema and Trentepohlia increased with stand age, while the abundance of Trebouxia decreased. The response to clear-felling differed between genera. The two cyanobacterial genera were able to persist in clear-cuts, although they were more abundant on the northern side of the remnant trees. The green-algae showed no consistent pattern, Trentepohlia was affected while Trebouxia was unaffected. Our study indicates that the prerequisites for new-establishment for spore dispersed lichen species, on remnant aspen, may be fulfilled in terms of availability of free-living photobionts on the northern side of the trunks. In support of this interpretation we found that the occurrence of cyanolichens was positively correlated with the occurrence of free-living cyanobacteria in the clear-cuts. We conclude that tree retention is likely to provide a useful tool for increasing biodiversity in managed forest landscapes provided that source populations still exist in the surrounding landscape.  相似文献   

Bryophyte species richness on boulders: relationship to area, habitat diversity and canopy tree species   总被引：1，自引：0，他引：1  

Henrik Weibull  Håkan Rydin 《Biological conservation》2005,122(1):71-79

Bryophytes growing on siliceous boulders (diameter 50-200 cm) were studied in two forests in east-central Sweden to investigate the influence of different canopy tree species on the bryophyte species richness. Granite boulders lying below crowns of Ulmus glabra (elm), Fraxinus excelsior (ash), Acer platanoides (maple), Quercus robur (oak), Betula pendula (birch), and Picea abies (Norway spruce) were studied in two mixed stands. Both boulder area and within-boulder habitat diversity were positively related to species richness. Boulders below the base-rich deciduous trees F. excelsior, U. glabra and A. platanoides held roughly twice as many species as those below P. abies, with Q. robur and B. pendula as intermediates. The rank order among trees was as expected from bark pH and litter decomposability in the literature. We also used sample plots to investigate species richness at a smaller scale. Within plots, intermediate levels of litter, inclination and exposed rock promoted species richness, and also the covering tree species had an effect. Individual plots were on average not more species-rich on large boulders than on small ones. This leads us to conclude that population extinctions on the plot-level, and re-colonisations from other parts of the boulder, are less important for species richness than within-boulder habitat diversity. Since species richness was lower under P. abies it is important to favour a diversity of tree species and to include base-rich deciduous trees in otherwise homogeneous Picea forests.  相似文献   

Metsulfuron methyl sorption-desorption in field-moist soils   总被引：4，自引：0，他引：4  

Berglöf T  Koskinen WC  Duffy MJ  Norberg KA  Kylin H 《Journal of agricultural and food chemistry》2003,51(12):3598-3603

Pesticide sorption coefficients (K(d)) are generally obtained using batch slurry methods. As a consequence, the results may not adequately reflect sorption processes in field-moist or unsaturated soil. The objective of this study was to determine sorption of metsulfuron methyl, a weak acid, in field-moist soils. Experiments were performed using low density (i.e., 0.3 g mL(-)(1)) supercritical fluid carbon dioxide (SF-CO(2)) to convert anionic metsulfuron methyl to the molecular species and remove it from the soil water phase only, thus allowing calculation of sorption coefficients (K(d)) at low water contents. K(d) values for sorption of the metsulfuron methyl molecular species on sandy loam, silt loam, and clay loam soil at 11% water content were 120, 180, and 320 mL g(-)(1), respectively. Using neutral species K(d) values, the pK(a) of metsulfuron methyl, and the pH of the soil, we could successfully predict the K(d) values obtained using the batch slurry technique, which typically has a predominance of anionic species in solution during the sorption characterization. This application of supercritical fluid extraction to determine sorption coefficients, combined with sulfonylureas' pK(a) values and the soil pH, will provide an easy method to predict sorption in soil at different pH levels.  相似文献