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THE meteorite Allan Hills (ALH) 84001, commonly accepted to be of martian origin, is unique among known martian meteorites in containing abundant, zoned, pre-terrestrial carbonate minerals(1-9). Previous studies of the oxygen isot...
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THE meteorite Allan Hills (ALH) 84001, commonly accepted to be of martian origin, is unique among known martian meteorites in containing abundant, zoned, pre-terrestrial carbonate minerals(1-9). Previous studies of the oxygen isotope compositions of these minerals(5,6,8) have suggested that they precipitated from a low-temperature (0-80 degrees C) aqueous fluid in the martian crust-perhaps in a near-surface hydrothermal system, Here we report analyses of the major-element compositions of the carbonates, which provide an independent constraint on the composition and temperature of the fluid from which they formed. We argue that the most likely explanation for the observed compositions, and for the absence of co-existing hydrous minerals, is that the carbonates were formed by reactions between hot (>650 degrees C), CO2-rich fluids and the ultramafic host rock during an impact event, Impact processes on the martian surface can produce both the hot, CO2-rich fluid (by volatilization of surface carbonates or other CO2 sources) and-by brecciation-the conduits through which it flowed, Impact metasomatism is also consistent with the observed oxygen isotope disequilibrium, sequence of mineral formation, and carbonate mineral zoning, reflecting carbonate formation during rapid cooling from high temperatures rather than prolonged exposure to low-temperature fluids(6,8). [References: 22]
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Using data from nine spacing experiments of Norway spruce (Picea abies (L.) Karst.) in Norway, covering wide ranges of site index and initial spacing, this study evaluated stand basal area and volume responses to initial spacing a...
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Using data from nine spacing experiments of Norway spruce (Picea abies (L.) Karst.) in Norway, covering wide ranges of site index and initial spacing, this study evaluated stand basal area and volume responses to initial spacing and examined whether these responses varied by stand ages or site quality. We developed nonlinear regression models that described the standing basal area or volume responses to initial spacing along with site index and stand ages. The results show that closer spacings produced higher standing basal area and volume than wider spacings. The response curves are highly nonlinear in younger stands and become nearly linear in mid-rotation stands, indicating stronger responses at younger ages and weaker responses as age increases. Furthermore, for young stands, spacing effects are stronger at closer than at wider spacings. The basal area and volume responses to initial spacing tend to be similar across site indices. However, the interaction of site index and stand age on spacing responses makes it difficult to isolate the effect of site index on spacing responses. Mortality is higher and begins earlier at closer spacings than wider. The mean diameter of the largest 100, 400, 600, and 800 trees ha-1 increased with spacing in three out of the nine experiments. Dominant height did not vary by initial spacing for any of the experiments. The findings suggest that the extra volume production in stands of closer initial spacing is restricted to early stand development.
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The main aims of this study are: (1) to test if temperature and related parameters are the primary determinants of the regional distribution of macrofungi (as is commonly recognized for plants); (2) to test if the success of model...
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The main aims of this study are: (1) to test if temperature and related parameters are the primary determinants of the regional distribution of macrofungi (as is commonly recognized for plants); (2) to test if the success of modelling fungal distribution patterns depends on species and distribution characteristics; and (3) to explore the potential of using herbarium data for modelling and predicting fungal species' distributions. The study area, Norway, spans 58-71p N latitude and 4-32p E longitude, and embraces extensive ecological gradients in a small area. The study is based on 1020 herbarium collections of nine selected species of macrofungi and a set of 75 environmental predictor variables, all recorded in a 5 x 5-km grid covering Norway. Primarily, generalized linear model (GLM; logistic regression) analyses were used to identify the environmental variables that best accounted for the species' recorded distributions in Norway. Second, Maxent analyses (using variables identified by GLM) were used to produce predictive potential distribution maps for these species. Variables relating to temperature and radiation were most frequently included in the GLMs, and between 24.8% and 59.8% of the variation in single-species occurrence was accounted for. The fraction of variation explained by the GLMs ranged from 41.6% to 59.8% for species with restricted distributions, and from 24.8% to 39.3% for species with widespread/scattered and intermediate distributions. The two-step procedure of GLM followed by Maxent gave predictions with very high values for the area under the curve (0.927-0.997), and maps of potential distribution were generally credible. We show that temperature is a key factor governing the distribution of macrofungi in Norway, indicating that fungi may respond strongly to global warming. We confirm that modelling success depends partly on species and distribution characteristics, notably on how the distribution relates to the extent of the study area. Our study demonstrates that the combination of GLM and Maxent may be a fruitful approach for biogeography. We conclude that herbarium data improve insight into factors that control the distributions of fungi, of particular value for research on fleshy fungi (mushrooms), which have largely cryptic life cycles.
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Little more than a year after the first reports of a new coronavirus in Wuhan, China, the world is in the middle of a pandemic that has brought dramatic changes in societies all over the world. This is our story, as seen from the ...
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Little more than a year after the first reports of a new coronavirus in Wuhan, China, the world is in the middle of a pandemic that has brought dramatic changes in societies all over the world. This is our story, as seen from the Department of Immunology and Transfusion at Oslo University Hospital (OUH).
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Several excavated sections along new roads in Buvika, mid-Norway, display records of large, prehistoric clay slides. Slightly undulating but otherwise intact laminated clay, with minor amounts of unsorted or sorted coarser-grained...
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Several excavated sections along new roads in Buvika, mid-Norway, display records of large, prehistoric clay slides. Slightly undulating but otherwise intact laminated clay, with minor amounts of unsorted or sorted coarser-grained debris, appears in the sections. Folding, shearing and internal slide surfaces have also been recorded, and the deposits are interpreted as slide debris. Slide-scar morphologies are diffuse or absent for most of these deposits, and the inferred slide mechanism is translation and rotation of blocks on a thin layer of remoulded quick clay. One section cuts through a slide block inside a classic, morphologically well-defined quick-clay slide scar. Varying results from C-14-datings of organic material in the deposits give only maximum ages of the slide events. The style of sliding reflected in several sections differs from slide events in the area known from historical records. These younger slide events seem to be characterised by collapse and remoulding of thicker quick-clay layers. The present study of slide deposits gives information on processes and deformation history of the slides. it is suggested that the gradual formation of quick clay has an important impact on long-term landscape degradation and on the character of the present day landscape. There may be far more signs of slide activity in Norwegian valleys than solely indicated by slide scars and also in the relatively high-lying parts of the valley fill, such as interfluve areas.
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A total of 21 acidified Norwegian rivers are now being limed to re-establish or restore Atlantic salmon, Salmo salar L., stocks. Natural reproduction of Atlantic salmon was evident 1 year after the first year of liming in all rive...
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A total of 21 acidified Norwegian rivers are now being limed to re-establish or restore Atlantic salmon, Salmo salar L., stocks. Natural reproduction of Atlantic salmon was evident 1 year after the first year of liming in all rivers that had lost their native stocks (n=9) except for one river. The density of fry (age 0+) developed significantly more rapidly in rivers that supported remnant stocks than in rivers that had lost their stocks, based on data 5 years after treatment. Nine of the study rivers were supplied with hatchery-reared salmon, mainly unfed fry. Of the rivers with lost stocks, those which were supplied with fish had significantly higher densities than those that were not enhanced. On the other hand, rivers with remnant stocks that were supplied with fish had significantly lower densities of salmon fry than those that did not undergo such mitigation measures. In 2001, all limed rivers yielded 41.9 t of salmon.
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In a 30-ha Picea abies mountain forest in the Swiss Alps, almost all trees were killed by bark beetles (Ips typographus) between 1992 and 1996. Snag decay was studied using full-callipering within transects, and the height of lyin...
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In a 30-ha Picea abies mountain forest in the Swiss Alps, almost all trees were killed by bark beetles (Ips typographus) between 1992 and 1996. Snag decay was studied using full-callipering within transects, and the height of lying logs above ground level was studied using the line intersect method. None of the dead trees had been uprooted, but 75% were found broken in 2000. The probability of snag breakage was independent of both tree diameter and time since stand death, but 28% of the snags broke close to the ground during a storm in December 1999. The log sections that were not in direct contact with the ground (73% of the log length sampled) were on average 85 cm above the soil surface in 2001. The orientation of the logs could be explained with the prevailing wind direction even on this steep slope. Leaving snag stands unharvested in P. abies forests on such slopes is likely to result in effective protection against rockfall and avalanche release for about 30 years.
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Twenty-three species were identified from the study of 302 specimens belonging to the family Paraonidae which were collected from Norwegian and adjacent waters. In this work Cirrophorus brevicirratus, C. furcatus, Levinsenia flava...
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Twenty-three species were identified from the study of 302 specimens belonging to the family Paraonidae which were collected from Norwegian and adjacent waters. In this work Cirrophorus brevicirratus, C. furcatus, Levinsenia flava, Paradoneis mikeli and Paraonides myriamae are recorded for the first time from the study region and two new species are described. Aricidea (Strelzovia) parabelgicae n. sp. is characterized by the absence of a frontal antenna, branchiae up to 7 pairs and beginning in chaetiger 5 and the ventral lip not indenting at chaetiger 2. Paradoneis andreae n. sp. is characterized by bearing single spine-like neurochaetae in posterior chaetigers and forked modified notochaetae, and by possessing 14-19 pairs of branchiae. A redescription of Paraonides nordica Strelzov, 1968 based on type material is also provided. A key to all the Paraonidae species known from the area, including also species not found in this investigation, is included.
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