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For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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During recent years laboratory studies have demonstrated the presence of metallothionein in several species of teleosts.1–3 The role of metallothionein (MT) in protection against cadmium toxicity has been investigated by exposing fish to high levels of cadmium in the water.4–6 So far, however, few field studies have focused on the existence of MT and its role in subcellular distribution of cadmium.7 In the present study the synthesis of MT as a possible mechanism by which perch adapt to cadmium contamination was investigated in a wild population of perch. An increased MT content of perch liver was found to correlate to an increase in cadmium present in the liver. 相似文献
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Wind profile data within the first two kilometres of a coast have been used to study the wind field modification downstream of this surface discontinuity. The land area is generally very flat, having an overall roughness length of 0.04 m. A wind model, suitable for practical applications and inexpensive to run, has been tested against the data and was found to give satisfactory results. Knowing the climatological statistics of wind and stratification, e.g., at the coast, the model may thus be used to estimate, on a climatological basis, how the wind field is modified with distance inland, at least in areas with only minor topography. This type of information is of great importance when locating wind turbines. It is in these cases also important to know the statistics of the internal boundary-layer (IBL) height, as the turbulence intensity may be quite different in and above the IBL, which in turn may influence load and fatigue calculations. Using the wind profile data, the IBL height was clearly discernible in the majority of cases. Having very unstable stratification over land, the IBL height could, however, not be determined from the wind profiles, as the wind in these cases did not decrease inland. This result was also obtained using the wind model. A simple model of the type z
IBL = a · x
b, was instead tested, and was shown to give reasonable results. 相似文献
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Scenarios indicate that the air temperature will increase in high latitude regions in coming decades, causing the snow covered
period to shorten, the growing season to lengthen and soil temperatures to change during the winter, spring and early summer.
To evaluate how a warmer climate is likely to alter the snow cover and soil temperature in Scots pine stands of varying ages
in northern Sweden, climate scenarios from the Swedish regional climate modelling programme SWECLIM were used to drive a Soil-Vegetation-Atmosphere
Transfer (SVAT)-model (COUP). Using the two CO2 emission scenarios A and B in the Hadley centres global climate model, HadleyA and HadleyB, SWECLIM predicts that the annual
mean air temperature and precipitation will increase at most 4.8°C and 315 mm, respectively, within a century in the study
region. The results of this analysis indicate that a warmer climate will shorten the period of persistent snow pack by 73–93 days,
increase the average soil temperature by 0.9–1.5°C at 10 cm depth, advance soil warming by 15–19 days in spring and cause
more soil freeze–thaw cycles by 31–38%. The results also predict that the large current variations in snow cover due to variations
in tree interception and topography will be enhanced in the coming century, resulting in increased spatial variability in
soil temperatures. 相似文献
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Manfred Sthli Lars Nyberg Per‐Erik Mellander Per‐Erik Jansson Kevin H. Bishop 《水文研究》2001,15(6):927-941
A physically based SVAT‐model was tested with soil and snow physical measurements, as well as runoff data from an 8600 m2 catchment in northern Sweden in order to quantify the influence of soil frost on spring snowmelt runoff in a moderately sloped, boreal forest. The model was run as an array of connected profiles cascading to the brook. For three winter seasons (1995–98) it was able to predict the onset and total accumulation of the runoff with satisfactory accuracy. Surface runoff was identified as only a minor fraction of the total runoff occurring during short periods in connection with ice blocking of the water‐conducting pores. Little surface runoff, though, does not mean that soil frost is unimportant for spring runoff. Simulations without frost routines systematically underestimated the total accumulated runoff. The possibility of major frost effects appearing in response to specific combinations of weather conditions were also tested. Different scenarios of critical initial conditions for the winter, e.g. high water saturation and delayed snow accumulation leading to an increased frost penetration, were tested. These showed that under special circumstances there is potential for increased spring runoff due to soil frost. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Sara E. Vero Nandita B. Basu Kimberly Van Meter Karl G. Richards Per-Erik Mellander Mark G. Healy Owen Fenton 《Hydrogeology Journal》2018,26(1):7-22
The efficacy of water quality policies aiming to reduce or prevent nitrate contamination of waterbodies may be constrained by the inherent delay or “time lag” of water and solute transport through unsaturated (soil) and saturated (groundwater) pathways. These delays must be quantified in order to establish realistic deadlines, thresholds and policy expectations, and to design effective best management practices. The objective of this review is to synthesise the current state of research on nitrate-related time lags in both the European and North American environmental and legislative contexts. The durations of time lags have been found to differ according to climatic, pedological, landscape and management scenarios. Elucidation of these driving factors at a watershed scale is essential where water quality is impaired or at risk. Finally, the existence of time lags is increasingly being acknowledged at a policy level and incorporated into the development of environmental legislation. However, the full impact of these time lags is not yet fully understood or appreciated, and continued outreach and education in scientific, public and policy venues is still required. 相似文献
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This research provides new data and insight on metropolitan areas worldwide. It summarizes new data, derived from satellite images of the world at night, to provide systematic estimates of the economic activity generated by cities and metropolitan areas worldwide. It identifies 681 global metropolitan areas each with more than 500,000 people. Taken as a whole, these large global metropolitan regions house 24 percent of the world's population but produce 60 percent of global output, measured as light emissions. Asia leads the way in global economic urbanization according to our findings, followed by North America, the emerging economies, and Europe. 相似文献
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Rainbow trout were exposed to 200 ppb cadmium in the water during four months at 5°C. The liver, kidney and gills were analyzed for cadmium, copper, zinc and metallothionein. Cadmium accumulated in all three organs and reached the highest concentration in the kidney. The zinc and copper concentrations were not altered during the experiment. The metallothionein concentration was significantly higher in liver of exposed fish than in control fish after three months. The kidneys reached significantly elevated levels of metallothionein in the exposed group after four months. These results demonstrate that metallothionein is induced by cadmium after exposure to the metal via water. 相似文献