article id 5505,
Swaying of trees as caused by wind: analysis of field measurements.
article id 5505.
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Measurements of wind and subsequent swaying of two Scots pines (Pinus sylvestris L.) were made at stand edge conditions. The horizontal windspeed was measured ten meters outside of the stand edge for four heights using cup anemometers. The compass directions were determined using a directional vane placed above the canopy. Tree swaying was measured by accelerometers at xy-coordinates. The shape of the wind profile at the stand edge varied to some degree depending on windspeed, but the form was a logarithmic one. Swaying of trees increased along with increasing windspeed. Furthermore, swaying was more or less irregular in relation to xy-coordinates, but it occurred, however, mainly perpendicularly to the direction of mean windspeed. The maximum bending of trees to the direction of mean windspeed varied also only little for various gusting windspeeds (average windspeed of 20 seconds) and dynamic wind loads. The maximum bending of trees was also in most cases less or equal to those predicted on the basis of static wind loads, when the mean windspeed for static load is taken as equal to the gusting windspeed.
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Category: Research article
article id 681,
category Research article
Open-top chamber fumigation system for exposure of field grown Pinus sylvestris to elevated carbon dioxide and ozone concentration.
article id 681.
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An open-top chamber fumigation system was built in a young Scots pine stand to study the effects of realistic elevated ozone (O3) and carbon dioxide (CO2) concentrations and their combination on trees in natural conditions. Doubled CO2 concentration compared to present ambient concentration, and O3 concentration between 40 ppb and 70 ppb in the first study year (1994) and doubled O3 concentration in years 1995 and 1996 were the target concentrations in the chambers. The O3 concentration in the chambers was successfully maintained close to the target concentration and differences between chambers were small. The mean CO2 concentration in the CO2 treatment was ca. 100 ppm below the target, but was maintained at this level throughout the growing season. Two degrees higher mean air temperature and slightly lower light intensity compared to open air were measured in the chambers. The operation of the fumigation system was satisfactory during the three study years and repeatability of the gas treatments can be regarded good in this low cost exposure system.