ISSN:
1573-2932
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
Notes:
Abstract Net photosynthesis (Phn), leaf resistance, and transpiration of a naturally occurring hybrid of Pinus contorta Loud. and P. banksiana Lamb. (lodgepole pine × jack pine) were measured as part of a case study investigating the chronic exposure of a forest ecosystem to low concentration S gas emissions from a S recovery gas plant in west central Alberta, Canada during 1975 and 1976. The objectives of this portion of the case study were to determine if chronic low concentration exposure to S gas emissions had produced any accumulative effect on the Phn of the pine trees and to determine if ambient SO2 concentrations had any immediate effect on Phn. Sulphur dioxide concentrations above 0.01 ppm occurred on 87% and 71 % of the monitoring days at the intensive experimental site during 1975 and 1976, respectively. The maximum half-hour daylight concentrations of SO2 were 0.21 ppm and 0.12 ppm in 1975 and 1976, respectively. Photosynthetic performance was not affected by controlled SO2 exposures in the laboratory below 0.23 ppm for 30 min, but it was always depressed by exposure to SO2 above 0.25 ppm for 30 min. Ambient concentrations of SO2 in the field had no measurable immediate effect on Phn. However, the seasonal mean rates of Phn of current year (1976) and 1-yr old (1975) pine foliage were significantly lower at the frequently exposed sites than the infrequently exposed site (3.9 and 3.4 mg CO2 g dw−1 h−1 versus 6.4 and 5.1 mg CO2 g dw−1 h−1, respectively). The current year's foliage sampled at the sites infrequently exposed to S gases achieved positive rates of net CO2 exchange one to three weeks earlier than foliage from the three frequently exposed sites. Foliar sulphate-S concentrations, however, were only poorly correlated with Phn rates. The reduced rates of net photosynthesis and shorter period of positive net CO2 exchange in current year's foliage frequently exposed to S gas emissions combined with the shorter needle retention time and foliar chlorosis may partly explain the previously reported lowered productivity of these trees as measured by basal area increment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00208404
Permalink
