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Articles containing the keyword 'gas exchange'

Category: Article

article id 5405, category Article
Pertti Hari, Eeva Korpilahti, Toivo Pohja, Pentti K. Räsänen. (1990). A field system for measuring the gas exchange of forest trees. Silva Fennica vol. 24 no. 1 article id 5405. https://doi.org/10.14214/sf.a15557
Keywords: photosynthesis; CO2; monitoring; measuring methods; transpiration; environment; gas exchange; respiration
Abstract | View details | Full text in PDF | Author Info

A third generation of forest tree gas exchange measuring system design for the use in the field is described. The system is designed to produce data for determining the dependence of the rate of tree photosynthesis, respiration and transpiration on environmental factors. The system consists of eight cuvettes, a tubing system, two infrared gas analysers, an air flow controller, a data logger, and a computer. The measuring cuvette is a clap type, i.e. it is mostly open, only closing during measurement. CO2 exchange is measured as the change in the cuvette concentration of CO2, and, transpiration is measured as the increase in water vapour concentration while the cuvette is closed. The environmental factors measured are temperature, irradiance and air pressure. The system was planned in 1987 and constructed in 1988. It worked reliably in late summer 1988 and the quality of data seems to be satisfactory. 

The PDF includes an abstract in Finnish.

  • Hari, E-mail: ph@mm.unknown (email)
  • Korpilahti, E-mail: eeva.korpilahti@luke.fi
  • Pohja, E-mail: tp@mm.unknown
  • Räsänen, E-mail: pr@mm.unknown

Category: Article

article id 7171, category Article
Erkki Lähde. (1966). Vertical distribution of biological activity in peat of some virgin and drained swamp types. Silva Fennica vol. 81 no. 6 article id 7171. https://doi.org/10.14214/aff.7171
Keywords: drained peatlands; peat; decomposition; peatlands; cellulose decomposition; gas exchange; biological activity
Abstract | View details | Full text in PDF | Author Info

The objective of this project was to determine the amount of gas exchange in peat samples collected from several swamps, using the Warburg method in the laboratory measurements. Special attention was directed on the influence of the lowering of the ground water level through drainage, on oxidation-reduction conditions in the samples from both forested and treeless peatlands, by measuring oxygen uptake and CO2 release. The biological activity in situ was determined by the cellulose decomposition rate in the sample plots. The six areas examined were both in drained peatlands and peatlands in natural condition.

The results show that in the sample plots in open swamps there was no consistent differences in the CO2 release rate in peat samples taken from different depths. However, in the sample plots on forested swamps rapid decrease is seen with increasing depth. The decreased biological activity of peat is caused by the oxidation-reduction conditions. The CO2 release rate may also be due to the respiration of tree roots, which are very shallow in peatlands.

The rate of in situ cellulose decomposition experiment and CO2 release indicated by the Warburg measurements appear to be correlated. The results indicate improved conditions for cellulose-decomposing microbes after draining. It is also possible that the biological activity of peat after draining increases to a considerable depth until the decrease of easily decomposable substances limit the activity in an old drainage area. The cellulose decomposition rate would still increase as the oxidation-reduction conditions improve.

  • Lähde, E-mail: el@mm.unknown (email)

Category: Research article

article id 10375, category Research article
Amy Wotherspoon, Nelson Thiffault, Robert L. Bradley. (2020). Resource availability and physiological response of black spruce to scarification in two climatic regions of Québec (Canada). Silva Fennica vol. 54 no. 4 article id 10375. https://doi.org/10.14214/sf.10375
Keywords: Picea mariana; foliar δ18O; foliar δ13C; needle gas exchange; photosynthetic nitrogen use efficiency; water use efficiency
Highlights: Mechanical scarification of clearcut sites in two climatic regions maintained high growth rates of regenerating black spruce 18 years after treatment; In both regions, scarification reduced soil moisture and increased water use efficiency; In the cooler-humid region, scarification improved soil nitrogen mineralization.
Abstract | Full text in HTML | Full text in PDF | Author Info

Scarification is a mechanical site preparation technique designed to create microsites that will favor the growth of planted tree seedlings after clearcutting. However, the positive growth response of black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) to scarification varies across different sites. We hypothesized that this was due to different forms of physiological stress induced by different climates or by the severity of competition from ericaceous shrubs. We thus compared the effects of scarification on black spruce needle gas exchange and other foliar properties, as well as on indices of soil water and nitrogen availability, in relatively warm-dry (Abitibi) vs. cool-humid (Côte-Nord) climates in the province of Québec (Canada). We found a similar positive effect of scarification on tree height in Abitibi and Côte-Nord. Scarification reduced soil moisture in both climatic regions, but increased soil N mineralization in Côte-Nord only. Accordingly, scarification increased the instantaneous water use efficiency in both climate regions, but decreased photosynthetic N use efficiency in Côte-Nord only. In both regions, we found a positive relationship between foliar δ18O and δ13C on scarified plots, providing further evidence that increased growth due to scarification depends on a decrease in stomatal conductance. We conclude that scarification increases total evapotranspiration of trees evenly across the east-to-west moisture gradient in the province of Québec, but also improves long-term soil nutritional quality in a cooler-humid climate.

  • Wotherspoon, Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada E-mail: amy.wotherspoon@usherbrooke.ca (email)
  • Thiffault, Canadian Wood Fibre Centre, Canadian Forest Service, Natural Resources Canada, 1055 du. P.E.P.S., P.O. Box 10380, Québec, G1V 4C7, Canada E-mail: nelson.thiffault@canada.ca
  • Bradley, Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada E-mail: robert.bradley@usherbrooke.ca

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