Prescribed burning of logging slash in the boreal forest in Finland: Emissions and effects on meteorological quantities and soil properties

Autor: Virkkula, A., J. Levula, T. Pohja, P. P. Aalto, P. Keronen, S. Schobesberger, C. B. Clements, L. Pirjola, A.-J. Kieloaho, L. Kulmala, H. Aaltonen, J. Patokoski, J. Pumpanen, J. Rinne, T. Ruuskanen, M. Pihlatie, H. E. Manninen, V. Aaltonen, H. Junninen, T. Petäjä, J. Backman, M. Dal Maso, T. Nieminen, T. Olsson, T. Grönholm, J. Aalto, T. H. Virtanen, M. Kajos, V.-M. Kerminen, D. M. Schultz, J. Kukkonen, M. Sofiev, G. De Leeuw, J. Bäck, P. Hari, and M. Kulmala
Jazyk: angličtina
Rok vydání: 2014
Popis: A prescribed fire experiment was conducted on 26 June 2009 in Hyytiälä, Finland, to study aerosol and trace gas emissions from prescribed fires of slash fuels and the ef- fects of fire on soil properties in a controlled environment. A 0.8 ha forest near the SMEAR II measurement station (Sta- tion for Measuring Ecosystem-Atmosphere Relations) was cut clear; some tree trunks, all tree tops and branches were left on the ground and burned. The amount of burned organic material was ∼46.8 tons (i.e., ∼60 tons ha−1). The flaming phase lasted 2 h 15 min, the smoldering phase 3 h. Measure- ments were conducted on the ground with both fixed and mo- bile instrumentation, and in the air from a research aircraft. In the middle of the burning area, CO2 concentration peaked around 2000–3000 ppm above the baseline, and peak verti- cal flow velocities were ∼9 m s−1, as measured with a 10 Hz 3-D sonic anemometer placed within the burn area. In the mobile measurements the peak particle number concentra- tions were approximately 1–2 × 106 cm−3 in the plume at a distance of 100–200 m from the burn area. On the ground at the SMEAR II station the geometric mean diameter of the mode with the highest concentration was 80 ± 1 nm dur- ing the flaming phase and in the middle of the smoldering phase, but, at the end of the smoldering phase, the largest mode was 122 nm. In the volume size distributions, geomet- ric mean diameter of the largest volume mode was 153 nm during the flaming phase and 300nm during the smolder- ing phase. The lowest single-scattering albedo of the ground- level measurements was 0.7 in the flaming-phase plume and ∼0.9 in the smoldering phase. Elevated concentrations of several volatile organic compounds (VOC) (including ace- tonitrile, a biomass burning marker) were observed in the smoke plume at ground level. Measurements at the forest floor (i.e., a richly organic layer of soil and debris, charac- teristic of forested land) showed that VOC fluxes were gen- erally low and consisted mainly of monoterpenes, and VOC flux peaked after the burning. After one year, the fluxes had nearly stabilized close to the level before the burning. The clear-cutting and burning of slash increased the total long- term CO2 release from the soil, and altered the physical, chemical and biological properties of the soil, such as in- creased the available nitrogen contents of the soil, which in turn, affected the long-term fluxes of greenhouse gases.
Databáze: OpenAIRE
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