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Effects of site preparation and stump harvest on carbon dynamics in forest soils

Mjöfors, Kristina (2015). Effects of site preparation and stump harvest on carbon dynamics in forest soils. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2015:69
ISBN 978-91-576-8336-6
eISBN 978-91-576-8337-3
[Doctoral thesis]

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Abstract

Efforts are being made to substitute fossil fuels with renewable alternatives to address increasing concerns regarding global climate change driven by anthropogenic emissions of CO₂ and other greenhouse gases. Stumps of harvested trees could make a significant contribution to these efforts in Scandinavia. Silvicultural measures may all impact on greenhouse gas fluxes. Site preparation, being one of these, is conducted on a major share of the annual clear-cut area in Sweden to promote seedling development. More information on the effects of stump harvesting and site preparation methods, on soil and ecosystem C stocks is needed as all of these treatments disturb the soil, creating for instance areas of exposed mineral soil, and/or a double humus layer and/or a humus layer mixed with mineral soil. The overall aim of this thesis is to assess changes in C stocks (in soils and ecosystems overall) following several common mechanical site preparation methods and stump harvest.

The results and conclusions yielded by the thesis are based on in-situ measurements of the following data: soil-surface CO₂ flux (Rs), weight loss of needle litter and coarse roots in litterbags, soil temperature and moisture, and assessments of C stocks in soil, ground vegetation and trees as well as percentage area disturbed by the different methods. The results showed that site preparation and stump harvests have no or reducing effects on soil-surface CO₂ flux (Rs), and that any initial increase in Rs is limited to the first few weeks. Removal of the humus layer, thereby exposing the mineral soil, led to lower Rs than in control plots. However, a double humus layer did not result in higher than control Rs values. Thus, Rs seems to be related to the presence of a humus layer rather than its thickness (if present). Mixing the humus layer and mineral soil did not lead to higher Rs than control fluxes, and in one experiment it even led to lower Rs. The location of incubated litter (in bags) strongly influenced the decomposition rate, as buried litter decomposed more rapidly than litter placed on the soil-surface. However, the higher decomposition rates associated with buried litter were not accompanied by increases in Rs from the entire soil profile.

After three decades, the most pronounced effects of site preparation on the entire ecosystem C stocks were increases due to enhancement of the growth of planted trees (Pinus sylvestris, Picea abies and Pinus contorta), relative to control.

General conclusions are that site preparation and stump harvests do not lead to reductions of the soil or ecosystem C stocks, and in the long-term promoting strong growth of forest trees is the most important measure for securing C stocks of entire forest ecosystems, including those of the soil.

Authors/Creators:Mjöfors, Kristina
Title:Effects of site preparation and stump harvest on carbon dynamics in forest soils
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :20 May 2015
Depositing date:20 May 2015
Volume:2015:69
Number of Pages:66
Papers/manuscripts:
NumberReferences
IStrömgren, M., Mjöfors, K., Holmström, B. & Grelle, A. (2012). Soil CO₂ flux during the first years after stump harvesting in two Swedish forests. Silva Fennica, 46, 67-79.
IIStrömgren, M. & Mjöfors, K. (2012). Soil-CO₂ flux after patch scarification, harrowing and stump harvest in a hemi-boreal forest. Scandinavian Journal of Forest Research, 27, 754-761.
IIIMjöfors, K., Strömgren, M., Nohrstedt H-Ö, Gärdenäs A.I (2015). Impact of site-preparation on soil-surface CO₂ fluxes and litter decomposition in a clear-cut in Sweden. (Silva Fennica, In revision)
IVMjöfors, K., Strömgren, M., Nohrstedt H-Ö, Johansson M-B, Gärdenäs A.I (2015). Indications that site preparation in the long-term increases overall carbon stocks in coniferous boreal forests but not in their soils. (Manuscript)
Place of Publication:Uppsala
Publisher:Department of Soil and Environment, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8336-6
ISBN for electronic version:978-91-576-8337-3
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:K Forestry > K10 Forestry production
P Natural resources > P01 Nature conservation and land resources
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
Agrovoc terms:coniferous forests, forest soils, mineral soils, carbon stock assessments, site preparation, stumps, humus, litter, degradation, sweden
Keywords:soil-surface CO₂, decomposition, Carbon stock
URN:NBN:urn:nbn:se:slu:epsilon-e-2675
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-2675
ID Code:12253
Faculty:S - Faculty of Forest Sciences
Department:(NL, NJ) > Dept. of Soil and Environment
(S) > Dept. of Soil and Environment
Deposited By: K Mjöfors
Deposited On:22 May 2015 11:23
Metadata Last Modified:01 Jun 2015 08:15

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