Distribution of macro charcoal from forest fires in shallow soils of the Northern Alps
- 278 Downloads
In our study area in the Northern Limestone Alps (Austria), forest fires are rare; however, they may be stand-replacing and can trigger severe erosion. The aim of our study was to find out if where and to which extent charcoal is stored in the Rendzic Leptosols of the affected slopes and if the charcoal can be used to reconstruct earlier forest fires.
Materials and methods
We took soil samples from shallow soil pits on >20 slopes affected by forest fires in the last few centuries. On four slopes of different age after fire (2003, 1962, 1946 and 1250 AD), samples were taken from each soil horizon. We pre-screened the samples in the field and investigated 167 of them in the laboratory for macroscopically visible charcoal fragments (>1 mm). We calculated the percentage of charcoal and derived a simplified model of spatial distribution and temporal behaviour.
Results and discussion
Mean charcoal concentration was 0.452 % (by bulk weight) for known forest fire sites and 0.067 % in their presumably unburnt surrounding. Significantly elevated charcoal concentrations (exceeding 0.15 %) can be used as evidence to delimit historical forest fire sites, even if there is a certain background concentration in the surrounding due to aeolian transport and to earlier fires, and small-scale spatial variability is very high. Charcoal may be found in very different positions within the profiles; frequently, the particles are concentrated on top of the Ah horizon and a post-fire O horizon has developed on top of them. 14C dating of buried charcoal assemblages revealed the existence of earlier events (c. 3 000–500 BP) well before the last known historical forest fires.
The vertical distribution of charcoal fragments is influenced by fire characteristics, elapsed time and by the intensity of erosion. Charcoal concentration and mean particle size decrease with age due to erosion and translocation; however, if erosion is moderate, charcoal can be conserved for centuries. A conceptual model of vertical charcoal distribution is presented.
KeywordsAlps Charcoal Forest fire Soil erosion
We wish to express our thanks to the Austrian Science Fund (FWF) for funding in the context of the Alpine Wildfires project (Lise-Meitner M982-N10). Furthermore, many thanks for the helpful comments of three anonymous reviewers and to John Boardman (ECI Oxford) for proofreading.
- Crutzen PJ, Goldammer JG (eds) (1993) Fire in the environment: the ecological, atmospheric, and climatic importance of vegetation fires. Wiley, ChichesterGoogle Scholar
- FAO (2007) Fire management-Global Assessment 2006. FAO Forestry Paper 151Google Scholar
- Grabherr W (1936) Die Dynamik der Brandflächenvegetation auf Kalk-und Dolomitböden des Karwendels. Beiheft Botanisches Centralblatt LV/B 1(2):1–94Google Scholar
- Sass O, Wetzel K-F, Friedmann A (2006) Landscape dynamics of sub-alpine forest fire slopes in the Northern Alps. Z Geomorphol Suppl 142:207–227Google Scholar
- Shakesby RA, Doerr SH (2006) Wildfire as a hydrological and geomorphological agent. Earth Sci Rev 74:269–307Google Scholar
- Skjemstad JO, Graetz RD (2003) The impact of burning on the nature of the soil organic matter in Australia. Agronomia 37:85–90Google Scholar
- Tirol Atlas (2007) Institute of Geography, University of Innsbruck: http://tirolatlas.uibk.ac.at/ Accessed Oct 2013
- Vacik H, Arndt N, Arpaci A, Koch V, Müller M, Gossow H (2011) Characterisation of forest fires in Austria. Austrian J Forest Sci 128:1–32Google Scholar
- Weber K (1999) Vegetations-und Klimageschichte im Werdenfelser Land. Augsburger Geographische Hefte 13Google Scholar