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3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/2490

Sirvi

Sirvi 3. Doktoritööd Märksõna "agrarian history" järgi

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    Role of historical slash and burn cultivation in the development of cultural landscapes and forest vegetation in south Estonia
    (Eesti Maaülikool, 2018) Tomson, Pille; Sepp, Kalev; Bunce, Robert Gerald Henry; Institute of Agricultural and Environmental Sciences; Lindbladh, Matts (opponent)
    The objective of this PhD thesis was to estimate the effects of historical rotational slash and burn cultivation on the formation of southern Estonian cultural landscapes and forest vegetation. Slash and burn cultivation was practised in Northern and Central Europe until the 20th century. With regard to Estonia, previous studies have suggested that slash and burn cultivation resulted in soil depletion, podsolization and the formation of species-poor forest habitats. This research was based on land use maps drawn in Livonian governorate in the 19th century. These maps depict the areas that were regularly used for slash and burn cultivation (buschlands in Baltic-German). Study areas were located in six protected areas across south-eastern Estonia. Map analysis demonstrated that in the studied areas buschlands used to cover 35-45% of total farmlands. The hilly landscapes of south-eastern Estonia, comprising Albeluvisols and Haplic Albeluvisols in moraines, were particularly suitable for slash and burn cultivation. Buschlands should be regarded as a specific category of land, which does not correspond to modern land cover or land use units. By the end of the 20th century, 78% of these lands had become afforested. The most common forest site type in former buschlands is Oxalis. The field research observed the forests grown in both former buschlands and areas mapped as forest in the 19th century. Different uni- and multivariate statistical methods were applied. The differences in vegetation occurred due to postponed forest development in buschlands, not due to fire. The analysis could not identify any fire-prone species or vegetation composition, which would reveal the changes in soil properties. The registered chemical properties of soil likewise did not differ across buschlands and former forest sites. Today, buschlands comprise secondary forests with impoverished ground vegetation, rather than semi-natural habitats that would require special management. Macroscopic fragments of soil charcoal were found in 97% of the observed sites. Slash and burn cultivation have therefore been an important factor in forming the soil charcoal deposits in boreal forests. The depth of charcoal can be associated with land use history. The charcoal fragments collected from the humus layer of buschlands dated from 1566 to 1805 calAD. At the footslopes of buschlands, slash and burn cultivation created characteristic field banks which consist of humus with dispersed charcoal. Similar banks were found in 22% of forest sites, which indicates that slash and burn cultivation was practised in larger areas than shown in the 19th century maps. The results demonstrate that the role of slash and burn cultivation in the formation of landscapes has previously been underestimated, while the effects on forest vegetation have been overestimated.