Långsiktig uppföljning efter naturvårdsbränningar i Dalarna: trädmortalitet och plantföryngring

• Main Author: Hammare, Annie
• Format: Others
• Language: Swedish
• Published: Uppsala universitet, Institutionen för biologisk grundutbildning 2017
• Subjects: naturvårdsbränning; skogsbrand; död ved; plantföryngring; viltbete; Natural Sciences; Naturvetenskap
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-322856

The County Administrative Board of Dalarna conducts controlled conservation burnings in nature reserves to increase biodiversity. The fire increases diversity in several ways by attracting fire dependent organisms, increasing the number deciduous trees, enhancing the volume of dead wood and bringing morphological diversity as fire scars on trees. After the burnings deciduous trees usually increase, but to reduce grazing from browsers (who would consume most of the deciduous biomass) fences can be used to exclude the grazers.   In the first part of my study I inventoried tree status after two controlled nature conservation burnings in eastern and northern Dalarna (Trollmosseskogen and Rensjön). The aim was to increase the knowledge of fire effects on trees and to find out if the desired results were achieved on diversity. The results show that the number of tree species has increased in Trollmosseskogen. Fire damages on trees were more common in Rensjön than in Trollmosseskogen. In both nature reserves the volume of dead wood has increased successively over time which suggests that the fire gives prolonged effects on tree mortality. This shows that long-term inventories are important to do to get an overall picture on the effect on tree mortality.   The second part of my study deals with Vändleberget, a nature reserve that was fenced 2005 after burning to protect particularly deciduous tree re-growth from browsers. Tree inventories and measurements were performed by placing plots both inside and outside the fenced area. Tree height and tree diversity showed a trend towards higher levels inside the fenced area, but the differences were not significant. Stem density, in total, is very high in the investigated area in Vändleberget and therefore I suggest selective logging to promote deciduous trees such as aspen (Populus tremula), ash (Fraxinus excelsior), oak (Quercus robur) and goat willow (Salix caprea). Spruce (Picea abies) and some trivial deciduous trees, especially birch (Betula spp.) can be removed. When the remaining trees are about four meters high I suggest that the fence can be taken down, as at that height the browsers can no longer harm the deciduous trees severely by eating the top of the trees or physically breaking the tree trunk.    To conclude, I found that conservation burning increases biodiversity on several levels such as number of species and morphological diversity. Fences can be used to reduce grazing which could promote tree diversity.