The impact of increasing fire frequency on forest transformations in southern Siberia

Wildfires are one of the main disturbances that impact structure, sustainability, and carbon budget of Siberian forests, as well as infrastructure and human safety. The Zabaikal region in the south of Siberia is characterized by one of the highest levels of fire activity in Russia. We have estimated fire disturbances in the Zabaikal region using both a satellite fire dataset and official fire statistics. Both datasets show a trend of increasing fire activity in the region. According to the satellite fire dataset, from 1996 to 2015 total annual area burned in the Zabaikal region varied from 0.12 to 6.33 M ha with forest area burned accounting for 0.04-5.60 M ha. The highest fire activity was observed in the central and southern parts of the Zabaikal region. About 13% (3.88 M ha) of the total forest area in the Zabaikal region was burned more than once during the 20-yr period of observation, with many sites burned multiple times. Fire disturbance was highest in forests dominated by Scots pine. We have evaluated fire impact on fuel loads, carbon emissions, and tree regeneration on about 150 sites in the light-coniferous (larch or Scots pine dominated) forests of the region. Carbon emissions from fires on repeatedly burned areas were 3-50% of those from previously undisturbed sites. Regeneration density depended on site conditions and fire characteristics. Inadequate regeneration for forest recovery was observed in Scots pine stands on dry nutrient-poor soils as well as on repeatedly-disturbed sites. This regeneration failure is leading to transformation of forests to steppe ecosystems on some sites. We conclude that negative impacts of fire disturbance on forests of the Zabaikal region could be decreased through implementation of fire prevention measures with emphasis on education of local communities as well as construction and maintenance of a fuel break system, first of all, nearby settlements and tree plantations. (C) 2016 Elsevier B.V. All rights reserved.