Possible implication of reconstructed natural fire regimes and climate in northeastern Mongolia

Abstract:

Major drivers of changes in forested ecosystems of northeastern Mongolia are fire, climate, and humans. However, specific interactions and impacts of these three factors are poorly known. Such information is critical for forecasting future ecosystem change in light of climate change, and for more informed management in light of increased human use of natural ecosystems. We reconstructed centuries-long fire histories in Scots pine (Pinus sylvestris L) forests in northeastern Mongolia using tree-ring data, and compared them to both human and climate histories to examine past interactions of these three factors. Reconstructed fire events were recorded in a total of 209 samples collected from 28 sites spanning 1650-2009. The results clearly showed fires were frequent from the beginnings of the records to the early 1900s, with mean fire intervals of 11-12 years (minimum fire intervals of 6-8 years). Mean fire intervals changed to 20-22 years after the 1920s, and several sites showed probable impacts of fire suppression efforts after the end of WWII. However, after the end of Soviet influence on fire suppression efforts after 1990, fire occurrences in all sites picked up again. The reconstructed hydroclimatic data showed that this region has experienced wet conditions during the 20th century, and droughts in the early 21st century are not severe as relative to previous centuries. Superposed epoch analysis (SEA) examined climate effects on these reconstructed fire events showed that climate is definitely playing a main role in regional fire years in forests of Northeast Mongolia.These result document that fires have always been present and frequent in Mongolia Scots pine forests, but have varied through time both in response to variations in climate and human forcings. These data also serve to guide fire and forest management into the future as climate and human land use pressures change.