Climate and wildfire effects on radial growth of Pinus sylvestris in the Khan Khentii Mountains, north-central Mongolia

Abstract

The warming climate of recent decades has led to further aridity of the Mongolian landscape and has had major effects on forest growth and wildfire occurrence. Here, we investigated drought and wildfire effects on the growth of Pinus sylvestris along an ecologically diverse transect in semiarid north-central Mongolia using two separate subsets. Tree-ring width series of the first subset, represented by trees without fire scars, were clustered into three regional chronologies reflecting environmental differences of delineated geo-vegetation zones. Tree-ring growth reflected June drought signal at all three zones. The increasing radial growth trend was found in the dark taiga zone, likely supported by permafrost summer thawing, primarily caused by temperature increases. The second subset, represented by injured trees, showed that most wildfires occurred during the dormant season and in the forest-steppe zone; April–May drought conditions substantially contributed to triggering wildfires. Nevertheless, an increased frequency of wildfires in the study area was not observed, despite temperature increases since 1940. Our study highlights the significance of the effect of the ongoing temperature increase on north-central Mongolian pine forests, and, correspondingly, the need to conserve an endangered ecosystem of the dark taiga and to undertake afforestation activities in devastated pine forests.