Mechanical stability of Scots pine across soil conditions and regeneration practices in hemiboreal forests

The intensification of wind disturbances increases the importance of maintaining tree mechanical stability in Northern European forests. Soil preparation during forest regeneration may influence long-term stability by modifying rooting conditions. We assessed the effects of site conditions, defined as combinations of soil type (e.g., freely draining mineral, waterlogged mineral, and drained peat soils) and site-specific soil preparation methods (disc trenching and mounding), on the mechanical stability of mid-aged Scots pine (Pinus sylvestris L.) stands in hemiboreal forests of northeastern Europe (Latvia). A static tree-pulling test was used to quantify resistance to primary and secondary failure, as well as the post-primary-failure stability margin. Trees growing on unprepared freely draining mineral soils exhibited the highest resistance to both primary and secondary failure, whereas trees on waterlogged mineral and peat soils showed reduced stability and a predominance of uprooting. Mounding on waterlogged sites did not consistently enhance long-term mechanical stability. Overall, soil physical properties and their interaction with tree size outweighed the long-term effects of soil preparation alone, highlighting the need for site-specific, climate-smart forest management strategies to enhance wind resistance in hemiboreal forests.