Historic disturbance events overruled climatic factors as drivers of ruderal species distributions in the Scandinavian mountains

The contemporary interaction of climate and disturbance drives vegetation composition and species distribution shifts, making their respective roles difficult to disentangle. This study describes the long‐term ruderal plant species distributions along the ‘Rallarvägen' in Abisko, subarctic Sweden. This trail currently serves as a hiking trail but was initially created as a construction road for a railroad from 1898 to 1903 and is paralleled by the E10 Highway since 1982. Using vegetation and climate data from 1903, 1913, 1983, and 2021, we found that warm‐adapted ruderal plant species were common along the Rallarvägen shortly after railroad construction in the early 20th century. Interestingly, many of these native and non‐native ruderals with relatively high temperature affinity that were present in 1903 and 1913 have since disappeared and have not reappeared, despite the substantial increase in regional temperature in recent decades. In addition, the historical disturbances have had long‐lasting effects on the current spatial distribution of the ruderal vegetation. Most ruderals still reside close to the railroad tracks and are progressively filtered out with increasing distance from anthropogenically disturbed introductory points, such as train stations, where they peak in species richness – a process we term ‘horizontal directional ecological filtering', in parallel to the established concept of ‘directional ecological filtering' along elevational gradients. The historical record of ruderal plant species in the region, influenced by a century‐old railroad construction, emphasizes the importance of knowing a system's disturbance history for understanding current vegetation dynamics and anticipating its future in a changing climate.