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