Does distance from a sand mine affect needle features in Pinus sylvestris L.?

Needle traits of P. sylvestris exhibit high variability depending on habitat conditions and thus may be used to assess the effect of anthropopressure on tree condition in this species. The variability of 22 needle features of Scots pine, collected from populations growing at different distances from the Bełżec-Podlesina eolian sand mine located in Poland, was investigated. No similar research has been conducted to date. The needles were collected from 40 trees growing in similar habitat conditions on four study plots located at a distance of 205.281 to 997.598 m from the sand mine. In total, 3460 needles from 117 samples were measured. It was observed that the distance of the study plots from the sand mine had a statistically significant effect on all the analysed needle traits, with the most extreme values recorded for the needles coming from trees growing on the plots most distant from the sand mine. The characteristics of greatest importance for assessing the impact of the sand mine on needle condition in the studied trees included: needle length/needle width, needle length, needle length/needle thickness, number of stomata on the convex side of the needle/needle length, needle width/resin duct diameter, resin duct diameter, number of stomata on the convex side of the needle/needle width, number of stomata on the concave side of the needle/needle length and number of stomata on the convex side of the needle. The effect of the distance of a given study plot from the sand mine depended on the age of the needles. The analyses confirmed that despite the adaptability of Scots pine to local environmental conditions, the morphological and anatomical characteristics of its needles changed under the influence of anthropopressure. Thus, selected features of the assimilatory organs may be used to monitor the impact of opencast operations on this important forest-forming species.