Trampling As A Major Ecological Factor Affecting The Radial Growth And Wood Anatomy Of Scots Pine (Pinus Sylvestris L.) Roots On A Hiking Trail

The impact of hiking in forested areas is one of the main factors affecting the condition of tree growth along hiking trails. Trampling causes common exposure of roots and quantification of the human impact on root radial growth and wood anatomy requires careful assessment. To accurately identify the radial growth changes in Pinus sylvestris roots, we conducted a stepwise cross-dating using trampled roots from a hiking trail and reference roots. Such approach was previously not applied in a lowland area. In addition, we investigated the factors that influence the root-stem radial growth coherency, including soil properties, root and trail morphology. Changes in radial growth and wood anatomy were examined in three parts of the root system: buried, transition and trampling zone. The radial growth for each root zone was compared with corresponding stem and reference root and stem chronology. In total, we investigated 204 roots and 97 tree stems for the common period 1970-2015. Missing rings were found to be a common phenomenon in all root zones, except in the exposed lateral mots in the trampling zone. The highest number of wedging and missing rings was observed in the trampling and transition zones, respectively. The total number of wedging rings increased with an increasing distance from the stem. The events of root exposure in the trampling zone were highly coupled with the formation of scars (r = 0.51, p < 0.001) and pronounced resin ducts (PRDs) (r = 0.52, p < 0.001). The majority of the wood anatomical changes (i.e., 84% of scars and 85% of PRDs) were identified in the trampling zone. The highest degree of correlation between raw stem chronology and raw mot chronology was found for the exposed trampled roots (r = 0.69, p < 0.001). In the trampling zone, the mot-stem radial growth coherency was determined primarily by mot type (77.3%) and root age (17.4%), whereas in the buried zone, by the soil organic matter content (55.4%) and soil compaction (39.7%). It has been proved that the record of radial growth and wood anatomy changes in Scots pine roots serve as a valuable ecological archive of trampling impact with high temporal resolution.