Abstract
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 roots 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 root chronology was found for the exposed trampled roots (r = 0.69, p < 0.001). In the trampling zone, the root-stem radial growth coherency was determined primarily by root 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.
Highlights
Increased trampling activity associated with hiking has a substantial ecological impact (Leung and Marion, 2000; Cole, 2004; Marion and Olive, 2006)
Trampling activity together with natural geomorphic processes induce common root exposure within the trail surface in Abbreviations: stem-root RGC, stem-root radial growth coherency; PRESSURE SITE (PRES), tree stems subjected to trampling pressure; REFERENCE SITE (REF), tree stems in a reference site; REF root, root in a reference site; MRWs, mean ring width; EREs, events of root exposure; PRDs, pronounced resin ducts
The largest variation in ring widths was determined for lateral exposed roots subjected to trampling along the hiking trail
Summary
Increased trampling activity associated with hiking has a substantial ecological impact (Leung and Marion, 2000; Cole, 2004; Marion and Olive, 2006). Trampling effects, both from humans and animals, can adversely impact natural habitats and forested trail surfaces (Tomczyk and Ewertowski, 2013), commonly leading to the degradation of plant communities (Kuss and Graefe, 1985; Sun and Walsh, 1998; Pescott and Stewart, 2014; but see Kidron, 2016, who reports an increase in annual plant cover following goat trampling on dune-covered biocrusts). Both exposed tree roots and stems growing along the trail can be used for dendrochronological analysis, combined studies using both are very rare
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