Weathering processes and soil evolution under trees

Within the current project, we focus on the problem of rock weathering processes and soil evolution under tree root impact. Our working hypothesis says that tree roots significantly contribute to weathering processes and alter soil properties. Through this, they change the course of geomorphic processes on hillslopes: for instance, erosion, mass movements, and soil creep. Soil samples were taken from two localities in Poland: 1) Sącz Beskidy Mountains, Outer Western Carpathians, SE Poland, and 2) the Stołowe Mountains, the Middle Sudety Mountains, SW Poland. We analyzed 145 soil samples: 111 samples from the Sącz Beskidy Mountains (one study plot) and 34 samples from the Stołowe Mountains (two study plots). The samples were taken from different parts of the tree root zone (rhizosphere, rock cracks) and control positions not occupied by trees and having no evidence of the past tree growth in the place. The following analyses have been conducted: the content of Fe and Al (amorphous and labile forms), the content of N, C, and soil pH. The results were analyzed statistically using ANOVA and ordination methods (PCA, RDA). In the Żegiestów plot, reference soil samples differ significantly from other microsites of the root zone except for rhizospheric soils samples. It applies to all chemical compounds and soil pH. In the Stołowe Mountains plots, reference soil plots differ significantly from all other microsite soils of the root zone. There is a strong correlation between Fe and Al forms and N and C in both study plots, whereas soil pH is negatively correlated with other chemical compounds. Our results suggest an essential role of trees and tree root systems in modifying weathering processes and soil properties in temperate forests.

The study has been financed by the Polish National Science Centre (project no: NCN2019/33/B/ST10/01009).