Soil Water Storage and Root Distribution under Picea abies and Fraxinus excelsior Plantations

The interaction between forest vegetation and soil can highly affect the soil water balance. In a holistic approach, forest managers are expected to have a better understanding of these interactions and the importance of soil water conservation. This will certainly lead to a required hydrologic balance in the forests. This research aims at studying the amount of soil water storage at different depths and its connection with changes in vegetation types and their root distribution. To this aim, soil volumetric water content and root distribution data collected under Picea abies and Fraxinus excelsior plantations were used to determine the soil water storage for different soil layers including 20, 40, 60, and 100 cm. A cumulative water storage for the whole soil profile (1-meter profile) was also calculated. Afterwards, the number of roots and the Root Area Ratio (RAR) were determined for different layers of soil with a 10 cm interval. Ultimately, the connections between soil water storage at given layers of soils with their corresponding root numbers and RAR values were investigated for each forest plantation. Friedman and Mann-Whitney non-parametric tests were used to compare the means of soil water storage, number of roots, and RAR values at different layers of soils and plantations studied. According to the results, an increasing trend in soil water storage and a decreasing trend in root numbers (and RAR) can be observed with soil depths. However, both root distribution and soil water storage experience a rapid increase and decrease to a depth of 40 cm, and then the trends remain relatively constant. In most cases, soil water storage at different soil depths and for the 1-meter soil profile under Picea abies was significantly lower than that under Fraxinus excelsior.