Water mapping in Scots pine stands after thinning

Abstract: Climate change is an ongoing issue in various fields, including forestry. More frequent and severe droughts have been already noted around the world, also in Europe. Visible reduction in available water in forests has adverse consequences such as increased tree mortality, higher vulnerability and smaller growth. Appropriate silviculture treatment can improve forest conditions. Proper thinning practices can reduce belowground competition for water. In the current study, water with a detectable isotope (deuterium, 2H) was applied in Scots pine stands with different intensities of thinning in order to investigate water route and horizontal root systems structure. Based on the amount of the label in the sapwood cores of trees, water uptake was examined. In addition the sapwood area of each analysed tree was calculated. Knowing the exact location of trees, the water route on the plot was mapped. The results showed a strong correlation between the place of water application and the distance of a tree. Belowground roots overlap was proven and reached 3,5 trees /m2. In heavily thinned plots labelled trees uptook the biggest amount of 2H. There was no correlation between the sapwood area of a tree and the amount of uptaken label. Visual presentation of trees distribution showed belowground avoidance of competition – root systems are not developed uniformly around tree stem. Although there are some limitations of this study such as the short time between thinning and experiment establishment, the results obtained gave a valuable insight into the root system and connected with other research, including examination of root development after thinning in a few years, can be helpful and useful in adjusting thinning practice in face of lack of water in the forest.