The effect of soil cultivation methods on rooting depth of young Sitka spruce (Picea sitchensis (Bong.) Carr.) trees on wet mineral soils in Ireland

The research reported in this article, carried out in the period 1995-1997, was part of a large-scale project investigating the impact of soil cultivation/drainage practices upon water-table depth, rooting depth, root architecture and biomass production of young Sitka spruce (Picea sitchensis (Bong.) Carr.) trees on surface water gley soils. On two sites in the mid-west of Ireland, a total of 207 trees, 5 and 7 years old, were excavated over a 2-year period, during which water-table depths were monitored. Results showed that neither mound drains nor mole drains had as great an effect on tree rooting depth as the presence of a planting mound. In the cultivation treatments that included planting on mounds, tree roots were mainly confined within the mounds, with the exception of the tree root systems in the mole-and-mound treatment on one of the sites, where the mean root depth of both the 5-year-old and 7-year-old trees reached almost 20 cm below the original soil level. Continued evaluation of these experiments is required to assess the long-term effectiveness of the different drainage and cultivation methods in increasing rooting depth and improving tree stability.