Influence of spot mounding on height growth and tending of Norway spruce: case study in Latvia

Norway spruce is commonly regenerated by planting and disc trenching is by far the most widely used soil preparation method in Latvia; however, in specific site conditions other methods might be beneficial. Therefore aim of our study was to assess influence of spot mounding on early growth and tending of Norway spruce in hemiboreal forests. Spot mounding was compared with disc trenching or no soil preparation in central part of Latvia (57° N 24° E) in five different forest types, where two-year-old containerized Norway spruce seedlings were planted. Influence of soil preparation method on tending was assessed in the same region in two different sites in a single forest type on drained fertile mineral soil. Spot mounding had positive effect on the height increment of the dominant trees at the 6^th to 8^th growing season. Mean height of Norway spruce at the end of 8^th growing season on mounds significantly exceeded that on unprepared soil: 179 ± 6.5 and 152 ± 6.2 cm, respectively. Similarly mean height on mounds was significantly larger than on furrows: 209 ± 3.9 and 154 ± 4.0 cm, respectively. Projective vegetation cover before the tending was significantly higher in spot-mounded, but after - in disc trenched sites. Networking time for brashsaw operators in spot-mounded (478 min/ha^-1) and disc trenched (462 min/ha^-1) sites was similar (p > 0.05). Overall, spot mounding ensured more suitable microenvironment resulting in higher productivity of planted trees and had no negative effect on quality or efficiency of tending, therefore its wider use is recommended.