Stand establishment and early growth of planted Pinus sylvestris and Picea abies related to microsite conditions
Stand establishment and early height growth of planted Scots pine and Norway spruce trees were investigated in relation to microsite conditions. The 20-year old pure and mixed stands studied are located on a six hectare experimental site with a harsh climate at high altitude in Swedish Lapland. Observations were made on 360 circular sample plots, each with a 3 m radius, laid out in a systematic pattern over the site. The site conditions were measured separately for each sample plot and were related to seedling survival and mortality, height, and height increment of single trees on individual sample plots. The results show that seedling survival and height increment of single trees are correlated with ground vegetation, frost holes, logging residues and stump occurrence at the local level of 3 m circular plots, as well as with local elevation and tree species mixture. In the stand establishment phase, Scots pine was found to be more sensitive to site conditions than Norway spruce. For Scots pine, this was seen in generally lower survival rates, and in more negative survival correlations with microsite conditions. In the early growth phase, Norway spruce was found to be more sensitive to site conditions than Scots pine. This was seen in both greater height variation among the spruce trees, and more obvious effects of microsite conditions on their height growth. The ground vegetation at the sites was also studied, with regard to its distribution in space and development in time.