Regeneration and tree growth dynamics of Picea abies, Betula pendula and Betula pubescens in regeneration areas treated with spot mounding in southern Finland

This study addresses the dynamics of young stands established in areas of southern Finland which have been site prepared with spot mounding and planted with Norway spruce. The principal attributes investigated were the density of natural birch on the major soil surface types associated with the method (mounds, patches and undisturbed soil) and the growth rate of the planted spruces compared with natural birches. The study material included 18 regeneration areas treated with spot mounding and planted with Norway spruce container seedlings, around three, six or nine growing seasons before measurement. Rather than permanent plots that would have constituted a genuine time series, the data collected for the study originated from a sample of stands of different ages. The results indicated that there were comparatively few birches on the mounds after 3 years, but greater average densities were evident at 6 and 9 years than on the patches and undisturbed soil. Compared with methods such as patch scarification and disc trenching, the observed delay in the emergence of birch probably gives spruce a competitive advantage during the most susceptible, earliest stages of development in spot mounding.