Effect of soil preparation method on economic result of Norway spruce regeneration chain

Abstract

Economic result of forest regeneration chains, based either on spot mounding or on disc trenching and planting of Norway spruce (Picea abies [L.] Karst.) seedlings, were clarified and compared to each other. First, effects of soil preparation method on early development of Norway spruce stands were measured from field experiments. Second, the effects of soil preparation method on stand level management programs were modelled. The modelling was based on growth simulation and investment calculations. The soil preparation methods substantially affected early development of a stand. The density of the removed trees in early cleaning was 56% higher on the disc-trenched area compared to the spot-mounded area. The difference was especially high (120%), close by (<25 cm) the remained spruce seedlings. There was also a difference between the methods in the growth of crop spruces; at biological age of 8 years, the mean height of spruce was 110 cm on the spot-mounded area and 68 cm on the disc-trenched area. The differences led to divergent management programs between the areas. The disc-trenched area needed three young stand management operations whereas two was enough at the spot-mounded area. Although disc trenching is a less expensive method than spot mounding, the total management costs were higher in disc trenching than in spot mounding. Furthermore, incomes from the first commercial thinning were higher when regeneration based on spot mounding. At the interest rate of 3%, the investment in spot mounding had 329 € ha -1 higher net present value than the investment in disc trenching.

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

“…Study in central Finland found that it has been present mainly on areas with ditch mounded and inverted soil (Heiskanen et al, 2013). Similar to our results, superior height growth of trees planted on mounds had been found also in numerous studies in Sweden and Finland (Saarinen, 2007;Lehtosalo et al, 2010;Uotila et al, 2010;Hallsby & Örlander, 2013). Even so the reported (Ör-lander et al, 1990, 1998) differences in tree height between the soil preparation methods were smaller than those found in our study, presumably due to slower growth in more northern climatic conditions.…”

“…forest types, however, these differences were non-signifi cant (p = 0.05 and p = 0.53, respectively). Differences were more pronounced, when trees growing on mounds were compared with those growing in unprepared soil: in these circumstances one third of trees in Oxalidosa forest type and as much as two thirds in Myrtilloso-polytrichosa forest type were lower than 1.5 m. Similar infl uence of soil preparation method on tree height distribution in young Norway spruce stand was found also in Finland (Uotila et al, 2010).…”

“…Furthermore, mound excluded competition from surrounding vegetation for a longer period of time than furrows (Lehtosalo et al, 2010). For example, in Finland it was found, that in sites where spot mounding was applied, tending was needed only in 2 nd -4 th year after planting in relative fertile soil, and in 4 th -6 th year in poor soil (Saksa, 2008;Uotila et al, 2010). Therefore, some authors (Uotila et al, 2010) suggest that fi nancial assessment of forest regeneration shall include not only planting (and survival of planted trees), but also tending: its frequency (number of occasion), quality and time spent (costs).…”

“…For example, in Finland it was found, that in sites where spot mounding was applied, tending was needed only in 2 nd -4 th year after planting in relative fertile soil, and in 4 th -6 th year in poor soil (Saksa, 2008;Uotila et al, 2010). Therefore, some authors (Uotila et al, 2010) suggest that fi nancial assessment of forest regeneration shall include not only planting (and survival of planted trees), but also tending: its frequency (number of occasion), quality and time spent (costs). Time spent for soil preparation (and thus also the costs and potential for their reduction) had been analysed in numerous studies Liepiņš et al, 2011).…”

Reliability of self-control method in the management of non-industrial private forests

“…For example, the number of prepared spots is the main CSF in soil preparation because it provides the foundation for planting and future performance of the seedling. High quality sites are for instance characterized by approximately 2000 mounds ha -1 that are large enough for planters to plant seedlings correctly but not so large as to provide substrate for opportunistic broadleaf trees (Uotila et al 2010). Planting work is evaluated in terms of the proportion of seedlings that are planted correctly, i.e., stems anchored well in the soil and their roots reaching nutritious humus layer when possible (Long 1991;Luoranen and Viiri 2016).…”