Browsing by Subject "silviculture"

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  • Kalela, Erkki K. (Suomen metsätieteellinen seura, 1949)
  • Vasander, Harri; Lindholm, Tapio (Suomen metsätieteellinen seura, 1985)
  • Raulo, Jyrki (Suomen metsätieteellinen seura, 1978)
  • Kojola, Soili; Penttilä, Timo; Laiho, Raija (2004)
    Drained peatlands in northern Europe comprise more than 10 million ha of forestland and thus constitute a considerable production potential in forestry. Much of this area consists of stands dominated by Scots pine and close to maturity regarding commercial thinning. The trees within these stands typically vary in terms of age, size, and growth rate. The impacts of silvicultural cuttings on these uneven-structured stands are inadequately known. We simulated the impacts of a control regime with no thinnings, and three different thinning regimes, involving different thinning intensities, on the development of fifteen pine-dominated stands in Finland. The simulations started from the first thinnings and were continued until regeneration maturity. The predicted total yields ranged from 244 to 595 m3ha-1, depending on site and thinning regime. The highest total yields were observed for the control regime in which 18-38% of the yield was, however, predicted to self-thin by the end of the simulation. Thus, the differences in the yields of merchantable wood were fairly small among the compared regimes. However, the regimes involving thinnings generally needed less time than the control regime to reach regeneration maturity. The mean annual increment of total stem volume was at its highest in the control regime. The highest mean annual increment of merchantable wood was obtained in the regime involving two moderate thinnings, but excluding the most low-productive sites where thinnings did not increase the yield of merchantable wood.
  • Kallioniemi, Paula (Helsingfors universitet, 2012)
    Tending of seedling stands and improvement of young stands are important steps in wood produc-tion, but they are often postponed or even neglected primarily due to high expenses and poor availability of labour. Machine tending of young stands requires special equipment and appropri-ately suited devices, restricting the method's feasibility to larger stands. For the present, clea-ring and thinning of young stands is mainly accomplished manually using a clearing saw due to lower cost of manual work compared with machine tending. Mechanized pre-commercial thinning further requires that strip roads must be opened, which will reduce the number of growing trees, resulting in diminished area for wood production. Trunk and root damages are a frequent phenomenon and furthermore the terrain can sustain damage. Dam-ages in standing crop and soil can reduce timber output during forest rotation time. The negative contribution of strip roads on timber output and poor forest health should be countered in devel-oping machine tending. The need for the development of machine tending and its benefits increas-es with receding availability of labour. This study focuses on the influence on timber production and trunk damages by a forestry vehicle equipped with a MenSe clearing head. The emphasis lies on examining strip roads and damages in young stands. In addition to conclusions from forest measurements, literature search was applied in studying the effects of machine tending on timber output. The corollary influence of strip roads on future timber output requires further research. The study observes a 10 % decrease in surface area resulting from laying strip roads for mechanized pre-commercial thinning. Trunk damages were present on average in 5 % of the remaining trees. Growth impeding trees surrounding growing trees amounted to 250 trees per hectare and need-lessly removed trees about 90 per hectare. The consumption of working time averaged 8,4 hours per hectare and hourly output 0,12 hectare on all sites. Nonnegligent divergencies in drivers regard-ing efficiency and procedure were observed. Attending to the education, motivation, advicement and supervision of the driver will be worthwhile in the future. Circumstances surrounding both the driver and the forest machine present a challenge in develop-ing the cost-efficiency and labour resultant of mechanized pre-commercial thinning. In the future more alternatives for wood production chain should be considered for research, for instance the possibility of entirely abandoning pre-commercial thinning after the preliminary cleaning of seed-ling stands with an uprooter, subsequently leading to energy wood thinning or first thinning.
  • Kellomäki, Seppo; Hänninen, Heikki; Kolström, Taneli (Suomen metsätieteellinen seura, 1988)
  • Varhimo, Antero; Kojola, Soili; Penttilä, Timo; Laiho, Raija (2003)
    The inherent structural dynamics of drained peatland forests may result in a great variation in various wood and fi ber properties. We examined variation in fi ber and pulp properties i) among stands, ii) among trees within stands, and iii) within trees in young stands dominated by Scots pine (Pinus sylvestris L.). The stands, selected to cover a maximal range of the potential variation, were all at a stage of development where the fi rst commercial thinnings would be feasible. Differences in the processability of the thinning removals were small. In similar kraft cooking conditions, a 5-unit variation in the kappa number of unbleached pulp was observed among the stands. Stand origin had no effect on pulp bleaching. The wood formed prior to drainage had a higher density, shorter fi bers, was slightly slower delignifi ed by cooking, and its yield was slightly lower than that of post-drainage wood. These properties, except for high density, are typical for juvenile wood in general, and at stand level they did not correlate with the proportion of pre-drainage wood. When the variation in fi ber and pulp properties was broken down into its components, most of it was derived from tree-level in all the cases. On average, the fi ber and pulp properties did not differ from those observed for fi rst-thinning pulpwood from upland sites. Consequently, peatland-grown pulpwood may be mixed with other pulpwood in industrial processes. It would probably be best suited as the raw material for pulps with high bonding requirements, e.g. in the top ply of multi-ply board grades or in some specialty grades.
  • Mikola, Peitsa; Kangas, Esko; Heikurainen, Leo (Suomen metsätieteellinen seura, 1959)
  • Ervasti, Seppo; Heikinheimo, Lauri; Holopainen, Viljo; Kuusela, Kullervo; Sirén, Gustaf (Suomen metsätieteellinen seura, 1965)
  • Persson, Johannes; Thorén, Henrik; Olsson, Lennart (2018)
    Interdisciplinary research in the fields of forestry and sustainability studies often encounters seemingly incompatible ontological assumptions deriving from natural and social sciences. The perceived incompatibilities might emerge from the epistemological and ontological claims of the theories or models directly employed in the interdisciplinary collaboration, or they might be created by other epistemological and ontological assumptions that these interdisciplinary researchers find no reason to question. In this paper we discuss the benefits and risks of two possible approaches, Popperian optimism and Kuhnian pessimism, to interdisciplinary knowledge integration where epistemological and ontological differences between the sciences involved can be expected.
  • Saarinen, Ninni; Calders, Kim; Kankare, Ville; Yrttimaa, Tuomas; Junttila, Samuli; Luoma, Ville; Huuskonen, Saija; Hynynen, Jari; Verbeeck, Hans (2021)
    Tree functional traits together with processes such as forest regeneration, growth, and mortality affect forest and tree structure. Forest management inherently impacts these processes. Moreover, forest structure, biodiversity, resilience, and carbon uptake can be sustained and enhanced with forest management activities. To assess structural complexity of individual trees, comprehensive and quantitative measures are needed, and they are often lacking for current forest management practices. Here, we utilized 3D information from individual Scots pine (Pinus sylvestris L.) trees obtained with terrestrial laser scanning to, first, assess effects of forest management on structural complexity of individual trees and, second, understand relationship between several tree attributes and structural complexity. We studied structural complexity of individual trees represented by a single scale-independent metric called "box dimension." This study aimed at identifying drivers affecting structural complexity of individual Scots pine trees in boreal forest conditions. The results showed that thinning increased structural complexity of individual Scots pine trees. Furthermore, we found a relationship between structural complexity and stem and crown size and shape as well as tree growth. Thus, it can be concluded that forest management affected structural complexity of individual Scots pine trees in managed boreal forests, and stem, crown, and growth attributes were identified as drivers of it.
  • Lindholm, Tapio; Vasander, Harri (Suomen metsätieteellinen seura, 1987)