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Articles by Jyrki Hytönen

Category: Research article

article id 9938, category Research article
Jyrki Hytönen, Egbert Beuker, Anneli Viherä-Aarnio. (2018). Clonal variation in basic density, moisture content and heating value of wood, bark and branches in hybrid aspen. Silva Fennica vol. 52 no. 2 article id 9938. https://doi.org/10.14214/sf.9938
Highlights: Hybrid aspen clones differed in their moisture content, ash content, basic density and heating value; Stem wood had lower ash content, basic density and effective heating value than stem bark; There was significant vertical variation in wood and bark along the stem in moisture content and basic density.

Hybrid aspen (Populus tremula × P. tremuloides) is one of the fastest growing tree species in Finland. During the mid-1990s, a breeding programme was started with the aim of selecting clones that were superior in producing pulpwood. Hybrid aspen can also be grown as a short-rotation crop for bioenergy. To study clonal variation in wood and bark properties, seven clones were selected from a 12-year-old field trial located in southern Finland. From each clone, five trees were harvested and samples were taken from stem wood, stem bark and branches to determine basic density, effective heating value, moisture and ash content. Vertical within-tree variation in moisture content and basic density was also studied. The differences between clones were significant for almost all studied properties. For all studied properties there was a significant difference between wood and bark. Wood had lower ash content (0.5% vs. 3.9%), basic density (378 kg m–3 vs. 450 kg m–3) and effective heating value (18.26 MJ kg–1 vs. 19.24 MJ kg–1), but higher moisture content (55% vs. 49%) than bark. The values for branches were intermediate. These results suggest that the properties of hybrid aspen important for energy use could be improved by clonal selection. However, selecting clones based on fast growth only may be challenging since it may lead to a decrease in hybrid aspen wood density.

  • Hytönen, Natural Resources Institute Finland (Luke), Natural resources, Teknologiakatu 7, FI-67100 Kokkola, Finland ORCID ID:E-mail: jyrki.hytonen@luke.fi (email)
  • Beuker, Natural Resources Institute Finland (Luke), Production systems, Vipusenkuja 6, FI-57200 Savonlinna, Finland ORCID ID:E-mail: egbert.beuker@luke.fi
  • Viherä-Aarnio, Natural Resources Institute Finland (Luke), Production systems, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: anneli.vihera-aarnio@luke.fi
article id 1734, category Research article
Jyrki Hytönen, Paula Jylhä, Keith Little. (2017). Positive effects of wood ash fertilization and weed control on the growth of Scots pine on former peat-based agricultural land – a 21-year study. Silva Fennica vol. 51 no. 3 article id 1734. https://doi.org/10.14214/sf.1734
Highlights: Weed control decreased and fertilization increased vegetation height and shading of seedlings; Weed control decreased mortality, but fertilization had no effect; Despite improved foliar K concentration though ash fertilization, all trees in the trial had severe K deficiency after 21 years; Weed control increased growth by 20 m3 ha–1 and fertilization by 35 m3 ha–1 in 21 years.

The impacts of weed control, ash fertilization and their interaction were tested for the afforestation of former agricultural peat-based soil with Scots pine (Pinus sylvestris L.) in northern Finland in a factorial arrangement of four treatments. Weed control with herbicides was carried out in July 1 and 2 years from planting, and wood ash (5 Mg ha–1) was applied in the spring of the 2nd year. Various vegetation, tree growth and nutrient assessments were made over the 21-year study period. Weed control decreased the weed cover by 36–56 percentage points, vegetation height by 4–26 cm and thus shading of seedlings by vegetation for at least 4 years after planting. For the same period, ash fertilization increased vegetation height by 6–15 cm and shading of seedlings. Weed control reduced seedling mortality by 27 percentage points in 21 years, but ash fertilization had no significant effect. Ash fertilization increased foliar potassium and boron concentrations, but its effect declined, and severe K-deficiency was recorded 21 years after planting. Up to the 9th year, weed control had a greater influence on growth than fertilization. Later the significance of fertilization increased due to an aggravated K-deficiency. Stand volume at year 21 for the untreated control plots was 8 m3 ha–1. Weed control and fertilization increased stand volume by 20 and 35 m3 ha–1, with a combined effect of 55 m3 ha–1. The effects of weed control and fertilization were additive and no significant interactions were found. Due to severe K-deficiencies, re-fertilization of all treatments would be necessary for the continued survival and growth of Scots pine.

  • Hytönen, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Teknologiakatu 7, FI-67100 Kokkola, Finland ORCID ID: http://orcid.org/0000-0001-8475-3568 E-mail: jyrki.hytonen@luke.fi (email)
  • Jylhä, Natural Resources Institute Finland (Luke), Green technology, Teknologiakatu 7, FI-67100 Kokkola, Finland ORCID ID:E-mail: paula.jylha@luke.fi
  • Little, Nelson Mandela Metropolitan University, George Campus, Western Cape, South Africa ORCID ID:E-mail: keith.little@nmmu.ac.za
article id 1301, category Research article
Mikko Moilanen, Jyrki Hytönen, Hannu Hökkä, Anssi Ahtikoski. (2015). Fertilization increased growth of Scots pine and financial performance of forest management in a drained peatland in Finland. Silva Fennica vol. 49 no. 3 article id 1301. https://doi.org/10.14214/sf.1301
Highlights: All fertilizers containing phosphorus and potassium improved the P and K status and the stem growth of Scots pine still 26 years from application; Wood ash, containing more nutrients than other fertilizers, gave the strongest stand growth response and the highest net present value; Ash fertilizer treatment outperformed other fertilizer treatments and control in net present value, regardless of the applied discount rate, 3%, 4% or 5%.

The long-term effects of fertilization on the needle nutrient concentrations, growth and financial performance of a Scots pine (Pinus sylvestris L.) stand was examined in a thick-peated drained peatland forest located in Central Finland. At the trial establishment in 1985, the trees were suffering from P and K deficiencies, but their N status was good. The fertilizer treatments were Control, PK (rock phosphate + potassium chloride), ApaBio (apatite phosphorus + biotite) and wood ash, applied both with and without N and replicated six times. All treatments containing phosphorus and potassium increased foliar P and K concentrations above the deficiency limits up to the end of the study period of 26 years. The effect of the fertilization on stand volume growth of Scots pine was strong and continued still at the end of the study period. The trees on ApaBio and PK plots grew nearly two-fold and those on Ash plots over two-fold compared with the control plots. In a thinning made at the end of the study period the total logging removal on fertilized plots was 1.5–2.2 times greater and included more saw logs than on the control plots. Ash fertilizer treatment outperformed other fertilizer treatments as well as the control. With a 5% discounted equivalent annual income (EAI) of Ash fertilizer treatment was statistically significantly (p=0.009) almost three times higher than that of control. As a conclusion, fertilization (either using PK fertilizers or Ash) in N-rich drained peatlands is a financially feasible method of management.

  • Moilanen, Natural Resources Institute Finland, Natural resources and bioproduction, Paavo Havaksen tie 3, FI-90014 Oulu, Finland ORCID ID:E-mail: mikko.moilanen@luke.fi (email)
  • Hytönen, Natural Resources Institute Finland, Natural resources and bioproduction, Silmäjärventie 2, FI-69100 Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@luke.fi
  • Hökkä, Natural Resources Institute Finland, Natural resources and bioproduction, Eteläranta 55, FI-96301 Rovaniemi, Finland ORCID ID:E-mail: hannu.hokka@luke.fi
  • Ahtikoski, Natural Resources Institute Finland, Natural resources and bioproduction, Paavo Havaksen tie 3, FI-90014 Oulu, Finland ORCID ID:E-mail: anssi.ahtikoski@luke.fi
article id 1260, category Research article
Jyrki Hytönen, Anna Saarsalmi. (2015). Biomass production of coppiced grey alder and the effect of fertilization. Silva Fennica vol. 49 no. 1 article id 1260. https://doi.org/10.14214/sf.1260
Highlights: Fertilisation (wood ash, N, PK) did not affect grey alder biomass production; Leafless above-ground biomass of 17–20 year old stands was 52–57 Mg ha–1; MAI increased with increase of rotation length to the end of the follow-up period of 17–20 years; Coppicing increased stand density manifold.
We studied biomass production of two naturally originated grey alder (Alnus incana (L.) Moench) stands having a mixture of birch and willow located in central Finland. One of the stands was growing on a peatland site (Muhos) and the other on a mineral soil site (Juuka). The stands were clear-cut and fertilization experiments were laid out with several treatments. At Muhos, the treatments included nitrogen fertilisation with different amounts of wood ash and an unfertilized control. At Juuka, the treatments included nitrogen fertilisation either with ash or with PK, and ash and PK treatments alone and an unfertilized control. The sprouts at Muhos were grown for 17 years and at Juuka for 20 years. At Juuka the stand was clear-cut second time at the age of 20 years and grown for 8 years. The stands were measured several times and foliar samples were taken twice during the study period. Clear-cutting increased stem number manifold. The stand density of new coppiced forests after the clear-cutting decreased from 67 000–89 000 stems ha–1 at the age of 3–6 years to 10 000–12 000 stems ha–1 at the age of 17–20 years. On neither site fertilization affected biomass production of alders during the study period. Leafless above-ground biomass was 52–57 Mg ha–1 after 17–20 years. Mean annual leafless above-ground biomass production (MAI) increased with increase of rotation time. At the age of 17–20 years the MAI was 2.8–3.0 Mg ha a–1. At Muhos, ash increased foliar P and Ca concentrations, but decreased those of Mn.
  • Hytönen, Natural Resources Institute Finland, Silmäjärventie 2, FI-69100 Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@luke.fi (email)
  • Saarsalmi, Natural Resources Institute Finland, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: anna.saarsalmi@luke.fi
article id 48, category Research article
Jyrki Hytönen, Lasse Aro. (2012). Biomass and nutrition of naturally regenerated and coppiced birch on cutaway peatland during 37 years. Silva Fennica vol. 46 no. 3 article id 48. https://doi.org/10.14214/sf.48
Biomass production and nutrient use of birch thickets with a mixture of willow on a cut away peatland in southern Finland over a period of 37 years was studied. Dense, naturally regenerated 16-year-old birch stands were cut down, fertilized with either wood ash (P 108 and K 339 kg ha–1) or PK fertilizer (P 50 and K 95 kg ha–1) or left unfertilized. The biomass production of the coppiced stands and one uncut stand was monitored for a period of 21 years. Soil nutrient and foliar nutrient concentrations were analyzed several times during the study period. Ash fertilization supplied more nutrients than PK fertilization and increased the soil nutrient amounts more. The foliar phosphorus concentration of birch on control plots indicated a severe phosphorus deficiency which was removed by PK and ash fertilization. Fertilization did not increase nutrient concentrations of the stem (wood + bark) nor the amount of nutrients bound in the biomass. Two energy wood rotations (16+21 years) produced 124–158 Mg ha–1 of leafless, above-ground biomass altogether corresponding to 61–78 Mg ha–1 of carbon. The highest biomass yield was achieved with a rotation of 37 years in the uncut stand (211 Mg ha–1). Corresponding values for mean annual increment (MAI) were 3.4–4.3 Mg ha–1 and 5.7 Mg ha–1. This study shows that the length of the rotation for birch in energy wood production should be longer than 21 years. PK and ash fertilization increased the biomass of coppiced 21-year-old birch by 23 Mg ha–1 and 33 Mg ha–1, respectively.
  • Hytönen, Finnish Forest Research Institute, Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@metla.fi (email)
  • Aro, Finnish Forest Research Institute, Kannus, Finland ORCID ID:E-mail: lasse.aro@metla.fi
article id 242, category Research article
Jyrki Hytönen, Paula Jylhä. (2008). Fifteen-year response of weed control intensity and seedling type on Norway spruce survival and growth on arable land. Silva Fennica vol. 42 no. 3 article id 242. https://doi.org/10.14214/sf.242
The effects of seedling type (2-year-old container seedlings vs. 4-year-old bare-rooted seedlings) and post-planting vegetation control intensity on the growth and survival of Norway spruce (Picea abies (L.) Karst.) seedlings were compared based on 15-year data from a field experiment established on arable land. Vegetation control treatments with terbuthylazine and glyphosate were carried out 1–3 times on successive years, either as overall or spot applications. The highest stand volumes were obtained with the combination of large bare-rooted seedlings and effective vegetation control. Volume of bare-rooted seedlings was greater than that of container seedlings in all treatments (e.g. on the control plots 9.5 m3/ha vs. 4.1 m3/ha). The best results were obtained with the most intensive weed control treatments (spot treatment repeated twice and overall application repeated three times). These treatments increased both bare-rooted and containerised seedlings’ survival by 33–40% units and their height, breast height diameter, and volume by 45–49%, 17–47%, and 249–279%, respectively. In terms of survival, the container seedlings, in due part to their smaller size, benefited from vegetation control more than the bare-rooted seedlings. Successive early summer frosts damaged the seedlings and significantly retarded their growth. The frequency of frost damage was not affected by vegetation control nor was it attributed to seedling type.
  • Hytönen, Finnish Forest Research Institute, Kannus Research Unit, P.O. Box 44, FI-69101, Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@metla.fi (email)
  • Jylhä, Finnish Forest Research Institute, Kannus Research Unit, P.O. Box 44, FI-69101, Kannus, Finland ORCID ID:E-mail:
article id 374, category Research article
Jyrki Hytönen, Paula Jylhä. (2005). Effects of competing vegetation and post-planting weed control on the mortality, growth and vole damages to Betula pendula planted on former agricultural land. Silva Fennica vol. 39 no. 3 article id 374. https://doi.org/10.14214/sf.374
Effects of competing vegetation and weed control methods (fibre board mulch, cover crop of clover, various herbicides) on the survival and growth of and vole damage to silver birch (Betula pendula Roth) were analysed based on data from a field experiment established in southern Finland. The cover percentage of competing vegetation and its shading effect were assessed, and seedling size and vitality were recorded several times during the 11-year research period. Mean seedling height and height increment decreased linearly with increasing vegetation cover. Seedling mortality started to significantly increase once the vegetation cover had reached the level of 60–80%. Herbicides significantly retarded increase of weed cover on the initially weedless areas for two to three years, and a cover crop promoted increase in cover percentage. Successful weed control with herbicides significantly increased seedling growth and survival. After 11 years, the average stem volume on the herbicide-treated plots (28.9 m3 ha–1) was 2.5-fold as compared to that of the control plots (11.6 m3 ha–1). Furthermore, seedling mortality on the control plots (21%) was almost 3.5-fold as compared to the seedling mortality on herbicide-treated plots (6%). Having a cover crop proved to be an ineffective weed control method both in terms of seedling growth and survival. The application of mulch had only a slight effect on height increment (0.6 m in 11 years), but on the other hand, it considerably decreased seedling mortality (control: 21%, mulch treatment: 1.5%). These differences were not, however, statistically significant. Small seedling size, high shading class, and high vegetation coverage percentage increased the risk of voles damaging the seedlings.
  • Hytönen, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FI-69101 Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@metla.fi (email)
  • Jylhä, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FI-69101 Kannus, Finland ORCID ID:E-mail:
article id 503, category Research article
Jyrki Hytönen. (2003). Effects of wood, peat and coal ash fertilization on Scots pine foliar nutrient concentrations and growth on afforested former agricultural peat soils. Silva Fennica vol. 37 no. 2 article id 503. https://doi.org/10.14214/sf.503
The effects of ash and commercial fertilizers on the foliar nutrient concentrations and stand growth of Scots pine were studied in four field experiments established on former cultivated peat soils. The aims were to compare ash types (wood, peat and coal ash), study the effects of ash treatment (pelletization), compare ash fertilization with commercial fertilizers, and to study the interaction between ash fertilization and weed control. Foliar samples were collected 1–3 years and 7–8 years after fertilization. In the unfertilized plots, the foliar nitrogen and phosphorus concentrations were fairly high, while those of potassium were low in all the experiments. The boron levels were low in three out of the four experiments. Application of either loose or pelletized wood ash, as well as of commercial fertilizers, increased foliar potassium and boron concentrations, and thus successfully remedied the existing nutrient imbalances and deficiencies. Since phosphorus deficiencies are rarely encountered on field afforestation sites, poor-quality wood ash with low phosphorus concentration could be used. Peat ash containing phosphorus, but only small amounts of potassium and boron, was not found to be very suitable for soil amelioration in connection with field afforestation. Coal ash, containing only small amounts of potassium, was a good source of boron for pine even when used in small amounts, and thus it can be used in cases where boron deficiencies alone are encountered. Wood ash significantly increased the height growth of Scots pines in two of the experiments, but peat ash and coal ash had no statistically significant effect. Wood ash increased the number of healthy seedlings. Vegetation control decreased seedling mortality by 24%, increased the growth of pine and decreased the proportion of trees damaged by elk and by deciduous trees.
  • Hytönen, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@metla.fi (email)

Category: Article

article id 5551, category Article
Jyrki Hytönen, Pekka Rossi, Anna Saarsalmi. (1995). Biomass production and nutrient uptake of short-rotation plantations. Silva Fennica vol. 29 no. 2 article id 5551. https://doi.org/10.14214/sf.a9202

The biomass production and nutrient uptake of silver birch (Betula pendula Roth), downy birch (Betula pubescens Erhr.), grey alder (Alnus incana (L.) Moench), native willows Salix triandra L. and S. phylicifolia L. and exotic willows S. x dasyclados and S. ’Aquatica’ growing on a clay mineral soil field (Sukeva) and on two cut-away peatland areas (Piipsanneva, Valkeasuo) were investigated.

Biomass production of downy birch was greater than that of silver birch, and the biomass production of the native willows greater than that of the exotic ones. The performance of S. phylicifolia was the best of the studied willow species. Exotic willows were susceptible to frost damage and their winter hardiness was poor. The production of all species was lower on the clay mineral soil field than on the cut-away peatland areas. Fertilization of birches and alder – on the double dose given to the willows – increased biomass production. After 6 growing seasons the leafless biomass production of fertilized silver birch at Piipsanneca was 21 t ha-1 (at Valkeasuo 34 t ha-1) and of grey alder 24 t ha-1, and that of S. triandra after five growing seasons 31 t ha-1, S. phylicifolia 38 t ha-1 and of S. x dasyclados 16 t ha-1.

6-year-old stands of silver birch bound more nutrients per unit biomass than downy birch stands. Grey alder bound more N, Ca and Co but less Mn and Zn per unit biomass than silver and downy birch. On the field more P was bound in grey alder per unit biomass compared to downy birch. The willows had more K per unit biomass than the other tree species, and the exotic willow species more N than the native ones. Less N, K and Mg were bound per unit biomass of S. phylicifolia compared to the other tree species.

  • Hytönen, ORCID ID:E-mail:
  • Rossi, ORCID ID:E-mail:
  • Saarsalmi, ORCID ID:E-mail:
article id 5550, category Article
Jyrki Hytönen. (1995). Effect of repeated fertilizer application on the nutrient status and biomass production of Salix ’Aquatica’ plantations on cut-away peatland areas. Silva Fennica vol. 29 no. 2 article id 5550. https://doi.org/10.14214/sf.a9201

The effects of repeated fertilizer treatment on biomass production and nutrient status of willow (Salix ’Aquatica’) plantations established on two cut-away peatland areas in western Finland were studied over a rotation period of three years. Comparisons were made between single fertilizer applications and repeated annual fertilization.

The annually repeated fertilizer application increased the amounts of acid ammonium acetate extractable phosphorus and potassium in the soil as well as the concentrations of foliar nitrogen, phosphorus and potassium compared to single application. Depending on the fertilizer treatment and application rate, annual fertilizer application resulted in over two times higher biomass production when compared to single fertilizer application over a three-year rotation period. The effect of phosphorus fertilizer application lasted longer than that of nitrogen. The optimum fertilization regime for biomass production requires that nitrogen fertilizer should be applied annually, but the effect of phosphorus can last at least over a rotation of three years. Potassium fertilizer treatment did not increase the yield in any of the experiments during the first three years. The leafless, above-ground yield of three-year-old, annually NP-fertilized willow plantations was 9.5 t ha-1 and the total biomass, including stems, leaves, roots and the stump, averaged 17 t ha-1.

  • Hytönen, ORCID ID:E-mail:
article id 5544, category Article
Jyrki Hytönen. (1995). Effect of fertilizer treatment on the biomass production and nutrient uptake of short-rotation willow on cut-away peatlands. Silva Fennica vol. 29 no. 1 article id 5544. https://doi.org/10.14214/sf.a9195

The effects of fertilized treatment on the soil nutrient concentrations, biomass production and nutrient consumption of Salix x dasyclados and Salix ’Aquatica’ were studied in five experiments on three cut-away peatland sites in western and eastern Finland during three years. Factorial experiments with all combinations of N (100 kg ha-1 a-1), P (30 kg ha-1 a-1) and K (80 kg ha-1 a-1) were conducted.

The application of P and K fertilizers increased the concentrations of corresponding extractable nutrients in the soil as well as in willow foliage. N-fertilization increased foliar nitrogen concentration. An increase in age usually led to decreases in bark and wood N, P and K concentrations and increases in bark Ca concentrations. N-fertilization increased the three-year biomass yield 1.5–2.7 times when compared to control plots. P-fertilization increased the yield only in those experimental fields whose substrates had the lowest phosphorus concentration. K-fertilization did not increase the yield in any of the experimental fields. The highest total biomass yield of NPK-fertilized willow after three growing seasons, 23 t ha-1, was distributed in the following way: wood 42%, bark 19%, foliage 17%, stumps 6% and roots 16%. As the yield and stand age increased, more biomass was allocated in above-ground wood. Three-year-old stands (above-ground biomass 18 t ha-1) contained as much as 196 kg N ha-1, 26 kg P ha-1, 101 kg K ha-1, 74 kg Ca ha-1 and 37 kg Mg ha -1. By far the highest proportion of nutrients accumulated in the foliage. The bark and wood contained relatively high proportions of calcium and phosphorus. With an increase in age and size, the amount of nitrogen and potassium bound in one dry-mass ton of willow biomass decreased while that of phosphorus remained unchanged.

  • Hytönen, ORCID ID:E-mail:
article id 5475, category Article
Jyrki Hytönen. (1992). Allelopathic potential of peatland plant species on germination and early seedling growth of Scots pine, silver birch and downy birch. Silva Fennica vol. 26 no. 2 article id 5475. https://doi.org/10.14214/sf.a15636

The potential alleopathic inhibitive effects of aqueous extracts of 13 peatland plant species on germination, radicle and seedling growth of Scots pine (Pinus sylvestris L.), silver and downy birch (Betula pendula Roth., B. pubescens Ehrh.) were studied. Freshly cut plant parts were finely ground, mixed with distilled water and agitated. The proportions of fresh plant mass in the mass-based extracts varied within the range of 1, 5, 10 and 20% (w/w). The seeds were germinated in petri dishes moistened with the plant extracts. In a separate experiment growth of birch seedlings irrigated with the extracts was studied.

Ledum palustre, Vaccinium uliginosum and Empetrum nigrum extracts, and in certain experiments extracts of other species, inhibited the germination of Scots pine and birch seeds. Results from the different experiments were not, however, fully consistent. None of the low (1% w/w) extract concentrations had any effect on germination. Strong extract concentrations (20% w/w) inhibited germination of pine seedlings significantly. The extracts affected only slightly the growth of potted birch seedlings.

The PDF includes an abstract in Finnish.

  • Hytönen, ORCID ID:E-mail:

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