Current issue: 53(3)
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.
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.
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.
Possibilities of developing suitable willow (Salix spp.) clones for short-rotation forestry on mined peatlands in the north-western area of Finland were studied in a field experiment in which 300 willow clones were tested during 1985–87. Most of the tested clones started to grow from cuttings on limed and fertilized peat soil. Salix viminalis L. clones of southern origin had a higher leafless above ground biomass production than the well adapted control clone and the local Finnish willows, but their winter hardiness was not satisfactory. The growth habit of some southern willows was also better than that of the control clone. It was also possible to select clones with good sprouting capacity. There were few Salix myrsinifolia Calisb. clones of Finnish origin, which had better cold tolerance than all other willows tested and higher biomass production than that of the control clone. The most critical factor to be selected for this is the optimal combination of winter hardiness and biomass production. This is attempted by selecting clones on the basis of this experiment for a breeding program.
The PDF includes a summary in Finnish.
In the first place the term short-rotation forestry is being used in the sense of intensive tree growing during a short rotation time using reproduction by coppice shoots from broad-leaved tree material which has been specially bred for this purpose, or of producing fast-growing varieties from planted stock during the course of somewhat longer rotation time (maximum 20 years). However, short-rotation forestry as such has already a long history.
In the Fertile Crescent in ancient Egypt grew no tree species suitable for short-rotation production, but reeds and bulrushes were used for the same purpose as willow-twigs, e.g. wickerwork or binding. At least in the Fertile Crescent reed harvesting using a rotation of one year was practiced already very long ago. The earliest information about coppice-shoot cultivation is found in Greek literature, but it was the Romans who developed short-rotation forestry based on the trees’ capacity of reproducing through coppice shoots into an extensive economic activity. Willows were by far the most important species used. Twigs intended for wickerwork were harvested once a year and thicker material, to be used for support and in basket framework, every fourth year. Chestnut and oak were used for the production of slightly thicker poles employing a longer rotation. Cypress poles were produced from seedlings using a rotation time of 12–13 years. Roman scholars give us plenty of information concerning the tending of plantations in short-rotation forestry.
The PDF includes a summary in English.