Jorma Issakainen

Effects of wood bark ash on the growth and nutrition of a Scots pine afforestation in central Finland

Results are presented from a fertilization experiment with wood bark ash (0, 1, 2, 5, 10, 20 Mg ha-1) applied to prevent and cure visible nutrient disorders of young Scots pine established on a peatland field. 13 years after fertilization, dieback of trees and other symptoms of nutrient disorders were substantially reduced or even eliminated, especially where higher doses had been applied. The volume of the growing stock was more than 70 m3 ha-1 for the highest dose while control plots produced less than 15 m3 ha-1. Vegetation characteristics changed following ash treatments with high ash doses favouring grasses and low ash doses promoting mosses. Some major changes in soil and foliar nutrient concentrations were evident due to ash fertilization. K and B, however, were clearly the most limiting nutrients that could be cycled where high doses of ash were used. This was particularly the case with a dose of 20 Mg ha-1. Decomposition of the topsoil was at its highest on plots with ash doses of 5 and 10 Mg ha-1 ash and at its lowest when the dose was 2 Mg ha-1. This was partly due to differences in the C/N ratio of the soil. All decomposition parameters indicated a high degree of humification in the topsoil. High N content (of organic material), low C/N in the soil and optimum levels of foliar N concentrations suggested sufficient N mineralization for tree growth to have occurred in the soil.

Effect of repeated harvesting on biomass production and sprouting of Betula pubescens

The effect of repeated coppicing and rotation length on the biomass production and sprouting of downy birch (Betula pubescens Ehrh.) was studied in two-field experiments established in central and northern Finland. The harvesting cycles studied were 1,2,4 and 8 years in central Finland and 1,2,4,8,12 and 16 years in north Finland. The randomized block design with four replications was used. Biomass was harvested, weighed and subsampled for determining the moisture content. Consecutive 1- and 2-year rotations led to a decrease in the dominant height of birches. Only 13% of the original birches were able to sprout after four 1-year rotations and 22% after two 2-year rotations. Some birches were, however, able to sprout for even more than 10 years. Annual harvests led to a rapid decrease in biomass production. Already the second 1-year-rotation yielded three times less biomass than the first and subsequent production decreased further. 4-year rotations, even though yielding much less biomass than longer rotations, did not lead to a decrease of the coppicing capacity or biomass production during consecutive rotations. The mean annual dry-mass production was very low when 1- or 2-year rotations were applied. 8-year rotations in central Finland yielded 7–8 times more and in northern Finland 9–13 times more than 1- and 2-year rotations. The longer the rotation, the higher the mean annual biomass production. The highest mean annual increment (MAI) was achieved with the longest (i.e. 16-year) rotation. Compared with the 1-year rotation, the MAI for the 16-year rotation was 20 times higher. The results show that downy birch is not suitable for biomass production when using short rotations. Three annual or biannual cuttings reduce the sprouting capacity and growth of birch considerably and help to control coppicing in softwood plantations.