- Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences
Wood ash application in spruce stands : effects on ground vegetation, tree nutrient status and soil chemistry
Abstract In order to decrease the use of fossil fuels and to reduce the emissions of greenhouse gases, plant biomass can be used as an energy source. In Sweden, logging residues from forest harvesting form a biomass resource that will presumably be increasingly used in the future. It is recommended that the wood ash from large-scale biomass burners should be returned to the harvested site in order to minimize the risk of soil acidification and depletion of base cations due to intensive harvesting. This thesis summarizes the results from four studies examining the effects of wood ash on ground vegetation, tree nutrient status, soil and soil water chemistry.
The experimental sites used in the thesis were 1-4 year old Norway spruce (Picea abies (L.) Karst.) stands within a fertility gradient that was replicated along a climate gradient. At each site, 3000 kg ha’1 crushed wood ash was applied in a randomized block design. The effects of wood ash application on the ground vegetation composition or cover were limited. The bryophytes showed no visible negative response to the ash application. The concentrations of P, K and Ca in the needles were higher in wood ash treated plots than in control plots. The needle concentrations of Mg and S were not affected by the ash applications. Wood ash application generally resulted in modestly but significantly increased concentrations of exchangeable Ca and Mg and CEC. The effects were most pronounced in the upper 0-5 cm layer. In the upper 5 cm of the soil, pH increased by on average 0.6 pH units in wood ash treated plots compared to control plots. Base saturation increased in the whole soil profile. Addition of wood ash did not affect the concentration of N 03-N in the soil water at 50 cm depth below the soil surface.
The conclusion I was able to draw from these studies was that a compensatory dose of crushed wood ash can be applied to young Norway spruce stands without any detrimental effects on forest plants or increased concentrations of nitrate in the soil water below the rooting zone. Wood ash application would most likely compensate for nutrients removed at intensive harvesting. This is an important aspect for the potential to maintain long-term forest production under sustainable nutritional conditions, even with intensive forest management.
ground vegetation biomass; cations; chemistry; clear-felling; Picea abies; forest soil; needle analyses; nutrients; species composition; species cover; whole-tree harvesting
Acta Universitatis Agriculturae Sueciae. Silvestria
2001, number: 221
Publisher: Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences
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