TY - BOOK
T1 - Environmental effects of ash application in forest ecosystems
T2 - from a soil perspective
AU - Hansen, Mette
PY - 2017
Y1 - 2017
N2 - Wood ash application in forest ecosystems has come into play as a means of counteracting acidification andnutrient losses as a consequence of intensified harvesting methods. A political focus on replacing fossilfuels with renewable energy sources like biomass will increase both the amount of ashes being producedand the export of nutrients from the forests. This PhD project aims at investigating how ash application inforest ecosystems affects soil and soil solution properties and whether ash application can be used in aDanish context without environmental harm but with positive effects to the soil environment, focusing onthe effect of applying ash at different doses.Field and laboratory experiments were conducted including field trials focusing on ash application rate anddifferent compositions of ashes at both short and long term scale and laboratory experiments using pHmicrosensors, soil incubation, FTIR-PAS and thermal analysis techniques. Based on these, I found that ashapplication can improve the forest soil conditions in terms of increasing the nutrient concentrations andsoil pH, primarily in the O-horizon. Higher doses of ash increase the effect while the composition of ashdoes not change the effect markedly. This study highlights the importance of sampling at small soilincrements to ensure the actual extreme conditions near the ash are being captured. The disadvantages ofash application is primarily the accumulation of heavy metals in the O-horizon, as ash application does notchange the mobility and flux of heavy metals out of the soil, independent of dose, in this study. Ashapplication can change the C cycle in the soil. The soil C concentrations tended to decrease after ashapplication as the mineralization rate increased, but no increased CO2 efflux was detected. The SOMcomposition and stability to microbial degradation changed in the O-horizon, but not in the mineral soil.The labile fraction of SOM increased and the thermal stability decreased in the O-horizon. If increased plantor microbial biomass input does not balance the increased mineralisation rate, ash application can havenegative impact on the soil capacity to store C.This PhD study shows that ash application can be used in a Danish context without environmental harm. Toensure the practice to be more widespread than it is today, measures can be made to improve the Danishlegislation defining the rules for ash application. Based on my findings, I suggest that the dose of ashapplied is increased to 6 Mg ha-1 instead of 3 Mg ha-1, while at the same time reducing the initial Cdconcentration in the ash and/or prohibiting the use of fly ashes alone.
AB - Wood ash application in forest ecosystems has come into play as a means of counteracting acidification andnutrient losses as a consequence of intensified harvesting methods. A political focus on replacing fossilfuels with renewable energy sources like biomass will increase both the amount of ashes being producedand the export of nutrients from the forests. This PhD project aims at investigating how ash application inforest ecosystems affects soil and soil solution properties and whether ash application can be used in aDanish context without environmental harm but with positive effects to the soil environment, focusing onthe effect of applying ash at different doses.Field and laboratory experiments were conducted including field trials focusing on ash application rate anddifferent compositions of ashes at both short and long term scale and laboratory experiments using pHmicrosensors, soil incubation, FTIR-PAS and thermal analysis techniques. Based on these, I found that ashapplication can improve the forest soil conditions in terms of increasing the nutrient concentrations andsoil pH, primarily in the O-horizon. Higher doses of ash increase the effect while the composition of ashdoes not change the effect markedly. This study highlights the importance of sampling at small soilincrements to ensure the actual extreme conditions near the ash are being captured. The disadvantages ofash application is primarily the accumulation of heavy metals in the O-horizon, as ash application does notchange the mobility and flux of heavy metals out of the soil, independent of dose, in this study. Ashapplication can change the C cycle in the soil. The soil C concentrations tended to decrease after ashapplication as the mineralization rate increased, but no increased CO2 efflux was detected. The SOMcomposition and stability to microbial degradation changed in the O-horizon, but not in the mineral soil.The labile fraction of SOM increased and the thermal stability decreased in the O-horizon. If increased plantor microbial biomass input does not balance the increased mineralisation rate, ash application can havenegative impact on the soil capacity to store C.This PhD study shows that ash application can be used in a Danish context without environmental harm. Toensure the practice to be more widespread than it is today, measures can be made to improve the Danishlegislation defining the rules for ash application. Based on my findings, I suggest that the dose of ashapplied is increased to 6 Mg ha-1 instead of 3 Mg ha-1, while at the same time reducing the initial Cdconcentration in the ash and/or prohibiting the use of fly ashes alone.
UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01010815543&context=L&vid=NUI&search_scope=KGL&tab=default_tab&lang=da_DK
M3 - Ph.D. thesis
BT - Environmental effects of ash application in forest ecosystems
PB - Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
ER -