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Different species of Salicaceae are of interest for bioenergy production in Sweden. Surplus agricultural land is available and can be used for bioenergy plantations. Documentation of the effects of afforestation on soil properties is of importance for future recommendations on the choice of tree species and management measures.Hybrid aspen (Populus tremula×Populus tremuloides), poplar (Populus spp.) and willow (Salix spp.) were planted on former arable land at four sites in Sweden. Planting densities were 1500plantsha-1 for hybrid aspen and poplar, and 14,800plantsha-1 for short rotation coppice (SRC) willow. The present study comprised five years following plantation with the aim to quantify the afforestation effects on mineral soil variables, i.e. soil organic carbon (SOC), nitrogen (N), phosphorus (P), base cations (K, Mg, Ca), C:N ratios and pH. The soil variables were estimated by repeated sampling, i.e. prior to planting and at the end of the fifth season. A litter layer was present in the fifth year and included in the C estimates.The SOC pools were generally unchanged compared to pre-planting conditions. Total N pools had increased in SRC willow plantations and P pools had decreased in hybrid aspen and poplar plantations. Plant available K and Mg concentrations increased in the upper 0-10. cm soil and decreased in the lower 10-30. cm for all species, indicating redistribution by plant uptake and recycling through litter decay. Concentrations and pools of Ca were unchanged. The C:N ratio and pH were reduced with ca 10% and 0.1 units, respectively, for all species. No specific effect of species was observed in the mineral soil, but SRC willow had lower C:N ratio in aboveground litter compared to the other species. Thus, five years growth of Salicaceae on former agricultural land resulted mainly in general soil effects associated with the cessation of annual management measures, enhanced litter production from trees and ground vegetation, and probably also with altered soil physical conditions, for example humidity and temperature, in the growing plantations. © 2015 Published by Elsevier B.V.

Rytter R.-M.,Rytter Science | Rytter L.,Forestry Research Institute of Sweden | Hogbom L.,Forestry Research Institute of Sweden
Biomass and Bioenergy | Year: 2015

Short rotation coppice (SRC) plantations are of interest as producers of biomass for fuel, but also as carbon (C) sinks to mitigate CO2 emissions. Carbon sequestration in biomass and soil was estimated in 5-year-old replicated SRC plantations with willows (Salix spp.) on former arable land at five sites in Sweden. Total standing C stocks, i.e. C stored in woody biomass above- and belowground, fine root standing crop, litter, and soil organic carbon (SOC) were estimated by repeated field sampling and C budget calculation.Overall, the SRC willow plantations represented a C sink after five years. Estimated increase of total standing C stock was 15% on average compared to pre-planting conditions. There was no change in SOC when including all sites. Analyses within sites revealed a decrease in SOC at one site, although the decrease was compensated for by C stored in willow biomass. After removal of stem biomass, C in other plant pools was sufficient to compensate for the SOC decrease. Remaining C in stumps, stool, and coarse roots was estimated at ca 20% of stem C.There was a discrepancy between SOC sequestration rates from soil sampling and C budget calculation, -2.1-1.0 and 0.15-0.45 Mg ha-1 y-1, respectively. Mineralization of old organic material from previous land-use and input to SOC from understory vegetation were not included in the calculations, which may explain part of the differences. The importance of understory litter in C budgets for young plantations was apparent, as it comprised 24-80% of aboveground litter C. © 2015 Elsevier Ltd.

Rytter L.,Forestry Research Institute of Sweden | Rytter R.-M.,Rytter Science
Forest Ecology and Management | Year: 2016

Biomass from woody crops is regarded as a future major source of renewable energy. Wood production therefore has to be enhanced to meet the energy needs of an increasing population. This can be reached by using fast-growing tree species. Grey alder (Alnus incana (L.) Moench.) is an indigenous and fast-growing species, which is well adapted to the harsh climate of northern Europe, and could complement other biomass-oriented species used today. This study aimed to assess the potential for wood production and carbon (C) sequestration in biomass and soil of grey alder plantations under north European conditions. The estimates were based on literature data on above- and below ground biomass production, including fine roots, biomass allocation patterns and litter decomposition. By applying logistic functions on production figures and adding an estimated breeding response, grey alder would be able to produce on average 6-7 Mg ha-1 yr-1 of above ground woody biomass during a rotation up to 25 years. This would significantly contribute to increased biomass availability in the Nordic and Baltic countries when applied on agricultural land. By assuming that grey alder will mostly be used on areas suitable for the species, e.g. sites with harsh climate or moist conditions, an estimate of 560,000 ha of newly abandoned agricultural land will be available. Thus, afforestation of those areas with grey alder would result in a total annual increase of aboveground woody biomass of 3.7 Tg, corresponding to 69,000 TJ yr-1. Grey alder would also be an efficient C sink when used on newly abandoned agricultural land. Using the same areas as for biomass the annual C sequestration in biomass and soil would reach 2.6 Tg C. These figures show that grey alder has a potential to be a significant contributor for increasing biomass supply and capture C in northern Europe. © 2016 Elsevier B.V..

Rytter R.-M.,Rytter Science | Rytter L.,Rytter Science
Plant and Soil | Year: 2012

Aims: A key issue related to the usefulness of the minirhizotron technique is whether root presence and behaviour in the soil zone at the minirhizotron interface are consistent with those in the bulk soil. We wanted to test the null hypotheses that there were no differences in root densities or specific root length (SRL) between those positions. The effects of different nutrient and water regimes, and different tree species (grey alder and basket willow) on the root variables were also examined. Methods: We quantified root mass and length densities, and calculated SRL, of three diameter classes from cores sampled around minirhizotrons and in the bulk soil, i. e. quartz sand. Fine root dynamics were monitored in the minirhizotrons during three consecutive years prior to sampling. The study was conducted on individual root systems within buried and covered lysimeters, placed in a stand structure, and with different water and nutrient regimes. Results: Significant discrepancies in root densities were found between positions. Plants subjected to limited water or nutrient supply had up to three times higher densities at the minirhizotrons. However, effects of species and treatments showed a similar pattern for the diameter class <1 mm between the two sampling positions and minirhizotron observations. The pulses of fine root growth and decay were coordinated in time for both species and treatments. The SRL was not affected by the tube in any diameter class. Conclusions: We concluded that the minirhizotron technique alone was of limited use for estimating root densities in the bulk soil. But the results showed that minirhizotrons could be useful, for example, combined with soil coring or in comparative studies. The patterns of fine root growth and decay were similar for species and treatments, and SRL was unaffected, suggesting that minirhizotrons can be used in studies of root dynamics and morphology. There is, however, a need for further studies concerning the influence on root survival and decay. © 2011 Springer Science+Business Media B.V.

Studies concerning the stoniness of arable soils are scarce since those soils are commonly regarded as composed mainly of fine earth. However, even the influence of lesser volumes of stones and gravel on estimates of nutrient stocks may be significant. Nutrient analyses are performed on the fine earth fraction. It is therefore necessary to determine the bulk density and the relative soil volume that is occupied by fine earth when expressing nutrient stocks per unit area and to a certain depth. In this study, relative volumes of stones and gravel were investigated in the top soils, i.e. down to 30. cm depth, of five Swedish arable sites. Bulk density and gravel volume were determined by soil coring and stone volume using the rod penetration method. A function for estimation of relative stone volume from mean penetration depth was developed. The function is suitable for soils with low stoniness, i.e. less than 10%. The results showed that although the relative volumes of stones and gravel were small, at most 8%, neglecting the volume occupied by rock fragments led to an overestimation of C and N stocks by 8-9%. The moderate volumes of stones and gravel also significantly affected comparisons between sites. It was concluded that the inclusion of stone and gravel volume of arable soils may be important if nutrient stocks of different sites are compared, or the effects of land use changes are scaled up to regional or global levels. © 2012 Elsevier B.V.

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