Relationships between tree and soil properties in Picea abies and Pinus sylvestris forests in Sweden

The exchange of elements between plants and the soil in which they are growing creates reciprocal control of their element composition. Within plants, the growth rate hypothesis from ecological stoichiometry implies a strong coupling between C, N, and P. No similar theory exists for predicting relationships between elements in the soil or relationships between plants and the soil. We used a data set of element concentrations in needles and humus of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) forests in Sweden to investigate the extent to which relationships between elements (C, N, P, S, K, Ca, Mg, Fe, Mn, Al) can be observed within and between plants and soils. We found element composition to be more strongly controlled in needles than in humus. Elements that are covalently bound were also more strongly controlled, with no apparent differences between macro- and micronutrients. With the exception of N/C, there were surprisingly few relationships between elements in needles and humus. We found no major differences between the two tree species studied, but investigations of additional forest types are needed for firm conclusions. More control over element composition was exercised with respect to N than C, particularly in needles, so it might be advantageous to express nutrient concentrations relative to N rather than on a dry weight or carbon basis. Variations in many ecosystem variables appeared to lack ecological significance and thus an important task is to identify the meaningful predictors

Polycentric spatial development: Institutional challenges

Most metropolitan regions advocate cooperation among municipalities and bewteen public and private actors to plan and fund new housing and transportation infrastructure. Just as many experience frustration that such cooperative structures fail to materialize or prove ineffective. A recent study of several municipalities north of Stockholm, Sweden investigated what hinders and opportunities may exist to improve the potential for cooperation and collective action in infrastructure provision. This included a special focus on the challenges of polycentric spatial development that presents a classic social dilemma with uneven payoffs and costs for individual communities. The study includes three cases focused on retail centres, transportation corridors and new housing

Fungerar kretsloppen om vi använder mera biobränslen?

• Biobränslen kan i praktiken betraktas som koldioxidneutrala. • Vid uttag av biobränslen bör blad och barr lämnas kvar för att minska näringsförlusterna. • Återföring av vedaska krävs förmodligen för omfattande utnyttjande av biobränslen från skog. • Upprätthållandet av kretsloppen för viktiga grundämnen är inte vad som kommer att sätta gränserna för hur mycket biobränslen som kan utnyttjas. Det är andra faktorer såsom upprätthållande av biodiversitet, landskapsbild, risk för näringsläckage samt ekonomi

Biobränsle från hushållsavfall

Förbränning med utvinning av el och fjärrvärme är det miljömässigt klart bästa alternativet för hushållens källsorterade matavfall. Biogasutvinning är ett sämre alternativ än förbränning, om energiutbytet och de problem som är förknippade med rötresten beaktas. Storskalig kompostering är ohållbar med hänsyn till föroreningsrisker och bör avvecklas för hushållsavfall. Det är tveksamt om småskalig kompostering ger någon miljövinst om miljöanpassad förbränning finns som alternativ. Hushållens källsortering bör ställas om till biobränsleistället för komposterbart avfall. Utsorterat biobränsleavfall kan klara en viktig del av den miljömässigt eftersträvade omställningen till förnyelsebara energikällor

Specific volatile hydrocarbons in smoke from oxidative pyrolysis of softwood pellets

Samples of smoke from laboratory burning of commercial sawdust-based softwood pellets were analysed by gas chromatography on an aluminium oxide column. Flaming burning was very efficient. Significant emitted hydrocarbons were methane, quantitatively followed by ethene and lower proportions of ethane, ethyne and propene. The even lower hydrocarbon emissions from final glowing combustion were strikingly different with ethyne and benzene as the only prominent non-methane hydrocarbons. Smouldering combustion caused much higher hydrocarbon concentrations. Prominent non-methane compounds were furan and ethene from initial smouldering, and ethane, ethene and benzene from after-flame smouldering. The large differences in the proportions of specific hydrocarbons should be considered in evaluations of emissions from residential burning of pellets, with respect to combustion technology and impact on environment and health

A Turbocharged Dual-Fuel HCCI Engine

A 6-cylinder truck engine is modified for turbocharged dual-fuel Homogeneous Charge Compression Ignition (HCCI) engine operation. Two different fuels, ethanol and n-heptane, are used to control the ignition timing. The objective of this study is to demonstrate high load operation of a full-size HCCI engine and to discuss some of the typical constraints associated with HCCI operation. This study proves the possibility to achieve high loads, up to 16 bar Brake Mean Effective Pressure (BMEP), and ultra-low NOdx emissions, using turbo charging and dual fuel. Although the system shows great potential, it is obvious that the lack of inlet air pre heating is a drawback at low loads, where combustion efficiency suffers. At high loads, the low exhaust temperature provides little energy for turbocharging, thus causing pump losses higher than for a comparable diesel engine. Design of turbocharger therefore, is a key issue in order to achieve high loads in combination with high efficiency. In spite of these limitations, brake thermal efficiencies and power rating close to those of the original diesel engine are achieved with significant reduction in NOdx emissions. The maximum efficiency is 41.2%, which is slightly lower than for the original diesel engine

Data Assimilation of Growing Stock Volume Using a Sequence of Remote Sensing Data from Different Sensors

Airborne Laser Scanning (ALS) has implied a disruptive transformation of how data are gathered for forest management planning in Nordic countries. We show in this study that the accuracy of ALS predictions of growing stock volume can be maintained and even improved over time if they are forecasted and assimilated with more frequent but less accurate remote sensing data sources like satellite images, digital photogrammetry, and InSAR. We obtained these results by introducing important methodological adaptations to data assimilation compared to previous forestry studies in Sweden. On a test site in the southwest of Sweden (58 degrees 27 ' N, 13 degrees 39 ' E), we evaluated the performance of the extended Kalman filter and a proposed modified filter that accounts for error correlations. We also applied classical calibration to the remote sensing predictions. We evaluated the developed methods using a dataset with nine different acquisitions of remotely sensed data from a mix of sensors over four years, starting and ending with ALS-based predictions of growing stock volume. The results showed that the modified filter and the calibrated predictions performed better than the standard extended Kalman filter and that at the endpoint the prediction based on data assimilation implied an improved accuracy (25.0% RMSE), compared to a new ALS-based prediction (27.5% RMSE)

Importance of Calibration for Improving the Efficiency of Data Assimilation for Predicting Forest Characteristics

Data assimilation (DA) is often used for merging observations to improve the predictions of the current and future states of characteristics of interest. In forest inventory, DA has so far found limited use, although dense time series of remotely sensed (RS) data have become available for estimating forest characteristics. A problem in forest inventory applications based on RS data is that errors from subsequent predictions tend to be strongly correlated, which limits the efficiency of DA. One reason for such a correlation is that model-based predictions, using techniques such as parametric or non-parametric regression, are normally biased conditional on the actual ground conditions, although they are unbiased conditional on the RS predictor variables. A typical case is that predictions are shifted towards the mean, i.e., small true values are overestimated, and large true values are underestimated. In this study, we evaluated if the classical calibration of RS-based predictions could remove this type of bias and improve DA results. Through a simulation study, we mimicked growing stock volume predictions from two different sensors: one from a metric strongly correlated with growing stock volume, mimicking airborne laser scanning, and one from a metric slightly less correlated with growing stock volume, mimicking data obtained from 3D digital photogrammetry. Consistent with previous findings, in areas such as chemistry, we found that classical calibration made the predictions approximately unbiased. Further, in most cases, calibration improved the DA results, evaluated in terms of the root mean square error of predicted volumes, evaluated at the end of a series of ten RS-based predictions

CALFEM as a Tool for Teaching University Mechanics

Classical mechanics benefits greatly from the ability to demonstrate many concepts experimentally. However, modern mechanics relies more and more on new analysis methods such as the finite element method. In the teaching of mechanics these methods should be introduced, but the desire to experiment and build should be retained as a core issue. One tool for tackling this topic is given by CALFEM1. CALFEM is an acronym for Computer Aided Learning of the Finite Element Method. It is a tool developed for teaching the finite element method but it is also used in research as well as engineering design. The aim of CALFEM has been to provide a transparent link, such that the student can fully appreciate the intimate relationship between the mathematical models of a phenomenon, the finite element method and its computer implementation. This knowledge is not obtained by operation of commercial finite element programs. The pedagogical aspect of CALFEM has been part of the design from the beginning. In research, CALFEM has proven to be an efficient link between ideas and implemented solutions. CALFEM runs as a toolbox to MATLAB2 and provides all of the necessary tools for finite element calculations. The program has been carefully documented in an extensive manual that consists of a reference and a user's manual. The introduction and usage of CALFEM are strengthened by the close connection to teaching materials such as textbooks and exercises. The effectiveness of the system relies upon the widespread use of MATLAB at Lund University. The implementation of a web-based CALFEM has increased the availability of the package and allows for feedback and distribution of updates and additional material