Evapotranspiration of forests in Fennoscandia - a synthesis based on eddy-covariance data and modeling

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Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest

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A look at aerosol formation using data mining techniques

International audienceAtmospheric aerosol particle formation is frequently observed throughout the atmosphere, but despite various attempts of explanation, the processes behind it remain unclear. In this study data mining techniques were used to find the key parameters needed for atmospheric aerosol particle formation to occur. A dataset of 8 years of 80 variables collected at the boreal forest station (SMEAR II) in Southern Finland was used, incorporating variables such as radiation, humidity, SO2, ozone and present aerosol surface area. Data analysis were done using clustering and classification methods. The aim of this approach was to gain new parameters independent of any subjective interpretation. This resulted in two key parameters, relative humidity and preexisting aerosol particle surface (condensation sink), capable in explaining 88% of the nucleation events. The inclusion of any further parameters did not improve the results notably. Using these two variables it was possible to derive a nucleation probability function. Interestingly, the two most important variables are related to mechanisms that prevent the nucleation from starting and particles from growing, while parameters related to initiation of particle formation seemed to be less important. Nucleation occurs only with low relative humidity and condensation sink values. One possible explanation for the effect of high water content is that it prevents biogenic hydrocarbon ozonolysis reactions from producing sufficient amounts of low volatility compounds, which might be able to nucleate. Unfortunately the most important biogenic hydrocarbon compound emissions were not available for this study. Another effect of water vapour may be due to its linkage to cloudiness which may prevent the formation of nucleating and/or condensing vapours. A high number of preexisting particles will act as a sink for condensable vapours that otherwise would have been able to form sufficient supersaturation and initiate the nucleation process

Could continuous cover forestry be an economically and environmentally feasible management option on drained boreal peatlands?

Environmental and economic performance of forestry on drained peatlands was reviewed to consider whether continuous cover forestry (CCF) could be a feasible alternative to even-aged management (EM). CCF was regarded feasible particularly because continuously maintaining a tree stand with significant transpiration and interception capacity would decrease the need for ditch network maintenance. Managing CCF forests in such a way that the ground water levels are lower than in clear-cut EM forests but higher than in mature EM forests could decrease greenhouse gas emissions and negative water quality impacts caused both by anoxic redox reactions and oxidation and mineralization of deep peat layers. Regeneration studies indicated potential for satisfactory natural regeneration under CCF on drained peatlands. An economic advantage in CCF over EM is that fewer investments are needed to establish the forest stand and sustain its growth. Thus, even if the growth of trees in CCF forests were lower than in EM forests, CCF could at least in some peatland sites turn out to be a more profitable forest management regime. An advantage of CCF from the viewpoint of socially optimal forest management is that it plausibly reduces the negative externalities of management compared to EM. We propose that future research in drained peatland forests should focus on assessing the economic and environmental feasibility of CCF.Peer reviewe

Assessing extraction trail trafficability using harvester CAN-bus data

Modern forest machines with a Controlled Area Network (CAN)-bus managed diesel engine and hydrostatic transmission can continuously measure power expended in traveling. At a constant speed on level ground, the power is expended in overcoming motion resistance, which is directly related to wheel sinkage and hence to site trafficability. In cut-to-length timber harvesting, the harvester precedes the forwarder on the site, making it feasible to utilize the harvester to collect data on site trafficability to produce a trafficability map for the forwarder. CAN-bus trafficability mapping was tested with an 8-wheeled Ponsse Scorpion King harvester and an 8-wheeled Ponsse Elk forwarder instrumented for collecting transmission power expenditure, in addition to appropriate available CAN-bus information. Trafficability was also mapped based solely on momentary engine power in order to eliminate the need for additional pressure transducers. The CANbus data showed good results for mapping site trafficability when compared to soil penetration resistance and harvesting machinery wheel rut depth measurements. Assessing harvester rolling resistance using CAN-bus data offers an interesting possibility to map harvesting site trafficability also in Big Data scale. Since modern harvesters are practically ready for indirect power recording, the additional cost of fully automated and comprehensive trafficability mapping as part of operative forestry is negligible

Nitrous oxide emissions from a beech forest floor measured by eddy covariance and soil enclosure technigues

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Autumn temperature and carbon balance of a boreal Scots pine forest in Southern Finland

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Is the water footprint an appropriate tool for forestry and forest products: The Fennoscandian case

The water footprint by the Water Footprint Network (WF) is an ambitious tool for measuring human appropriation and promoting sustainable use of fresh water. Using recent case studies and examples from water-abundant Fennoscandia, we consider whether it is an appropriate tool for evaluating the water use of forestry and forest-based products. We show that aggregating catchment level water consumption over a product life cycle does not consider fresh water as a renewable resource and is inconsistent with the principles of the hydrologic cycle. Currently, the WF assumes that all evapotranspiration (ET) from forests is a human appropriation of water although ET from managed forests in Fennoscandia is indistinguishable from that of unmanaged forests. We suggest that ET should not be included in the water footprint of rain-fed forestry and forest-based products. Tools for sustainable water management should always contextualize water use and water impacts with local water availability and environmental sensitivity

Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake

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