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Skovsgaard J.P.,Swedish University of Agricultural Sciences | Bald C.,Danish Nature Agency | Nord-Larsen T.,Copenhagen University
Scandinavian Journal of Forest Research | Year: 2011

Models for predicting the biomass of forest trees are becoming increasingly important for assessing forest resources and carbon sequestration in forests. We developed functions for predicting the biomass and basic density of above- and belowground parts of Norway spruce (Picea abies (L.) Karst.) in Denmark. Separate models were developed for branches (including foliage), stem and the below-ground stump and root system as well as for the aggregate components of total above-ground biomass and total tree biomass. Trees were sampled in 14 forest stands, reflecting the range of growth conditions and thinning practises of Norway spruce in Denmark. Because of inclusion of experimental plots, data reflected a wider range of thinning practices than commonly used in forestry practice. The data included measurements of biomass and basic density from 114 trees, two of which were regarded as outliers and consequently excluded in the final model estimation. The final models reflected known properties of tree growth and allocation of biomass among different tree components of even-aged Norway spruce. The models were successful in predicting biomass, basic density and biomass expansion factors across a wide variety of tree sizes, stand treatments and growth conditions. The models are believed to substantially improve national estimates of carbon sequestration and biomass resources. © 2011 Taylor & Francis. Source

Jessen S.,Copenhagen University | Holmslykke H.D.,Geological Survey of Denmark | Rasmussen K.,Danish Nature Agency | Richardt N.,Ramboll | Holm P.E.,Copenhagen University
Water Resources Research | Year: 2014

Hydrological and geochemical processes controlling the pore water chemistry in a permafrost wetland, with loam overlain by sphagnum peat, were investigated. The vertical distributions of dissolved Cl, and of pore water δ18O, appeared unrelated to ion freeze-out and isotope ice-water fractionation processes, respectively, dismissing solute freeze-out as a main control on the water chemistry. However, concentrations of major ions, others than Cl, generally increased with depth into the active layer. A conceptual model for water and solute movement in the active layer was derived. The model indicates upward diffusive transport of elements, released in the loam layer by mineral weathering, to the peat layer, in which lateral advective transport dominates. Active layer pore water and water of melted core sections of permafrost were of Ca-Mg-HCO3 type (1:1:4 stoichiometry) and were subsaturated for calcite and dolomite. The results are consistent with an annual cycling of inorganic carbon species, Ca and Mg, via cryogenic carbonate precipitation during fall freeze-up and their redissolution following spring thaw. Similarly, elevated Fe2+ concentrations appear to be related to cryogenic siderite formation. Pore water in the active layer showed high partial pressures of CO2, indicating the feasibility of bubble ebullition as a greenhouse gas emission pathway from permafrost wetlands. Elevated concentrations of geogenic trace elements (Ni, Al, and As) were observed, and the controlling geochemical processes are discussed. The conceptual model for water and solute movement was applied to quantify the contribution of released trace elements to a downstream lake in the permafrost catchment. © 2014. American Geophysical Union. All Rights Reserved. Source

Rasmussen P.,Geological Survey of Denmark | Sonnenborg T.O.,Geological Survey of Denmark | Goncear G.,Danish Nature Agency | Hinsby K.,Geological Survey of Denmark
Hydrology and Earth System Sciences | Year: 2013

Groundwater abstraction from coastal aquifers is vulnerable to climate change and sea level rise because both may potentially impact saltwater intrusion and hence groundwater quality depending on the hydrogeological setting. In the present study the impacts of sea level rise and changes in groundwater recharge are quantified for an island located in the Western Baltic Sea. The low-lying central area of the investigated part of the island was extensively drained and reclaimed during the second half of the 19th century by a system of artificial drainage canals that significantly affects the flow dynamics of the area. The drinking water, mainly for summer cottages, is abstracted from 11 wells drilled to a depth of around 20 m into the upper 5-10 m of a confined chalk aquifer, and the total pumping is only 5-6% of the drainage pumping. Increasing chloride concentrations have been observed in several abstraction wells and in some cases the WHO drinking water standard has been exceeded. Using the modeling package MODFLOW/MT3D/SEAWAT the historical, present and future freshwater-sea water distribution is simulated. The model is calibrated against hydraulic head observations and validated against geochemical and geophysical data from new investigation wells, including borehole logs, and from an airborne transient electromagnetic survey. The impact of climate changes on saltwater intrusion is found to be sensitive to the boundary conditions of the investigated system. For the flux-controlled aquifer to the west of the drained area only changes in groundwater recharge impacts the freshwater-sea water interface whereas sea level rise does not result in increasing sea water intrusion. However, on the barrier islands to the east of the reclaimed area, below which the sea is hydraulically connected to the drainage canals, and the boundary of the flow system therefore controlled, the projected changes in sea level, groundwater recharge and stage of the drainage canals all have significant impacts on saltwater intrusion and the chloride concentrations found in abstraction wells. © 2013 Author(s). Source

Koskela J.,Third University of Rome | Lefevre F.,French National Institute for Agricultural Research | Schueler S.,Federal Research and Training Center for Forests | Kraigher H.,Slovenian Forestry Institute | And 18 more authors.
Biological Conservation | Year: 2013

This paper provides a review of theoretical and practical aspects related to genetic management of forest trees. The implementation of international commitments on forest genetic diversity has been slow and partly neglected. Conservation of forest genetic diversity is still riddled with problems, and complexities of national legal and administrative structures. Europe is an example of a complex region where the distribution ranges of tree species extend across large geographical areas with profound environmental differences, and include many countries. Conservation of forest genetic diversity in Europe has been hampered by a lack of common understanding on the management requirements for genetic conservation units of forest trees. The challenge resides in integrating scientific knowledge on conservation genetics into management of tree populations so that recommendations are feasible to implement across different countries. Here, we present pan-European minimum requirements for dynamic conservation units of forest genetic diversity. The units are natural or man-made tree populations which are managed for maintaining evolutionary processes and adaptive potential across generations. Each unit should have a designated status and a management plan, and one or more tree species recognized as target species for genetic conservation. The minimum sizes of the units are set at 500, 50 or 15 reproducing individuals depending on tree species and conservation objectives. Furthermore, silvicultural interventions should be allowed to enhance genetic processes, as needed, and field inventories carried out to monitor regeneration and the population size. These minimum requirements are now used by 36 countries to improve management of forest genetic diversity. © 2012 Elsevier Ltd. Source

Canal-Verges P.,University of Southern Denmark | Canal-Verges P.,DHI Water - Environment - Health | Potthoff M.,DHI Water - Environment - Health | Hansen F.T.,DHI Water - Environment - Health | And 3 more authors.
Ecological Modelling | Year: 2014

It has been suggested that bedload transport of macroalgae in shallow lagoons and estuaries may negatively impact eelgrass through increased turbidity and physical stress. Increased turbidity and reduced benthic light availability for eelgrass occur when bedload transport of macroalgae erode surface sediment. Furthermore, drifting macroalgae ballistically damage eelgrass beds and increase seedling mortality. The frequency and impact of drifting macroalgae in Odense Fjord was evaluated with an agent-based model. The aims of this model were to understand and predict the mobility of opportunistic (Chaetomorpha linum) and non-ephemeral (Fucus vesiculosus) macroalgae and to describe and quantify the intensity and spatial distribution of bottom substrate physically affected by drifting macroalgae. The longest simulated movement by macroalgae was found to be 270 and 170km for brown and green algae respectively; while the macroalgae losses (export) out of the fjord were up to 11% of the total biomass; the simulated area impacted by macroalgae drift varied between 16% and 96.5% of the total fjord area; finally the degree on physically impacted area varied from 0.01 to 28.5m of algae trackm-2. The simulated pattern of drift distribution and hot spots for both brown and green algae fitted the geographical locations in which the algae community was observed on the field. Such high values for sea bed disturbances will have a major impact on the light availability due to sediment resuspension in bare bottoms and on rooted vegetation due to ballistic impacts in areas affected by algae drift. © 2013 Elsevier B.V. Source

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