1990
Forfattere
Leiv M. Mortensen Oddvar SkreSammendrag
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Forfattere
Leiv M. Mortensen Oddvar SkreSammendrag
Seedlings of Betula Pubescens, B. verrucosa and Alnus Incana were grown for 50 days in growth chambers at four ozone concentrations for 7 hr per day. Shoot and root dry weight decreased almost linearly with increasing ozone concentration in the three species. Shoot/root and leaf/stem dry weight werealmost unaffected by the treatment, while leaf senescence was significantly enhanced. Visible injury was observed at 53 nl per l and above.
Forfattere
Oddvar Skre Leiv M. MortensenSammendrag
3-year old Norway spruce seedlings from two clonal families were exposed to 10 hours per day with varying concentrations of ozone during the two months shoot elongation period. The plants were then placed in a cold climate chamber with 12 hours photoperiod and tested for frost resistace during the period of dormancy induction.There was a non-linear response on ozone, i.e. the highest sensitivity in one of the families was found at low (40 ppm) concentration. The other family showed no ozone response on frost hardiness.At low ozone concentrations there was a significant increase in shoot growth, relative to control plants, but at 80 and 160 ppm there was significant reduction in all growth parameters.Chloroplast damage and reduced chlorophyll content was found at the highest concentration. The carbohydrate amounts (mg/plant) decreased with increasing ozone concentrations, indicating reduced photosynthesis rates and/or increased respiration rates. There was also reduced formation of new roots already at 40 ppm ozone.
Forfattere
Erik Christiansen Petter NilsenSammendrag
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Forfattere
Hans Fredrik Hoen Tron EidSammendrag
This report describes a model for economical and biological analysis of long term investment- and felling strategies for a forest. The model might also be used in applied long term forest planning.The model is programmed in FORTRAN77 and can be executed on IBM-compatible personal computers with a mathematical coprosessor. Execution can be done under MS-DOS v3.3 or OS-2 vl.l.The model utilizes a combination of simulations and linear programming. Minos version 5.1 is used to solve the linear programming problem. The stand simulator projects the future development of a stand, i.e. diameter-, height-, volume-, and value increment over time. The user is not bound to follow a certain thinning programme or certain rotation ages, i.e. many different treatment schedules including different thinning programmes and rotation ages can be calculated.The calculations are done in steps of 5- or 10-year periods. The simulation of stand development is done for a specified number of periods, decided by the user depending on how far into the future it is desireable to do the predictions. The simulations are monitored from a data file where the treatments during the young growth phase and treatments like thinnings and final fellings are defined.Certain criteria deciding when the different treatments are allowed are also defined here. These criteria are based on the condition of the forest; age, number of trees, height, site class, etc. A data base for establishing new stands is connected to the model. This is used for initialization of new stands after final fellings. Both planting and natural regeneration can be simulated for the same stand in the same computer run.The increment models are based on the \"mean tree. The mean tree is characterized by the variables basal area mean diameter (Dg), and the basal area weighted mean height (H1). Price- and cost calculations are based on the mean tree. A net present value is calculated for all treatment schedules. The value of the ending inventory is included.Linear programming is used to select the best combination of stand treatment schedules (activities) for the whole forest. This evaluation is done considering the objective and the restrictions imposed on the forest activity. Column generation is applied to handle large problems, which are unsolvable with current PC-technology.The problem is then solved in many steps; only parts of the treatment schedules are chosen from the total LP-matrix and this sub-problem is solved. The \"shadow prices\" from the dual solution of the sub-problem are utilized to evaluate the rest of the treatment schedules in the total LP-matrix, and those with potential of improving the objective function are inserted to a new sub-problem.The new sub-problem is solved and the procedure is repeated until the potential increase for the whole problem is less than 0.1%, i.e. maximum increase for each stand summed over the whole forest in relation to the objective function value of the present solution.Many different problems can be formulated and solved as a LP-problem. Important parameteres which can be included as restrictions and/or in the objective are; net present value, periodic total fellings, periodic clear cuttings, thinnings, removal of sawlogs and pulpwood, net income and volume of remaining trees after treatment in each period. Decision problems which can be solved are; maximum net present value (at a given interest rate), non-declining quantity- or income path, maximum-, minimum-, absolute-, or interval values connected to one or more of the parameters included as restrictions and/or object value.
Forfattere
Bjørn Olav Rosseland Toril Drabløs Eldhuset M. StaurnesSammendrag
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Forfattere
Dan AamlidSammendrag
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Forfattere
Mette M. HandlerSammendrag
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Sammendrag
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Forfattere
Geir Harald StrandSammendrag
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