Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
1995
Forfattere
Erik NæssetSammendrag
In Norway, about 5500 km2 are surveyed annually for forest management planning. Approximately 50 % of that area is recorded by means of aerial photo interpretation. A method for determination of gross value for individual forest stands by means of aerial photo interpretation has previously been developed (Nsset 1990, 1991a). The logging costs can be calculated by means of cost functions (Anon. 1994) utilizing stand characteristics related to the trees and characteristics related to the terrain, such as slope and skidding distance. Some properties related to the terrain can be derived from digital elevation models (DEM). The objective of the present work was to develop an integrated method for determination of gross value and logging costs for individual mature forest stands by means of aerial photo interpretation, DEMs, and geographical information systems (GIS). Computation of gross value as well as logging costs were based on the so-called mean tree of a stand, i.e. a tree defined by mean diameter by basal area and Loreys mean height. The models for computation of gross value and logging costs are shown in Fig. 1 and Fig. 2, respectively. In addition to stand characteristics related to the trees, Fig. 2 shows that slope and skidding distance must be derived in order to compute the logging costs. The method for computation of gross value and logging costs was demonstrated by means of a case study from a forest area in Froland municipality, South Norway, of about 710 ha. Black-and-white aerial photographs at an approximate scale of 1:15000 and a stereoplotter of the second order (Wild B8) were used to delineate the stands, measure stand mean height, and interpret crown closure, site quality, and tree species distribution of the individual stands. For all the mature stands within the area, information on topography and ground conditions interpreted in the aerial photos were used to suggest skid paths for timber transportation from the stands via existing skid roads to landings along the forest roads or public roads.The stand boundaries, the suggested skid paths, existing skid roads, existing forest roads and public roads, and contour lines taken from the official Economic Map Series at the scale 1:5000 with 5 m contour interval were digitized into separate map layers applying the pcARC/INFO software. All the forest stand characteristics were related to the stand map layer.The stand characteristics required for the gross value computation were exported to the SAS package (Anon. 1985), which was used for calculation of gross value as well as logging costs. The data flow is shown in Fig. 4. The gross value was calculated according to the model displayed in Fig. 1. The average slope and skidding distance of the individual stands were required for the logging costs calculation. The grid based GIS package IDRISI (Eastman 1992) was used for determination of slope and distance (Fig. 4) before the logging costs could be computed by means of the model shown in Fig. 2. A DEM was generated with IDRISI from the digitized contour lines (Fig. 5).The slope was computed (Fig. 6), and average slope of the individual stands was found and exported to the SAS package via pcARC/INFO (Fig. 4). The skidding distance for a stand was defined as the average distance on the terrain from the individual grid cells of a stand via the digitized skid paths and skid roads to landings along the forest roads or public roads.The crossings between the skid paths/roads and the forest/public roads were used for landing points. However, IDRISI provides procedures for calculation of ground plane distances only. A method for computation of approximate on terrain distances was therefore developed. The average extension of distance due to slope for traversing a grid cell was found (Eq. 3). A grid map where the grid cells were assigned the values of the average extensions due to slope was generated. A stand boundary layer where the stand boundaries were assigned the value -1 was produced. The average extension layer was overlaid the stand boundaries and the various path and road maps (Fig. 7 and Fig. 8), such that all stand boundary cells, except the crossings between the boundaries and the roads, attained the value -1. All other cells, including the crossing cells, attained the average extension values. The resulting layer (Fig. 10) was used as friction layer and the forest/public road layer was used as source layer to indicate the cells from which skidding distances should be determined utilizing the COST procedure (COSTGROW algorithm) of IDRISI. The cells of the friction layer assigned the value -1 (the stand boundary cells) served as absolute transportation barriers. The computed skidding distances (Fig. 11) were, however, based on an on the terrain straight line distance within the individual stands (Fig. 3). The computed distance for each grid cell was therefore multiplied by an average ground plane winding factor of 1.16 found for 28 of the stands within the study area (Table 1). Finally, the average corrected skidding distance for each stand was derived and exported to pcARC/INFO and SAS for logging costs computation. Computed gross value, logging costs, and gross profit are displayed in Figs. 12, 13, and 14, respectively. The suggested method for computation of gross value of mature stands is likely to give satisfying accuracy.Assuming that some of the calculations of the logging costs model (Hkl and n, Fig. 2) be corrected by means of sample plot inventories, a random error (standard deviation) of about 10 % should be expected. At present, practical large scale application of the presented method is hindered by a lack of proper digital elevation data. Implementation of the method requires also integrated computer programs on more powerful computer platforms than the one used here.
Forfattere
Dan AamlidSammendrag
Det er ikke registrert sammendrag
Forfattere
S. Forberg Richard HorntvedtSammendrag
Omfanget av fluorskader på furuskogen i Vettismorki (Sogn og Fjordane: Årdal) ble registrert i 1993/94 for å se hvordan skadene hadde utviklet seg etter en tilsvarende registrering i 1970. I denne perioden er fluorutslippet fra Årdal Verk redusert fra ca 60 til 15 kg/h. Fluorinnholdet i furunåler var redusert fra 49 til 13 µg g-1 som gjennomsnitt for hele Vettismorki, og fra 97 til 21 µg g-1 på den mest eksponerte prøveflaten. I 1970 var det tildels sterke sviskader på furunålene i store deler av området. I 1993 ble det bare funnet svake nåleskader på de mest eksponerte lokalitetene. Skogens vitalitet (kroneskade) hadde forandret seg i to retninger siden 1970. Andelen av døde trær hadde øket fra 3 til 30%. Økningen tilsvarer litt mer enn andelen av trær som i 1970 ble klassifisert som sterkt skadde (døende). På den annen side hadde også andelen av friske trær øket, fra 22 til 33%. Borprøver fra levende trær viste at siden ca 1960 har årringbredden avtatt i forskjellig grad, i samsvar med kroneskaden. Gjennomsnittlig årringbredde for perioden 1970-93 i prosent av 1900-50 var 62, 31, 16 og 11 hos henholdsvis gruppene frisk, svak skade, middels skade og sterk skade. Hos svakt skadde trær viste årringbredden tydelig økning etter 1980. Gjenveksten av furuplanter var i gjennomsnitt 32 planter pr. daa. Det var mest gjenvekst i de lavereliggende områdene nærmest Utladalen, til tross for at det var der fluorskadene tidligere var sterkest. Konklusjonen er at selv om skogskadene har vært tildels meget alvorlige, så har omlag to tredjeparter av de gamle furutrærne overlevet. Det er etter forholdene tilfredsstillende gjenvekst av furu.
Forfattere
Erik Trømborg Birger SolbergSammendrag
This report describes the model used in the project Modelling the Norwegian Forest Sector. The purpose of this project is to do consistent analyzes of how different changes in factors affecting the business environment of forestry and forest industries in Norway will effect the forest sector. The model used is developed by professor Markku Kallio at Helsinki School of Economics. The model is based on the same main principles as the model developed at the International Institute for Applied System Analysis in the 80s, IIASAs Global Trade Model, GTM. The model is named the Norwegian Trade Model, NTM. NTM is a regional partial equilibrium model with linear constraints (like production capacity limits and upper bounds on harvesting), and a non-linear object function (through non-linear timber supply functions). The model maximizes net social pay-off for all products and regions. Net social pay-off is calculated as the area under all demand functions, minus the sum of transportation costs resulting from trade with other regions, and minus productions costs in the forest industry including timber costs given by non-linear supply curves. This describes according to economic theory, a situation under perfect competition where all consumers and producers maximize their surplus. The model consists of four main parts: A model for timber supply, including the connection between harvesting level and timber costs, and between todays harvesting and future timber production and harvesting. A model for the forest industry that describes how timber is transformed to intermediate- and endproducts and how central factors such as capacity, locations and production costs change over time. A model for product demand that relates demand for forest products to factors such as price, volume, economic growth and exchange rates. A model for trade between regions that relates a fixed location of timber resources and forest industry to demand and supply of forest products. The model consists of 10 domestic regions and two regions for respectively export and import. 27 products are included in the model of which there are six roundwood assortments, 5 pulp grades, 2 board grades, 3 sawnwood products and 9 different paper and board products in addition to recycled paper and energy wood. The dynamics of the model is created through recursive programming where the equilibrium problem for the analyzing period is split into a number of equilibrium solutions, one for each time step. The equilibrium for the first time step t, gives together with changes in timber supply, production capacity, costs and demand, basis for the equilibrium solution in next time step t1. The model describes 5 time steps of 5 years each from year 1990 to year 2010, where the model estimates product prices, harvesting, production on plant and regional level and trade between regions in each time step. A model will always be a strong simplification of the real world. It is therefore important that results from the model are evaluated on the basis of assumptions within the model and the uncertainty of data used. It is our opinion that NTM is a appropriate model for analyzes of the Norwegian Forest Sector. Compared with other models we feel that NTM has the following advantages:The regional aspects is very well taken care of.The forest sector is well described as the forest sector is included at individual plant level. The optimization algorithms secure economic consistency in each scenario alternative. The non-linear timber supply equations used gives most likely a more realistic descriptions of the forest owners behaviour than linear supply equations.The algorithm applied is highly efficient, making possible solutions in short time. Every model has shortcomings towards the real world and it is important that the results from the model are evaluated in relation to these shortcomings. In NTM is it our opinion that the following factors are burdened with highest uncertainty:The linearization of the demand functions might give too large changes in demand when price change.The substitution between different timber assortments on both the supply and demand side is just described to a limited extent in the model.The model is not very user friendly.There will in general be significant uncertainty linked to the huge amount of data demanded by the model. The main purpose with the model is to quantify relative changes connected to certain assumptions and to clarify mechanisms. This purpose has to be emphasized when both results and model are evaluated. Used in this way, it is our opinion that NTM can give valuable insight in many aspects of the forest sector.
Sammendrag
Interessa for naturleg forynging av furu er aukande på Vestlandet. For å betra spire- og veksetilhøva er det ofte ein føremon å blottleggja mineraljorda. Forsøk med markberedning med lette gravemaskinar og landbrukstraktor, har vore gjennomført i fire felt i Voss kommune. Landbrukstraktoren (51 kW) var utstyrt med eit markberedningsaggregat laga for flekkopptaking i ei rad. Dei tre beltegravemaskinane (8-9 tonn) var alle utstyrde med 80-90 cm brei skuffe. Traktor og gravemaskin vart køyrde ved sida av kvarandre i kvart felt for å samanlikne produktivitet og arbeidskvalitet. Førarane hadde som mål å laga minimum 250 flekker pr. dekar, med ein flekkstorleik på omlag 0,5 m2 blottlagt mineraljord. Produktiviteten, målt i markbereidd areal pr. virketime, vart høgast ved bruk av gravemaskin. Landbrukstraktoren fekk seinka produktivitet når terrenget vart bratt. I stigning over 20 prosent markbereidde traktoren berre i nedoverbakke. Gravemaskinen synte ingen produktivitetsreduksjon i bratt terreng. Båe maskintypane fekk færrast flekker i feltet med den vanskelegaste terrengoverflata. Flekkstorleik og blottleggingsprosent (mineraljord) vart noko større med gravemaskin enn med landbrukstraktor, unnateke på det feltet som var lettast å køyra. Generelt syntest gravemaskinane å vera minst påverka av vanskeleg terreng. Gravemaskinar greier seg med færre køyredrag enn traktorar og kan derfor unngå ein del terrenghindringar som ein landbrukstraktor ikkje klarer. Førarane i desse forsøka var røynde med maskinane sine, men hadde ikkje markbereidd før. For landbrukstraktoren er det nytta ein noko høgare produktivitet i sluttanalysene enn det resultatet som vart oppnådd i feltforsøka. For landbrukstraktor vil dessutan feltstorleik og -form ha innverknad på køyre- og snutid og dermed produktiviteten. Gravemaskin har høgare markberedningskostnad enn landbrukstraktor. Båe maskintypar får høg dekarkostnad på små areal, fordi ein får mykje flyttetid i høve til arbeidstid på flatene. Redusert framkomstevne og lågare kvalitet på arbeidet i ujamnt terreng, set grenser for bruk av landbrukstraktoraggregat til markberedning på Vestlandet. Etter erfaringane i dette forsøket, er mindre beltegravemaskinar (8-9 tonn) godt eigna til markberedning. Gravemaskin kan forutan til markberedning og nyttast til grøfting, sporreparasjon og vegvedlikehald.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Tore SkrøppaSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor J. JohansenSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
1994
Forfattere
Arnfinn Nes Arne Hjeltnes Mekjell Meland Mons Flønes Rolf NestbySammendrag
Det er ikke registrert sammendrag