Search

An ex-ante impact assessment of land use plans is required in the preparation or revision phase to inform planners and other stakeholders about the possible or likely impacts of the plans. This stu...

Planning a forest inventory comprises making decisions related to the sampling strategy: cluster configuration, sample size and sample allocation within the survey area. Cluster configurati...

Root rot in Norway spruce (Picea abies (L.) Karst.) causes substantial economic losses to the forestry sector. In this study, we developed a probability model for decay at breast height utilizing 1...

Assessing the need for and timing of tending in seedling stands is based on the stem numbers and heights of crop trees and competing broadleaves, as well as the expected forthcoming development of ...

We developed individual tree height growth models for Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in Norway based on national forest inventory data. Potential height growth is based on existing dominant height growth models and reduced due to competition by functions developed in this study. Three spatially explicit and two spatially non-explicit competition indices were tested. Distance effects and diameter ratio effects were estimated from the data simultaneously with parameters of the potential modifier functions. Large height measurement errors in the national forest inventory data caused large residual variation of the models. However, the effects of competition on height growth were significant and plausible. The potential modifier functions show that height growth of dominant trees is largely unaffected by competition. Only at higher levels of competition, height growth is reduced as a consequence of competition. However, Scots pine also reduced height growt...

This study provides an analysis on the variability of structural timber of Norway spruce (Picea abies) grown in Norway. Density, modulus of elasticity (MOE) and bending strength were measured on 1188 boards from 205 trees, sampled from 14 sites throughout Southern Norway, Eastern Norway and Trondelag. The area represents the procurement area for the majority of Norwegian sawmills. The variability of the timber properties was analysed in a linear mixed model where the random variance was divided into variance due to site, variance due to trees and within-tree variance. Models describing variance due to site based on site index, altitude and latitude were developed, and combined with data from the Norwegian National Forest Inventory to estimate mean values and variability of the timber properties. The results showed that major parts of the variance due to site are explained by altitude and site index, and for density also by latitude. Major parts of the variance due to site and the variance due to t...

Mixed or broadleaf forests were once common in many regions of Northern Europe, whereas today conifers often dominate. The aim of the study was to investigate the spatial and temporal patterns and processes which underlie this transition to Picea abies dominance in southern Sweden. We use recently developed paleoecological methods to determine long-term changes in the relative abundance of tree species, and digitalized National Forest Inventory (NFI) databases to assess more recent changes in the spatial coverage of Picea throughout the region. The novel combination of the two databases reveals that Picea became a widespread and abundant species in many parts of southern Sweden around 1000 years ago. After a brief decline in abundance starting around 500 years ago, NFI data indicate a rapid increase in the volume of Picea between 1920 and 1950, prior to the large-scale introduction of Picea-dominated plantation forests. The available evidence suggests that abandonment of forest grazing and slash-and-burn cultivation, as well as selection cutting benefited the natural establishment and growth of Picea during the first half of the twentieth century. Hence, prior to the impacts of industrialized forestry that began in the 1950s, other processes were already favouring increased Picea abundance.

Use of harvest residues for bioenergy is minimal in Norway, and the proposed increase of 14 TWh in annual bioenergy use by year 2020 may thus to a large part be based on residues from conventional timber harvesting. To judge the potential of harvest residues for bioenergy both in the short and long run, we present cost-supply curves for residue harvesting at national and regional levels. We produce different harvesting scenarios using the detailed forest model Gaya/J and a representative description of the Norwegian forest area from Norwegian national forest inventory (NFI) sample plots including environmental restrictions. Forest information is sufficiently detailed to estimate necessary biomass fractions and calculate costs of harvest residue extraction at plot level. We estimate a maximum annual energy production of 5.3 TWh from harvest residues with the present harvest level, which is far from the official target. In principle, there are two solutions for achieving this target; increase harve...

This study quantified, across a landscape in Eastern Finland, the influence of administrative land-use and technical land-form constraints on timber production. Spatially explicit data about the nature conservation areas, land use plans and steep slopes were integrated with Multi-source National Forest Inventory (MS-NFI) data. The Finnish forestry model MELA was used in the calculations related to updating forest data and estimating different scenarios of timber production with and without constraints. In the study area, the annual volume of maximum sustainable cutting removal defined for the next 30 years was decreased by one-third due to restrictions. The presented approach could be used, for example, to assess timber availability at the landscape level. Future challenges include ensuring the compatibility of spatially explicit data obtained from different sources, identifying the feasibility of forest management operations in the restricted area, and incorporating near-nature forest management...

Distance-independent, non-linear models of 5-year diameter increment for Norway spruce, Scots pine, birch and other broadleaved trees were developed, evaluated and compared on data from the Norwegian National Forest Inventory. The models were based on a Weibull curve dependent on diameter and a modifier function dependent on site parameters. A non-linear mixed model approach was used to fit the models. Model fit was assessed by the Pseudo-R 2 on total level and on plot level reflecting a random plot effect. The values were 0.31, 0.20, 0.13 and 0.10 for Norway spruce, Scots pine, birch and other broadleaves, respectively. The bias estimates from an independent validation were 0.1, 0.0, 0.1 and 0.3 mm for Norway spruce, Scots pine, birch and other broadleaves, respectively. The results from the independent validation were compared with results from identical tests of three other sets of models. The comparison indicated good model performance of the current models. The models were also compared by e...

Models for predicting mortality in even‐aged stands were developed. The models rely on data from the Norwegian National Forest Inventory, and were designed for use in large‐scale forestry scenario models. A two‐step modelling strategy was applied: (1) logistic regression models predicting the probability of complete survival occurring,” and (2) multiplicative regression models for stem number reduction and diameter calibration. A joint model for all species predicting the probability of survival occurring on a plot was developed. Separate models for forests dominated by spruce, pine and broadleaved trees were developed for stem number reduction, while no appropriate models for diameter calibration were found. The phenomenon mortality is a stochastic, rare and irregular event, and this was reflected as low R 2 in the models. However, the model performance appeared logical and the results of validations based on independent data were reasonably good, i.e. the presented models may be applied to large‐scale f...

To measure many small areas in a forest, each to the required detail and precision, and sufficiently frequently, is too expensive using ground-based inventories alone. The Finnish satellite image-aided National Forest Inventory (NFI) method was modified and tested with a view to developing a new preharvesting forest inventory method for assessing the volumes of potential timber assortments (log products) in New Zealand radiata pine (Pinus radiata D. Don) plantations. Data from 188 ground plots were supplied by a forest company for a 1000 ha block of radiata pine. This material was combined with known stand boundaries from maps and data from a Landsat TM image in order to predict for each pixel and each stand the pruned and unpruned sawlog, pulp and total standing volumes. A k-nearest neighbour algorithm was applied for the estimation. Some stand characteristics, obtained from stand histories, were used as co-variates, in addition to spectral features. Cross-validation tests indicated that estimates of plo...

Average diameter of the thickest knot of each whorl within a specific stem section of Scots pine (TK) was studied using functions based on growth ring widths, diameter of dry branches, site index, stand age, and latitude. Data from the Pine Stem Bank - a database of external and internal properties where knots were detected by computerized tomography (CT) scanning - were used. A high value of the corrected coefficient of determination, R2(adj)=0.63, was found between TK and two independent variables, average width of growth rings 11 - 20 at stump height and latitude. It is argued that TK is a good parameter for describing timber quality, and that it now is predictable on standing trees as well as on existing data from the National Forest Inventory (NFI). An attempt was made to quantify the change in the TK - value by site index, tree class, age class, and region by applying functions to NFI data from 1988 - 92. In a second analysis, also based on NFI data, the TK - value had increased by 17% from 1966 to ...

The aim of the study was to establish single‐tree functions to predict crown height, defined as the height from the ground to the attachment of the lowest living branch to the trunk. Data from the Swedish National Forest Inventory 1983–1992 were used to construct country‐wide functions for Scots pine (Pinus sylvestris L.) and for Norway spruce (Picea abies (L.) Karst.). The model derived was based on the assumption that crown recession in closed forests is caused primarily by lack of light. A crown height function and a relative crown height (crown height/total tree height) function were calculated for each species and were found to predict crown height fairly accurately. Crown height was generally predicted more accurately for Scots pine than for Norway spruce. The crown height functions developed here can be used as an input for predicting the quality of timber. The functions are meant to form part of a system for the long‐term forecasting of timber yields, but they can also be used in calculations of t...

Nearest‐neighbour regression was tested for generalizing sample tree information in data from the national forest inventory of Finland. The following variables were found to be good regressors: stem diameter, mean diameter, density and age of growing stock, and plot location. The nearest‐neighbour estimator appears to maintain the natural variation of the variables to be estimated well. Reliable volume and height estimates can be obtained even when using only one nearest neighbour. Increasing the number of neighbours improves the accuracy of estimates.

Average tree height and basal area growth for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) in Sweden were studied as functions of species, age, stand density, location and year of inventory in the period 1953–1992, on the basis of sample tree data from the National Forest Inventory. A highly significant annual increase of both height and basal area growth was found, of the magnitude 0.5–0.8%, during the 40 yr period. Possible reasons for the trend are discussed. The altered way of cutting in the early 1950s, from selective cutting to clear felling and thinning from below, has had a large impact. Also, improved regeneration methods, nitrogen fertilization and ditching have increased growth. The increasing atmospheric deposition of nitrogen is another possible factor.

The study deals with the structure of advanced virgin forests in Finland based on the national forest inventory carried out in the 1920's. At that time, virgin forests covered 2/3 of the forested area of Finland. Stand structure was described in terms of the d.b.h. distribution. The study material consisting of 10 x 50 m sample plots was grouped according to geographical region, site type and the age class of the overstorey. A stand was classified to be advanced if the age of the overstorey was at least half of the currently applied rotation age and if the stem volume exceeded 40 m3/nectare. About 60% of all virgin forests (i.e. 932 sample plots) were classified to be advanced. In the 1920's. the majority of advanced virgin forests were mixed stands with an all‐sized structure. Trees of small diameter prevailed and the stem number diminished rather steadily with increasing d.b.h. Even‐sized stands with a d.b.h. range of 15 or 20 cm and a normally distributed diameter frequency accounted for only 10 sample...