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Only abstract. Paper copies of master’s theses are listed in the Helka database (http://www.helsinki.fi/helka). Electronic copies of master’s theses are either available as open access or only on thesis terminals in the Helsinki University Library. Vain tiivistelmä. Sidottujen gradujen saatavuuden voit tarkistaa Helka-tietokannasta (http://www.helsinki.fi/helka). Digitaaliset gradut voivat olla luettavissa avoimesti verkossa tai rajoitetusti kirjaston opinnäytekioskeilla. Endast sammandrag. Inbundna avhandlingar kan sökas i Helka-databasen (http://www.helsinki.fi/helka). Elektroniska kopior av avhandlingar finns antingen öppet på nätet eller endast tillgängliga i bibliotekets avhandlingsterminaler. Tutkielman sovelluskohteena on metsänuudistusalan inventointi. Uudistusalalta pyritään tällöin selvittämään taimitiheys eli se, kuinka monta tainta kasvaa yhtä hehtaaria kohden. Inventointi toteutetaan sijoittamalla uudistusalalle koealoja jonkin otanta-asetelman, yleensä systemaattisen otannan mukaisesti. Työn konkreettisena ongelmana on arvioida taimitiheysestimaattorin luotettavuutta tämän virhevarianssin avulla. Perinteisen asetelmapohjaisen (design-based) otannan sijasta tutkielmassa tarkastellaan mallipohjaista (model-based) otantaa. Taimikon mallina ovat spatiaaliset pisteprosessit (spatial point processes). Taimikon tilajärjestys eli taimien keskinäinen sijainti tason pistekuviona ajatellaan tällöin prosessin realisaatioksi. Koska nykymuotoisten taimikoiden rakenteessa esiintyy suurta vaihtelua metsän uudistus- ja muokkaustavoista riippuen, tarvitaan taimikon malliksi joukko erityyppisiä pisteprosesseja. Näistä tutkielmassa esitellään homogeeninen Poisson-prosessi, epähomogeeninen Poisson-prosessi, Poisson-ryväsprosessit, Cox-prosessit sekä kolme erilaista säännöllistä prosessia. Esiteltävät pisteprosessit ovat kaikki (lukuunottamatta epähomogeenista Poisson-prosessia) sekä stationaarisia eli siirtoinvariantteja että isotrooppisia eli kiertoinvariantteja. Nämä vahvat teoreettiset oletukset toteutuvat riittävässä määrin muokkaamattomien uudistusalojen tilajärjestyksissä, joihin tutkielmassa rajoitutaan. Pisteprosesseja luonnehtivista tunnusluvuista tutkimusasetelman kannalta keskeisimmät käsitteet ovat intensiteetti (intensity) ja parikorrelaatiofunktio (pair correlation function). Tutkimusongelma ratkaistaan jatkuvaparametrisen satunnaiskentän konstruktiolla, joka määritellään pisteprosessin ominaisuuksien ja koealojen havainnointimekanismin kautta. Otantateoria jatkuvaparametrisen satunnaiskentän tilanteessa tunnetaan tiettyjen oletusten vallitessa. Käytännön laskelmissa kuitenkin kohdataan usein huomattavia hankaluuksia. Tutkielman otantateoriaa havainnollistetaan pienen esimerkkiaineiston avulla. Tältä 10 x 10 neliömetrin kokoiselta, luontaiselta männyn uudistusalalta tunnetaan jokaisen taimen sijaintikoordinaatit. Tarkastelut havainnollistavat yleisesti tiedossa olevaa systemaattisen otannan suhteellista tehokkuutta tasaiseen satunnaisotantaan verrattuna. Esimerkkilaskelmissa ero on kuitenkin hyvin vähäinen. Tutkielman tärkeimmät lähteet ovat pisteprosessien osalta teokset Diggle (1983): Statistical Analysis of Spatial Point Patterns (Academic Press) sekä Stoyan & Stoyan (1994): Fractals, Random Shapes and Point Fields (Wiley). Jatkuvaparametrisen satunnaiskentän otantateoriaa käsitellään klassikkoteoksen Matérn (1960): Spatial Variation (Meddelanden från Statens Skogsforskningsinstitut, 49:5) pohjalta.

Two methods of pre-harvest inventory were designed and tested on three cutting sites containing a total of 197 500 m3 of wood. These sites were located on flat-ground boreal forests located in northwestern Quebec. Both methods studied involved scaling of trees harvested to clear the road path one year (or more) prior to harvest of adjacent cut-blocks. The first method (ROAD) considers the total road right-of-way volume divided by the total road area cleared. The resulting volume per hectare is then multiplied by the total cut-block area scheduled for harvest during the following year to obtain the total estimated cutting volume. The second method (STRATIFIED) also involves scaling of trees cleared from the road. However, in STRATIFIED, log scaling data are stratified by forest stand location. A volume per hectare is calculated for each stretch of road that crosses a single forest stand. This volume per hectare is then multiplied by the remaining area of the same forest stand scheduled for harvest one year later. The sum of all resulting estimated volumes per stand gives the total estimated cutting-volume for all cut-blocks adjacent to the studied road. A third method (MNR) was also used to estimate cut-volumes of the sites studied. This method represents the actual existing technique for estimating cutting volume in the province of Quebec. It involves summing the cut volume for all forest stands. The cut volume is estimated by multiplying the area of each stand by its estimated volume per hectare obtained from standard stock tables provided by the governement. The resulting total estimated volume per cut-block for all three methods was then compared with the actual measured cut-block volume (MEASURED). This analysis revealed a significant difference between MEASURED and MNR methods with the MNR volume estimate being 30 % higher than MEASURED. However, no significant difference from MEASURED was observed for volume estimates for the ROAD and STRATIFIED methods which respectively had estimated cutting volumes 19 % and 5 % lower than MEASURED. Thus the ROAD and STRATIFIED methods are good ways to estimate cut-block volumes after road right-of-way harvest for conditions similar to those examined in this study.

Cut-off importance sampling (CIS) is introduced as a means of sampling individual trees for the purpose of estimating bole volume. The novel feature of this variant of importance sampling is the establishment on the bole of a cut-off height, He, above which sampling is precluded. An estimator of bole volume between predetermined heights Hi and Hu > Hc is proposed, and its design-based bias and mean square error are derived. In an application of CIS as the second stage of a two-stage sample to estimate aggregate bole volume, the gain in precision realized from CIS more than offset its bias when compared to the precision of importance sampling when He = HJJ.

The purpose of this study was to test the benefits of a forest site quality map, when applying satellite image-based forest inventory. By combining field sample plot data from national forest inventories with satellite imagery and forest site quality data, it is possible to estimate forest stand characteristics with higher accuracy for smaller areas. The reliability of the estimates was evaluated using the data from a stand-wise survey for area sizes ranging from 0.06 ha to 300 ha. When the mean volume was estimated, a relative error of 14 per cent was obtained for areas of 50 ha; for areas of 30 ha the corresponding figure was below 20 per cent. The relative gain in interpretation accuracy, when including the forest site quality information, ranged between 1 and 6 per cent. The advantage increased according to the size of the target area. The forest site quality map had the effect of decreasing the relative error in Norway spruce () volume estimations, but it did not contribute to Scots pine () volume estimation procedure.Picea abiesPinus sylvestris

A calculation procedure is presented for calculating and analysing remeasured permanent sample plots. Data for eight different fixed and variable size plot types were simulated on the basis of two stands whose trees were mapped and measured in 1982 and 1986. The accuracy and efficiency of the plot types were assessed and compared. The calculation procedure is based on treewise expansion factors and the division of trees sampled into state/measurement classes. Nine classes were required for variable size plots and six for fixed size plots. A relascope plot with basal-area factor 1 (m2/ha) proved to be most efficient for estimating basal-area at a given time and a fixed size circular plot with radius 10 m for estimating basal-area increment over a given time period. The main problems were related to the estimation of non-measurable variables, e.g., the initial diameters of ingrowth trees, i.e., trees having passed the threshold size during the measurement period. Most problematic were cut trees belonging to the ingrowth or sample enlargement classes. It is nevertheless thought that the system is appropriate for monitoring forest changes and making sensitivity analyses with permanent sample plots.

Semiparametric models, ordinary regression models and mixed models were compared for modelling stem volume in National Forest Inventory data. MSE was lowest for the mixed model. Examination of spatial distribution of residuals showed that spatial correlation of residuals is lower for semiparametric and mixed models than for parametric models with fixed regressors. Mixed models and semiparametric models can both be used for describing the effect of geographic location on stem form.

Schreuder, Hans T., Gregoire, Timothy G., Wood, Geoffrey B., Sampling methods for multiresource forest inventory. John Wiley & Sons. xv + 446 p. ISBN 0-471-55245-3.

In this study, model based and design based inference methods are used for estimating mean volume and its standard error for systematic cluster sampling. Results obtained with models are compared to results obtained with classical methods. The data are from the Finnish National Forest Inventory. The variation of volume in ten forestry board districts in southern Finland is studied. The variation is divided into two components: trend and correlated random errors. The effect of the trend and the covariance structure on the obtained mean volume and standard error estimates is discussed. The larger the coefficient of determination of the trend model, the smaller the model based estimates of standard error, when compared to classical estimates. On the other hand, the wider the range and level of autocorrelation between the sample plots, the larger the model based estimates of standard error.

Regression models for estimating stem volume of Scots pine ( L.) were constructed using sample tree data measured in the 7th and 8th National Forest Inventory of Finland. Stem volume were regressed on diameter, basal area of growing stock, and geographic location. The results of the study show that using second order trend surface to describe the geographic variation of the residuals gives satisfactory results. Using mixed estimation for combining old and new sample tree data improves the efficiency of an inventory. The weight of the prior information must be low, because remarkable differences in stem form was found in the two inventories.Pinus sylvestris

Models for estimating the upper diameter of trees were constructed using sample tree data measured in the 7th National Forest Inventory in Finland. Calibration of the models was tested with data from the 8th National Forest Inventory. The results showed that using mixed estimation for combining the two data sets improves the reliability of the models. Models and methods used in this study can be recommended for use in forest inventories. The PDF includes an abstract in Finnish.

Correlation functions of the mean volume, land use class and soil class were estimated using the data of the Finnish National Forest Inventory. Estimated functions were used for approximating the standard error of e.g. the mean volume of a cluster of plots. Standard error estimates can be used for comparing different inventory designs. The PDF includes an abstract in Finnish.

Old inventory data has widely been used as prior information in forest inventory using the method of sampling with partial replacement (SPR). In this method knowledge about forest growth has not been utilized. However, the accuracy of the inventory results can be improved if this knowledge is utilized. The usability of the inventory results can be improved if the prior information is updated by treewise growth models. In this paper a statistical basis is presented for a method in which such information can be used. The applicability of the method is also discussed. An example is given to demonstrate the method. The PDF includes an abstract in Finnish.

Data are presented from 1312 km of inventory transect, 6030 relascope sample plots and 21 700 ditches. Of the Finnish peatlands studied, more than 60% were pine mires, almost 20% were spruce mires and less than 10% each were treeless mires and paludified upland forest sites. The survey included the condition of the drainage networks, and the post-drainage development of the tree stands, their structure and silvicultural condition.

Three replacement strategies in continuous forest inventory of the Enso-Gutzeit Company have been presented and discussed. The first strategy adopts data from only the last two inventory occasions; the second strategy employs data from all four occasions, in which there are two groups of permanent plots measured on the first three occasions and independently on the last two occasions; the third strategy also utilizes data from all four occasions, but includes only one group permanent plots measured on all four occasions. Results indicate that the last strategy is best for efficiency. The difference between the first two strategies is small. The PDF includes an abstract in Finnish.

A study of a 194.3 ha area of forest land dominated by Norway spruce and Scots pine in central S. Finland. A general procedure is presented and discussed for integrating data from permanent sample plots and from satellite images for continuous forest inventory of large areas and for compartment estimations. Methods for estimation, updating and statistical analysis are examined.

Theoretical and practical aspects of permanent sample plots are discussed in this paper. A study material of 6,871 permanent sample plots was generated using increment sample plots of the 7th National Forest Inventory of Finland. The effect of measurement errors and use of increment functions as âa prioriâ information was studied via simulation experiments. The change in the growing stock volume between two consecutive measurement rounds was divided into the components drain, growth and mortality. Finally, a hypothetical inventory design using permanent sample plots was evaluated. The PDF includes an abstract in Finnish.

Metsänhoitajien jatkokurssit 1937. 3