Browsing by department "Department of Forest Sciences"

The use of remote sensing imagery as auxiliary data in forest inventory is based on the correlation between features extracted from the images and the ground truth. The bidirectional reflectance and radial displacement cause variation in image features located in different segments of the image but forest characteristics remaining the same. The variation has so far been diminished by different radiometric corrections. In this study the use of sun azimuth based converted image co-ordinates was examined to supplement auxiliary data extracted from digitised aerial photographs. The method was considered as an alternative for radiometric corrections. Additionally, the usefulness of multi-image interpretation of digitised aerial photographs in regression estimation of forest characteristics was studied. The state owned study area located in Leivonmäki, Central Finland and the study material consisted of five digitised and ortho-rectified colour-infrared (CIR) aerial photographs and field measurements of 388 plots, out of which 194 were relascope (Bitterlich) plots and 194 were concentric circular plots. Both the image data and the field measurements were from the year 1999. When examining the effect of the location of the image point on pixel values and texture features of Finnish forest plots in digitised CIR photographs the clearest differences were found between front-and back-lighted image halves. Inside the image half the differences between different blocks were clearly bigger on the front-lighted half than on the back-lighted half. The strength of the phenomenon varied by forest category. The differences between pixel values extracted from different image blocks were greatest in developed and mature stands and smallest in young stands. The differences between texture features were greatest in developing stands and smallest in young and mature stands. The logarithm of timber volume per hectare and the angular transformation of the proportion of broadleaved trees of the total volume were used as dependent variables in regression models. Five different converted image co-ordinates based trend surfaces were used in models in order to diminish the effect of the bidirectional reflectance. The reference model of total volume, in which the location of the image point had been ignored, resulted in RMSE of 1,268 calculated from test material. The best of the trend surfaces was the complete third order surface, which resulted in RMSE of 1,107. The reference model of the proportion of broadleaved trees resulted in RMSE of 0,4292 and the second order trend surface was the best, resulting in RMSE of 0,4270. The trend surface method is applicable, but it has to be applied by forest category and by variable. The usefulness of multi-image interpretation of digitised aerial photographs was studied by building comparable regression models using either the front-lighted image features, back-lighted image features or both. The two-image model turned out to be slightly better than the one-image models in total volume estimation. The best one-image model resulted in RMSE of 1,098 and the two-image model resulted in RMSE of 1,090. The homologous features did not improve the models of the proportion of broadleaved trees. The overall result gives motivation for further research of multi-image interpretation. The focus may be improving regression estimation and feature selection or examination of stratification used in two-phase sampling inventory techniques.

In Finland thinning quality is assessed on a yearly basis by the Finnish Forest Centre. During recent years the results of these assessments have been a source of concern within the coastal region of operation. Metsäliitto, being one of the largest forest operators within the coastal region and Finland as a whole, is concerned by the high residual stand damage found. Metsäliitto perform follow-ups on the feedback received from the Finnish Forest Centre but also performs thinning quality assessments off their own. The thinning quality method used by the Finnish Forest Centre is time consuming and therefore poorly suitable for use by wood procurement companies. This led to the development of an alternative method by Metsäteho Oy. Metsäliitto was represented in the work group that developed this new method but has chosen to develop a method of its own. The purpose of this master thesis is to clarify whether the results from Metsäliittos thinning quality assessment method correlate in a sufficient manner with those of the method developed by the Forestry Development Centre TAPIO. Furthermore the thesis study how the results of two alternative methods correlate. Focus is placed on residual stand damage but also the possibility of a potential connection between TAPIOs placement of sample plots and residual stand damage results is studied. As Metsäliittos method includes a complete inventory of soil compaction it is studied how TAPIOs and Metsätehos results hold up against those of Metsäliittos method. A study of the correlation between results for forwarder track distance between Metsäliittos and Metsätehos methods is also conducted. The sites of this study were chosen based on the Finnish Forest Centres random sampling for thinning quality assessments performed during 2010 and 2011. From those thinning quality assessments the ones performed in the Swedish speaking parts of Ostrobotnia where thinning actions had been performed by Metsäliittos contractors were sieved and chosen to form the sample of this study. The fieldwork of this study was performed in July 2011. Thinning quality assessments according to Metsäliittos and Metsätehos models were performed on all sites. The results of the thinning quality assessments performed according to TAPIOs method were acquired from the Finnish Forest Centre. This study being a method comparison study where the true values of the objects are not known, methods of analysis based on hypothesis testing was not used. In order to create an overview of the trends in results for the different methods, as well as their correlation to each other, Bland&Altman diagrams were created (Altman & Bland 1983 and Bland & Altman 1999). The main results of this study show that Metsäliittos and TAPIOs results for residual stand damage do not differ in a statistically significant way. Metsäliittos and Metsätehos results on the other hand are not to be compared. Metsätehos and TAPIOs results are not either to be compared which has been stated by Poikela (2003b). TAPIOs and Metsätehos methods estimate the proportion of soil compaction in a sufficient manner compared to Metsäliittos method. Furthermore it was concluded that results for forwarder track distance correlate well between Metsäliittos and Metsätehos methods. Any connection between TAPIOs sample plot placement and results for residual stand damage could not be detected. The conclusions of this study are that Metsäliittos and TAPIOs results for residual stand damage, with reservation for the small sample size of this study, are comparable. Metsäliittos and Metsätehos results are not compatible from which we conclude that Metsäliittos method is not replaceable with the one developed by Metsäteho. Nor shall Metsätehos method be used as a complement to Metsäliittos as one will then acquire two incompatible data sets. Both Metsätehos and TAPIOs results for soil compaction are compatible with those of Metsäliittos method. This could be utilized in order to improve the time effectiveness of Metsäliittos method. For further method improvement Metsäliitto could adopt Metsätehos method for determination of forwarder track distance. As results from Metsäliittos and TAPIOs thinning quality assessments can be compared without a loss of reliability, Metsäliitto could compile the results from their own assessments and TAPIOs assessments in order to get a more statistically representative picture of the quality of their thinnings. This would result in even better future possibilities of monitoring and evaluating how well the company’s goals are met.

Natural disturbances are important for regeneration and biodiversity of forests. Restoration imitates natural disturbances in order to return ecosystems towards its natural state. Knowledge is lacking about the efficiency of restoration, as well as early tree successions. The objects of this study were to investigate the effects of fire and coarse woody debris (CWD) increment on early tree succession and tree species diversity along forest – gap gradient 10 years after restorative partial cuttings in southern Finland. Seedling densities and heights, microhabitat distributions and tree species diversity were compared between four restoration treatments; unburned treatments with 5 and 60 m3 CWD ha-1, and burned treatments with 5 and 60 m3 CWD ha-1. Total seedling densities were tested with two-way analysis of variance. Species diversity was analyzed by species richness and Shannon index, which were tested with two-way analysis of variance. In general, the burned treatments included higher seedling densities and higher seedlings. The different amounts of dead wood revealed differences in deciduous tree species. The density of birch was higher in the treatments with 60 m3 CWD ha-1 and the heights of birch and other deciduous tree species were higher in burned treatment with 60 m3 CWD ha-1. Pine and birch were abundant in the burned treatments. The densities of spruce were very high in the unburned treatment with 5 m3 CWD ha-1, but fairly low in the other treatments. The seedling densities and heights were the lowest in the forest. Seedling densities did not vary significantly between the edge and gap segment. Microhabitat distributions of the coniferous seedlings differed between the unburned and burned treatments, but no clear differences were observed between the low (5 m3 ha-1) and high amount (60 m3 ha-1) of CWD. Microhabitat distributions of seedlings between forest, edge and gap did not differ noticeably, except with spruce in the burned treatments between the edge and gap. Tree species diversity of regeneration was slightly higher in the burned than in the unburned treatments. Different amounts of CWD did not affect the tree species diversity. The tree species diversity was significantly lower in the forest than in the treatment area, but it did not differ between the edge and gap. The results indicate that early tree succession is likely to be more abundant after burning than without. Fire as a restoration tool can be suggested for the regeneration of pine and birch. Dead wood appears to be insignificant for early tree succession. The limited size of restoration areas does not impede the tree succession, since the densities and heights of seedlings were generally the highest near the forest edge. Fire might increase tree species diversity.

This study aimed at conducting a baseline for optimal harvesting schedules with economic criteria for Scots pine, Norway spruce and silver birch in Estonia. Additionally, this study aimed at providing comparison to previous findings about optimal schedules in boreal forests and recommendation for practitioners. Faustmann’s (1849) forest rotation theory provides the theoretical foundation for the thesis. The study was performed by including Estonian whole-stand forest growth models and local timber prices and forest regeneration costs in the optimization, which was based on the Hooke and Jeeves’ (1961) direct optimization method. Scots pine was found to be the optimal species in most site classes, silver birch being the optimum in the most fertile site. The schedules for silver birch were found to be less sensitive to changes in the rate of interest, site fertility and timber price than the conifers. The current legal restrictions lead to longer rotations, more thinnings and economic losses when compared to the unrestricted optimal scenarios. The optimal number of thinnings in most scenarios for all species turned out to be three, if the legal restrictions are followed. In general, the optimal rotation periods were found to be shorter and the timing of the first thinning earlier in many scenarios than in Finland. Also the optimal number of thinnings was found to be more stable in Estonia than in Finland. It was found that if the initial stand stocking for the main tree species falls below a certain threshold in mid-rotation mixed-species stands including less valuable broadleaves, it is optimal to clear fell the stand immediately and regenerate the stand according to the optimal stocking recommendations. From the practical point of view, given the current limitations regarding the timing of clear fell, forestry practitioners have the most value creation potential in improving the forest regeneration methods and thinning schedule. In comparison to Finnish studies, it was found that there exists many similarities regarding the schedules and the suitability of species for different forest sites between the findings of this study and previous Finnish studies and the Finnish silvicultural recommendations. Thus, the extensive Finnish recommendations and findings provide a good basis for practitioners also in Estonia. However, given also the found differences, harvesting schedules in Estonia should be developed in more detail for more sophisticated recommendations for local practices.

The main aim of this thesis was to study the ecosystem services provided by large-scale industrial eucalypt plantations of UPM in Paysandú region, Uruguay. In the landscape, natural pastures and forests are combined with rows of planted trees. The second aim was to study how various stakeholder groups use ecosystem services from the plantation landscape, and to what extent the rights and expectations related to their use vary among these groups. The third aim was to study the best ways to combine the production of ecosystem services with large-scale industrial tree plantations in the study area. The data used in this study consisted of 55 semi-structured interviews, which were recorded in Uruguay during summer of 2015. Among the persons interviewed, 15 people were classified as key-informants with a broad view on plantation industry in the study area. They were from educational institutions, companies, ministries and from non-governmental organizations. Based on results of the key-informants interviews, a total of 40 persons were selected for stakeholder interviews. They represented four groups; 1) cattle ranchers, 2) honey producers, 3) tree growers and 4) general public from the surrounding communities. With stakeholder interviews, the aim was to collect quantitative data with structured questionnaires. The key-informants and stakeholders were asked about the same issues, but the key-informant interviews had open questions for collecting both qualitative and quantitative data. The results of this study show that industrial tree plantation landscapes provide a plenitude of ecosystem services. However, the perceived changes in the landscape during the past ten years were in some cases more negative than positive. According to the key-informants, the most important ecosystem services provided included industrial wood, animal shelter, fodder and foods. This indicates that local livelihoods can be combined with industrial plantations and the stakeholders benefit from them in many ways. The cattle ranchers obtained mainly animal shelter and fodder. For them, also the regulation of natural hazards was important. The honey producers valued foods, pollination and biodiversity services. The tree growers valued industrial wood and, similarly as the cattle ranchers, animal shelter and fodder. For the general community, educational information was the most important service. Food, honey and mushrooms, and fuel wood were also highly valued ecosystem services. Industrial tree plantations create a wealth of ecosystem services, often with low or no cost. UPM Uruguay considers local stakeholders and their livelihoods in many ways. According to the company, the best ways to integrate industrial tree plantations and ecosystem services are already used in many parts, although there was no data disclosed about all of them. However, it seems that UPM is well aware of the local conditions. In the future, there is a need to study the monetary value and benefit sharing of ecosystem services e.g. through payments of ecosystem services schemes.

Plantation forestry has increased dramatically in Uruguay during the past 25 years. Thus, planted forests have an increasing importance in providing other ecosystem services in addition to wood provision in landscape scale. Forest sector company UPM owns more than 250 000 hectares of Eucalyptus plantations in Uruguay. UPM seeks to enhance their systems to measure and monitor ecosystem services, to better understand sustainable provision of ecosystem services in their plantation landscapes, and to mitigate negative and maximize positive impacts. Benefits of monitoring and incorporating ecosystem services at management level include strengthened decision-making and communication, license to operate in long-term and better corporate image. Four ecosystem services were selected for analysis based on their relevance in UPM’s corporate strategy: wood provision, climate regulation, water provision and biodiversity maintenance. Provision of the ecosystem services were estimated quantitatively and compared to a pasture land baseline. Provision of ecosystem services was also linked to product level, tonne of pulp, when applicable. Data for the analysis was partly provided by UPM and partly by literature meta-analysis. Climate benefit of converting pasture to Eucalyptus is 8–31 MgC/ha or 29–115 MgCO2/ha depending on species and rotation number. Planting 40% of a micro water-shed with Eucalyptus reduces water streamflow approximately by 20–27%, while reducing streamflow of peak rainfall months by up to 40%, potentially alleviating floods. Pastures in UPM’s landscapes are well connected, but provided little core habitats. Native riparian forests are fragmented and maintain biodiversity poorly. Suggestions for future monitoring and measuring are presented. This thesis works as a waypoint for future studies of holistic ecosystem services provision in UPM assets.

The effect of forest health and structure to the relative surface temperature captured by airborne thermal imagery was investigated in Norway Spruce-dominated stands in Southern Finland. Canopy surface temperature has long been recognized useful in monitoring vegetation water status. Recent studies have shown also its potential in monitoring vegetation health. Airborne thermal imagery, Airborne Light Detection and Ranging (LiDAR) and field measurements were acquired from the area of interest (AOI). The relative surface temperature correlated most negatively with the logarithm of stem volume, Lorey’s height and logarithm of basal area at resolution of 254m2 (9-m radius). In other words, taller and older stands had colder surface temperatures. In addition, LiDAR metrics, such as height percentiles and canopy cover percentage, were compared with surface temperature. Standard deviation of canopy height model, height features (H90, CHM_max) and canopy cover percentage were most strongly negatively correlated with the surface temperature. On average, higher surface temperatures were detected in defoliated canopies indicating that thermal images may provide some additional information for classifying forests health status. However, the surface temperature of defoliated plots varied considerably. It was also found that surface temperature differences between canopy and ground responses were higher in defoliated plots. Based on the results, forest health and structure affect to the surface temperature captured by airborne thermal imagery and these effects should be taken into account when developing forest health mapping applications using thermal imagery.

Overall warming of climate, causing drought and sometimes co-occurring with insect outbreaks poses a risk to tree health and has been linked to tree mortality in many areas. The drought of 2003 was particularly severe in many regions in Europe, including Finland. It exceeded many previous drought years in its severity and intensity. Also, in the summer of 2006, 25% of the permanent forest sample plots of Finland National Forestry Inventory showed symptoms of drought damages. The Finnish south-west archipelago is high-risk drought area, and dry summers becoming more frequent and severe may cause severe forest damages in the area. In this study we investigated forest damages in Kemiönsaari, South-West Finland, approximately 60° 11'N, 22° 33'E. The forest damages there were first discovered in 2009, by local forest society, and has been spreading in the area. The crowns of Scots Pines (Pinus sylvestris) in the area were partially or completely defoliated. The defoliation started from the top of the canopy and spread evenly downwards. The central research questions of this study were: 1. Has the past drought years affected the growth of Pinus sylvestris in Kemiönsaari? 2. How is the Pine bark bug, Aradus cinnamomeus, affecting the trees hydraulic conductivity? 3. How is the Crumenulopsis sororia affecting the trees hydraulic conductivity? The findings provide support for the first research question stating that there has been a notable reduction in growth of the trees in the study area. The superposed epoch analysis revealed that droughts occurred in the past 20 years, reduced the radial growth of Scots pines. However, the results from this were within the lower 95% bootstrapped confidence limit and are not statistically significant. The results indicated that the most limiting factor to radial growth of Pinus sylvestris was precipitation in June, and last year July. Water shortage during the growing season decreases photosynthetic production and causes physiological stress to tree and is known to promote outbreaks of many insect. This study showed that the hydraulic conductivity of Scots pines in this area is not decreased by the pathogen Crumenulopsis sororia or Aradus cinnamomeus, in contrary, there was a clear correlation with higher hydraulic conductivity in the top of the crown of Scots pine’s where Crumenulopsis sororia or Aradus cinnamomeus were present.

Tämän pro gradu-tutkielman tarkoituksena on tutkia eliöstön asettumista ja monimuotoisuuden kehittymistä rakennetuilla kosteikoilla. Luonnonkosteikkojen tiedetään olevan biodiversiteetiltään rikkaita alueita. Kosteikkoja rakennetaan pääasiallisesti joko vedenlaadun parantamiseksi tai lintukosteikoiksi, mutta linnuston ohella niiden ylläpitämää eliöstön monimuotoisuutta ei ole juuri tutkittu Suomessa. Helsingin yliopiston, Vihdin kunnan, Vantaanjoen ja Helsingin seudun vesiensuojeluyhdistyksen sekä Uudenmaan ELY-keskuksen yhteinen EU Life+-rahoitteinen Keidas-hanke on seurannut kahta hulevesikosteikkoa Vihdin kunnan alueella Nummelassa; YK:n luonnon monimuotoisuuden juhlavuonna 2010 rakennettua Portin kosteikkoa ja Life+ Keidas- projektissa vuosina 2011–2014 rakennettua Niitun kosteikkoa. Kosteikkojen perustamisen tavoitteina on ollut puhdistaa valumavesiä ennen niiden purkua Vihdin Enäjärveen sekä lisätä taajama-alueen asukkaiden viihtyisyyttä ja tarjota heille virkistyskäyttöalueita ja luontokokemuksia. Hankkeen tarkoituksena on kuitenkin myös kehittää muita kosteikkojen tarjoamia ekosysteemipalveluja. Yksi tällainen tavoite on luoda uusia elinympäristöjä ja lisätä alueella elävän eliöstön monimuotoisuutta. Tutkielmassa seurataan, miten eliöstö asettui vastarakennetuille taajamakosteikoille. Tässä tutkielmassa keskitytään vesiselkärangattomiin, sillä ne toimivat merkittävänä linkkinä primäärituotannon ja suurempien kuluttajien välillä ja ovat siksi tärkeä tekijä kosteikkoympäristön eliöstön monimuotoisuudelle. Vesiselkärangattomien esiintymiseen vaikuttavia tekijöitä ovat erityisesti kalojen esiintyminen sekä kasvillisuuden määrä. Seurantoja suoritin kolmena peräkkäisenä vuotena 2014-2016. Vertailukohteena ja esimerkkinä luonnonvesistöstä käytin kosteikkojen alajuoksulla sijaitsevaa Vihdin Enäjärveä. Vesiselkärangattomien seuranta suoritettiin aktiivipyydyksin, jotka olivat kaikilla tutkimuskohteilla 2 vuorokautta jokaisena seurantakesänä. Vesiselkärangattomat jaettiin koon perusteella viiteen eri kokoluokkaan, joiden välistä yleisyyttä vertailtiin eri kohteiden kesken. Vesiselkärangattomille laskettiin myös biomassaindeksi kokonaistuotannon vertailemista varten. Lisäksi vesiselkärangattomien yhteisöjen monimuotoisuutta arvioitiin Shannonin ja Jaccardin monimuotoisuusindeksien avulla. Kokoluokkien vertailussa näkyi, että altaissa, joissa kasvillisuus ei ollut vielä asettunut, oli vesiselkärangattomien kokoluokkajakauma painottunut pienimpään luokkaan. Vuosittaista vaihtelua esiintyi, mutta pääpiirteissään esiintyi Portin kosteikolla enemmän suurempien kokoluokkien vesiselkärangattomia kuin nuoremmalla Niitun kosteikolla tai Enäjärvessä. Enäjärvessä kalojen aiheuttama suuri saalistuspaine on todennäköisin selitys vesiselkärangattomien suurempien kokoluokkien vähäisyyteen. Biomassaindeksin kehitys kummallakin kosteikolla oli epätasaista ensimmäisen vuoden biomassaindeksin ollessa suurin piirtein yhtä suuri kuin viimeisenkin, kun toisaalta Enäjärven biomassaindeksi laski jokaisena vuonna. Vesiselkärangattomien populaatioissa tapahtuneet muutoksen ilmenevätkin paremmin kokoluokkajakaumista. Vesiselkärangattomien monimuotoisuus Portin kosteikolla oli suurin piirtein yhtä suurta kuin Enäjärvellä, kun taas Niitun kosteikolla monimuotoisuus oli hieman alhaisempaa. Tämä vastaa teoriaa siitä, että vie noin neljä vuotta ennen kuin vesiselkärangattomien monimuotoisuus on saavuttanut maksiminsa kosteikon rakentamisen jälkeen. Pidempiaikainen seuranta ja eritoten suurempi otos antaisi tarkempia tietoja tutkimuskosteikkojen vesiselkärangattomista, mutta tämän tutkielman tulosten perusteella voidaan päätellä, että vesiselkärangattomien kannat ovat kehittyneet kosteikoilla toivotulla tavalla ja kosteikkojen voidaan olettaa tarjoavan habitaatteja monille vesiselkärangattomia ravinnokseen hyödyntäville lajeille.