Browsing by discipline "Forest Ecology and Management"

Birch wood discoloration called pith flecks is caused by a birch stem miner Phytobia betulae Kangas (Diptera: Agromyzidae), which is a very common species in Finland in both silver and downy birch (Betula pendula Erhr. and Betula pubescens Roth). There is a strong positive correlation between fast tree growth and abundance of P. betulae. Female flies lay their eggs into the young upper shoots of the birch, and the larvae start to move downwards in the stem in the newly differentiated xylem layer under the bark and phloem. The larvae form long vertical tunnels which the tree fills with brown parenchyma cells. In tangential cutting the tunnels look like brown stripes, but in cross-sectional cutting they are like small brown spots in the annual growth rings of the stem. The larval tunnels don’t affect the wood strength, but they cause an aesthetic disadvantage especially for veneer and furniture industry. So far the only reliable and accurate method for counting the larval tunnels has been to cut the trees, take experimental discs from breast height and count the tunnels by using stereomicroscope. The tree trials for forest tree breeding are extensive. To study the genetic susceptibility of birch to P. betulae a quicker and more feasible method would be needed for measuring the larval tunnels of P. betulae. The aim of this study was to investigate: 1) whether it is reliable to count the pith flecks by naked eye and how equivalent the different measuring methods are, and 2) if it would be possible to use an increment core for measuring pith flecks from a growing tree. Genetic susceptibility of silver birch families to P. betulae was studied from forest tree breeding field trials in which the larval tunnels were counted by naked eye. The research data was collected from the experimental field trials of Natural Resources Institute Finland in Parikkala and Punkaharju. Reliability of different measuring methods was studied in young trees by comparing the amount of larval tunnels counted by naked eye, from one sector of the disc and from an increment core to the amount of tunnels counted by using stereomicro-scope. The clones were ranked by their susceptibility to P. betulae from the lowest to the highest by using every method of the test. In aged trees with big diameters the larval tunnels were counted from one vertical slice and from one sector of the experimental disc. When studying the open-pollinated progeny of B. pendula with southern and central Finnish provenances the birch families were ranked by their susceptibility to P. betulae. In that data the larval tunnels were measured by naked eye. The order of the families was compared before taking the growth effect into account and after that, when the most and least susceptible families could be separated from the others. The results of the study revealed that the amount of the larval tunnels of P. betulae can be counted pretty reliably by naked eye and the counting can be done from one part of the experimental disc. Cutting the trees is still demanded, because the results of the increment cores were far too unreliable. In case of aged trees both counting the tunnels from one vertical slice and from one sector of the disc proved to be useful methods. When studying the birch families the results showed that fast tree growth alone does not increase the birch susceptibility to P. betulae, but there are also other factors affecting it. Heritabil-ity in the progeny trials on former agricultural land varied from 0.18 to 0.34. Measuring the pith flecks from large breeding data is too slow and laborious, and a quick method for counting the larval tunnels would be needed e.g. if a genetic marker would be searched for the trait in the future.

Metsänomistajakunnan rakenteen muutos on vähentänyt metsänomistajien omatoimisuutta metsän-hoitotöihin. Samanaikaisesti työvoiman saatavuus työvoimavaltaisiin metsänhoitotöihin on vaikeutunut. Koneellista taimikonhoitoa on kehitetty korvaamaan miestyönä tehtävää taimikonhoitoa. Koneellisen taimikonhoidon osuus on tällä hetkellä noin 1 % kaikesta tehdystä taimikonhoidosta. Konekitkentää on kehitetty yhtenä vaihtoehtona taimikonhoidon, tarkemmin varhaisperkauksen koneellistamiseksi. Tutkimuksen tavoitteena oli selvittää miten eri kasvupaikkatekijät vaikuttavat kuusen vapaana kasvamiseen kitkennän jälkeen. Tarkastelua tehtiin puu-, koeala- ja metsikkötasolla kasvatettavan kuusen ja häiritsevän puuston pituussuhteen avulla. Tavoitteena oli myös selvittää MOTTI-ohjelmiston avulla miten kuusen ja rauduskoivun välinen pituussuhde kehittyy kitkennästä ensiharvennusvaiheeseen. Aineisto kerättiin syksyn 2017 aikana maastomittauksin vuosina 2012–2014 konekitketyistä kuusen istutustaimikoista. Mitattuja kuvioita oli 66 ja laskennassa oli mukana 1152 koealaa. Aineiston analyysi tehtiin SPSS -ohjelmistolla. Koealatasolla mallinnettiin vapaana kasvavien kuusten suhteellista osuutta yleistetyllä lineaarisella sekamallilla. Kaikista kasvatettavista kuusista kasvoi vapaana 65,6 %. Pidempinä kitketyistä suurempi osa kasvoi vapaana. Kuivemmilla kasvupaikoilla ja karummilla kasvupaikoilla vapaana kasvavia kuusia oli suurempi osuus kosteampiin ja rehevämpiin kasvupaikkoihin verrattuna. Metsikkötasolla vapaana kasva-vien kuusten runkoluku oli yli 1000 kpl/ha 61 % kuvioista. Yli 1200 vapaana kasvavaa kuusta/ha oli 33 %:ssa kuvioista. MOTTI-simuloinnin perusteella OMT ja MT-kasvupaikoilla rauduskoivu ohittaa kuusen pituudessa ensiharvennukseen mennessä 80 %:ssa kohteista. Kuusia pidemmistä koivuista kuusta enintään metrin pidempiä oli 57 % ja yli 2 metriä pidempiä 11%. Mallinnuksessa tilastollisesti merkitseviksi tekijöiksi koealatasolla osoittautui kasvatettavan kuusen pituus kitkentähetkellä, kasvupaikan kosteus, kitkentäajankohdan ja mittaushetken välinen aika. Kannonnostolla, kasvupaikan metsätyypillä ja maalajilla ei ollut tilastollista merkitsevyyttä. Tulokset vapaana kasvavien kuusien osuudesta ja kuvioiden osuudesta, joilla on yli 1000 kpl/ha vapaana kasvavaa kuusta, tukevat aiempien tutkimusten tuloksia.

Tiivistelmä – Referat – Abstract Finland has one of the highest percentage of peatlands in the world, so peatlands have inevitably been taken into cultivation use. Agricultural peatlands however generate a significant amount of greenhouse gas emissions, especially carbon dioxide (CO2) and nitrous oxide (N2O). Thus, agricultural usage of peatlands is considered one of the most unfavorable uses of land for the climate. Peatlands have been drained in order to improve food services, which in turn negatively affects other ecosystem services. Some of the ecosystem services can be restored by rewetting the land. If rewetting is combined with paludiculture, the land’s production services will not be lost. The goal of this thesis was to compare the greenhouse gas emissions and the carbon footprints of two paludicultural products’ life cycles. The compared products were cattail insulation board and common reed seedbed. The intent was to produce comparable data on different options for the paludiculture of agricultural peatlands. The data obtained from the life cycle assessment of the products was compared to similar non-paladiculture products, rock wool insulation board and horticultural peat. The material was reviewed with the life cycle assessment method following the ISO 144040 standard, but the work was limited only on climatic effects. Based on the analysis, key sources of climatic effect in the product system were identified and means to reduce them were considered. The intent was to calculate the carbon footprint and to identify where in the life cycle the emissions were generated. After this, the portion of agricultural peatlands in in the life cycle’s environmental effects was estimated. The material for this thesis was collected from scientific literature and life cycle assessment databases (ecoinvent v.3). The material of peatlands and other parts of the process were collected from studies made around the world in the boreal and temperate zone. A model was assembled based on the material, which included all phases of the paludicultural product’s life cycle and their effects on the climate with regards to carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), The emissions in a paludicultural product’s life cycle are mostly generated during its cultivation and processing. The carbon footprint of both paludicultural products was most likely negative, so they slowed down climate change. Based on the study, the most benefit was achieved by moving the cultivation of barley from agricultural peatlands to mineral soil and replacing it with paludiculture. By using paludiculture, it’s possible to reduce greenhouse gas emissions of agricultural peatlands, but it won’t achieve carbon neutrality. The study had a significant amount of uncertainty, so further studies are recommended especially in Finland.

Reducing the use of plastic has become an important topic and at the same time the forest industry is looking for new opportunities for fiber use. Increased environmental awareness, together with environmental regulations and legislation, have forced manufacturers and industry to choose environmentally friendly solutions for products. Natural fiber reinforced composites have great potential because they are biodegradable, environmentally friendly, abundant and cost-effective when compared to synthetic reinforcements. Natural fibers also have favorable mechanical properties such as low density and good tensile strength and elastic modulus. The aim of this study is to examine the use of natural fibers in composites and how fiber properties affect the properties of natural fiber composites. In the experimental part of the research handsheets of birch and eucalyptus pulp were prepared. In addition, composites were prepared combining handsheets and two polymers. The differences between the birch and eucalyptus fibers were studied and also the effect of refining on the properties. In addition, the mechanical properties of sheets and composites were compared and also differences between polypropylene (PP) and polylactide (PLA). The mechanical properties tested were tensile strength, bending stiffness, elastic modulus and break elongation. In addition, the structure of composites and sheets were examined with optical microscopy. Composites made from polylactide had a better tensile strength and higher elastic modulus when comparing to polypropylene composites. Elongation and bending stiffness were improved with the polypropylene composites. On the sheets there is a clearly better elastic modulus than in the case of polypropylene. When the sheets and polypropylene are combined, the elastic modulus decreases when compared to the fibers. In addition, the elongation of the sheets was good, especially when comparing the polylactide composites. By refining the fibers, the mechanical properties of the sheets were improved. The refining of the fibers was generally seen to have the same effects on the composite results. The differences between birch and eucalyptus fibers are relatively small. With the birch fibers slightly better tensile strength and elongation are obtained but the eucalyptus sheets are stiffer. The results show that when combining fibers and plastic as a composite, many good mechanical properties are obtained in comparison with the properties of the sheets or the pure polymer.

Spruce shoots are the young, light green, annual growth of branches that burst from buds during May - July. It is forbidden to gather spruce shoots without the permission of the land owner. The Finnish natural resource department studied, that one-time gathering of spruce shoots does not damage the growth and health of the tree, if the upper canopy is left untouched. Spruce shoots are known to contain a rich amount of C-vitamin and minerals. Spruce shoots were widely used as a folk medicine for several centuries to prevent symptoms of cold. Spruce shoots also have a unique taste, and during the last years there has been an increasing interest to use spruce shoots in food and drink applications in the restaurant and food industry. There is a large potential to gather spruce shoots from Finnish forests, and it might be a new potential source of income for the forest owners. Although, more study is required to investigate the demand as well as ways to use the spruce shoots. The objective of this study was to examine how common the use of spruce shoots is in the Helsinki area restaurants and how the restaurants use it. 22 restaurants were chosen for the study and a survey was done by e-form and interviews. Questions consisted about the ways of using spruce shoots, purchasing channels, future prospects, amounts of yearly use, and pricing. Another objective was to study the time consumed to gather the spruce shoots. Time consumption was compared by gathering different size of shoots during the growth period. Time consumption of the gathering was measured in two plots in the Ruotsinkylä research forest during summer 2017 and 2018. 18 Restaurants answered the survey and the conclusion was that spruce shoots are commonly used. 88 % of the restaurants used spruce shoots as an ingredient and all of the restaurants were interested in using spruce shoots in the future. There was variation between the demand with different restaurants. The average yearly use was 9 kg and most of the restaurants used spruce shoots in length of 15-30 mm. There was also a demand for the longer ( > 30 mm) spruce shoots but they prefer smaller (15-30 mm) spruce shoots, because with this length the taste and variability in the use is considered better. In field measurements, it was found that the length of the spruce shoots greatly affect to the time consumed while gathering. Smaller spruce shoots were gathered on average 820 g/h and longer spruce shoots 1440 g/h. Restaurants are interested in using spruce shoots and as an ingredient it has a wide variability of uses. Restaurants prefer smaller spruce shoots and there should be more study about the potential use of larger shoots, for example in the food industry. It is easy to gather spruce shoots but the challenges are a short and yearly changing growing period as well as insufficient knowledge about the preservation of spruce shoots.

Tutkimus käsittelee kuusikuitupuun tuoretiheyden vaihtelua. Tuoretiheyden yksikkö on kg/m³. Tutkimuksen tavoitteena on selvittää, kuinka suurta vaihtelu on kahden eri vastaanottopisteen välillä. Lisäksi saadaan selville, voidaanko eri tehtailla mitattuja tietoja käyttää toisella maantieteellisellä alueella sijaitsevalla tehtaalla. Tutkimuksessa vertailtiin kahdelta eri tehtaalla mitattuja tuoretiheyksiä sekä metsäntutkimuslaitoksen alueellisia tuoretiheyslukuja. Tutkimusaineisto koostui 254 otantanipusta, jotka mitattiin Rauman paperitehtaalla 22.6.–30.12.2015. Otanta käsitti 3859,8 m³ kuusikuitupuuta, joka jakautui 254 nippuun. Otantanippujen keskimääräinen kiintotilavuus oli 15,5 m³. Pölkyt mitattiin mittasaksilla keskuskiintomittauksella. Pituus mitattiin 5 cm tasaavaa luokitusta käyttäen ja läpimitta 1 mm:n tarkkuudella. Vertailuaineistona käytettiin nipun saapumisajankohtana Jämsänkosken paperitehtaan vastaanotossa käytössä ollutta keskimääräistä tuoretiheyttä. Vertailussa oli mukana myös vuodesta 2012 alkaen kuukausittaisia tuoretiheyksien keskiarvoja. Aineistoista selvitettiin tuoretiheyksien vaihtelun aiheuttamien tilavuuserojen tilastollinen merkitsevyys t-testillä sekä tutkittiin erojen ja hajonnan suuruutta ja suuntaa. Lisäksi selvitettiin vuorokauden keskilämpötilan ja haihdunnan vaikutusta tuoretiheyteen. Tuoretiheyksien erojen todettiin olevan eri maantieteellisillä alueilla niin suuria, että paras keino päästä puunmittauslain asettamien raja-arvojen sisälle on käyttöpaikoittainen mittaus. Syyksi eroihin todettiin sää- ja varastointiolosuhteiden sekä puuvirtojen suuruuden vaihtelu. Eri tehtaille raakapuuta saapuu eri tahdissa, jolloin myös tuoretiheyden päivitystaajuus on erilainen.

Trees play an important ecological role also after their death. Earlier studies have introduced various methods of modelling coarse woody debris (CWD). However, CWD models that would consider different types of CWD, and their decay class dynamics are lacking from the Finnish commercial forests. The aim of this study was to predict the development of CWD for UPM-Kymmene owned FSC-certified forests in Finland. For that purpose, models for simulating CWD dynamics in Finnish commercial forests were developed for Pinus sylvestris, Picea abies and hardwoods. Trees were classified to different decay classes based on their visual appearance and softness of the wood. The mean residence time of each decay class was used to develop transition matrix model for predicting the possibilities of transitions between different decay classes. In the generated model a tree can stay in the class m or move to classes m+1 or m+2 in a time frame of five years. In addition snags had a possibility to fall i.e. move to down woody debris pool. The results showed that within all the studied tree species, the half-life of snags was 15–20 years. Hardwood logs decomposed faster than softwoods: the half-life of softwood logs was 35–40 years and the half-life of hardwoods was about 25 years. In a hypothetical equilibrium state reached by a continuous CWD input, most snags were in early decay class, whereas most logs were in the advanced decay class. Volume and quality of future CWD in UPM-Kymmene owned FSC-certified forests was predicted, using their current CWD pool and future tree mortality predicted by the forest simulation system MELA. In these simulations, the volume of CWD increased in the future. At the end of the 50-year simulation period, the predicted volume of CWD was 5,9 m3 ha-1. Pinus sylvesris was the dominant CWD species and advanced decayed wood was dominant decay class. The simulation approach demonstrated here has much potential as a useful decision-making tool for CWD management in commercial forests. Incorporating these models into forest management planning could provide valuable information about the effects of management practices on CWD dynamics in commercial forests.

Site index and site type are methods for describing a habitat’s highest annual production of tree (m3/ha/a). Site index is based on the growth of trees’ dominant height, and site type on the existence of plant communities in a habitat. This research examined whether site type can be estimated with site index derived by airborne laser scanning (ALS). ALS is a remote sensing method by which trees’ characteristics are predicted based on the height distribution and density values of laser pulses. Data were gathered from Syöte, Northern Ostrobothnia. Arbonaut Oy provided the ALS-data, and Metsähallitus provided age and habitat data of microstands. Site type, trees’ ages and dominant heights were also measured by field surveying. Experimental data from plots were generalized to microstand data. There were 208 experimental plots that were generalized to 39 microstands. Site indexes for experimental plots and microstands were calculated to index age 100 years with Vuokila and Väliaho’s (1980) growth models for dominant height and with Schumacher’s (1939) guide curve. Site indexes were converted to site types with Vuokila and Väliaho’s (1980) conversion diagram and then compared to site types of the field surveys. The accuracy of the site indexes was evaluated with an error matrix. Accuracy of age and dominant height was evaluated with a paired t-test. Variation of index aged dominant height inside a site type was examined with root mean square error (RMSE). The effect of the proportions of tree species on the site index was analyzed with a correlation coefficient. The percentage of properly classified site types was 57 % at best when using Schumacher’s (1939) guide curve and two site types (rich and poor). With Vuokila and Väliaho’s (1980) growth models for dominant height the best percentage of correctly classified site types was 46 %. The variation (RMSE) of index aged dominant height as an average in all site types was 3,2 m. The maximum variation of index aged dominant height in one site type was 6 m. This indicated that the dependency between site index and site type was poor with this data. The proportions of tree species did not have a significant effect on site index. Based on this study, predicting site types with ALS does not work. One problem is the absence of very rich site types. There are also many sources of error: SutiGIS’ (position knowledge system) age data, prescribed burning, possible fertilization of stands, and the problems of fitting site index and site type. Vuokila and Väliaho’s (1980) growth models for dominant height were made in the 1980s, so they do not acknowledge the increased growth of present-day trees. Site index cannot reliably predict the site type, but site index gives valuable extra information about the trees for example when evaluating the value of forest estates.

The large area forest mapping is traditionally based on satellite images and laborious field plots. The newer lidar plot concept is the Airborne Laser Scanning (ALS) and a small amount of field plots based plot-level attribute estimation, which is treated similar to the field plots in satellite based mapping. The target of the study was to evaluate the satellite-based, the ALS-based and their combination based forest mapping in the large area by comparing the accuracy of the forest attribute estimations per different amounts of plots. The study area of 3 128 000 hectares in southern Finland included 3630 field plots from the Metsäkeskus of Finland. The attribute estimates were computed from the Landsat 8 image and from the low-density lidar dataset to the field plot locations. The plot-level attribute estimates were calculated for the volume, height, basal area and biomass using k-NN-method (k=5). The accuracy of the mapping methods was evaluated by relative RMSE (Root Mean Square Error), which measured the differences between the estimated and the measured attributes of the validation plots. From the results it can be seen that the relative RMSEs of the attribute estimates from the Landsat-image based mapping on plot-level were at their best 47.6 % for the volume, similarly 26.2 % for the height, 34.6 % for the basal area and 47.7 % for the biomass. For the ALS-based mapping, they were 23.2 %, 9.8 %, 21.0% and 23.7 % respectively. By using 400 field plots to estimate attributes for 2900 lidar plots, and these lidar plots were used further for Landsat-based attribute estimations, these results were quite close to the accuracy of field plots-based Landsat attribute estimations. In addition a small sample of the lidar cover of the area was needed, in this case having less than 1 % area coverage. The lidar plots in Landsat-based mapping could be used for the biomass and carbon mappings in large area even if there are no roads available in the area and only a small amount of plots can be measured. Also, it is suitable for the areas where forest mapping has not started. It can be used also to follow up the changes in large forest areas, due the frequent updates of the satellite image measurements.

The balance between incoming precipitation (rainfall and snowfall) and outgoing evapotranspiration (ET), runoff and drainage to and from an ecosystem plus changes in soil moisture storage and the water equivalent of the snowpack is known as the water balance. A dominating feature of the water balance in the boreal zone is snowpack accumulation over winter and the spring snowmelt, both of which are affected by forest. In Finland, there are strong north-south gradients in the amount of precipitation, the proportion of rainfall and snowfall and temperature, and therefore latitudinal differences in the water balances components can be expected. Furthermore, the large canopy and deeper rooting of trees, together with the presence of a permanent ground vegetation cover, result in significant differences in interception, infiltration and water balance outputs of forests compared to other forms of land-use. Because of morphological and ecophysiological differences between the trees species, the water balance of Norway spruce and Scots pine dominated forests can be expected to differ. Determining the water balance of forest ecosystems across Finland would, therefore, help in assessing the hydrological ecosystem services provided by forests and form a basis for examining the effects of climate change and forest management on the water balance. This study aimed to compute the daily water balance of six Norway spruce, and three Scots pine dominated mature forest stands (plots) located throughout Finland over a 26-year study period (1990-2015). It was hypothesized that the various water balance components would systematically vary with latitude, a surrogate for climate, and differ between spruce and pine stands. The daily version of the water balance model “WATBAL” developed by Mike Starr (University of Helsinki, Dept. Forest sciences) was used for this study. The model requires daily meteorological data (precipitation, temperature, global radiation), stand parameters (canopy cover, rooting, crop coefficient), soil parameters (including infiltration coefficient, soil moisture contents at permanent wilting point, field capacity and saturation, and two soil moisture parameters for a plant available water content function). Six of the plots had soil developed in till and 3 plots had soil developed in sorted glaciofluvial deposits. Plot meteorological data for 1990-2015 was derived using spatially interpolated gridded data. If the daily air temperature was ≤0°C, any precipitation was assumed to be snowfall. The stand and soil parameters were derived from data collected from the 9 study plots by Luke (formerly Metla). The nine plots belong to the Finnish network of ICP-Forest level II plots that have been established throughout Europe. Pedotransfer functions (PTF) based on soil texture and organic matter contents were used to derive initial values for the soil hydraulic parameters. Time domain reflectometry (TDR) measured soil moisture data was available for 7 of the plots and, after carrying out careful quality control and rejection of outliers, used for calibration of modelled soil moisture and optimization of soil hydraulic parameters for those plots. Optimization was carried out using the non-linear Marquardt regression method. Goodness-of-fit for soil moisture was evaluated using correlation and R2 values from linear regression. After computing the daily water balance with the WATBAL model (using optimized soil hydraulic parameter values for the 7 plots and initial PTF values for the remaining 2 plots) the long-term mean annual and mean daily water balance components (with a 7-day moving average smoothing) were calculated. The water balances were computed for the humus layer plus 0-40 cm soil layer, which, based on literature, would have included most if not all of the roots. The dependence of the mean annual water balance components on latitude was evaluated using correlation analysis and linear regression, and the effect of tree species was tested for using the t-test on pairs of spruce-pine plots located close to each other. The raw TDR data was found to contain a considerable amount of gaps and erroneous (too high) values, often associated with the spring snowmelt. Optimization of the soil hydraulic parameters using the measured soil moisture contents calculated from the “cleaned” TDR data for the snow-free period resulted in a highly significant (p<0.001) Pearson correlation of +0.85 (R2 = 0.75) for the fit between measured and modelled soil moisture contents calculated across all 7 plots. The correlations for the individual plots were also highly significant. Based on the optimized WATBAL output, the fraction of plot mean annual precipitation as snowfall ranged from 20 to 29%. Corresponding ranges for ET, drainage and runoff were respectively 33 to 57%, 24 to 42%, and 18 to 25%. The mean annual water balance components were found to be significantly correlated to latitude, reflecting trends in precipitation and temperature. Evapotranspiration decreased with increasing latitude while maximum snow-on-ground, snowmelt and associated runoff increased with increasing latitude. Spruce mean annual ET was 9% higher than pine in one of the paired plot sets and 37% higher in the other set. For drainage, pine was 15% greater than spruce in one of the paired plot set and 74% higher in the other set of paired plots. There were no significant differences between spruce and pine plots for snowmelt and runoff. Variation around these trends were related to differences in soil hydraulic properties among the plots which, in turn, were related to differences in parent material and soil texture. The overall conclusion from this study was that the daily water balance of the forested plots could be realistically modelled using such a relatively simple water balance model as WATBAL. The importance of spatially representative and accurate soil moisture measurements for model calibration purposes was highlighted. While the importance of snowfall on the water balance increased northwards regardless of tree species, evapotranspiration was determined by both latitude and by species. Climate change can therefore be expected to have a significant impact on the water balance of Finnish forests resulting in environmentally important changes in leaching and runoff.