Browsing by Subject "Betula pubescens"

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  • Finér, Leena (The Society of Forestry in Finland - The Finnish Forest Research Institute, 1989)
    Biomass, biomass increment and nutrient cycling were studied in (1) a Scots pine (Pinus sylvestris) stand, (2) a Norway spruce (Picea abies) stand and (3) a mixed birch (Betula pubescens)/pine stand on a drained mire at Ilomantsi, eastern Finland in 1979-85. In addition, the effect of NPK and micronutrient fertilizer treatment was studied. Above-ground and root measurements were taken. These data formed the basis of stand biomass and nutrient cycle simulations of fertilized and unfertilized stands. The increases in biomass were greater in (1) and (2) in the fertilized simulation than in the unfertilized one. For (3), the effect of fertilization on biomass increment was small. In six years only part of the applied fertilizer had been fixed in the biomass of the model stands and proportionally less micronutrients than macronutrients. The potassium stores were small compared to the nutrient amounts fixed by the stands. This supports the notion that there is a shortage of potassium on deep-peat soils.
  • Haikarainen, Iikka (Helsingfors universitet, 2016)
    Metaani (CH4) on yksi tärkeimmästä kasvihuonekaasusta. Sen ilmastoa lämmittävä vaikutus on 100 vuoden lämmi-tyspotentiaalina 28-kertainen hiilidioksidiin verrattuna. Lisäksi metaanin määrä ilmakehässä on yli kaksinkertaistunut esiteollisen ajan alun jälkeen ja sen lähteiden tuntemisessa on puutteita. Ilmakehän metaanista suurimman osan on arveltu olevan peräisin anaerobisissa olosuhteissa tapahtuvasta metanogeneesistä. Boreaaliset metsät on mielletty CH4-nieluiksi maan hapellisessa kerroksessa tapahtuvan metaaninsitoutumisen vuoksi. Myös puut toimivat CH4-lähteinä joko helpottamalla maassa anaerobisesti syntyneen metaanin pääsyä ilmakehään tai tuottamalla sitä itse. Vaikka ensimmäiset havainnot puiden CH4-päästöistä tehtiin jo lähes 20 vuotta sitten, on vasta viimeaikainen tutkimus osoittanut että puiden CH4-päästöt voivat vaikuttaa huomattavasti metsien CH4-taseeseen. Suurimpien arvioiden mu-kaan puiden vapauttaman metaanin osuus on jopa 10–40 % globaalista CH4-budjetista. Puiden CH4-päästöjen tutki-mus on tähän asti suuntautunut enimmäkseen trooppiselle ja temperaattiselle kasvillisuusvyöhykkeelle, mutta tutki-mus boreaalisella kasvillisuusvyöhykkeellä on jäänyt vähäiseksi. Tämän pro gradu -työn tavoitteena on arvioida boreaalisella havumetsävyöhykkeellä tavanomaisesti esiintyvien kah-den puulajin, hieskoivun (Betula pubescens) ja kuusen (Picea abies), CH4-vuota ja sen vaihtelua kasvukauden alussa. Työn aineistona on käytetty 28.4.–11.6.2015 Hyytiälässä kahdella eri koealalla havaittuja puiden ja metsänpohjan CH4-voita, jotka on mitattu hieskoivujen ja kuusien rungoista ja oksista käyttäen suljettua kammiomittausmenetelmää. Koealoina olivat soistunut alue (metsäkortekorpi), jolta valittiin 4 koepuuta (2 hieskoivua, 2 kuusta) ja kivennäismaa-alue (kuivahko kangas), jolta valittiin yksi koepuu (hieskoivu). Tutkimuksissa havaittiin, että sekä hieskoivut että kuuset toimivat CH4-lähteinä rungoista ja oksista, vaikka ne myös ajoittain sitoivat metaania. Havaitut CH4-vuot olivat suuruusluokaltaan hyvin vaihtelevia. Suurimmat CH4-päästöt ha-vaittiin soistuneella kasvupaikalla kasvavien hieskoivujen rungoista, joissa runkopinta-ala kohtaiset päästöt vähenivät eksponentiaalisesti puun pituusprofiilissa tyvestä latvaa, ja rungon tyveltä mitatut suurimmat päästöt myös kasvoivat kevään edetessä. Soistuneella koealalla puiden runkojen CH4-vuo korreloi maalämpötilojen kanssa sekä positiivisesti (hieskoivut) että negatiivisesti (kuuset). Sadekertymän havaittiin korreloivan negatiivisesti koivujen runkojen vuon kanssa. Muilla taustamuuttujilla (esim. ilman lämpötila, säteily, mahlan virtausnopeus) ei ollut havaittavaa yhteyttä puiden CH4-vuohon. Korrelaatioita ei myöskään havaittu kivennäismaakohteella olleen hieskoivun keskiarvoisten CH4-voiden ja taustamuuttujien välillä. Puiden CH4-vuosta tehtiin yleistys metsikkötasolle, mikä osoitti kuusien päästö-jen (6,15 g ha−1 vrk−1) olevan suurempia kuin hieskoivujen päästöt (5,82 g ha−1 vrk−1) johtuen kuusien oksiin sitoutu-neesta suuremmasta biomassan määrästä verrattuna hieskoivuihin. Tästä syystä kuuset voivat olla merkittävämpiä metaanin vapauttajia kuin hieskoivut. Työn tulokset vahvistavat aiempien tutkimusten havainnot puiden CH4-päästöistä ja osoittavat että myös boreaalisen kasvillisuusvyöhykkeen puilla voi olla merkittävä rooli globaalissa CH4-budjetissa, jossa puiden CH4-vuota ei ole tähän asti lainkaan huomioitu. Hieskoivujen ja kuusien erilainen vaste kasvukauden alkuun, maalämpötilaan ja sateisuuteen viittaa puulajien välisiin eroihin CH4-vuota säätelevissä tekijöissä tai metaanin kuljetukseen liittyvässä fysiologiassa.
  • Liepiņš, Rob. (Suomen metsätieteellinen seura, 1933)
  • Luomajoki, Alpo (The Society of Forestry in Finland - The Finnish Forest Research Institute, 1999)
    Male flowering was studied at the canopy level in 10 silver birch (Betula pendula Roth) stands from 8 localities and in 14 downy birch (B. pubescens Ehrh.) stands from 10 localities in Finland from 1963 to 1973. Distributions of cumulative pollen catches were compared to the normal Gaussian distribution. The basis for the timing of flowering was the 50 per cent point of the anthesis-fitted normal distribution. To eliminate effects of background pollen, only the central, normally distributed part of the cumulative distribution was used. Development up to the median point of the distribution was measured and tested in calendar days, in degree days (> 5 °C) and in period units. The count of each parameter began on and included March 19. Male flowering in silver birch occurred from late April to late June depending on latitude, and flowering in downy birch took place from early May to early July. The heat sums needed for male flowering varied in downy birch stands latitudinally but there was practically no latitudinal variation in heat sums needed for silver birch flowering. The amount of male flowering in stands of both birch species were found to have a large annual variation but without any clear periodicity. The between years pollen catch variation in stands of either birch species did not show any significant latitudinal correlation in contrast to Norway spruce stands. The period unit heat sum gave the most accurate forecast of the timing of flowering for 60 per cent of the silver birch stands and for 78.6 per cent of the for downy birch stands. Calendar days, however, gave the best forecast for silver birch in 25 per cent of the cases, while degree days gave the best forecast for downy birch in 21.4 per cent of the cases. Silver birch seems to have a local inclination for a more fixed flowering date compared to downy birch, which could mean a considerable photoperiodic influence on flowering time of silver birch. Silver birch and downy birch had different geographical correlations. Frequent hybridization of birch species occurs more often in northern Finland in than in more southern latitudes. The different timing in flowering caused increasing scatter in flowering times in the north, especially in the case of downy birch. The chance of simultaneous flowering of silver birch and downy birch so increased northwards due to a more variable climate and also higher altitudinal variations. Compared with conifers, the reproduction cycles of both birch species were found to be well protected from damage by frost.
  • Bhat, K. M.; Kärkkäinen, Matti (Suomen metsätieteellinen seura, 1980)
  • Ollinmaa, Paavo J. (Suomen metsätieteellinen seura, 1960)
  • Kartano, Pauli (Helsingin yliopisto, 2020)
    Downy birch (Betula pubescens Ehrh.) is by far the most common tree species in Finland when considering stem count. The num-ber of the downy birches are almost double compared to pine (Pinus sylvestris). Downy birch is not very demanding of its sur-rounding and it grows in both dry and wet places in forests, marshes, shores and abandoned fields. Downy birch grows in all areas in Finland except the northernmost Lapland. Compared to Downy birch silver birch (Betula pendula) is smaller, short-lived and the appearance is more varied. Downy birch can grow up to 20 meters high and 70 to 90 years old. Downy birch has not been exceedingly popular tree in Finland, and it is mostly used as an energy wood. Downy birch and silver birch are not separated in commercial use. The aim for this study was to develop cumulative model for above ground volume and biomass for downy birch with 15 tree sample. Diameter, length and weight were manually measured from each section of the sample tree stems. Weight of branches were measured for every stems section. Volume and weight of each stem section and branches were measured by sinking them into water. Relative taper curves were calculated for each sample tree and with those the general taper curve was calculated. From stem and branch volumes separate volume curves were calculated. General volume curves for were calculated based on the separate curves. With those curves different cumulative whole tree volume curves were created. In addition to volumes, also densities for stem sections and branches were calculated. With those and volume curves biomass model can be calculated Calculated taper curves differed from Laasasenaho’s taper curves mostly on the base of the stem but above 10 % relative height the taper curves behaved similarly. Whole tree volumes were calculated with nine different methods and the results were com-pared to Hoppi’s and Repola’s equations and measured volumes. Equations where the tree height was the only explanatory factor gave much more varied results than those equations which also took the diameter in consideration. Smallest relative standard deviations were 4,1 %, 4,2 % and 4,6 %. Smallest standard deviations of the volume were 8,3 l, 7,4 l and 7,4 l. These equations used tree height and diameter. Hoppi’s and Repola’s equations gave relative standard deviations of 5,7 % and 12,7 % and stand-ard deviations of the volume were 10,7 l and 9,4 l, respectively. Similar comparisons were not done with biomass model because reliable results of the branch and stem densities were available only from three sample trees. The equations presented here are different than previous models because of the cumulative nature- Only other downy birch model was Hoppi’s model. Cumulative approach makes it possible to calculate volume (or biomass) from any relative height range and previous models do not offer that possibility. Other models give out the volume or the biomass of the whole tree (or stem). Comparison with the other models demonstrates that it is possible to create models that work well at the local level with very few sample trees. Comparisons with Repola’s model shows that result can be generalized well. Results verifies the assumption that the proportions of different size trees behave consistently.
  • Hoppi, Anni-Sofia (Helsingin yliopisto, 2018)
    Hieskoivu (Betula pubescens) on Suomen kolmanneksi yleisin puulaji, ja sen osuus puuston tilavuudesta on noin 12 %. Soistuneilla kivennäismailla ja turvemailla viihtyvä hieskoivu sopii parhaiten kuitu- ja energiapuun tuottamiseen, koska sen tukit eivät yleensä täytä vanerin tai sahatavaran laatuvaatimuksia. Kansainväliset ja kansalliset uusiutuvan energian käyttötavoitteet pyrkivät nostamaan erityisesti metsähakkeen käyttöä Suomessa. Hieskoivun korkea lämpöarvo ja metsähakkeen tuorepoltosta saadut lupaavat tulokset voisivat laskea logistiikka- ja varastointikustannuksia, jolloin hakkeen käyttö energiantuotannossa olisi kannattavampaa. Tutkielman tavoitteena oli laatia kuorellisen kokonaistilavuuden biomassamallit hieskoivulle. 11 koepuun aineisto mitattiin Hyytiälän tutkimusasemalla huhtikuussa 2017. Puun rungon ja oksien tilavuus määritettiin pätkä kerrallaan veteen upottamalla. Koepuista mitattiin lisäksi manuaalisesti pätkien pituudet sekä ristiläpimitat oksista ja rungon katkaisukohdista. Rungon sekä rungon ja oksien yhteenlaskettujen pohjapinta-alojen korrelaatioita vertailtiin rungon suhteellisilla korkeuksilla. Biomassamalleja varten koepuille tehtiin koepuukohtainen lineaarinen regressioanalyysi, jonka avulla estimoitiin elävän latvuksen kokonaistilavuuden lineaarista riippuvuutta selittävistä tunnuksista. Mallien muuttujat muunnettiin logaritmimuotoon, jotta muuttujien väliset pienet epälineaarisuudet saatiin korjattua. Selittävänä muuttujana oli ensin pelkkä elävän latvuksen rajan läpimitta, ja sen jälkeen myös elävän latvuksen pituus. Koepuukohtaisten mallien lisäksi laadittiin yksi kaikki koepuut sisältävä malli. Lopuksi omasta aineistosta laadittiin vielä kokonaistilavuuden malli, jossa käytettiin samoja tunnuksia kuin Laasasenahon koivun läpimittaan ja puun pituuteen perustuvassa tilavuusyhtälössä. Koepuiden runkojen sekä rungon ja oksien yhteenlaskettujen pohjapinta-alojen välillä oli korkea lähellä yhtä oleva korrelaatio suhteellisilla korkeuksilla tarkasteltuna. Ainoastaan puun latvassa korrelaatiot olivat alle 0,9. Oksat sisältävien pohjapinta-alojen korrelaatiot olivat pelkkää runkoa suurempia puun latvassa. Jokaisen koepuukohtaisen elävän latvuksen biomassamallin korjattu selitysaste parani ja suhteellinen keskivirhe pieneni, kun malleissa oli mukana selittävänä tekijänä läpimitan lisäksi elävän latvuksen pituus. Koko aineistoon perustuvan mallin korjattu selitysaste oli 0,998 ja suhteellinen keskivirhe 7,8 %. Pelkälle rungolle laaditun mallin kertoimet olivat hyvin lähellä Laasasenahon tilavuusyhtälön vastaavia kertoimia. Rungon biomassamallin selitysaste oli 0,999 ja suhteellinen keskivirhe 4,5 %. Omaan aineistoon perustuva malli antoi rungolle keskimäärin 4 % suuremman tilavuuden verrattuna Laasasenahon tilavuusmallilla laskettuun runkotilavuuteen. Kokonaisbiomassan mallin selitysaste ja keskivirhe olivat samat kuin pelkälle rungolle laaditussa. Kokonaistilavuuden mallilla laskettu tilavuus oli keskimäärin 8 % pienempi Repolan koivun biomassamalliin verrattuna. Tutkimustulosteni mukaan pienellä koepuuaineistolla saadaan laadittua biomassamalleja, joilla on korkea selitysaste ja pieni suhteellinen keskivirhe, kun hieskoivun biomassaa selitetään läpimitalla ja pituudella. Hieskoivujen runkomuodot olivat samansuuntaisia erikokoisilla puilla, ja oksien sekä rungon yhteenlasketuilla pohjapinta-aloilla oli suhteellisilla korkeuksilla tilastollisesti merkitsevä korrelaatio, minkä perusteella hieskoivun biomassan pystysuuntainen jakaantuminen on erikokoisten puiden välillä samankaltaista. Pohjapinta-alojen korkeat korrelaatiot vahvistavat johtopäätöstä siitä, että runkokäyrätekniikkaa hyödyntämällä saadaan käyttökelpoisia tuloksia aikaan jo muutamalla koepuulla.
  • Laitakari, Erkki (Suomen metsätieteellinen seura, 1934)
  • Ollinmaa, Paavo J. (Suomen metsätieteellinen seura, 1955)
  • Kärkkäinen, Matti (Suomen metsätieteellinen seura, 1986)
  • Kärkkäinen, Matti (Suomen metsätieteellinen seura, 1986)
  • Keltikangas, Matti; Seppälä, Kustaa (Suomen metsätieteellinen seura, 1977)
  • Bhat, K. M.; Ferm, Ari; Kärkkäinen, Matti (Suomen metsätieteellinen seura, 1981)
  • Bhat, K. M. (Suomen metsätieteellinen seura, 1980)
  • Downey, Margot (Helsingfors universitet, 2015)
    The creation of forest gaps in disturbance emulation forestry alters local environmental conditions, which causes variability in natural seedling regeneration. Understory vegetation plays an important role in early seedling regeneration success and is sensitive to variations in topography and resource availability. Its analysis can uncover the finer-scale impacts of gap characteristics and competition on the patterns of tree regeneration. The objective of this study was to examine the impact of gap characteristics on patterns of natural vegetation and tree seedling regeneration 5 years post-harvest across 18 gaps in Norway spruce (Picea abies (L.) Karst.) dominated forests of Central Finland. Gap characteristics included distance from edge (into residual forest and gap interior), cardinal position in the gap (N, S, E or W), microsite type and dominant topography. All seedlings (≤5m) were counted and measured on 1m2 plots situated along linear strips (2 for each N-S and E-W orientations). On these same plots, vegetation and microsite types were assessed by percent cover for several key categories. Results show that distance from gap edge was the most influential gap characteristic, especially in the ±10m zone. The 0–15m zone inside the gap supported the greatest abundance of seedlings, as well as the highest diversity of both vegetation types and seedling species. The edge zone inside the forest supported shade-tolerant species (dwarf shrubs, mosses). Gap centers (~15m+) supported shade-intolerant species (grasses, shrubs, herbs), creating a highly competitive growing environment. The position within the gap was also an influential characteristic. The N gap positions showed the most statistically significant difference from the others; they had fewer birch seedlings, a greater percent cover of grasses and dwarf shrubs, and a smaller percent cover of ferns. This effect was generally more pronounced in the gap interior. The results of this study support that natural regeneration of seedlings in gaps is quite variable. The mean number of seedlings per ha inside the gaps were 20 360 for Norway spruce, and 6 820 for birch spp. combined; up to 62% were germinants (≤3cm). In the 15m+ region from the gap edge towards the gap center, the mean number of seedlings per m2 was on average ~58% smaller than for the rest of the strip. The presence and abundance of different vegetation species clearly demonstrate that distance from edge and within-gap position strongly affect resource availability and competition. The most significant gap characteristics affecting these patterns of early regeneration for Norway spruce and birch were revealed with the help of generalized additive models (GAMs). Since these gaps are in their early stages of regeneration, the future dynamics and final outcome are still fairly uncertain. However, the current mean number of seedlings inside the gaps suggests a promising potential for natural regeneration. These models point to management actions which could facilitate long-term natural regeneration in similar forest gaps.
  • Heikurainen, Leo (Suomen metsätieteellinen seura, 1958)
  • Xu, Yi (Helsingin yliopisto, 2020)
    Tiivistelmä/Referat – Abstract Global warming and its coinstantaneous disturbance are intensively influencing the northern area. As a major natural disturbance in northern forest, winter moth (Operophtera brumata) and autumn moth (Epirrita autumnata) has caused wide defoliation in the mountain birch forest (Betula pubescens ssp. czerepanovii) at the subarctic area, exerting great impact on soil C stocks. Increasing temperature has promoted the vegetation expansion in the northern area and elevated the plant productivity, leading to higher C input to soil C stock. Litter decomposition may be accelerated by higher temperature, which decreases soil C storage. Moth herbivory usually increases the soil C stock in the short-term through litter and frass deposition, despite its aboveground suppression on photosynthesis. Belowground microbial community and composition shift would happen after moth outbreak, mediating the soil C turnover. However, the long-term effect of moth outbreak on soil C stock is still uncertain. This study investigated the influence of different tree status on soil C stock at subarctic mountain birch treeline forest, which went through severe moth outbreaks at 10 and 60 years ago. Living trees have observed with higher soil C stock than dead trees and treeless tundra, indicating the living tree may have a positive impact on soil C stock probably due to great aboveground photosynthesis. Living tree and its understory vegetation enhanced the soil respiration and ecosystem respiration, which would speed the C turnover, especially in the peak growing season. Dead trees were observed with slightly higher soil C stock than treeless tundra, both at 10 and 60 years’ perspectives. In contrast to direct C input provided by the living tree, the positive effect of dead tree on soil C stock is mainly due to the recalcitrant accumulation in the soil organic layer. Thus, soil C stock at the subarctic treeline after moth outbreak showed variations depending on the tree status, but overall remained as a C sink, which is good for mitigating the climate change. The mechanism behind the changes of soil C stock needs to be further investigated in future.
  • Aakala, Tuomas; Berninger, Frank; Starr, Mike (2018)
    Questions How have tree growth and growth trends varied in structurally complex old-growth forests? What determines this variation and how this differs among species? Location Natural boreal old-growth forests, northern Finland. Methods We sampled trees over 10-cm diameter on 48 randomly located 0.1-ha plots in three landscapes and compiled a data set of 1,565 trees including all three main species, and a full range of sizes and competitive states in northern boreal old-growth forests. We extracted tree ring samples from every tree and used ring widths to reconstruct tree sizes and their neighbourhood for the past 50 years for Pinus sylvestris and Picea abies, and 30 years for Betula pubescens. We used mixed-effects models to study variation in tree growth. In the models, we used annually varying environmental variables, forest and tree structural variables and site variables as predictors. We also measured soil hydraulic properties for a water balance model to specifically include soil moisture deficits as predictors. Results Tree growth rates had increased during the analysis period for all three species, with the highest increases for P. sylvestris and B. pubescens. All three species grew well during warm summers, but P. sylvestris and P. abies growth was also negatively influenced by soil moisture deficits. Competition in these sparse forests had a small influence on growth. However, its influence increased over time. Conclusions The trees showed positive growth trends, but the increasing competition means that such strong positive trends are unlikely to continue over the long term. For year-to-year variability, negative influence of droughts implied that increasing temperatures are not only beneficial to tree growth even in these high-latitude forests. Overall, the findings demonstrate the site- and species-dependent complexity in tree responses to environmental and structural changes we may expect in the future.