Ilmastonmuutos ja biotalous – Metsäsektorilla vaaditaan paradigman muutosta

Tieteen tori: Metsien kestävä käyttö biotalouden aikan

Kuusen, männyn ja koivun juuristojen ominaisuudet boreaalisessa sekametsikössä : juuriston arkkitehtuurin, morfologian ja anatomian analyysi

The aim of this thesis was to unravel the functional-structural characteristics of root systems of Betula pendula Roth., Picea abies (L.) Karst., and Pinus sylvestris L. in mixed boreal forest stands differing in their developmental stage and site fertility. The root systems of these species had similar structural regularities: horizontally-oriented shallow roots defined the horizontal area of influence, and within this area, each species placed fine roots in the uppermost soil layers, while sinker roots defined the maximum rooting depth. Large radial spread and high ramification of coarse roots, and the high specific root length (SRL) and root length density (RLD) of fine roots indicated the high belowground competitiveness and root plasticity of B. pendula. Smaller radial root spread and sparser branching of coarse roots, and low SRL and RLD of fine roots of the conifers could indicate their more conservative resource use and high association with and dependence on ectomycorrhiza-forming fungi. The vertical fine root distributions of the species were mostly overlapping, implying the possibility for intense belowground competition for nutrients. In each species, conduits tapered and their frequency increased from distal roots to the stem, from the stem to the branches, and to leaf petioles in B. pendula. Conduit tapering was organ-specific in each species violating the assumptions of the general vascular scaling model (WBE). This reflects the hierarchical organization of a tree and differences between organs in the relative importance of transport, safety, and mechanical demands. The applied root model was capable of depicting the mass, length and spread of coarse roots of B. pendula and P. abies, and to the lesser extent in P. sylvestris. The roots did not follow self-similar fractal branching, because the parameter values varied within the root systems. Model parameters indicate differences in rooting behavior, and therefore different ecophysiological adaptations between species.Tämän tutkimuksen tavoitteena oli selvittää koivun, kuusen ja männyn juuristojen toiminnallis-rakenteellisia ominaisuuksia boreaalisen sekametsikön eri kehitysvaiheissa ja erilaisilla maaperän ravinteisuuksilla. Tutkittujen lajien juuristot noudattivat samanlaisia rakenteellisia säännönmukaisuuksia. Pintajuuret määrittivät juuriston horisontaalisen vaikutusalueen. Vaikutusalueen sisällä hienojuuret sijaitsivat pääasiallisesti humuskerroksessa ja ylimmässä mineraalimaakerroksessa. Syväjuuret määrittivät juuriston maksimaalisen syvyyden. Koivun pintajuurten suuri ulottuvuus ja voimakas haaroittuminen, sekä hienojuurten suuri spesifinen pituus (SRL) ja tiheys (RLD) osoittavat koivun suurta kilpailukykyä juuristokilpailussa ja juurten ominaisuuksien suurta plastisuutta. Havupuiden paksujuurten pienempi ulottuvuus, sekä matalat SRL- ja RLD-arvot voivat viitata niiden konservatiivisempaan resurssien käyttöön sekä suurempaan riippuvuuteen ektomykorritsoista ravinteiden otossa. Lajien hienojuurijakaumien selkeä päällekkäisyys syvyyssuunnassa voi viitata voimakkaaseen lajien väliseen ravinnekilpailuun ylimmissä maakerroksissa. Kunkin lajin vedenkuljetussolut kapenivat ja lukumäärä pinta-alayksikköä kohden kasvoi etäällä olleista 2-mm-läpimittaisista juurista runkoon, rungosta oksiin, sekä koivussa oksista lehtien petioleihin. Kapeneminen erosi eri ositteiden välillä, mikä rikkoo putkilokasvien yleisen skaalautumismallin (WBE) oletusta tasaisesta kapenemisesta puun sisällä. Havainto kuvaa puun eri ositteiden rakenteellista hierarkisuutta, sekä eri tehtävien (kuljetus, embolisaation estäminen, mekaaninen tuki) suhteellisen merkityksen eroja eri ositteiden välillä. Tutkimuksessa käytetty juurimalli pystyi kuvaamaan koivun ja kuusen paksujuurten biomassan, pituuden ja laajuuden. Mallin antamat ennusteet männyn juuriston ominaisuuksille poikkesivat havainnoista muita lajeja enemmän. Juurten haaroittuminen ei toteuttanut fraktaalisuuden olettamuksia, koska parametriarvot vaihtelivat yksittäisen juuriston sisällä. Mallin parametrit osoittivat lajien välisiä eroja juuriston kehityksessä, mikä viittaa lajien ekofysiologisiin sopeutumiin

On the trade-offs and synergies between forest carbon sequestration and substitution

Forest biomass can be used in two different ways to limit the growth of the atmospheric greenhouse gas (GHG) concentrations: (1) to provide negative emissions through sequestration of carbon into forests and harvested wood products or (2) to avoid GHG emissions through substitution of non-renewable raw materials with wood. We study the trade-offs and synergies between these strategies using three different Finnish national-level forest scenarios between 2015 and 2044 as examples. We demonstrate how GHG emissions change when wood harvest rates are increased. We take into account CO2 and other greenhouse gas flows in the forest, the decay rate of harvested wood products and fossil-based CO2 emissions that can be avoided by substituting alternative materials with wood derived from increased harvests. We considered uncertainties of key parameters by using stochastic simulation. According to our results, an increase in harvest rates in Finland increased the total net GHG flow to the atmosphere virtually certainly or very likely, given the uncertainties and time frame considered. This was because the increased biomass-based CO2 and other greenhouse gas emissions to the atmosphere together with decreased carbon sequestration into the forest were very likely higher than the avoided fossil-based CO2 emissions. The reverse of this conclusion would require that compared to what was studied in this paper, the share of long-living wood products in the product mix would be higher, carbon dioxide from bioenergy production would be captured and stored, and reduction in forest carbon equivalent net sink due to wood harvesting would be minimized.Peer reviewe

Decomposing sources of uncertainty in climate change projections of boreal forest primary production

We are bound to large uncertainties when considering impacts of climate change on forest productivity. Studies formally acknowledging and determining the relative importance of different sources of this uncertainty are still scarce, although the choice of the climate scenario, and e.g. the assumption of the CO2 effects on tree water use can easily result in contradicting conclusions of future forest productivity. In a large scale, forest productivity is primarily driven by two large fluxes, gross primary production (GPP), which is the source for all carbon in forest ecosystems, and heterotrophic respiration. Here we show how uncertainty of GPP projections of Finnish boreal forests divides between input, mechanistic and parametric uncertainty. We used the simple semi-empirical stand GPP and water balance model PRELES with an ensemble of downscaled global circulation model (GCM) projections for the 21st century under different emissions and forcing scenarios (both RCP and SRES). We also evaluated the sensitivity of assumptions of the relationships between atmospheric CO2 concentration (C-a), photosynthesis and water use of trees. Even mean changes in climate projections of different meteorological variables for Finland were so high that it is likely that the primary productivity of forests will increase by the end of the century. The scale of productivity change largely depends on the long-term C-a fertilization effect on GPP and transpiration. However, GCM variability was the major source of uncertainty until 2060, after which emission scenario/pathway became the dominant factor. Large uncertainties with a wide range of projections can make it more difficult to draw ecologically meaningful conclusions especially on the local to regional scales, yet a thorough assessment of uncertainties is important for drawing robust conclusions.We are bound to large uncertainties when considering impacts of climate change on forest productivity. Studies formally acknowledging and determining the relative importance of different sources of this uncertainty are still scarce, although the choice of the climate scenario, and e.g. the assumption of the CO2 effects on tree water use can easily result in contradicting conclusions of future forest productivity. In a large scale, forest productivity is primarily driven by two large fluxes, gross primary production (GPP), which is the source for all carbon in forest ecosystems, and heterotrophic respiration. Here we show how uncertainty of GPP projections of Finnish boreal forests divides between input, mechanistic and parametric uncertainty. We used the simple semi-empirical stand GPP and water balance model PRELES with an ensemble of downscaled global circulation model (GCM) projections for the 21st century under different emissions and forcing scenarios (both RCP and SRES). We also evaluated the sensitivity of assumptions of the relationships between atmospheric CO2 concentration (C-a), photosynthesis and water use of trees. Even mean changes in climate projections of different meteorological variables for Finland were so high that it is likely that the primary productivity of forests will increase by the end of the century. The scale of productivity change largely depends on the long-term C-a fertilization effect on GPP and transpiration. However, GCM variability was the major source of uncertainty until 2060, after which emission scenario/pathway became the dominant factor. Large uncertainties with a wide range of projections can make it more difficult to draw ecologically meaningful conclusions especially on the local to regional scales, yet a thorough assessment of uncertainties is important for drawing robust conclusions.Peer reviewe

Early root growth and architecture of fast- and slow-growing Norway spruce (Picea abies) families differ-potential for functional adaptation

The relationship between the growth rate of aboveground parts of trees and fine root development is largely unknown. We investigated the early root development of fast-and slow-growing Norway spruce (Picea abies (L.) H. Karst.) families at a developmental stage when the difference in size is not yet observed. Seedling root architecture data, describing root branching, were collected with the WinRHIZO (TM) image analysis system, and mixed models were used to determine possible differences between the two growth phenotypes. A new approach was used to investigate the spatial extent of root properties along the whole sample root from the base of 1-year-old seedlings to the most distal part of a root. The root architecture of seedlings representing fastgrowing phenotypes showed similar to 30% higher numbers of root branches and tips, which resulted in larger root extensions and potentially a better ability to acquire nutrients. Seedlings of fast-growing phenotypes oriented and allocated root tips and bio-mass further away from the base of the seedling than those growing slowly, a possible advantage in nutrient-limited and heterogeneous boreal forest soils. We conclude that a higher long-term growth rate of the aboveground parts in Norway spruce may relate to greater allocation of resources to explorative roots that confers a competitive edge during early growth phases in forest ecosystems.Peer reviewe

User guide for PRELES, a simple model for the assessment of gross primary production and water balance of forests

Climforisk EU Life+ (EU/ENV/FI/00571) http://www.metla.fi/life/climforisk. Deliverable of the Action 3 of the Climforisk project: Modelling software and documentation , 30.6.2012.Simple models of ecosystem processes are useful tools for various kind of ecosystem impact studies. We built a simple model of ecosystem gross primary production, evapotranspiration and soil water content, which requires minimal input data, and which is efficient to run. In this report, we briefly describe the model equations, document the model program and provide user guide for the current version of the model. We also use the model to run a few example simulations that describe how the model responds to the environment, and test the model predictions of soil water in reference conditions with ICP level II data on soil water. The model is intended to be used in large scale prediction of GPP, ET, and drought in the Climforisk EU Life+ project

Bayesian calibration of a carbon balance model PREBAS using data from permanent growth experiments and national forest inventory

Policy-relevant forest models must be environment and management sensitive and provide unbiased estimates of predicted variables over their intended areas of application. While empirical models derive their structure and parameters from representative data sets, process-based model (PBM) parameters should be evaluated in ranges that have a biological meaning independently of output data. At the same time PBMs should be calibrated against observations in order to obtain unbiased estimates and an understanding of their predictive capability. By means of model data assimilation, we Bayesian calibrated a forest model (PREBAS) using an extensive dataset that covered a wide range of climatic conditions, species composition and management practices. PREBAS was calibrated for three species in Finland: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies [L.] H. Karst.) and Silver birch (Betula pendula L.). Data assimilation was strongly effective in reducing the uncertainty of PREBAS parameters and predictions. A country-generic calibration showed robust performances in predicting forest variables and the results were consistent with yield tables and national forest statistics. The posterior predictive uncertainty of the model was mainly influenced by the uncertainty of the structural and measurement error.Peer reviewe

Ilmastonmuutos ajurina metsäsektorin muutokselle

Kirjoitus perustuu Tieteen päivien podcast-ohjelmaan 14.1.2021, jossa aiheena oli, mitä ilmastonmuutos merkitsee metsäsektorilla ja toisaalta mitä metsäsektori voi tehdä ilmastonmuutoksen hillitsemiseksi. Keskustelun puheenjohtaja oli Anneli Pauli, ja keskustelijat olivat eritaustaisia asiantuntijoita

Evaluation of stand-level hybrid PipeQual model with permanent sample plot data of Norway spruce

The evaluation of process-based models (PBM) includes ascertaining their ability to produce results consistent with forest growth in the past. In this study, we parameterized and evaluated the hybrid model PipeQual with datasets containing traditional mensuration variables collected from permanent sample plots (PSP) of even-aged Norway spruce (Picea abies (L.) Karst.) stands in Finland. To initialize the model in the middle of stand development and reproduce observed changes in Norway spruce crown structure, the built-in empirical relationships of crown characteristics were made explicitly dependent on the light environment. After these modifications, the model accuracy at the whole dataset level was high, with slope values of linear regressions between the observations and simulations ranging from 0.77 to 0.99 depending on the variable. The average bias ranged between -0.72 and 0.07 m in stand dominant height, -0.68 and 0.57 cm in stand mean diameter, -2.62 and 1.92 m(2) in stand basal area, and 20 and 29 m(3) in stand total stem volume. Stand dynamics after thinning also followed reasonable closely the observed patterns. Accurate predictions illustrate the potential of the model for predicting forest stand growth and forest management effects in changing environmental conditions.Peer reviewe