Raisa Mäkipää

Indirect methods of large-scale forest biomass estimation

Forest biomass and its change over time have been measured at both local and large scales, an example for the latter being forest greenhouse gas inventories. Currently used methodologies to obtain stock change estimates for large forest areas are mostly based on forest inventory information as well as various factors, referred to as biomass factors, or biomass equations, which transform diameter, height or volume data into biomass estimates. However, while forest inventories usually apply statistically sound sampling and can provide representative estimates for large forest areas, the biomass factors or equations used are, in most cases, not representative, because they are based on local studies. Moreover, their application is controversial due to the inconsistent or inappropriate use of definitions involved. There is no standardized terminology of the various factors, and the use of terms and definitions is often confusing. The present contribution aims at systematically summarizing the main types of biomass factors (BF) and biomass equations (BE) and providing guidance on how to proceed when selecting, developing and applying proper factors or equations to be used in forest biomass estimation. The contribution builds on the guidance given by the IPCC (Good practice guidance for land use, land-use change and forestry, 2003) and suggests that proper application and reporting of biomass factors and equations and transparent and consistent reporting of forest carbon inventories are needed in both scientific literature and the greenhouse gas inventory reports of countries.

Fungal community dynamics in relation to substrate quality of decaying Norway spruce (Picea abies [L.] Karst.) logs in boreal forests

Decaying wood plays an important role in forest biodiversity, nutrient cycling and carbon balance. Community structure of wood-inhabiting fungi changes with mass loss of wood, but the relationship between substrate quality and decomposers is poorly understood. This limits the extent to which these ecosystem services can be effectively managed. We studied the fungal community and physico-chemical quality (stage of decay, dimensions, density, moisture, C : N ratio, lignin and water or ethanol extractives) of 543 Norway spruce logs in five unmanaged boreal forest sites of southern Finland. Fungi were identified using denaturing gradient gel electrophoresis and sequencing of DNA extracted directly from wood samples. Macroscopic fruiting bodies were also recorded. Results showed a fungal community succession with decreasing wood density and C : N ratio, and increasing moisture and lignin content. Fungal diversity peaked in the most decayed substrates. Ascomycetes typically colonized recently fallen wood. Brown-rot fungi preferred the intermediate decay stages. White-rot fungi represented approximately one-fifth of sequenced species in all decay phases excluding the final phase, where ectomycorrhizal (ECM) fungi became dominant. Lignin content of logs with white-rot fungi was low, and ECM fungi were associated with substrates containing abundant nitrogen. Macroscopic fruiting bodies were observed for only a small number of species detected with molecular techniques.

Forest carbon sequestration and harvests in Scots pine stand under different climate and nitrogen deposition scenarios

Abstract In this study, effects of altered rotation length, nitrogen deposition and changing climate on harvest removal and carbon sequestration of forest, as well as on economic profitability of forestry, were assessed. This study was based on simulations with a gap-type forest succession model in the conditions that represent Scots pine stands in southern Finland. Both warmer climatic conditions and increased nitrogen deposition enhanced forest productivity and timber yield. This also shortened the optimum rotations based on mean annual yield and soil expectation value. The highest carbon stock in forests, i.e. the highest mean annual carbon stock in the forest over a rotation period, was achieved with long rotations and higher nitrogen deposition. However, a warmer climate had an opposite effect on the forest carbon stock, because enhanced decomposition of soil organic matter resulted in a lower carbon stock in the forest soil.

Large-scale changes in abundance of terricolous bryophytes and macrolichens in Finland

Abstract Major changes in forest floor vegetation were identified on the basis of three nationwide surveys conducted as part of national forest inventories in 1951–1953, 1985–1986 and 1995. These surveys provided objectively selected, statistically representative samples of all forested land in Finland. The 1951–1953 data consist of over 10000 sample plots, while the later surveys were conducted on ca. 3000 permanent plots. Changes in relative abundance of dominant species (i.e. in the proportions of species of the total cover of forest floor vegetation) were analysed across biogeographical provinces. Spatial correlation, systematic sampling, partial re-measurement and multiple testing were taken into account in assessment of the statistical significance of the observed changes. The most notable changes in forest floor vegetation were a decrease in the relative abundance of Hylocomium splendens and an increase in Dicranum polysetum. In N Finland, where forests are grazed by semi-domestic reindeer, we observed a decline in the abundance of Cladina lichens and an increase in Dicranum mosses. Peltigera aphthosa declined throughout the country. Polytrichum juniperinum, Pohlia nutans, and Brachythecium species, which occupy disturbed sites or grow on litter, increased in abundance. The relative abundance of Sphagnum species decreased, particularly in W Finland, where Pleurozium schreberi was favoured. A major decline in S. fuscum was also recorded in C and E Finland. Many of the changes detected in this study are apparently related to intensified forest management; but solely on the basis of this study, its effects cannot be distinguished from those of other large-scale environmental changes. Nomenclature: Vitikainen et al. (1997) for lichens; Blockeel & Long (1998) for bryophytes.

Effect of nitrogen input on carbon accumulation of boreal forest soils and ground vegetation

Abstract The effects of nitrogen deposition on the carbon balance of forest soils and ground vegetation were estimated in long-term fertilization experiments. The experiments were established during 1958–1962. They were situated on 36- to 63-year-old Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies Karst.) stands of different levels of fertility. The experiments received nitrogen fertilization five to seven times over a 30-year period, and the total input of nitrogen was 596–926 kg ha −1 . Nitrogen input increased the amount of carbon in the humus layer and mineral soil. With one exception, the carbon storage of the humus layer was increased by 14–87%, and carbon storage of the mineral soil by 15–167%. The humus layer was thicker on the fertilized plots due to accumulation of organic matter during the study period. In the changing environment, nitrogen deposition reinforces the accumulation of organic matter in forest soils, and may enhance carbon accumulation in boreal forests. On the other hand, both the biomass and the amount of carbon in the ground vegetation were decreased by the addition of nitrogen. The ground vegetation under a closed canopy does not have the potential to respond positively to addition of nitrogen, because the vegetation is dominated by slow-growing mosses and dwarf shrubs. Thus, the ground vegetation of the boreal forests is not a sink for carbon in the changing environment.

Uncertainty estimation of biomass expansion factors for Norway spruce in the Czech Republic

Nation wide estimates of the changes in forest biomass are needed for the greenhouse gas (GHG) reporting under the Climate Convention. The bases for national GHG reporting concerning forest sector are the national forest inventory (NFI) programmes. Since these programmes were mostly established for monitoring of timber resources, one of the current challenges for the NFIs is the development of methodology, such as biomass expansion factors (BEFs). The methodology for carbon stock change estimation should be transparent and verifiable, but this demand is not currently met due to the fact that the source data and uncertainty in the applied BEFs are not known. Here we developed BEFs with uncertainty estimation applicable to stand wise inventory of Norway spruce forests in the Czech Republic. BEFs were constructed, based on tree wise data from permanent research plots, by applying biomass and volume models to tree-level data. These BEFs were age-dependent and their uncertainty was sensitive to the dependencies among errors. Most of the uncertainty in the BEFs was due to uncertainty in the biomass and volume models applied.RésuméLes estimations de la biomasse des forêts servent à évaluer les effets des changements climatiques et à dresser des rapports internationaux. En foresterie, les rapports nationaux sur les gaz à effet de serre (GES) sont basés sur l’inventaire forestier national. L’objectif premier de cet inventaire étant la prévision des ressources de bois brut, l’inventaire des GES appelle des méthodes de prévision basée sur les facteurs d’expansion de la biomasse. Les méthodes d’estimation des GES devraient être transparentes et vérifiables — objectif souvent non atteint parce que l’origine et l’incertitude des facteurs d’expansion de la biomasse ne sont pas connues. Dans cette étude nous avons développé des facteurs d’expansion de la biomasse des forêts de sapin dans la République tchèque et calculé l’incertitude de ceux-ci. Les facteurs ont été estimés en fonction des mesures au niveau de l’arbre dans des zones d’échantillonnage permanentes et de l’application des modèles de volume et de biomasse. Ces facteurs d’expansion étaient dépendants de l’âge et leur incertitude sensible aux corrélations entre les erreurs. L’incertitude des facteurs d’expansion était principalement due aux modèles de biomasse et de volume appliqués.

Response patterns of Vaccinium myrtillus and V. vitis-idaea along nutrient gradients in boreal forest

The relationships between biomass of dwarf shrub species and nutrient gradients of forest soils was studied under field conditions in boreal forests. The biomass-re- sponse curves of Vaccinium myrtillus and V. vitis-idaea were fitted against soil nutrient gradients using Generalized Lin- ear Models (GLM). Ecological niches of Vaccinium myrtillus and V. vitis-idaea were evaluated, and effects of nitrogen addition (manipulation of the nutrient gradient) on response function were tested. The Vaccinium species showed statistically significant Gaussian responses along soil nitrogen, phosphorus and cal- cium gradients, but not along other gradients (K and Mg). Furthermore, manipulation of the nitrogen gradient seemed to have a minor effect on response functions, i.e. addition of nitrogen did not change ecological niches of these species. Ecological optima of V. myrtillus and V. vitis-idaea on the nutrient gradients were about the same. This study suggests that differences in dominance between Vaccinium myrtillus and V. vitis-idaea in boreal forest is not determined by nutrient gradients, but may rather be explained by light conditions and/ or moisture availability.

Scenarios for the carbon balance of Finnish forests and wood products

Abstract The objective of this paper is to compare different scenarios for carbon (C) sequestration in the forest sector in Finland. Forest inventory data was used as input data to simulate the dynamics of C sequestration with a gap-type forest simulation model and a wood product model. In the baseline scenario, current forest management practices were applied. In another scenario, current recommendations for forest management were applied, which resulted in more intensive harvesting than in the baseline scenario. Both scenarios were also applied under changing climatic conditions to demonstrate the possible effect of climate change on C sequestration. This study demonstrates that C sequestration assessments should include not only C in the biomass of trees, but also C in the soil and in the wood products, as well as interactions between the respective pools. Partial assessments are likely to result in misleading estimates of the actual C sequestration. Forest management affects the distribution of C between the pools and the changing climate is likely to change this distribution. The Kyoto Protocol deals with only a limited part of the forestry and forest C cycle and C accounting accordingly can provide results that depart substantially from more complete accounting.

Change Detection of Tree Biomass with Terrestrial Laser Scanning and Quantitative Structure Modelling

We present a new application of terrestrial laser scanning and mathematical modelling for the quantitative change detection of tree biomass, volume, and structure. We investigate the feasibility of the approach with two case studies on trees, assess the accuracy with laboratory reference measurements, and identify the main sources of error, and the ways to mitigate their effect on the results. We show that the changes in the tree branching structure can be reproduced with about ±10% accuracy. As the current biomass detection is based on destructive sampling, and the change detection is based on empirical models, our approach provides a non-destructive tool for monitoring important forest characteristics without laborious biomass sampling. The efficiency of the approach enables the repeating of these measurements over time for a large number of samples, providing a fast and effective means for monitoring forest growth, mortality, and biomass in 3D.

Potential contribution of the forest sector to carbon sequestration in Finland

Abstract Although Finlands forest resources have been utilized intensively, the size of the total volume of the growing stock has increased since the mid-1960s, and hence increasing amounts of carbon have been sequestered by forests. The net sequestration by forests has also been substantial when compared with the CO 2 emissions resulting from energy generation and consumption based on fossil fuels and peat. It is also important, from the point of view of mitigating the effects of climate change, to assess how the sequestration capacity of forests may change under changing climatic conditions. This paper presents the results of a study assessing the development of the forest and wood-product carbon budget for Finland, based on regionally measured data, detailed dynamic models, and recent predictions concerning the changing climate. At the starting point for the simulation (1990), nearly 90% of the forest sectors carbon storage was found in the forest. Regular management transferred carbon from forests to wood products. Under the current climatic conditions, the simulated forest carbon storage increased 45% by the year 2100, and the wood-product storage by 320%, as a consequence of continuous production. Under changing climate conditions, the forest carbon storage increased, but started to decline when the temperature increase exceeded 2.5°C within 40 years.