Svein Solberg
Research Professor
Authors
Svein Solberg Ole Martin Bollandsås Terje Gobakken Erik Næsset Paromita Basak Laura Innice DuncansonAbstract
Mapping and quantification of forest biomass change are key for forest management and for forests’ contribution to the global carbon budget. We explored the potential of covering this with repeated acquisitions with TanDEM-X. We used an eight-year period in a Tanzanian miombo woodland as a test case, having repeated TanDEM-X elevation data for this period and repeated field inventory data. We also investigated the use of GEDI space–LiDAR footprint AGB estimates as an alternative to field inventory. The map of TanDEM-X elevation change appeared to be an accurate representation of the geography of forest biomass change. The relationship between TanDEM-X phase height and above-ground biomass (AGB) could be represented as a straight line passing through the origin, and this relationship was the same at both the beginning and end of the period. We obtained a similar relationship when we replaced field plot data with the GEDI data. In conclusion, temporal change in miombo woodland biomass is closely related to change in InSAR elevation, and this enabled both an accurate mapping and quantification wall to wall within 5–10% error margins. The combination of TanDEM-X and GEDI may have a near-global potential for estimation of temporal change in forest biomass.
Abstract
Forests, especially in the northern latitudes, are vulnerable ecosystems to climate change, and tree-ring data offer insights into growth-climate relationships as an important effect. Using the National Forest Inventory plot network, we analysed these correlations for the two dominant conifer species in Norway – Norway spruce and Scots pine – for the 1960–2020 period. For both species, the June climate was an important driver of radial growth during this period. Countrywide, the climate-growth correlations divided the Norwegian forests into spatial clusters following a broad shift from temperature- to water-sensitivity of growth with latitude and altitude. The clusters were delineated by a mean 1960–2020 June temperature of ca. 12°C for Norway spruce and Scots pine. The annual mean growing season and July temperatures – but not June temperature – has increased by 1.0 °C between the 1960–1990 and 1990–2020 periods, with a slight increase in precipitation. Despite this warming and wetting trend, the long-term growth-climate relationship has remained relatively stable between 1960 and 1990 and 1990–2020 for both species. The threshold between temperature and water-sensitive growth has not changed in the last two 31-year periods, following the stability of the June temperature compared with other months during the growing season. These findings highlight geographically coherent regions in Norway, segregating between temperature- and water-sensitive radial growth for the two major conifer species, temporally stable in the long-term for the 1960–2020 period studied.
Authors
Adam Kristensson Paul Miller Holger Lange Thomas Holst Jaana Bäck Pontus Roldin Natascha Kljun Anne Klosterhalfen Anders Ahlström Thomas A. Pugh Liesbet Vranken Mark Rounsevell Svein Solberg James AtkinsonAbstract
Forests are a key plank of European policies to mitigate and adapt to climate change and to promote biodiversity. These policies are starting to become more nuanced with respect to the account of their impacts on carbon storage, considering the effect of long-lived wood products and value of conserving old-growth forests, along with indirect land-use change impacts. However, a CO2-focused perspective means that many processes are still omitted for the quantification of the true extent of climate effects. Emissions of the greenhouse gases nitrous oxide and methane, short-lived climate forcers and effects from albedo changes and heat fluxes are also relevant. These processes are interconnected and influence the climate mitigation of forests in a complex way and need to be considered. The CLImate Mitigation and Bioeconomy pathways for sustainable FORESTry (CLIMB-FOREST) Horizon Europe project that runs until 2027 uses a holistic approach to estimate the climate impacts of various management alternatives. The foundation of CLIMB-FOREST is the use of European-wide empirical data, as well as an advanced coupled vegetation and earth-system modelling framework that includes biodiversity indicators and the interaction of forestry stakeholders in a global trade system. This framework is used to model management, forest tree species and climate on short- to long-term in Europe. We present first results of the climate effects and ecosystem functioning for a range of management alternatives in boreal, temperate, and Mediterranean forests. For example, introducing broadleaved trees in a coniferous forest promotes resilience and increased cooling from higher solar light scattering and latent heat flux of broadleaved trees. On the other hand, higher evapotranspiration might lead to an accelerated soil moisture depletion and reduced monoterpene emissions. The latter would have a warming effect because terpenes produce atmospheric particles, which are effective cooling agents through their involvement in cloud formation. Consequently, understanding these complex climate effects is key for appropriate climate-smart-forestry policies and approaches. The main outcomes and impacts of CLIMB-FOREST are to suggest alternative pathways for the forest sector to mitigate climate change in entire Europe, create attitude change in the policymaking process and influence foresters to adopt to new forest management strategies.