Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2021
Abstract
There is a need for mapping of forest areas with young stands under regeneration in Norway, as a basis for conducting tending, or precommercial thinning (PCT), whenever necessary. The main objective of this article is to show the potential of multitemporal Sentinel-1 (S-1) and Sentinel-2 (S-2) data for characterization and detection of forest stands under regeneration. We identify the most powerful radar and optical features for discrimination of forest stands under regeneration versus other forest stands. A number of optical and radar features derived from multitemporal S-1 and S-2 data were used for the class separability and cross-correlation analysis. The analysis was performed on forest resource maps consisting of the forest development classes and age in two study sites from south-eastern Norway. Important features were used to train the classical random forest (RF) classification algorithm. A comparative study of performance of the algorithm was used in three cases: I) using only S-1 features, II) using only S-2 optical bands, and III) using combination of S-1 and S-2 features. RF classification results pointed to increased class discrimination when using S-1 and S-2 data in relation to S-1 or S-2 data only. The study shows that forest stands under regeneration in the height interval for PCT can be detected with a detection rate of 91% and F-1 score of 73.2% in case III as most accurate, while tree density and broadleaf fraction could be estimated with coefficient of determination ( R2 ) of about 0.70 and 0.80, respectively.
Authors
Johannes Breidenbach Janis Ivanovs Annika Kangas Thomas Nord-Larsen Mats Nilsson Rasmus AstrupAbstract
Policy measures and management decisions aimed at enhancing the role of forests in mitigating climate change require reliable estimates of carbon (C)-stock dynamics in greenhouse gas inventories (GHGIs). The aim of this study was to assemble design-based estimators to provide estimates relevant for GHGIs using National Forest Inventory (NFI) data. We improve basic expansion (BE) estimators of living-biomass C-stock loss using only field data, by leveraging with remote sensing auxiliary data in model-assisted (MA) estimators. Our case studies from Norway, Sweden, Denmark, and Latvia covered an area of >70 Mha. Landsat-based forest cover loss (FCL) and one-time wall-to-wall airborne laser scanning (ALS) served as auxiliary data. ALS provided information on the C stock before a potential disturbance indicated by FCL. The use of FCL in MA estimators resulted in considerable efficiency gains, which in most cases were further increased by adding ALS. A doubling of efficiency was possible for national estimates and even larger efficiencies were observed at the subnational level. Average annual estimates were considerably more precise than pooled estimates of the NFI data from all years at once. The combination of remotely sensed and NFI field data yields reliable estimators, which is not necessarily the case when using remotely sensed data without reference observations.
Abstract
No abstract has been registered
Abstract
Diameter at breast height (DBH) distributions offer valuable information for operational and strategic forest management decisions. We predicted DBH distributions using Norwegian national forest inventory and airborne laser scanning data and compared the predictive performances of linear mixed-effects (PPM), generalized linear-mixed (GLM), and k nearest-neighbor (NN) models. While GLM resulted in smaller prediction errors than PPM, both were clearly outperformed by NN. We therefore studied the ability of the NN model to improve the precision of stem frequency estimates by DBH classes in the 8.7 Mha study area using a model-assisted (MA) estimator suitable for systematic sampling. MA estimates yielded greater than or approximately equal efficiencies as direct estimates using field data only. The relative efficiencies (REs) associated with the MA estimates ranged between 0.95–1.47 and 0.96–1.67 for 2 and 6 cm DBH class widths, respectively, when dominant tree species were assumed to be known. The use of a predicted tree species map, instead of the observed information, decreased the REs by up to 10%.
Abstract
Genetic variation and phenotypic stability in Norway spruce were studied based on provenances, families, and clones planted in trials at 12 sites in four Nordic countries. The families were generated in a factorial cross between 10 parents of Norwegian origin and 10 parents of Eastern European origin, and the clones were propagated from seedlings within 20 of the same families. Traits analyzed were survival, proportion of trees with stem defects, and tree heights. Stability was analyzed by regression analyses with the genetic entries’ annual shoot increment as the dependent variable and the total site mean as an environmental index. Information about growth and phenology traits were available from short-term tests. For tree heights, significant variance components were present both among female and male parents, but not for their interactions, indicating that non-additive genetic effects are small. Genotype × environment interactions were significant at all three genetic levels, but their variance components had considerably lower values than the variance components estimated for the effects of families and clones. For the set of families of Norwegian origin, strong relationships were observed between the timing of annual shot elongation, mortality, and height growth. Large variation was found at all three genetic levels for phenotypic stability measured by regression coefficients. A positive relationship was present between the regression coefficient and the timing of annual shoot growth for families, indicating that later flushing families responded more to a high site index. The regression coefficient can be a useful supplement to the breeding value when selecting for superior and stable genotypes.
Abstract
No abstract has been registered
Abstract
In the last century, local or individual-based forest management was introduced by various forest scientists including Schädelin, Abetz and Pollanschütz as an alternative to traditional global thinning methods. They suggested breaking large forest stands down into smaller neighbourhood-based units. The centre of each of these neighbourhood-based units is a frame tree (also referred to as final crop tree, elite tree or target tree) with clearly defined properties that depend on the management objectives. In each management intervention, trees in the neighbourhood of frame trees that in the next 5–10 years are likely to influence the frame trees negatively are removed selectively. In contrast to global methods, management is only carried out where there are frame trees. Local or individual-based forest management methods were first introduced in a commercial forestry context, but rather constitute generic methods that can be efficiently applied in management for conservation, carbon sequestration and recreation. They are also often applied in the context of continuous cover forestry (CCF). In this study, we analysed the behaviour of test persons selecting frame trees in 26 training sites, so-called marteloscopes, from all over Great Britain. Although the test persons were new to individual-based management, statistical performance indicators suggested that frame trees were selected in accordance with the theory of local or individual-based forest management. Unexpectedly the test persons even achieved a comparatively high degree of agreement. This result contrasts the low agreement and partly unsatisfying performance indicators incurred in the selection of frame-tree competitors, the second step of local forest management. The outcomes of this study highlight that training in individual-based forest management needs to put more emphasis on the identification of frame-tree competitors.
Authors
Sigitas Girdziušas Magnus Löf Kjersti Holt Hanssen Dagnija Lazdiņa Palle Madsen Timo Saksa Kaspars Liepiņš Inger Sundheim Fløistad Marek MetslaidAbstract
Since the beginning of the twentieth century, forest regeneration management and policy in the Nordic–Baltic region (Denmark, Sweden, Norway, Finland, Estonia, Latvia and Lithuania) have gone through significant changes. For decades forest as a key natural resource was managed with main focus on timber production. However, several factors influenced shifting forest management, including forest regeneration to meet a wide range of society needs. This review study aims to reveal the historical development of forest regeneration identifying knowledge gaps and supporting decisions that promote sustainable regeneration of future forests. The development of forest regeneration management and policy in the Nordic–Baltic countries is analyzed through reforestation and afforestation practices as well as legislation aspects using a narrative review approach. Trends in forest regeneration practices within the region are identified and explored over a timeframe spanning from 1900 until today. Despite diverse forestry management structures and differing political, social situations, the study shows that forest regeneration development has followed similar patterns over time in all Nordic–Baltic region countries: extensive forestry, clear-cut forestry, retention forestry and currently evolving climate-adaptive forestry. Nevertheless, regional differences among the Nordic–Baltic countries, especially in forest regeneration-related legislation, were identified due to a mixture of international and local driving forces.
Abstract
No abstract has been registered
Authors
Robert Schneider Laurie Dupont-Leduc Vincent Gauthray-Guyénet Nicolas Cattaneo Lara Melo Tommy Simard Alexis Begni Raphael Turquin Annabelle Morache-Mercier Samuel Pinna Ulysse Rémillard Charles NockAbstract
No abstract has been registered