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.
2022
Authors
Gry Alfredsen Christian Brischke Richard Acquah Tolgay Akkurt Per Otto Flæte Eva Frühwald Hansson Geir Wæhler Gustavsen Hasan Hosseini Targo Kalamees Jaan Kers Villu Kukk Roja Modaresi Jonas Niklewski Anna Sandak Sandak Jakub Philip van NiekerkAbstract
No abstract has been registered
Abstract
Aim Grasslands of varying land-use intensity and history were studied to describe and test species richness and compositional patterns and their relationships with the physical environment, land cover of the surrounding landscape, patch geometry, and grazing. Location The mainland of Norway. Methods We utilized data from the Norwegian Monitoring Programme for Agricultural Landscapes, which recorded vascular plants from 569 plots, placed within 97 monitoring squares systematically distributed throughout agricultural land on the Norwegian mainland. We identified four grassland types: (i) moderately fertilized, moist meadows; (ii) overgrown agricultural land; (iii) cultivated pastures and disturbed ground; and (iv) natural/unfertilized and outfield pastures. Results Soil moisture and grazing measures were found to be important in explaining species compositional variation in all grassland types. Richness patterns were best explained by complex and differing combinations of environmental indicators. Nevertheless, negative (nitrogen and light level) or unimodal (pH) responses were similar across grassland types. Vegetation plots adjacent to areas historically and/or currently dominated by mires, forests, or pastures, as well as abandoned and overgrown grasslands, had a slightly higher species richness. Larger grasslands surrounding the vegetation plots had slightly less species than smaller grasslands. Conclusions This study demonstrates that data from a national monitoring programme on agricultural grasslands can be used for plant ecological research. The results indicate that climate-change-related shifts along moisture and nutrient gradients (increases) may alter both species composition and species richness in the studied grasslands. It is likely that large and contiguous managed (grass)land might affect areas perceived as remnants, probably caused by the transformation to homogeneous (agri)cultural landscapes reducing edge zones, which in turn may threaten the species pool and richness. The importance of land use and land-cover composition should be considered when planning management actions in extensively used high-latitude grasslands.
Abstract
Heat Field Deformation (HFD) is a widely used method to measure sap flow of trees based on empirical relationships between heat transfer within tree stems and the sap flow rates. As an alternative, the Linear Heat Balance (LHB) method implements the same instrumental configuration as HFD but calculates the sap flow rates using analytical equations that are derived from fundamental conduction-convection heat transfer theories. In this study, we systematically compared the sap flow calculated using the two methods based on data that were recorded using the same instrument. The measurements were conducted on four Norway spruce trees. We aimed to evaluate the discrepancies between the sap flow estimates from the two methods and determine the underlying causes. Diurnal and day-to-day patterns were consistent between the sap flow estimates from the two methods. However, the magnitudes of the estimated sap flow were different between them, where LHB resulted in much lower estimates in three trees and slightly higher estimates in one compared to HFD. We also observed larger discrepancies in negative (reversed flow) than in positive sap flow, where the LHB resulted in lower reversed flow than HFD. Consequently, the seasonal budget estimated by LHB can be as low as ∼20% of that estimated by HFD. The discrepancies can be mainly attributed to the low wood thermal conductivities for the studied trees that lead to substantial underestimations using the LHB method. In addition, the sap flow estimates were very sensitive to the value changes of the empirical parameters in the calculations and, thus, using a proper case-specific value is recommended, especially for the LHB method. Overall, we suggest that, despite the strong theoretical support, the correctness of LHB outputs depends largely on the tree individuals and should be carefully evaluated.
Abstract
As a way to estimate evapotranspiration (ET), Heat Field Deformation (HFD) is a widely used method to measure sap flow of trees based on empirical relationships between heat transfer within tree stems and the sap flow rates. As an alternative, the Linear Heat Balance (LHB) method implements the same instrumental configuration as HFD but calculates the sap flow rates using analytical equations that are derived from fundamental conduction-convection heat transfer equations.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Sunil Mundra Håvard Kauserud Tonje Økland Jørn-Frode Nordbakken Yngvild Eidissen Ransedokken O. Janne KjønaasAbstract
The replacement of native birch with Norway spruce has been initiated in Norway to increase long-term carbon storage in forests. However, there is limited knowledge on the impacts that aboveground changes will have on the belowground microbiota. We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC). Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species-mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs. The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass.
Abstract
No abstract has been registered
Authors
Nina Elisabeth Nagy Hans Ragnar Norli Monica Fongen Runa Berg Østby Inger Heldal Jahn Davik Ari HietalaAbstract
Tree defense against xylem pathogens involves both constitutive and induced phenylpropanoids and terpenoids. The induced defenses include compartmentalization of compromised wood with a reaction zone (RZ) characterized by polyphenol deposition, whereas the role of terpenoids has remained poorly understood. To further elucidate the tree–pathogen interaction, we profiled spatial patterns in lignan (low-molecular-weight polyphenols) and terpenoid content in Norway spruce (Picea abies) trees showing heartwood colonization by the pathogenic white-rot fungus Heterobasidion parviporum. There was pronounced variation in the amount and composition of lignans between different xylem tissue zones of diseased and healthy trees. Intact RZ at basal stem regions, where colonization is the oldest, showed the highest level and diversity of these compounds. The antioxidant properties of lignans obviously hinder oxidative degradation of wood: RZ with lignans removed by extraction showed significantly higher mass loss than unextracted RZ when subjected to Fenton degradation. The reduced diversity and amount of lignans in pathogen-compromised RZ and decaying heartwood in comparison to intact RZ and healthy heartwood suggest that α-conindendrin isomer is an intermediate metabolite in lignan decomposition by H. parviporum. Diterpenes and diterpene alcohols constituted above 90% of the terpenes detected in sapwood of healthy and diseased trees. A significant finding was that traumatic resin canals, predominated by monoterpenes, were commonly associated with RZ. The findings clarify the roles and fate of lignan during wood decay and raise questions about the potential roles of terpenoids in signal transduction, synthesis, and translocation of defense compounds upon wood compartmentalization against decay fungi.