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.
2007
Abstract
River floods may cause considerable damage. Water management strategies intend tomoderate or mitigate the severe effects of extreme discharge events. In this context,techniques for the detection and attribution of changes is of crucial importance. Extremeflood events seem to occur more frequently in recent decades in central Europe.It is anticipated that climate change and weather regime shifts may contribute to this...
Authors
Miguel D. Mahecha Markus Reichstein Holger Lange Nuño Carvalhais T. Grünwald Dario Papale G. SeufertAbstract
Characterizing ecosystem-atmosphere interactions in terms of carbon and water exchange on different time scales is considered a major challenge in terrestrial biogeochemical cycle research. The respective time series currently comprise an observation period of up to one decade. In this study, we explored whether the observation period is already sufficient to detect cross-relationships between the variables beyond the annual cycle, as they are expected from comparable studies in climatology. We investigated the potential of Singular System Analysis (SSA) to extract arbitrary kinds of oscillatory patterns. The method is completely data adaptive and performs an effective signal to noise separation. We found that most observations (Net Ecosystem Exchange, NEE, Gross Primary Productivity, GPP, Ecosystem Respiration, Reco, Vapor Pressure Deficit, VPD, Latent Heat, LE, Sensible Heat, H, Wind Speed, u, and Precipitation, P) were influenced significantly by low-frequency components (interannual variability). Furthermore, we extracted a set of nontrivial relationships and found clear seasonal hysteresis effects except for the interrelation of NEE with Global Radiation (Rg). SSA provides a new tool for the investigation of these phenomena explicitly on different time scales. Furthermore, we showed that SSA has great potential for eddy covariance data processing, since it can be applied as a novel gap filling approach relying on the temporal correlation structure of the time series structure only.
Abstract
No abstract has been registered
Abstract
Ecological studies are often confronted with short and fragmented or unevenly sampled time series. Examples are, e.g., time series of biogeochemical fluxes measured on a variety of scales. Characterizing the observed time series patterns, particularly the correlation structure is crucial for an integrated ecosystem assessment or possibly for improved processes understanding.
Abstract
In the context of an ongoing project on REMote sensing of FORest health (REM-FOR), we analyze airborne high-resolution hyperspectral images of a pine-dominated region in southeast Norway heavily attacked by the Pine sawfly Neodiprion sertifer, leading to severe defoliation. Leaf Area Index (LAI) is used as a proxy of the crown density, and comparing LAI maps from before and after the attack lead to indicators for damage extent. We discuss the application of the Forest Reflectance Model (FRT) of Kuusk and Nilson, which was designed for the application to (managed) Northern European Forests, to model the spectral response from the canopy. It is based on conventional forest inventory data, species-dependent parametrized crown shapes, canopy LAI, needle clumping index, and needle optical properties. Here, however, we run the model in an inverse mode, by iteratively minimizing the discrepancy between measured and simulated reflectances, and predicting the LAI, keeping known parameters of the model fixed. The LAI values are then compared to those obtained with either ground-based Licor LAI2000 measurements, or with airborne laser-scanning. Some preliminary results of this modelling concept for the case study are discussed.
Authors
Holger LangeAbstract
The net ecosystem productivity (NEP) of a sequence of threemonoaged Norway spruce stands located in southeast Norway is modelled using the biogeochemical model Biome-BGC. For calibration, we use estimated biomass stocks at the plot level and Leaf Area Index measurements. The model is run for 30 years of historical temperature measurements as well as for a regional climate scenario. It is shown that under current conditions, NEP develops from negative values for a young stand (30 years) to clearly positive for a middleaged (60 years) to slightly negative again for a very old and decaying stand (120 years). However, the old stand benefits substantially from the predicted increased temperatures in the climate scenario, rendering NEP positive again. For the 30 and 60 years stands, almost no change is predicted from Biome-BGC.
Abstract
No abstract has been registered
Abstract
Since the formation of the International Herbage Seed Group (IHSG, formerly IHSPRG) in 1978, International Herbage Seed Conferences have been organized, mostly at four year intervals. The Sixth Conference was held at Gjennestad Horticultural College in Vestfold, Norway, from 18 to 20 June 2007. As for other IHSG activities, the objective of the conference was ‘to encourage cooperation and communication between workers actively engaged in herbage seed production research’. About 80 delegates from 20 countries attended the conference. Four invited and almost sixty voluntary papers were presented, either orally or as posters. The topics were split into the following sessions: 1. Opening session with overview over herbage seed production and seed trade, world wide. 2. Herbage seed for the future: Biodiversity, GMOs and the role of seed yield capacity in herbage breeding programs. 3. Seed production of tropical species and species for stressful environments. 4. Physiological restraints to seed set and seed filling. 5. Establishing the potential for high and pure seed yields. 6. Fertility, plant growth regulators, and plant protection. 7. Statistical methods, seed harvest, and post-harvest issues.
Authors
P Benoit J Perceval Marianne Stenrød C Moni Ole Martin Eklo E Barriuso Tore E. Sveistrup Jens KværnerAbstract
No abstract has been registered
Abstract
The control of Alopecurus geniculatus, Poa annua and Poa trivialis using iodosulfuron (Hussar/Hussar OD) was investigated in field experiments in the seed harvest year in timothy (Phleum pratense), and in the sowing year and seed harvest year in smooth meadow-grass (Poa pratensis) and red fescue (Festuca rubra). Iodosulfuron (10 g a.i. ha-1) usually had good effect on Poa trivialis and Alopecurus geniculatus. As for Poa annua the effect on seed contamination was better than on weed coverage in the field. Early application improved weed control in the seed harvest years, and iodosulfuron was shown to perform well at low temperatures. The herbicide often delayed timothy development, but caused seed yield reduction only in two out of eight experiments, both with moist soil at treatment. The visual damage increased with increasing rates and use of additives (alcoholetoxylate or rape oil). A questionnaire investigation among timothy growers in 2004 showed that farmers using Hussar had 43% lower contamination of P. trivialis in cleaned seed yield and 20% lower yield than the farmers not using Hussar. In some trials in timothy and smooth meadow-grass, the new formulation Hussar OD gave slightly more damage than the old formulation Hussar. While well-established timothy crops seem to tolerate some visual damage without seed yield reduction, the risk of yield reduction in first year crops can usually be avoided by splitting the application into 5 g a.i. ha-1 at 14 days intervals. In smooth meadow-grass and red fescue established without cover crop, repeated applications of 5 g a.i. ha-1 in the sowing year resulted in better control of P. annua and significant seed yield improvements compared to application only in the seed harvest year. Both Hussar and Hussar OD have off-label approvals for members of the Norwegian Seed Growers Association.