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.
2017
Sammendrag
No abstract has been registered
Sammendrag
Small-area estimation is a subject area of growing importance in forest inventories. Modelling the link between a study variable Y and auxiliary variables X— in pursuit of an improved accuracy in estimators—is typically done at the level of a sampling unit. However, for various reasons, it may only be possible to formulate a linking model at the level of an area of interest (AOI). Area-level models and their potential have rarely been explored in forestry. This study demonstrates, with data (Y = stem volume per ha) from four actual inventories aided by aerial laser scanner data (3 cases) or photogrammetric point clouds (1 case), application of three distinct models representing the currency of area-level modelling. The studied AOIs varied in size from forest management units to forest districts, and municipalities. The variance explained by X declined sharply with the average size of an AOI. In comparison with a direct estimate mean of Y in an AOI, all three models achieved practically important reduction in the relative root-mean-squared error of an AOI mean. In terms of the reduction in mean-squared errors, a model with a spatial location effect was overall most attractive. We recommend the pursuit of a spatial model component in area-level modelling as promising within the context of a forest inventory.
Forfattere
Jihong Liu Clarke Lisa Paruch Mihaela-Olivia Dobrica Iuliana Caras Catalin Tucureanu Adrian Onu Sonya Ciulean Crina Stavaru Andre van Eerde Hege Særvold Steen Sissel Haugslien Catalina Petrareanu Catalin Lazar Ioan Popescu Ralph Bock Jean Dubuisson Norica Branza-NichitaSammendrag
No abstract has been registered
Forfattere
Jihong Liu Clarke Andre van Eerde Lisa Paruch Inger Heldal Hege Særvold Steen Yanliang Wang Astrid Sivertsen Sissel HaugslienSammendrag
No abstract has been registered
Sammendrag
Forest stands are important units of management. A stand-by-stand estimation of the mean and variance of an attribute of interest (Y) remains a priority in forest enterprise inventories. The advent of powerful and cost effective remotely sensed auxiliary variables (X) correlated with Y means that a census of X in the forest enterprise is increasingly available. In combination with a probability sample of Y, the census affords a modeldependent stand-level inference. It is important, however, that the sampling design affords an estimation of possible stand-effects in the model linking X to Y.We demonstrate, with simulated data, that failing to quantify non-zero stand-effects in the intercept of a linear population-level model can lead to a serious underestimation of the uncertainty in a model-dependent estimate of a stand mean, and by extension a confidence interval with poor coverage.We also provide an approximation to the variance of stand-effects in an intercept for the case when a sampling design does not afford estimation. Furthermore, we propose a method to correct a potential negative bias in an estimate of the variance of stand-effects when a sampling design prescribes few stands with small within-stand sample sizes.
Forfattere
Svetlana Saarela Johannes Breidenbach Pasi Raumonen Anton Grafström Göran Ståhl Mark J. Ducey Rasmus AstrupSammendrag
This study presents an approach for predicting stand-level forest attributes utilizing mobile laser scanning data collected as a nonprobability sample. Firstly, recordings of stem density were made at point locations every 10th metre along a subjectively chosen mobile laser scanning track in a forest stand. Secondly, kriging was applied to predict stem density values for the centre point of all grid cells ina5m×5m lattice across the stand. Thirdly, due to nondetectability issues, a correction term was computed based on distance sampling theory. Lastly, the mean stem density at stand level was predicted as the mean of the point-level predictions multiplied with the correction factor, and the corresponding variance was estimated. Many factors contribute to the uncertainty of the stand-level prediction; in the variance estimator, we accounted for the uncertainties due to kriging prediction and due to estimating a detectability model from the laser scanning data. The results from our new approach were found to correspond fairly well to estimates obtained using field measurements from an independent set of 54 circular sample plots. The predicted number of stems in the stand based on the proposed methodology was 1366 with a 12.9% relative standard error. The corresponding estimate based on the field plots was 1677 with a 7.5% relative standard error.
Forfattere
Anna Sandak Jakub Sandak Athanasios Dimitriou Ingunn Burud Thomas Kringlebotn Thiis Lone Ross Graham Alan Ormondroyd Dimitrios KraniotisSammendrag
No abstract has been registered
Forfattere
Laur Manea Roger Manea Ole Martin EkloSammendrag
Enzymes are major components of organism defense against toxic chemicals in their environment. Despite the passage of more than 200 million years of life presence these enzymes now play an important role in detoxifying chemicals man-made addiction and it may be a useful biomarker. Lactate dehydrogenase (LDH or LD) is intracellular enzyme year found early in all living cells (animals, plants, and prokaryotes). LDH catalyzes the conversion of pyruvic acid to lactic acid and back, as it converts NAD + to NADH and back. A dehydrogenase enzyme transfers a hydride from one molecule to another. LDH enzyme exists in four distinct classes: first is NAD (P) -dependent L-lactate dehydrogenase; other LDHs act on D-lactic and / or is dependent on cytochome C: Dlactate dehydrogenase (cytochome) and L-lactate (L-lactate dehydrogenase (cytochome). LDH is expressed extensively in body tissues, such as blood cells and heart muscle. Lactate dehydrogenase (LDH) is widely distributed throughout the body, as seen mainly in the kidney, myocardium, skeletal muscle, brain, liver and lungs. Because it is released during tissue damage, it is a marker of common injuries such as heart failure and disease.
Sammendrag
Schistidium relictum is described as a new northwest North American and Siberian species of moss. Important distinguishing characters include dull, nearly black plants, with stems densely and evenly foliated, weakly spreading leaves that usually lack awns, and the mostly 1-stratose distal leaf laminae with 2(–3) -stratose margins. The species has a remarkable disjunct distribution pattern with most of the sites where it has been found having been unglaciated during the Pleistocene glaciations. It is restricted to areas with occurrence of calcareous bedrock, especially limestones. It appears to be rather isolated genetically based on molecular studies of total ITS. It is sister to the large clade, ‘Apocarpum’, which consists of species which probably embody its closest known extant relatives.
Forfattere
Alexandre Foito Christine Anne Hackett Derek Stewart Janaki Velmurugan Dan Milbourne Stephen L. Byrne Susanne BarthSammendrag
No abstract has been registered