Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2012
Forfattere
Liv Guri Velle Vigdis Vandvik Liv S. NilsenSammendrag
Our study demonstrates that old stands do develop characteristic heathland vegetation and structure after fire, and while potential invasives into the system such as trees and rhizomatous species are present, they do not impair Calluna regeneration or vegetation development towards the target heathland community composition and structure. Further, as our young stands are only in their second fire rotation after restoration, we suggest that characteristic dynamics of managed heathlands can re-establish relatively rapidly, even in severely degenerated sites (50 years since last fire). Site-specific factors also need to be considered. We conclude that there is restoration potential in old heaths, despite slow dynamics in the first rotation.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Simon WeldonSammendrag
Det er ikke registrert sammendrag
Forfattere
Hrefna Sigurjonsdottir Anna Thorhallsdottir Helga M. Hafthorsdottir Sandra M. GranquistSammendrag
A permanent herd of Icelandic horses with four stallions and their harems was studied for a total of 316 hours in a large pasture (215 ha) in May 2007 in Iceland. Interactions between stallions of different harems and other aspects of the horses' behaviour were studied. One stallion and nine horses were introduced into the pasture prior to the study to examine the reactions of the resident stallions to a newcomer. The stallions spent significantly less time grazing than other horses and were more vigilant. Home ranges overlapped, but harems never mixed. The stallions prevented interactions between members of different harems indirectly by herding. Generally, interactions between resident stallions were nonviolent. However, encounters with the introduced stallion were more aggressive and more frequent than between the other stallions. Here, we show that four harems can share the same enclosure peacefully. The social network seems to keep aggression at a low level both within the harems and the herd as a whole. We encourage horse owners to consider the feasibility of keeping their horses in large groups because of low aggression and because such a strategy gives the young horses good opportunities to develop normally, both physically and socially.
Forfattere
Ingeborg KlingenSammendrag
Det er ikke registrert sammendrag
Forfattere
Richard MeadowSammendrag
Det er ikke registrert sammendrag
Sammendrag
Our aim is to investigate the temporal dynamics of the Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) on a global scale and its relation to the main meteorological variables across space. We focus on complex patterns in time, which are neither regular (trend and seasonality) nor random (noise), but somewhere in between. We quantify complexity and information content or entropy using methods from order statistics and complexity sciences.Time series with high entropy are difficult to predict, whereas time series with high complexity are difficult to describe. This leads to a spatially explicit characterization of complex patterns in a very sensitive way. We use FAPAR observations (SeaWiFS and MERIS, 1998 to 2012) along with gridded global surface air temperature, precipitation and shortwave radiation.All these time series are explored on a pixelbypixel basis and clustered according to a very recent classification system of the land surface. In addition, we quantify the time reversal asymmetry of these data. We compare environmental time series with data from a stochastic candidate process temporally symmetric and long range correlated artificial knoise.Results were plotted in the ComplexityversusEntropy plane (CH plane), showing the particular footprint of each variable in a very sensitive way. Visualized in world maps, results revealed unexpected complex pattern in some dry regions, in particular on pixels surrounding deserts and in eastern Sahara. In this respect, the results provide a new classification of the climate and the biosphere. http://dames.pik-potsdam.de/Abstracts.pdf
Sammendrag
We exploit two recently developed informationtheoretic quantities (or measures) designed to quantify information content and complexity of ordered data (time series), respectively. Both are based on order statistics of given data sets, and probe into the shortterm structure of the data only due to finite length restrictions. Their usage requires fixing one parameter, word length or order depth D. The information measure is the orderbased Shannon entropy HS, and the complexity measures is the JensenShannon divergence CJS. The latter requires a chosen reference distribution, i.e. CJS represents a class of measures. Entropy HS and complexity CJS of data series may be represented against each other in a twodimensional diagram which we will refer to as ComplexityEntropy Causality Plane, or CECP. Very long realizations of classic stochastic processes and chaotic deterministic maps each obey one location in the CECP, specific for the process. This can be used to differentiate chaos from correlated noise (Rosso et al. 2007), which is notoriously difficult otherwise. For observed data, a mixture of deterministic (signal) and stochastic (noise) parts is to be expected. We use an ensemble of longterm river runoff time series as example, which are known to exhibit powerlaw decaying longrange correlations. We compare these data with a longrange correlated candidate process, the k noise, from the perspective of order statistics and the CECP. Although these processes resemble runoff series in their correlation behavior and may be even tuned to any runoff series by changing the value of k, the CECP locations and in particular the order pattern statistics reveals qualitative differences between them. We give a detailed account of these differences, and use them to conclude on the deterministic nature of the (shortterm) dynamics of the runoff time series. The proposed methodology also represents a stringent test bed for hydrological or other environmental models. http://dames.pik-potsdam.de/Abstracts.pdf
Forfattere
Dag-Ragnar BlystadSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag