Search results for "ABUNDANCE"
showing 10 items of 529 documents
Optimal timing of power line rights-of-ways management for the conservation of butterflies
2012
Habitat loss, fragmentation, and degradation are the main threats to biodiversity. Human activities also create new habitat types that might fulfil ecological requirements for a variety of species. This study investigates whether the vegetation clearing (=shrub and tree cutting) on drained mire patches on power line rights-of-ways (ROWs) keep plant communities in an early successional stage and thus provide habitats for mire specialist and non-mire butterflies. It was further studied what would be the optimal clearing interval in terms of butterfly species richness and abundance. The results show that tree height, especially the height of birch, increases linearly over the 7-year period fol…
The Coexistence of Three Species of Daphnia in the Klostersee: iii. The Simulation Model Coda
1991
The population dynamics of three coexisting Daphnia species are described by means of a discrete event simulation model. The model is formulated in the algorithmic language SIMULA which allows very convenient object-oriented programming. Different compartments of a lake are simulated at different levels of integration, each represented by a PROCESS CLASS in SIMULA: The properties of the lake are deposited in a set of meteorological data which were measured in the field. Fish are simulated as a population with properties which are derived from field observations and Daphnia are represented as individuals. The model shows that hypotheses about the stabilizing mechanisms (seasonal change of en…
The relationship between stocking eggs in boreal spawning rivers and the abundance of brown trout parr
2015
Abstract Stocking with eggs has been widely used as a management measure to support degraded salmonid stocks. In Finland, Atlantic salmon and both sea-migrating and lake-migrating brown trout are stocked as eggs, alevins, fry, parr, and smolt, whereas trout are also stocked as mature fish. The aim of this stocking is to improve catches and to support collapsed spawning stocks. We assessed the success of stocking with brown trout eggs in a study of 17 Finnish boreal forest rivers, of which 9 were subject to egg stocking. All rivers contained some naturally spawning trout. In 16 rivers, including non-stocking years and unstocked rivers, egg stocking did not increase the total (wild and stocke…
Burrowing behaviour affects Paraergasilus rylovi abundance in Anodonta piscinalis.
2006
Burrowing depth may affect predation rate, feeding ability and reproduction in bivalve clams. We studied the effect of burrowing depth on the abundance of the ergasilid Paraergasilus rylovi in the freshwater bivalve clam Anodonta piscinalis. We transplanted uninfected clams to a lake where they were allowed to choose their preferred burrowing depth, and were exposed naturally to copepodids of the parasite. There was a significant positive correlation between proportionate burrowing depth (PBD) and the abundance of P. rylovi at the end of the 17-day experiment, the deeper-burrowed clams harbouring more P. rylovi. Original PBD (0%, 50%, 100%) did not influence the final PBD or parasite abunda…
Distribution patterns of epiphytic reed-associated macroinvertebrate communities across European shallow lakes
2021
So far, research on plant-associated macroinvertebrates, even if conducted on a large number of water bodies, has mostly focused on a relatively small area, permitting limited conclusions to be drawn regarding potentially broader geographic effects, including climate. Some recent studies have shown that the composition of epiphytic communities may differ considerably among climatic zones. To assess this phenomenon, we studied macroinvertebrates associated with the common reed Phragmites australis (Cav.) Trin. ex Steud in 46 shallow lakes using a common protocol. The lakes, located in nine countries, covered almost the entire European latitudinal range (from <48°N to 61°N) and captured much …
Comparing the effects of introduced signal crayfish and native noble crayfish on the littoral invertebrate assemblages of boreal lakes
2015
The introduced North American signal crayfish Pacifastacus leniusculus (Dana) has replaced the native noble crayfish (Astacus astacus) in many European freshwaters and can be considered a new component of these ecosystems. The 2 species are apparently similar in many respects, but their ecological equivalence is uncertain and has been little investigated, especially at the whole-lake scale. We compared the effects of the 2 species on the abundance, species richness, and composition of littoral macroinvertebrate assemblages in a set of small- and mediumsized boreal lakes, which included 8 lakes with noble crayfish, 8 lakes with signal crayfish, and 8 lakes without crayfish. We collected semi…
H-2, H-3(+) and the age of molecular clouds and prestellar cores
2012
Measuring the age of molecular clouds and prestellar cores is a difficult task that has not yet been successfully accomplished although the information is of paramount importance to help in understanding and discriminating between different formation scenarios. Most chemical clocks suffer from unknown initial conditions and are therefore difficult to use. We propose a new approach based on a subset of deuterium chemistry that takes place in the gas phase and for which initial conditions are relatively well known. It relies primarily on the conversion of H 3 + into H 2D + to initiate deuterium enrichment of the molecular gas. This conversion is controlled by the ortho/para ratio of H2 that i…
Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance?
2011
Context: Dark cloud chemical models usually predict large amounts of O2, often above observational limits. Aims: We investigate the reason for this discrepancy from a theoretical point of view, inspired by the studies of Jenkins and Whittet on oxygen depletion. Methods: We use the gas-grain code Nautilus with an up-to-date gas-phase network to study the sensitivity of the molecular oxygen abundance to the oxygen elemental abundance. We use the rate coefficient for the reaction O + OH at 10 K recommended by the KIDA (KInetic Database for Astrochemistry) experts. Results: The updates of rate coefficients and branching ratios of the reactions of our gas-phase chemical network, especially N + C…
The Gaia-ESO survey: Metallicity of the chamaeleon i star-forming region
2014
Context. Recent metallicity determinations in young open clusters and star-forming regions suggest that the latter may be characterized by a slightly lower metallicity than the Sun and older clusters in the solar vicinity. However, these results are based on small statistics and inhomogeneous analyses. The Gaia-ESO Survey is observing and homogeneously analyzing large samples of stars in several young clusters and star-forming regions, hence allowing us to further investigate this issue. Aims. We present a new metallicity determination of the Chamaeleon I star-forming region, based on the products distributed in the first internal release of the Gaia-ESO Survey. Methods. 48 candidate member…
APOKASC-2 catalog of Kepler evolved stars
2019
We present a catalog of stellar properties for a large sample of 6676 evolved stars with Apache Point Observatory Galactic Evolution Experiment spectroscopic parameters and Kepler asteroseismic data analyzed using five independent techniques. Our data include evolutionary state, surface gravity, mean density, mass, radius, age, and the spectroscopic and asteroseismic measurements used to derive them. We employ a new empirical approach for combining asteroseismic measurements from different methods, calibrating the inferred stellar parameters, and estimating uncertainties. With high statistical significance, we find that asteroseismic parameters inferred from the different pipelines have sys…