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51.
Jeroen Staelens Tobias Rütting Dries Huygens An De Schrijver Christoph Müller Kris Verheyen Pascal Boeckx 《Biogeochemistry》2012,108(1-3):259-277
Despite long-term enhanced nitrogen (N) inputs, forests can retain considerable amounts of N. While rates of N inputs via throughfall and N leaching are increased in coniferous stands relative to deciduous stands at comparable sites, N leaching below coniferous stands is disproportionally enhanced relative to the N input. A better understanding of factors affecting N retention is needed to assess the impact of changing N deposition on N cycling and N loss of forests. Therefore, gross N transformation pathways were quantified in undisturbed well-drained sandy soils of adjacent equal-aged deciduous (pedunculate oak (Quercus robur L.)) and coniferous (Scots pine (Pinus sylvestris L.)) planted forest stands located in a region with high N deposition (north Belgium). In situ inorganic 15N labelling of the mineral topsoil (0–10?cm) combined with numerical data analysis demonstrated that (i) all gross N transformations differed significantly (p?<?0.05) between the two forest soils, (ii) gross N mineralization in the pine soil was less than half the rate in the oak soil, (iii) meaningful N immobilization was only observed for ammonium, (iv) nitrate production via oxidation of organic N occurred three times faster in the pine soil while ammonium oxidation was similar in both soils, and (v) dissimilatory nitrate reduction to ammonium was detected in both soils but was higher in the oak soil. We conclude that the higher gross nitrification (including oxidation of organic N) in the pine soil compared to the oak soil, combined with negligible nitrate immobilization, is in line with the observed higher nitrate leaching under the pine forest. 相似文献
52.
53.
Sofie Sjögersten Dries P. J. Kuijper René van der Wal Maarten J. J. E. Loonen Ad H. L. Huiskes Sarah J. Woodin 《Polar Biology》2010,33(9):1195-1203
Herbivores may increase the productivity of forage plants; however, this depends on the return of nutrients from faeces to
the forage plants. The aim of this study was to test if nitrogen (N) from faeces is available to forage plants and whether
the return of nutrients differs between plant species using 15N natural abundance in faeces and plant tissue. To investigate the effect of grazing on N transfer, we carried out a grazing
experiment in wet and mesic tundra on high Arctic Spitsbergen using barnacle geese (Branta leucopsis) as the model herbivore. N inputs (from faeces) increased with grazing pressure at both the wet and mesic sites, with the
greatest N input from faeces at the wet site. The δ15N ratio in plant tissue from grazed plots was enriched in mosses and the dwarf shrub species, reflecting the δ15N signature of faeces-derived N, but no such pattern was observed in the dominant grasses. This study demonstrates that the
δ15N signature of faeces and forage species is a useful tool to explore how grazing impacts on N acquisition. Our findings suggest
that plant species which acquire their N close to the soil surface (e.g. mosses) access more of the N from faeces than species
with deeper root systems (e.g. grasses) suggesting a transfer of N from the preferred forage species to the mosses and dwarf
shrubs, which are less preferred by the geese. In conclusion, the moss layer appears to disrupt the nitrogen return from herbivores
to their forage species. 相似文献
54.
Inna Kuperstein Kerensa Broersen Iryna Benilova Jef Rozenski Wim Jonckheere Maja Debulpaep Annelies Vandersteen Ine Segers-Nolten Kees Van Der Werf Vinod Subramaniam Dries Braeken Geert Callewaert Carmen Bartic Rudi D'Hooge Ivo Cristiano Martins Frederic Rousseau Joost Schymkowitz Bart De Strooper 《The EMBO journal》2010,29(19):3408-3420
The amyloid peptides Aβ40 and Aβ42 of Alzheimer's disease are thought to contribute differentially to the disease process. Although Aβ42 seems more pathogenic than Aβ40, the reason for this is not well understood. We show here that small alterations in the Aβ42:Aβ40 ratio dramatically affect the biophysical and biological properties of the Aβ mixtures reflected in their aggregation kinetics, the morphology of the resulting amyloid fibrils and synaptic function tested in vitro and in vivo. A minor increase in the Aβ42:Aβ40 ratio stabilizes toxic oligomeric species with intermediate conformations. The initial toxic impact of these Aβ species is synaptic in nature, but this can spread into the cells leading to neuronal cell death. The fact that the relative ratio of Aβ peptides is more crucial than the absolute amounts of peptides for the induction of neurotoxic conformations has important implications for anti‐amyloid therapy. Our work also suggests the dynamic nature of the equilibrium between toxic and non‐toxic intermediates. 相似文献
55.
Julien Pétillon Kevin Lambeets William Montaigne Jean-Pierre Maelfait Dries Bonte 《Biological invasions》2010,12(9):3219-3226
Vegetation and underground structures are known to influence flood avoidance and flood resistance in invertebrates. In bimonthly-flooded
European salt marshes, recent invasions by the nitrophilous grass Elymus athericus strongly modified usual habitat structure, notably by the production of a deep litter layer. Consequently, invaded habitats
provide more interstitial spaces that may act as a refuge during flood events. By using both controlled and field designs,
we tested whether invaded habitats may change the ability to resist flooding by the creation of new refuges during tides for
a ground-living, predatory arthropod. The wolf spider Arctosa fulvolineata was employed as a model species since it occurs abundantly in both invaded and uninvaded salt-marsh habitats. In the field,
its abundance strongly decreased (divided by three) after tidal flooding in uninvaded habitats by but did not change in invaded
patches. Under controlled laboratory conditions, ten times more individuals withstood simulated flooding in the presence of
litter and less decided to float. The presence of litter did not influence flood resistance, i.e. survival underwater. Our
results show that habitat structure (i.e. the presence of litter) influences flood-avoiding behavior of A. fulvolineata, by providing more refuges. As the invasion of E. athericus alters salt-marsh habitat structure, it may enhance population size of a rare predatory spider by changing its behavior during
flooding and resulting in less deleterious impacts of tides. Yet biological invasions are detrimental for biodiversity conservation,
our study shows that an invasive species might indirectly benefit a few mobile rare species in a flood-disturbed habitat. 相似文献
56.
Habitat Use and Mobility of Two Threatened Coastal Dune Insects: Implications for Conservation 总被引:2,自引:0,他引:2
Dirk Maes Anneleen Ghesquiere Mieke Logie Dries Bonte 《Journal of Insect Conservation》2006,10(2):105-115
We studied the habitat use and mobility of the Grayling butterfly (Hipparchia semele) and the Blue-Winged Grasshopper (Oedipoda caerulescens), two threatened insects within spatially structured blond and grey dunes in a nature reserve along the Belgian coast. Although
both species occur in the same biotope, H. semele were more abundant in open, dynamic sites with a relatively high amount of bare sand, while O. caerulescens preferred sheltered, more stable environments with a lower amount of bare sand. Unlike H. semele, substrate use varied in accordance to body colouration in O. caerulescens, especially on cold days, with light-coloured animals being more abundant on sand and dark-coloured animals more abundant
on moss. During a mark-recapture-study, we marked 493 Grayling butterflies and 1289 Blue-Winged Grasshoppers. On average,
both sexes of H. semele were equally mobile (about 150 m/day; maximum recorded distance of about 1700 m) while male O. caerulescens were significantly more mobile than females (daily average 47 vs. 5 m; maximum distances observed for O. caerulescens were about 800 m). The importance of habitat heterogeneity (within and among patches) and the consequences of habitat use
and mobility of both species for the conservation of typical coastal dune habitats are discussed. The complementary use of
species-specific information to site-based management measures is advocated. 相似文献
57.
Population studies often focus on demographic and genetic consequences of dispersal strategies, generally within an evolutionary framework. Adaptive investment in dispersal is generally assessed from single types of (pre-)dispersal behaviour that are presumed to reliably reflect the dispersal strategy adopted. Various spider families show a striking and quantifiable display, known as tiptoe behaviour that prepares individuals for take-off prior to (passive) aerial dispersal (ballooning). The lack of efficient control mechanisms during ballooning prevents individuals from actively selecting a suitable habitat for landing. Ballooning dispersal is therefore often regarded as a wind lottery preceded by individual-based risk assessment. Our laboratory experiments showed that the duration of tiptoe behaviour can be used as an indicator of silk thread length, which is related to the potential dispersal distance. For two related species, Erigone arctica and E. dentiplapis, tiptoe duration decreased independently of sex after starvation, while more complex reaction norms were observed for tiptoe frequency.
Because these two aspects of dispersal behaviours show different responses towards a simple stress-factor (starvation) in two related spider species, we conclude that the level of plasticity in dispersal investment can be subject to selective forces affecting different dispersal properties in different ways. Our results, hence, plead for a more holistic approach when addressing evolutionary and applied questions related to dispersal. 相似文献
58.
Negin Karimian Alix P.M. Matton Andrie C. Westerkamp Laura C. Burlage Sanna op den Dries Henri G.D. Leuvenink Ton Lisman Korkut Uygun James F. Markmann Robert J. Porte 《Journal of visualized experiments : JoVE》2015,(99)
In contrast to conventional static cold preservation (0-4 °C), ex situ machine perfusion may provide better preservation of donor livers. Continuous perfusion of organs provides the opportunity to improve organ quality and allows ex situ viability assessment of donor livers prior to transplantation. This video article provides a step by step protocol for ex situ normothermic machine perfusion (37 °C) of human donor livers using a device that provides a pressure and temperature controlled pulsatile perfusion of the hepatic artery and continuous perfusion of the portal vein. The perfusion fluid is oxygenated by two hollow fiber membrane oxygenators and the temperature can be regulated between 10 °C and 37 °C. During perfusion, the metabolic activity of the liver as well as the degree of injury can be assessed by biochemical analysis of samples taken from the perfusion fluid. Machine perfusion is a very promising tool to increase the number of livers that are suitable for transplantation. 相似文献
59.
Dries P. J. Kuijper Mart Verwijmeren Marcin Churski Adam Zbyryt Krzysztof Schmidt Bogumi?a J?drzejewska Chris Smit 《PloS one》2014,9(1)
Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in the Białowieża Primeval Forest (Poland), whether perceived predation risk in red deer (Cervus elaphus) and wild boar (Sus scrofa) is related to habitat visibility or olfactory cues of a predator. We used camera traps in two different set-ups to record undisturbed ungulate behavior and fresh wolf (Canis lupus) scats as olfactory cue. Habitat visibility at fixed locations in deciduous old growth forest affected neither vigilance levels nor visitation rate and cumulative visitation time of both ungulate species. However, red deer showed a more than two-fold increase of vigilance level from 22% of the time present on control plots to 46% on experimental plots containing one wolf scat. Higher vigilance came at the expense of time spent foraging, which decreased from 32% to 12% while exposed to the wolf scat. These behavioral changes were most pronounced during the first week of the experiment but continuous monitoring of the plots suggested that they might last for several weeks. Wild boar did not show behavioral responses indicating higher perceived predation risk. Visitation rate and cumulative visitation time were not affected by the presence of a wolf scat in both ungulate species. The current study showed that perceived predation risk in red deer and wild boar is not related to habitat visibility in a dense forest ecosystem. However, olfactory cues of wolves affected foraging behavior of their preferred prey species red deer. We showed that odor of wolves in an ecologically equivalent dose is sufficient to create fine-scale risk factors for red deer. 相似文献
60.
Marta Hlad Barbara Veselka Dawnie Wolfe Steadman Baptiste Herregods Marc Elskens Rica Annaert Mathieu Boudin Giacomo Capuzzo Sarah Dalle Guy De Mulder Charlotte Sabaux Kevin Salesse Amanda Sengeløv Elisavet Stamataki Martine Vercauteren Eugène Warmenbol Dries Tys Christophe Snoeck 《American journal of physical anthropology》2021,175(4):777-793