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H. Skuja 《Plant Systematics and Evolution》1969,116(1-5):55-64
Zusammenfassung Ein neues, in verschiedener Hinsicht interessantesBatrachospermum aus dem engeren Verwandtschaftskreis vonB. vagum wird beschrieben und diskutiert. Es handelt sich dabei um eine Form von Stromschnellen des brasilianischen Rio Negro. Sie ist besonders durch die eigentümlich umgewandelte Berindung (der Zentralachse) bemerkenswert: Die Berindungsfäden umhüllen bei ihr nicht wie gewöhnlich die Internodialzellen, sondern wachsen in der Regel abaxial und bedecken die ganzen Sprosse von außen mit locker niederlaufenden, jedoch starken und elastischen Fasern. Biologisch erfüllen sie offensichtlich unter anderem die Funktion einer höchst wirksamen Schutzeinrichtung gegen mögliche mechanische Schädigungen vor allem der empfindlichen Assimilations-und Reproduktionssysteme im wirbelnden Wasser. Eine Tendenz zur Auflockerung der Berindung ist freilich schon bei dem gewöhnlichen, für lenitische, dystrophe Gewässer charakteristischemB. vagum festzustellen. Die neue Alge, die var.periplocum genannt wird, zeigt auch in den meisten anderen vegetativen Merkmalen wie in der weitgehenden Rückbildung der sexuellen Reproduktion ihre nahe Verwandtschaft mitB. vagum an. Als ein vermittelndes Glied in dieser Entwicklungsreihe konnte dabei noch eine weitere Form derselben Art aus Venezuela angeführt werden.Herrn Prof. Dr. L.Geitler zum 70. Geburtstag gewidmet. 相似文献
2.
Capsule: The nesting habitat of the Common Buzzard Buteo buteo and Lesser Spotted Eagle Clanga pomarina extensively overlap, indicating that they exploit similar resources.Aim: We aimed to determine the overlap in the nest platforms, nest trees and nest stands used by these raptors, find any evidence for the avoidance of the larger Lesser Spotted Eagle by the smaller Common Buzzard, and provide conservation implications for habitat protection of the former species in habitats that overlap extensively.Methods: Nest sites were mapped during 2012–2014 in the Bir?ai Forest Spatial Protection Area, northern Lithuania. Fifty-three nest sites occupied by Common Buzzards and 26 by Lesser Spotted Eagles were compared.Results: The nest platforms of both raptors were similarly placed in the tree canopies. Most Lesser Spotted Eagle nests were built in spruce, while the Common Buzzard usually nested in birch. The nest stands of the eagles were on wetter soil and located closer to the forest edge than those of the buzzards, otherwise, the nest stands did not differ significantly. There was no evidence for spatial avoidance of the larger raptor by the Common Buzzard.Conclusions: The different components of the nesting habitats extensively overlapped, and the distribution of the interspecific pairs lacked spatial avoidance. We suggest that the nest sites of both raptors were a largely shared resource, especially if located close to the forest edges. We propose, as a rule of thumb, applying protection by way of buffer zones around buzzard nest sites if they are located close to eagle nest sites and the forest edge. 相似文献
3.
Rimgaudas Treinys Deivis Dementavičius Gintautas Mozgeris Saulis Skuja Saulius Rumbutis Darius Stončius 《European Journal of Wildlife Research》2011,57(6):1165-1174
The processes of competition and predation determine the degree to which species can coexist; the importance of competition
in particular has been emphasized at high trophic levels. Competition exclusion will occur when habitat overlap between sympatric
species is high. In this study, we investigated nesting habitat overlap between internationally protected diurnal tree-nesting
avian predators of central Europe, namely, White-tailed Eagle (Haliaeetus albicilla), Lesser Spotted Eagle (Aquila pomarina), Black Stork (Ciconia nigra), and Osprey (Pandion haliaetus). We found significantly different nesting habitats among the study species and suggest that this could be a consequence
of the resource-based segregation, but not a consequence of asymmetrical interspecific competition. The results also show
that habitat of the recovering populations of White-tailed Eagle overlapped with the habitat used by the Lesser Spotted Eagle,
Black Stork, and Osprey to varying extents with a niche overlap values being below the competition exclusion threshold. Nevertheless,
we suggest that competition by White-tailed Eagle at a population level may limit Osprey, though not Lesser Spotted Eagle
or Black Stork. 相似文献
4.
H. Skuja 《Protoplasma》1959,50(3):493-497
Ohne Zusammenfassung 相似文献
5.
Rimgaudas Treinys Asko L?hmus Darius Stonius Saulis Skuja Eugenijus Drobelis Bronius ableviius Saulius Rumbutis Deivis Dementaviius Vladas Narueviius Antanas Petraka Danas Augutis 《Journal of Ornithology》2008,149(1):75-81
Recent trends in the European Black Stork Ciconia nigra population are geographically distinct: range expansion and adaptation to human activity dominate in western and central
Europe, while declines—probably induced by landscape change—are reported in the east. We studied the large Lithuanian Black
Stork population in the transition zone to explore whether, and how, the detrimental influences of recent Baltic landscape
changes are balanced by the West European tendency of behavioural adaptation to human activity. Based on monitoring in sample
plots, the current population was estimated at 650–950 pairs, indicating a significant decrease (possibly over 20%) during
the last two decades. In comparison to the Latvian and Estonian populations, however, this decline is smaller, and the reproductive
success remains at a high level [66% breeding success and 2.99 ± 0.97 (SD) fledglings per successful attempt, 2000–2006];
this north–south gradient suggests a climate-mediated impact of habitat degradation in the Baltic countries. The storks are
also nesting closer to forest edges and in younger stands than 15–30 years ago, which has probably reduced the nest-tree limitation,
as indicated by an increased use of large oaks. Thus, habitat degradation and adaptation seem to be taking place simultaneously
in the Lithuanian Black Stork population, as was expected from its geographical location. In general, our study supports the
view that, whenever possible, species conservation strategies and the use of indicator species should be geographically explicit. 相似文献
6.
Biological quality metrics: their variability and appropriate scale for assessing streams 总被引:4,自引:4,他引:0
The concept of spatial scale is at the research frontier in ecology, and although focus has been placed on trying to determine
the role of spatial scale in structuring communities, there still is a further need to standardize which organism groups are
to be used at which scale and under which circumstances in environmental assessment. This paper contributes to the understanding
of the variability at different spatial scales (reach, stream, river basin) of metrics characterizing communities of different
biological quality elements (macrophytes, fishes, macroinvertebrates and benthic diatoms) as defined by the Water Framework
Directive. For this purpose, high-quality reaches from medium-sized lowland streams of Latvia, Ecoregion 15 (Baltic) were
sampled using a nested hierarchical sampling design: (river basin → stream → reach). The variability of metrics within the
different groups of biological quality elements confirmed that large-bodied organisms (macrophytes and fish) were less variable
than small-bodied organisms (macroinvertebrates and benthic diatoms) at reach, stream and river basin scales. Single metrics
of biological quality elements had the largest variation at the reach scale compared with stream and basin scales. There were
no significant correlations between biodiversity indices of the different organism groups. The correlation between diversity
indices (Shannon’s and Simpson’s) of the biological quality elements (macrophytes, fish, benthic macroinvertebrates and benthic
diatoms) and a number of measured environmental variables varied among the different organism groups. Relationships between
diversity indices and environmental factors were established for all groups of biological quality elements. Our results showed
that metrics of macrophytes and fish could be used for assessing ecological quality at the river basin scale, whereas metrics
of macroinvertebrates and benthic diatoms were most appropriate at a smaller scale. 相似文献
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