The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Peter Zwick - One of the best experts on this subject based on the ideXlab platform.
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Emergence, maturation and upstream oviposition flights of Plecoptera from the Breitenbach, with notes on the adult phase as a possible control of stream insect populations
Hydrobiologia, 1990Co-Authors: Peter ZwickAbstract:Upstream oviposition flights of several Plecoptera species of the genera Leuctra, Nemoura, Isoperla and Siphonoperla along the Breitenbach, Hesse, Germany are inferred from 1. oviposition occuring upstream from Emergence areas; 2. size differences and size-shifts between emerging and egg-laying females; 3. concentration of oviposition in upstream sections of the Emergence area. The last point relies on direct catches of egg-laying females with sticky Traps, and on over-representation of old, mature females in upstream Emergence Traps towards the end of, or even after actual Emergence periods. Criteria for age class discrimination of the respective taxa are described. The validity of the present and of other indirect evidence for directed adult flights and the significance of adult upstream displacement are discussed. Optical orientation cues are suggested. Females of Leuctra prima and Siphonoperla torrentium are shown to gain 25–50% dry weight by feeding in the terrestrial environment; general information indicates many other Plecoptera may be similar in this respect. Terrestrial adult life is shown to last for 3–8 weeks. This long time, evidence of important flight activity and feeding together suggest that the terrestrial phase is spent as an active adult, the inevitable risks of which may form an important control of population dynamics.
J. F. Flannagan - One of the best experts on this subject based on the ideXlab platform.
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Trichoptera and substrate stability in the Ochre River, Manitoba
Hydrobiologia, 1990Co-Authors: D. G. Cobb, J. F. FlannaganAbstract:A total of 3999 Trichoptera adults, represented by 8 families, 17 genera and 33 species was collected in Emergence Traps in 1983 and 1984 from five stations on the Ochre River, Manitoba (50° 04′ N, 99° 48′ W). Species composition for the two years was comparable, but as the result of a summer spate in 1984, abundance was only 40% of that in 1983. Species diversity by station was negatively correlated with substrate instability of the reach, whereas density per trap was negatively correlated with substrate instability and local factors such as sedimentation in some reaches following peak discharges. Analysis of historical peak discharge records indicated that relatively infrequent mid-summer spates had a detrimental effect on subsequent Emergence of the Trichoptera fauna. The combination of spates and unstable stream bed substrate resulting from land use practices in the drainage basin have resulted in an impoverished caddisfly fauna in the Ochre River in comparison with other rivers in Manitoba.
Joakim Hjalten - One of the best experts on this subject based on the ideXlab platform.
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saproxylic beetle assemblages on low stumps high stumps and logs implications for environmental effects of stump harvesting
Forest Ecology and Management, 2010Co-Authors: Joakim Hjalten, Fredrik Stenbacka, Jon AnderssonAbstract:The aim of this study was to evaluate how future harvesting of spruce low stumps as a renewable energy source, might influence the saproxylic (wood living) beetle fauna. Species richness, abundance and assemblages of saproxylic beetles were compared on low stumps, high stumps and logs of spruce on 10 clear-cuts in northern Sweden. The sampling was conducted with Emergence Traps and a total of 929 individuals and 120 species were collected. No significant differences in beetle abundance or species richness were detected between substrate types. However, there were clear differences in assemblage composition between all substrate types. Our results suggest that low stumps created at final felling support as many species and individuals per volume dead wood as other dead wood substrates and that they are therefore overlooked as substrates for wood living organisms. Consequently, harvesting of low stumps might have negative effects on the diversity of saproxylic beetles, as up to 80% of the dead wood remaining on clear-cuts is in the form of low stumps. Future studies should evaluate if compensatory measures can be performed to minimize negative impacts.
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saproxylic parasitoid hymenoptera ichneumonoidea communities in managed boreal forest landscapes
Insect Conservation and Diversity, 2010Co-Authors: Fredrik Stenbacka, Joakim Hjalten, Jacek Hilszczański, John P Ball, Heloise Gibb, Therese Johansson, Roger Pettersson, Kjell DanellAbstract:Species of higher trophic levels are predicted to be more vulnerable to disturbances (e.g. by forestry) than their prey because of low population densities, extreme specialisation and reliance on intact trophic chains. 2. The aim of this study was to acquire some much-needed basic information on saproxylic parasitoids in boreal forest landscapes. To obtain reliable estimates of spe- cies richness, abundance, assemblage composition and host associations of saproxy- lic parasitoids in different stand types (clear-cuts, mature managed forests and old- growth reserves), we used two different methods (Emergence Traps and window Traps). 3. Window Traps caught more species and gave a better measure of the species pool in different stand types, while Emergence Traps were more suitable for detailed analyses concerning substrate requirements, hatching periods and to some extent host choice. 4. The general distribution pattern revealed no significant differences in species richness among stand types, but parasitoid assemblages were affected by forest suc- cessional stage. Idiobionts, dominated by Ontsira antica and Bracon obscurator ,p re- ferred clear-cuts over forested sites, while koinobionts, especially Cosmophorus regius, were more common in mature forests and reserves. We conclude that the stand types studied were complementary in assemblage composition, but that none held a complete assemblage of saproxylic parasitoids and we suggest that a range of successional stages be retained to help conserve the entire parasitoid community.
Jon Andersson - One of the best experts on this subject based on the ideXlab platform.
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saproxylic beetle assemblages on low stumps high stumps and logs implications for environmental effects of stump harvesting
Forest Ecology and Management, 2010Co-Authors: Joakim Hjalten, Fredrik Stenbacka, Jon AnderssonAbstract:The aim of this study was to evaluate how future harvesting of spruce low stumps as a renewable energy source, might influence the saproxylic (wood living) beetle fauna. Species richness, abundance and assemblages of saproxylic beetles were compared on low stumps, high stumps and logs of spruce on 10 clear-cuts in northern Sweden. The sampling was conducted with Emergence Traps and a total of 929 individuals and 120 species were collected. No significant differences in beetle abundance or species richness were detected between substrate types. However, there were clear differences in assemblage composition between all substrate types. Our results suggest that low stumps created at final felling support as many species and individuals per volume dead wood as other dead wood substrates and that they are therefore overlooked as substrates for wood living organisms. Consequently, harvesting of low stumps might have negative effects on the diversity of saproxylic beetles, as up to 80% of the dead wood remaining on clear-cuts is in the form of low stumps. Future studies should evaluate if compensatory measures can be performed to minimize negative impacts.
D. G. Cobb - One of the best experts on this subject based on the ideXlab platform.
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Trichoptera and substrate stability in the Ochre River, Manitoba
Hydrobiologia, 1990Co-Authors: D. G. Cobb, J. F. FlannaganAbstract:A total of 3999 Trichoptera adults, represented by 8 families, 17 genera and 33 species was collected in Emergence Traps in 1983 and 1984 from five stations on the Ochre River, Manitoba (50° 04′ N, 99° 48′ W). Species composition for the two years was comparable, but as the result of a summer spate in 1984, abundance was only 40% of that in 1983. Species diversity by station was negatively correlated with substrate instability of the reach, whereas density per trap was negatively correlated with substrate instability and local factors such as sedimentation in some reaches following peak discharges. Analysis of historical peak discharge records indicated that relatively infrequent mid-summer spates had a detrimental effect on subsequent Emergence of the Trichoptera fauna. The combination of spates and unstable stream bed substrate resulting from land use practices in the drainage basin have resulted in an impoverished caddisfly fauna in the Ochre River in comparison with other rivers in Manitoba.