Managing successional trajectories in alien-dominated, novel ecosystems by facilitating seedling regeneration: A case study     

Christoph Kueffer  Eva Schumacher  Hansjörg Dietz  Karl Fleischmann  Peter J. Edwards 《Biological conservation》2010,143(7):1792-1802

Managing novel ecosystems that emerge after strong anthropogenic disturbance and the spread of alien species poses complex problems. As a case example, we discuss efforts on the tropical oceanic island Mahé (Seychelles) to promote the regeneration of native trees in tropical secondary forest dominated by the invasive tree Cinnamomum verum (true cinnamon).We monitored the growth of transplanted and self-sown native and alien tree seedlings in both artificially created forest gaps and in the understorey of closed forest. In the understorey, native species survived but grew very slowly, indicating that any recovery of native tree populations would also be very slow. In larger gaps, seedlings of certain invasive species grew particularly fast, suggesting that these species would rapidly dominate. Nutrient addition had only a minor positive effect on seedling growth, especially in the understorey.Although neither closed canopy conditions nor large gaps are conducive to the recovery of native seedlings, our data indicate that intermediate levels of canopy disturbance, i.e. those attained by felling one or a few trees, provide a combination of below- and aboveground resource limitation of seedling growth that may favour native species over invasive species. Based on these findings, we propose a strategy for restoring native vegetation that entails making small gaps in cinnamon-dominated forest and planting them with native tree species.This study illustrates how management strategies can be improved by combining insights gained from past interventions with the results of field and greenhouse experiments.  相似文献   

Chemical deterrents in podurid Collembola     

Christoph Messer  Jessica Walther  Konrad Dettner  Stefan Schulz 《Pedobiologia》2000,44(3-4)

Four aromatic compounds (2,4-dimethoxyaniline, 1,3-dimethoxybenzene, 2-aminophenol, phenol) found in Neanura muscorum (Collembola, Neanuridae) have been investigated for their role as deterrents against the predatory mite Pergamasus norvegicus (Acarina, Parasitidae). 2-Aminophenol has deterring properties against P. norvegicus, the other substances show no effect as single substances nor is there a synergistic effect.The reaction of three predators, Microvelia reticulata (Heteroptera, Veliidae), Gambusia affinis (Teleostei, Cyprinodontidae) and Rana temporaria (Amphibia, Ranidae) on Podura aquatica (Collembola, Poduridae) is reported. The strongest deterring effects of P. aquatica could be observed with G. affinis. M. reticulata also shows behavioural changes that can be attributed to deterring effects of P. aquatica. The collembolan has no deterring effects on R. temporaria.A synopsis of literature dealing with deterring effects of collembola on arthropod predators is given.  相似文献   

Functional diversity of soil organisms — a review of recent research activities in Germany     

Christoph Emmerling  Michael Schloter  Anton Hartmann  Ellen Kandeler 《植物养料与土壤学杂志》2002,165(4):408-420

The aim of this review is to provide an overview of recent investigations on the functional diversity of soil organisms and to elucidate whether a combination of different phenotypic and genotypic assessment methods can give new insights into the relation of structural (phylogenetic) and functional diversity of soil microbial and faunal communities. The knowledge of functional gene sequences for the major microbial transformations enables studies of their presence and diversity in soils. The concomitant evaluation of phylogenetic identification and functional activity of even individual microbial cells in situ is now possible using such as fluorescence in situ hybridization and microautoradiography. Studies about microbial‐faunal interactions clarifies the importance of soil organisms for soil processes.  相似文献   

Mysterious syndrome causing high mortality in wild brown trout in Eastern Switzerland,pathology and search for a possible cause     

Heike Schmidt-Posthaus  Michel Koch  Torsten Seuberlich  Christoph Birrer  Regula Hirschi  Michael Kugler 《Journal of fish diseases》2020,43(10):1317-1324

Since 2016, annually occurring species-specific die-offs of brown trout (Salmo trutta fario) occurred in the Thur River, situated in the Eastern part of Switzerland. These events lead to drastically reduced population densities in the impacted river regions. Clinical signs in brown trout and mortality were restricted to few weeks in August/September. To characterize the syndrome and to find possible causes, from end of March to November 2018, one-year-old brown trout (Salmo trutta fario) and rainbow trout (Oncorhynchus mykiss) were exposed to water from Thur River, fish were sampled regularly and screened for infectious agents, including viral metagenomics, and pathology was described. Starting approximately four months post-exposure, brown trout showed severe lymphohistiocytic pancarditis and necrotizing and haemorrhagic hepatitis. These lesions were recorded until the end of the experiment in November. Rainbow trout were not affected at any point in time. No infectious agents could be identified so far as cause of disease, especially no viral aetiology. Even if pathogenesis and pathology point in the direction of an infectious agent, a causative relationship could not be confirmed and aetiology remains unclear.  相似文献   

Warum fehlt den Gipsbuchenwäldern des Kyffhäusers (Thüringen) eine Krautschicht?     

Iris Schmid  Christoph Leuschner 《European Journal of Forest Research》1998,117(1-6):277-288

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Newcomers in the Baltic Sea: an attempt to trace the origins and whereabouts of thicklip grey mullet <Emphasis Type="Italic">Chelon labrosus</Emphasis>     

Matthias Schaber  Lasse Marohn  Christoph Petereit  Jan P. Schroeder  Karsten Zumholz  Reinhold Hanel 《Fisheries Science》2011,77(5):757-764

In recent years, thicklip grey mullet Chelon labrosus has shown increasing expansion of its native habitats in the north-eastern Atlantic into northerly adjacent areas including the North Sea and the brackish Baltic Sea. Despite the regular annual and seasonal occurrence of C. labrosus in the western Baltic during the warm months, nothing is known of the origin or whereabouts of the mullet during the cold season. As different possible migration scenarios can be considered, we performed otolith microchemistry analyses on specimens from the western Baltic Sea to identify the origin of this nonindigenous species. Comparison with North Sea samples revealed common habitat preferences and underlined the highly euryhaline nature of C. labrosus in different recently occupied habitats. Occasional fluctuations of Sr/Ca ratio along the growth axis suggest periodical migration between waters of different salinities but did not reveal distinct migration pathways.  相似文献