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Göttingen, Germany

Beyer F.,University of Gottingen | Beyer F.,Institute of Agronomy | Hertel D.,University of Gottingen | Jung K.,University of Gottingen | And 2 more authors.
Forest Ecology and Management | Year: 2013

Belowground competition has been identified as a major force structuring plant communities, but it is not well known how inter- and intraspecific root competition are influencing the survivorship of individual roots. We investigated the impact of inter- and intraspecific competition between European ash (Fraxinus excelsior) and European beech (Fagus sylvatica) on fine root survivorship, root system size and plant productivity in a competition experiment with direct fine root growth observation.Ash and beech saplings were grown either in mixture, monoculture or in isolation (single plant) in rhizoboxes with a transparent observation window that allowed quantifying root growth as well as root longevity dependent on neighbour presence. Root survival was analysed using Cox proportional hazards regression and Kaplan-Meier estimations. Standing root biomass and root productivity were quantified at a final harvest, allowing the calculation of competition indices and biomass partitioning in the plant.With competition indices indicating asymmetric competition in favour of ash, our experiment supports earlier findings on the competitive superiority of juvenile ash over beech plants. Mean root lifespan differed significantly among species (higher longevity of ash fine roots) and also in dependence of the competition treatment. The risk of fine root mortality increased when beech roots grew in mixture with ash or in beech monoculture as compared to beech plants growing in isolation. In contrast, ash fine roots had a lower mortality in mixture with beech than when grown in isolation.Our data indicate that ash fine roots apparently profit from the presence of beech roots while beech root growth and survival are negatively affected, indicating size-asymmetric belowground competition. Competition may represent an important force influencing the fine root lifespan of these tree species. © 2013 Elsevier B.V.

Vuts J.,Plant Protection Institute | Baric B.,University of Zagreb | Razov J.,University of Zadar | Toshova T.B.,Bulgarian Academy of Science | And 5 more authors.
Crop Protection | Year: 2010

Trapping tests were performed concurrently in several countries of Central and Southern Europe throughout the spring and summer of 2008, to study the selectivity and performance of floral attractant-baited traps developed for catching Epicometis (Tropinota) hirta Poda (CA-baited traps), Cetonia a. aurata L./. Potosia (Protaetia) cuprea Fabr. (ME-baited traps) or Oxythyrea funesta Poda (PH-baited traps) (Coleoptera: Scarabaeidae, Cetoniinae). Amongst the species caught, E. hirta showed strongest attraction to the CA-baited and ME-baited traps. O. funesta was mostly caught by PH-baited traps. In capturing C. a. aurata and P. cuprea, the ME-baited trap appeared to be the most efficient. At two sites in Italy, a related scarab, Tropinota squalida Scop. (Coleoptera: Scarabaeidae, Cetoniinae), was attracted in similar numbers to both CA-baited and ME-baited traps. For the scarab Valgus hemipterus L. (Coleoptera: Scarabaeidae, Valginae), ME-baited traps proved to be the most attractive.Of the scarabs coming to the CA-baited trap, E. hirta was the most abundant, except at the two Italian sites where large percentages were shown to be T. squalida. The most abundant species in the catch by the PH-baited trap was O. funesta, although at some sites, C. a. aurata and E. hirta were captured in sizeable numbers. ME-baited traps caught mostly C. a. aurata at sites with large C. a. aurata populations, whereas at sites with low populations, good numbers of E. hirta or T. squalida were caught. © 2010 Elsevier Ltd.

Djilali K.,University of Ouargla | Sekour M.,University of Ouargla | Souttou K.,Ziane Achour University of Djelfa | Ababsa L.,University of Ouargla | And 3 more authors.
Zoology and Ecology | Year: 2016

The diet of the Short-eared Owl Asio flammeus was analysed in an arid environment in Hassi El Gara located in the southeast of El Golea (Ghardaia, Algeria). The diet was determined by analysing 138 pellets. Our data showed that the diet was dominated by mammals (Chiroptera and Rodentia). Based on relative biomass, birds were the main prey species. Mammals were the second most important prey. Mammals were the major food item throughout the seasons and their contribution to the diet ranged from 50.7% in spring to 73.6% in summer. Birds were the second numerous prey with 8.1% in summer and 29.6% in spring. The dominant prey species was Myotis sp., making up 37.8%. It was followed by Gerbillus nanus (5.4%), Columba livia (4.3%) and Bufo mauritanicus (4.1%). © 2016 Nature Research Centre

Merzouki Y.,University of Bordj Bou Arreridj | Souttou K.,Ziane Achour University of Djelfa | Sekour M.,University of Ouargla | Daoudi-Hacini S.,Institute of Agronomy | Doumandji S.,Institute of Agronomy
Comptes Rendus - Biologies | Year: 2014

The diet of the House Martin Delichon urbica was analyzed in a suburban area in Pins maritimes, northeast of Algiers (Algeria). The diet was determined by analyzing 120 faecal samples collected from a breeding colony between April and September 2007. Insects were the most numerous prey types (99.86%). Hymenopterans were the dominant preys (56.99%), followed by Coleopterans (20.14%), Homopterans (14.22%), Heteropterans (5.45%), and Dipterans (3.10%). Division of the prey items into families demonstrated that the highest relative frequency was large Hymenopterans in the family Formicidae (54.0%). The dominant species in the diet was Tetramorium biskrensis, which comprised 32.6% of the diet. It was followed by Camponotus barbaricus (6.9%) and Monomorium salomonis (5.6%). Comparison between diet and availability of preys using the Savage index showed that T. biskrensis, Crematogaster scutelaris, Pheidole pallidula, Diptera sp. unident. and Aphidae sp. unident. were positively selected by D. urbica. © 2013 Académie des sciences.

van Oijen M.,UK Center for Ecology and Hydrology | Reyer C.,Potsdam Institute for Climate Impact Research | Bohn F.J.,Helmholtz Center for Environmental Research | Cameron D.R.,UK Center for Ecology and Hydrology | And 11 more authors.
Forest Ecology and Management | Year: 2013

Forest management requires prediction of forest growth, but there is no general agreement about which models best predict growth, how to quantify model parameters, and how to assess the uncertainty of model predictions. In this paper, we show how Bayesian calibration (BC), Bayesian model comparison (BMC) and Bayesian model averaging (BMA) can help address these issues.We used six models, ranging from simple parameter-sparse models to complex process-based models: 3PG, 4C, ANAFORE, BASFOR, BRIDGING and FORMIND. For each model, the initial degree of uncertainty about parameter values was expressed in a prior probability distribution. Inventory data for Scots pine on tree height and diameter, with estimates of measurement uncertainty, were assembled for twelve sites, from four countries: Austria, Belgium, Estonia and Finland. From each country, we used data from two sites of the National Forest Inventories (NFIs), and one Permanent Sample Plot (PSP). The models were calibrated using the NFI-data and tested against the PSP-data. Calibration was done both per country and for all countries simultaneously, thus yielding country-specific and generic parameter distributions. We assessed model performance by sampling from prior and posterior distributions and comparing the growth predictions of these samples to the observations at the PSPs.We found that BC reduced uncertainties strongly in all but the most complex model. Surprisingly, country-specific BC did not lead to clearly better within-country predictions than generic BC. BMC identified the BRIDGING model, which is of intermediate complexity, as the most plausible model before calibration, with 4C taking its place after calibration. In this BMC, model plausibility was quantified as the relative probability of a model being correct given the information in the PSP-data. We discuss how the method of model initialisation affects model performance. Finally, we show how BMA affords a robust way of predicting forest growth that accounts for both parametric and model structural uncertainty. © 2012 Elsevier B.V.

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