Aridification determines changes in forest growth in Pinus halepensis forests under semiarid Mediterranean climate conditions.

Vicente-Serrano SM, Lasanta T, Gracia C (2010) Aridification determines changes in forest growth in Pinus halepensis forests under semiarid Mediterranean climate conditions. Agricultural and Forest Meteorology 150: 614-628.

Dispersal mechanisms of the narrow endemic Polygala vayredae: Dispersal syndromes and spatio-temporal variations in ant dispersal assemblages

Castro S., Ferrero V., Loureiro J., Espadaler X., Silveira P., Navarro L. (2010) Dispersal mechanisms of the narrow endemic Polygala vayredae: Dispersal syndromes and spatio-temporal variations in ant dispersal assemblages. Plant Ecology. 207: 359-372.
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Doi: 10.1007/s11258-009-9679-z

Resum:

This study assesses the dispersal mechanisms of the narrow endemic Polygala vayredae, analysing the functioning of its dispersal syndromes (anemochory and myrmecochory), the spatio-temporal variability of the disperser assemblage, foraging behaviour and dispersal ability, and the role of the elaiosome in ant attraction and seed germination. The dispersion of diaspores begins when either (1) capsules or seeds fall beneath the mother plant (barochory) or (2) the seeds are directly collected in the suspended capsules by ants (myrmecochory). As capsules frequently open and expose/disseminate seeds before leaving the mother plant, the adaptation for anemochory appears to be reduced and rarely functional, possibly with only occasional events of long-distance dispersal (e. g. under extreme weather conditions). P. vayredae is essentially myrmecochorous and a diverse array of ant species are involved in seed manipulation, with the elaiosome playing a major role in ant attraction. From the plant's perspective for dispersal, the majority of ant species had a positive interaction with the seeds, but negative and potential neutral interactions were also observed. Overall, dispersal distances were limited and were mainly determined by ant body size. The frequency of interactions and the ant assemblage varied significantly both spatially and temporally, and these factors may have an effect on directing or disrupting the selection of plant traits. Low seed predation and similar germination rates of intact seeds compared with seeds without elaiosome indicate that seed predator avoidance and seed germination improvement after ant manipulation are not among the selective advantages of myrmecochory operating at present. Dispersal mechanisms that enhance seed dispersal within the population and only occasionally lead to long-distance dispersal events, along with the rarity and patchiness of suitable habitats, may be the main factors explaining the actual density and narrow distribution of this species. © Springer Science+Business Media B.V. 2009.

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Resistance mechanism to the pod-sucking bug Clavigralla tomentosicollis (Hemiptera: Coreidae) in the cowpea IT86D-716 variety

Dabire-Binso C.L., Ba N.M., Sanon A., Drabo I., Bi K.F. (2010) Resistance mechanism to the pod-sucking bug Clavigralla tomentosicollis (Hemiptera: Coreidae) in the cowpea IT86D-716 variety. International Journal of Tropical Insect Science. 30: 192-199.
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Doi: 10.1017/S1742758410000354

Resum:

Resistance mechanisms to the pod-sucking bug (PSB) Clavigralla tomentosicollis Stäl, in cowpea genotype IT86D-716, were studied in field and laboratory. Non-preference was evaluated on three cowpea varieties (IT86D-716, Moussa local and KVx396-4-5-2D) through measuring differences in population parameters and extent of damage under field and laboratory conditions. Antibiosis was evaluated based on development parameters of C. tomentosicollis when reared on pods of the aforementioned varieties. The variety IT86D-716 consistently exhibited both non-preference and antibiosis resistance mechanisms to C. tomentosicollis. A chemical analysis of the pods was conducted to identify compounds conferring antibiosis. Several compounds including cyanogenic heterosides, flavonoids, tannins and trypsin inhibitors were present in pods of IT86D-716. Evidence suggests that antibiosis due to these compounds may contribute to the resistance to PSB. In the case of antibiosis, 5-day long exposures were adequate to observe nymphal mortality. Based on this finding, a fast, reliable and low-cost screening of pods can be carried out in the laboratory for identification of lines that are C. tomentosicollis resistant. © 2010 icipe.

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Dissecting biological invasions.

Sol D (2010) Dissecting biological invasions. Trends in Ecology and Evolution 25: 133

Effects of Different Types of Sludge on Soil Microbial Properties: A Field Experiment on Degraded Mediterranean Soils.

Tarrasón D, Ojeda G, Ortiz O, Alcañiz JM (2010) Effects of Different Types of Sludge on Soil Microbial Properties: A Field Experiment on Degraded Mediterranean Soils. Pedosphere 20: 681-691.

Effects of nonylphenol on a soil community using microcosms

Domene X., Chelinho S., Sousa J.P. (2010) Effects of nonylphenol on a soil community using microcosms. Journal of Soils and Sediments. 10: 556-567.
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Doi: 10.1007/s11368-009-0167-9

Resum:

Purpose: Nonylphenol polyethoxylates (NPEOs) are a group of surfactants known to be toxic and able to mimic estrogen compounds and thus interfere with the action of an animal's endogenous hormones. NPEOs are easily biodegraded in the environment, but the last end product, nonylphenol (NP), is the most toxic and recalcitrant form and hence can have a longer half-life in the environment. Despite the fact that most NP is finally degraded, a small fraction may remain in soil for longer periods. In soils, the application of sewage sludge is the main source of NPEOs. The aim of this study is to provide data on the effects of NP on a simplified soil invertebrate community since only a few studies using single-species bioassays are available for terrestrial ecosystems in comparison with aquatic ecosystems. Materials and methods: In our study, we assessed the effect of increasing NP concentrations (0, 10, 30, 90, and 270 mg NP kg-1) in soil microcosms containing a simplified soil community consisting of natural microorganisms, a primary producer (an oat seedling of Avena sativa), several consumers (the isopod Porcellionides sexfasciatus, the enchytraeid Enchytraeus crypticus, and the collembolans Folsomia candida, Ceratophysella (Hypogastrura) denticulata, and Proisotoma minuta), and a predator species (the mite Hypoaspis aculeifer). The effects on the different taxa of the different NP concentrations were assessed over three sampling dates (28, 56, and 112 days) using the principal response curves method. Results and discussion: The soil community did not change significantly at concentrations below 90 mg NP kg-1, which was selected as the nonobserved effect concentration (NOEC). The highest concentration (270 mg NP kg-1) changed the community significantly after 28 and 56 days, but this effect disappeared after 112 days, in accordance with the known rapid biodegradation of this compound in soil. Conclusions: Taking into account the usual NP concentrations in soils with repeated applications of sludge, the environmental risk of NP to soils seems to be limited because the derived NOEC was clearly above the usual concentrations in soil reported in the literature. However, the use of highly polluted sludges or accidental spillages, together with the possible pollution exportation by runoff to aquatic ecosystems, which are highly sensitive to NP pollution, recommend the careful monitoring of this chemical in the environment. © Springer-Verlag 2010.

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Role of soil properties in sewage sludge toxicity to soil collembolans

Domene X., Colón J., Uras M.V., Izquierdo R., Àvila A., Alcañiz J.M. (2010) Role of soil properties in sewage sludge toxicity to soil collembolans. Soil Biology and Biochemistry. 42: 1982-1990.
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Doi: 10.1016/j.soilbio.2010.07.019

Resum:

Soil properties are one of the most important factors explaining the different toxicity results found in different soils. Although there is knowledge about the role of soil properties on the toxicity of individual chemicals, not much is known about its relevance for sewage sludge amendments. In particular little is known about the effect of soil properties on the toxicity modulation of these complex wastes. In addition, in most studies on sewage sludges the identity of the main substances linked to the toxicity and the influence of soil properties on their bioavailability remains unknown.In this study, the toxicity of a sewage sludge to the soil collembolan Folsomia candida was assessed in nine natural soils from agricultural, grassland and woodland sites, together with the OECD soil. Correlations between the relative toxicity of sludge for collembolans in the different soils and their physical and chemical soil properties were assessed in order to identify the main compounds responsible for the effects observed. Furthermore, the relationships between the toxic effects to collembolans and water-soluble ions released by sludge, pH and electric conductivity were also assessed, together with the modulating effects of soil properties.Sludge toxicity was directly linked to the water extractable ammonium, which explained most of the mortality of the collembolans, and part of the inhibition of reproduction. For the last endpoint, nitrite also contributed significantly to the inhibition observed. The varied levels in water extractable ammonium in the different soils at equal dosages seem to be, in turn, modulated by some soil properties. Higher organic carbon contents were associated with lower toxicity of sludge, both for survival and reproduction, probably related to its higher ammonium sorption capacity. In addition, for reproduction, increasing the C/N ratio and pH appeared to increase the toxicity, probably due to both the greater difficultly in nitrification and the known unsuitability of alkaline soils for this species. © 2010 Elsevier Ltd.

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Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata (Taxaceae), with great dispersal capability

Dubreuil M., Riba M., González-Martínez S.C., Vendramin G.G., Sebastiani F., Mayol M. (2010) Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata (Taxaceae), with great dispersal capability. American Journal of Botany. 97: 303-310.
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Doi: 10.3732/ajb.0900148

Resum:

Tree species are thought to be relatively resistant to habitat fragmentation because of their longevity and their aptitude for extensive gene flow, although recent empirical studies have reported negative genetic consequences, in particular after long-term habitat fragmentation in European temperate regions. Yet the response of each species to habitat loss may differ greatly depending on their biological attributes, in particular seed dispersal ability. In this study, we used demographic and molecular data to investigate the genetic consequences of chronic habitat fragmentation in remnant populations of Taxus baccata in the Montseny Mountains, northeast Spain. The age structure of populations revealed demographic bottlenecks and recruitment events associated with exploitation and management practices. We found a strong genetic structure, both at the landscape and within-population levels. We also detected high levels of inbreeding for a strictly outcrossing species. Chronic forest fragmentation resulting from long-term exploitation in the Montseny Mountains seems the most plausible explanation for the strong genetic structure observed. Our results support the view that, contrary to some predictions, tree species are not buffered from the adverse effects of habitat fragmentation, even in the case of species with a high dispersal potential.

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Atles d’espècies llenyoses dels bosos de Catalunya.

Lloret F, Vayreda J, Terradas J (2010) Atles d’espècies llenyoses dels bosos de Catalunya. Notícies de la Institució Catalana d’Història Natural, gener-febrer: 1-2.

Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies.

Saura-Mas S, Paula S, Pausas JG, Lloret F (2010) Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies. International Journal of Wildland Fire 19: 783-794.

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