Impact of an invasive plant (Elymus athericus) on the conservation value of tidal salt marshes in western France and implications for management: Responses of spider populations     

Julien Pétillon  Frédéric Ysnel  Jean-Claude Lefeuvre 《Biological conservation》2005,126(1):103-117

As a result of Elymus athericus (Poaceae) invasion in the last 10 years, a major change in vegetation cover has occurred in salt marshes of the Mont Saint-Michel bay (France). Such invasions are known to modify biodiversity and consequently ecosystem proprieties and functions as well as the conservation value of invaded areas. In this study, we especially focus (1) on the impact of the invasive species on the conservation value of the invaded ecosystems and (2) on the impact of mowing in the invaded parts of salt marshes. Among the various biological models, spiders were selected for the present study because they are an abundant, diversified, taxonomic group of generalist predators. Furthermore, data are available on this group since 1984, allowing a comparison of species distribution ranges in salt marshes before and after the E. athericus invasion. This diachronic approach showed that the invasion of salt marshes promoted the progression of non-coastal species, web-building spiders and cursorial spiders, but did not interfere with resident species distributions, finally resulting in higher spider densities and species richness in the entire area.The species composition, functional groups, abundances and densities of spider assemblages were also compared using complementary sampling techniques (i.e., pitfall traps, collecting by hand and quadrat technique) between natural and invaded stations in 2002 for synchronic approach. One main result is that some halophilic species decreased in abundances and densities in invaded plots, which is thought to alter the marine character of salt marsh arthropod assemblages. Lastly, mowing, by reducing non-coastal species and enhancing halophilic ones, tends to reduce the negative effects of Elymus on salt marsh conservation value. The relation between the treatments tested (invasive species and mowing) and the spider assemblages by changes in environmental variables confirms the high value of this group as bioindicators.  相似文献   

Sur une nouvelle methode de dosage du dioxyde d'azote present dans les atmospheres polluees,derivee de la methode de Griess-Saltzmann     

Jacques Alary  Pierre Bourbon  Paul Chovin  Claude Delaunay  Jean Esclassan  Jean-Claude Lepert 《Water, air, and soil pollution》1974,3(4):555-562

This paper discusses a procedure involving absorption of NO₂ on triethanolamine impregnated-papers according to a recent study of Levaggi, Siu and Feldstein. The used solid surfaces are Millipore filters, first impregnated by stirring them in a solution containing triethanolamine, glycerol and acetone before drying in an oven. Storage is made in a closed glass container. For sampling, check air flow rate to be about 30 l h^?1 through filters. The sampling time depends on the actual concentration. Samples are then analyzed in a laboratory under Saltzman's colorimetric reaction. The composition of the reagents is slightly modificated (acetic acid is replaced by phosphoric acid to obtain pH 1). Color development needs 30 min and then absorbance is compared with a standardization curve built from dilute solutions of Na NO₂. Absorption efficiencies of over 95% are attained with two impregnated filters in a filter holder and at about 301 h^?1 flow rate. Stability of filters after sampling is evaluated at 2 or 3 weeks, so it is possible to store several filters before sending them (for example by mail) to the laboratory for analysis. The stoichiometric factor depends on the weight (expressed in μg) of NO₂ collected on the filters and varies between 1.0 and 0.84. To measure NO, oxidation into NO₂ is first required, for example with an O₃ lamp.  相似文献   

Quality assessment of strawberries (Fragaria species)     

Azodanlou R  Darbellay C  Luisier JL  Villettaz JC  Amadò R 《Journal of agricultural and food chemistry》2003,51(3):715-721

Several cultivars of strawberries (Fragaria sp.), grown under different conditions, were analyzed by both sensory and instrumental methods. The overall appreciation, as expressed by consumers, was mainly reflected by attributes such as sweetness and aroma. No strong correlation was obtained with odor, acidity, juiciness, or firmness. The sensory quality of strawberries can be assessed with a good level of confidence by measuring the total sugar level ( degrees Brix) and the total amount of volatile compounds. Sorting out samples using the score obtained with a hedonic test (called the "hedonic classification method") allowed the correlation between consumers' appreciation and instrumental data to be considerably strengthened. On the basis of the results obtained, a quality model was proposed. Quantitative GC-FID analyses were performed to determine the major aroma components of strawberries. Methyl butanoate, ethyl butanoate, methyl hexanoate, cis-3-hexenyl acetate, and linalool were identified as the most important compounds for the taste and aroma of strawberries.  相似文献   

Understanding the decline and extinction of monarchs (Aves) in Polynesian Islands     

Jean-Claude Thibault  Jean-Louis MartinAura Penloup  Jean-Yves Meyer 《Biological conservation》2002,108(2):161-174

Understanding the decline and extinction of species has become critical to conservation biology. The five monarch species of the genus Pomarea, endemic to the southeastern Pacific, are all listed as threatened. Introduced mammals and birds are believed to be responsible for their rarefaction. We analyzed the historical and current distribution of monarchs and introduced animals and found no relation between presence of Polynesian rats (Rattus exculans) and monarch distribution. There was a highly significant correlation between the arrival of the black rat (Rattus rattus) and the decline and extinction of monarch populations. The extinction of monarch populations after colonization by black rats tended to take longer on larger islands than on smaller ones. On islands without black rats, monarchs persisted even where forests have been reduced by more than 75%. After an island was colonized by black rats the number of monarch pairs with young decreased dramatically. Eggs in artificial nests placed in sites used by monarchs were only preyed upon by black rats. No eggs were preyed upon by Polynesian rats (Rattus exulans) or introduced birds. Monarch nests were mainly placed on horizontal branches inside the canopy and were more accessible than nests of Polynesian warbler (Acrocephalus caffer), a species still locally abundant. Warbler nests were placed higher up on vertical branches near the top of trees. These studies suggest that nest predation by black rats has been the main cause of monarch decline. However observations of direct aggression of adult monarchs by introduced red-vented bulbuls (Pycnonotus cafer), especially when monarchs raise their young, suggest that introduced birds could aggravate the decline of monarch populations already weakened by black rats. We discuss the practical implications of these findings for monarch conservation.  相似文献   

Use of a Plackett-Burman experimental design to examine the impact of extraction parameters on yields and compositions of pectins extracted from chicory roots (Chicorium intybus L.)     

Robert C  Devillers T  Wathelet B  Van Herck JC  Paquot M 《Journal of agricultural and food chemistry》2006,54(19):7167-7174

Chicory root pectin was isolated by acid extraction followed by alcohol precipitation. Because the extraction conditions have important effects on the features of pectins, an experimental design was used to study the influence of 17 different extraction parameters on yield and composition of pectin: pH, temperature, time of extraction, solid/liquid ratio, and different pretreatments of the pulps before extraction. Twenty extractions were conducted and examined for their significance on yield and sugar content using the Plackett-Burman factorial design. The acid extraction of chicory roots resulted in an average yield of 11% containing 86% of sugars. It was found that extraction temperature, time, protease pretreatment, water purity, and water washing of pulps significantly affected yield and pectin composition with an increase of yield and purity of pectin in harsher extraction conditions.  相似文献   

Soil water storage appears to compensate for climatic aridity at the xeric margin of European tree species distribution     

Karl H. Mellert  Jonathan Lenoir  Susanne Winter  Christian Kölling  Andraž Čarni  Isabel Dorado-Liñán  Jean-Claude Gégout  Axel Göttlein  Daniel Hornstein  Matthias Jantsch  Nina Juvan  Eckart Kolb  Eduardo López-Senespleda  Annette Menzel  Dejan Stojanović  Steffen Täger  Ioannis Tsiripidis  Thomas Wohlgemuth  Joerg Ewald 《European Journal of Forest Research》2018,137(1):79-92

Based on macroecological data, we test the hypothesis whether European tree species of temperate and boreal distribution maintain their water and nutrient supply in the more arid southern margin of their distribution range by shifting to more fertile soils with higher water storage than in their humid core distribution range (cf. soil compensatory effects). To answer this question, we gathered a large dataset with more than 200,000 plots that we related to summer aridity (SA), derived from WorldClim data, as well as soil available water capacity (AWC) and soil nutrient status, derived from the European soil database. The soil compensatory effects on tree species distribution were tested through generalized additive models. The hypothesis of soil compensatory effects on tree species distribution under limiting aridity was supported in terms of statistical significance and plausibility. Compared to a bioclimatic baseline model, inclusion of soil variables systematically improved the models’ goodness of fit. However, the relevance measured as the gain in predictive performance was small, with largest improvements for P. sylvestris, Q. petraea and A. alba. All studied species, except P. sylvestris, preferred high AWC under high SA. For F. sylvatica, P. abies and Q. petraea, the compensatory effect of soil AWC under high SA was even more pronounced on acidic soils. Soil compensatory effects might have decisive implications for tree species redistribution and forest management strategies under anthropogenic climate change. Therefore, soil compensatory effects deserve more intensive investigation, ideally, in studies combining different spatial scales to reduce the uncertainty associated with the precision of soil information.  相似文献