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Diaz M.,CSIC - Center for Environmental Sciences | Parra A.,University of Castilla - La Mancha | Gallardo C.,University of Castilla - La Mancha
Behavioral Ecology

Increasing levels of anthropogenic noise interferes with the acoustic communication of birds. Adaptive shifts in song characteristics (frequency and amplitude) and in the spatial and temporal patterns of singing behavior in the face of noise pollution have been documented. We provide evidence for another response, increased time spent singing, in a successful suburban bird, the serin Serinus serinus. Serins increased the proportion of time spent singing at posts in relation to changes in noise levels both in space and in time up to a threshold at approximately 70 dBA, whereas time spent at singing posts was not related to noise levels. This response could be related to the characteristics of the serin's song (high pitch and presumably low metabolic and neuromuscular costs) that would reduce the relative effectiveness of song shifts. However, vocal activity decreased sharply above the 70 dBA threshold, suggesting that this strategy is costly. Because singing time may trade off with vigilance time, our data suggest that bird populations in noisy city environments may face an increased challenge for survival compared with quiet areas, even for species whose song characteristics reduce the interference of urban noise with acoustic communication. © 2011 The Author. Source

Sanz-Perez V.,CSIC - Center for Environmental Sciences | Castro-Diez P.,University of Alcala
Trees - Structure and Function

Current environmental conditions are known to affect plant growth, morphology, phenology, and therefore, plant performance. However, effects of the previous-year environmental conditions can also affect plant structure by altering bud growth, and proportion and date of budburst. Here, we analysed the effects of previous-year water stress and shade on bud size, percentage, and date of budburst in seedlings of three co-occurring Iberian Quercus species in two independent experiments. Responses of apical, lateral, and basal buds were checked during an annual cycle. In the first experiment, seedlings of two evergreens (Q. coccifera L., Q. ilex subsp. ballota (Desf.) Samp.) and a deciduous-marcescent tree (Q. faginea Lam.) were grown under two levels of summer watering. In the second experiment, seedlings were grown under three light intensities. Soluble sugars and starch in shoots and roots were measured before budburst. Summer drought increased bud size of all species and advanced budburst of Q. ilex and Q. coccifera. Moderate and/or intense shade tended to reduce bud size and delay budburst in all species. These responses seem related to changes in the date of bud formation rather than to the amount of carbon reserves, which were reduced both by drought and shade. Treatments affected percentage of budburst in lateral buds, which was reduced by shade and water stress, probably leading to narrower crowns. These results show that previous-year environmental conditions are relevant for plant phenology and structure. The different responses in budburst date between the deciduous and the evergreens might alter their competition relationships at seedling stage. © Springer-Verlag 2009. Source

Delgado-Moreno L.,CSIC - Experimental Station of El Zaidin | Pena A.,CSIC - Experimental Station of El Zaidin | Almenbdros G.,CSIC - Center for Environmental Sciences
Journal of Hazardous Materials

A soil, olive cake, compost and vermicompost of olive cake, were subjected to sequential laboratory extraction to progressively remove water-soluble, lipid and alkali-soluble (humic-type) fractions. Sorption experiments with triazines were carried out with non-amended and amended soil and with soil residues in the intermediate stages during the laboratory removal of the different organic fractions. Herbicide sorption in soil amended with olive cake was between two and three times higher than sorption in composted substrates. In non-amended soil, the removal of humic and fulvic acids led to a decrease of triazines sorption indicating the importance of these fractions in the sorption of these pesticides. The greater triazines sorption in soil amended with olive cake could be associated with the high concentration of water-soluble substances. In contrast, olive cake lipids did not favour the sorption of the more hydrophobic herbicides as indicated by the fact that the sorbed amount increased 30-40% when this fraction was removed. No significant (P > 0.05) differences in Koc values were found in soils amended with compost and vermicompost in the course of the progressive removal of the different organic fractions, indicating triazine sorption was related more with the total amount of organic matter than with its chemical composition. © 2009 Elsevier B.V. All rights reserved. Source

de Blas E.,University of Vigo | Rodriguez-Alleres M.,University of Vigo | Almendros G.,CSIC - Center for Environmental Sciences

Soil organic matter characteristics in extremely water-repellent soils developed under forests of Pinus pinaster and Eucalyptus globulus in Galicia (Northwestern Spain) were analyzed with special emphasis paid in lipid and humic acid fractions. A total of sixteen soils were studied including Leptic Regosols and Leptic Umbrisols developed on granites and schists, and showing extreme water repellency: up to 6 h using water drop penetration time (WDPT) test, i.e., ranging from strongly to extremely hydrophobic (ethanol percentage test, MED). The experimental design involved the measurement of the water repellency as WDPT after the successive removal of lipid and humic fractions by: (i) direct extraction of the soil free lipid with petroleum ether (40-60 °C), (ii) extraction of the 'fixed' lipid from the soil residue after 2m H3PO4 treatment and further recovery from the aqueous phase with petroleum ether and (iii) final extraction of humic substances with alkaline solutions. The results showed significant decrease in the WDPT (from class 6 to classes 4 or 5) after removing free lipid. Nevertheless, removal of 'fixed' lipid resulted into the most substantial decrease of the WDPT, which occurred on almost all soils (to classes 0-3). This fact is to large extent associated to the simultaneous removal of hydrophobic particulate fractions (free organic matter) which - even after extraction of free lipid - resulted extremely water-repellent in laboratory conditions (>1 h WDPT). Finally, the extraction of humic and fulvic acids was required for the total disappearance of the water repellency (class 0). Regarding vegetation types, lipid removal (free + 'fixed' fractions) was significantly more effective in increasing wettability in the case of forest soil samples under pine than under eucalypt. Concerning geological substrate, water repellency in soils under granites remained comparatively more persistent than in soils under schists. After treatment with 2m H3PO4, all samples from soils on granite-eucalyptus remained slightly water-repellent, whereas all samples from soils developed on schist-pine samples became wettable. Multivariate data treatments (multiple regression models, variable ordination by multidimensional scaling, and discriminant analysis) were useful to identify the soil characteristics most significantly associated to its water repellency. These treatments suggest that water repellency in the soils under study is a complex emergent property, reflected in specific patterns depending on vegetation type and geological substrate and arising from the interaction between different soil organizational levels (mainly free lipid, 'fixed' lipid, macroscopic particulate organic matter and the concentration and maturity of humic substances). © 2009 Elsevier B.V. All rights reserved. Source

Garcia-Palacios P.,Rey Juan Carlos University | Garcia-Palacios P.,CSIC - Center for Environmental Sciences | Maestre F.T.,Rey Juan Carlos University | Gallardo A.,Pablo De Olavide University
Journal of Ecology

Recent research has shown that biodiversity may have its greatest impact on ecosystem functioning in heterogeneous environments. However, the role of soil heterogeneity as a modulator of ecosystem responses to changes in biodiversity remains poorly understood, as few biodiversity studies have explicitly considered this important ecosystem feature. We conducted a microcosm experiment over two growing seasons to evaluate the joint effects of changes in plant functional groups (grasses, legumes, non-legume forbs and a combination of them), spatial distribution of soil nutrients (homogeneous and heterogeneous) and nutrient availability (50 and 100mg of nitrogen (N) added as organic material) on plant productivity and surrogates of carbon, phosphorous and N cycling (β-glucosidase and acid phosphatase enzymes and in situ N availability, respectively). Soil nutrient heterogeneity interacted with nutrient availability and plant functional diversity to determine productivity and nutrient cycling responses. All the functional groups exhibited precise root foraging patterns. Above- and below-ground productivity increased under heterogeneous nutrient supply. Surrogates of nutrient cycling were not directly affected by soil nutrient heterogeneity. Regardless of their above- and below-ground biomass, legumes increased the availability of soil inorganic N and the activity of the acid phosphatase and β-glucosidase enzymes. Our study emphasizes the role of soil nutrient heterogeneity as a modulator of ecosystem responses to changes in functional diversity beyond the species level. Functional group identity, rather than richness, can play a key role in determining the effects of biodiversity on ecosystem functioning. Synthesis. Our results highlight the importance of explicitly considering soil heterogeneity in diversity-ecosystem functioning experiments, where the identity of the plant functional group is of major importance. Such consideration will improve our ability to fully understand the role of plant diversity on ecosystem functioning in ubiquitous heterogeneous environments. © 2010 The Authors. Journal of Ecology © 2010 British Ecological Society. Source

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