Sanz-Perez V.,CSIC - Center for Environmental Sciences |
Castro-Diez P.,University of Alcalá
Trees - Structure and Function | Year: 2010
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.
Ochoa-Hueso R.,CSIC - Center for Environmental Sciences |
Manrique E.,CSIC - Center for Environmental Sciences
Plant Ecology | Year: 2010
Anthropogenic nitrogen (N) inputs in terrestrial ecosystems are higher than those that occur naturally and have been related to global biodiversity loss and altered ecosystem functioning. However, its effects on Mediterranean-type ecosystems, where production is water-limited and N regulated, remain unclear. We conducted a green-house experiment where we evaluated the effects of four simulated scenarios of N pollution (0, 10, 20 and 50 kg N ha-1 year-1) and two differential water supply regimes on the germination (experiment 1) and early plant establishment (experiment 2) of a seed bank from a semi-arid Mediterranean ecosystem of central Spain. Seed bank density was estimated as 62,374 ± 3,279 seeds m-2. Approximately 99.5% of emerged seeds corresponded to only 14 species of a total of 52, the majority of which were the annual forb Sagina apetala. The responses for N treatments were species-specific, mainly positive or unimodal, with watering treatments having some interactive effects. N and water supply also affected total and specific productivity; the responses found for N treatments were mainly humpback-shaped and an increased water supply had additive effects on community establishment in terms of total plant biomass. This response was linked to forb responsiveness. Contrary to predictions, grass biomass did not change with N supply; however, grass to forb ratio was affected because of changes in the latter. Overall, these experiments suggest a critical load for plant biomass production and conclude that N and water availability and supply can modify germination and plant establishment. This should be taken into account when analysing the effects of global change on the dynamics of plant communities where annuals are dominant or vegetation must establish from seed following a natural or anthropogenic disturbance regime. © 2010 Springer Science+Business Media B.V.
Diaz M.,CSIC - Center for Environmental Sciences |
Parra A.,University of Castilla - La Mancha |
Gallardo C.,University of Castilla - La Mancha
Behavioral Ecology | Year: 2011
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.
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 | Year: 2011
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.
Delgado-Moreno L.,CSIC - Experimental Station of El Zaidín |
Pena A.,CSIC - Experimental Station of El Zaidín |
Almenbdros G.,CSIC - Center for Environmental Sciences
Journal of Hazardous Materials | Year: 2010
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.
Cid M.,CSIC - Center for Environmental Sciences |
Fereres A.,CSIC - Center for Environmental Sciences
Annals of the Entomological Society of America | Year: 2010
The citrus mealybug, Phnococcus citri (Risso) (Hemiptera: Pseudococcidae), is a vector of Grapevine leafroll-associated virus 3 (GLRaV-3), which causes severe damage to grapevines (Vitis spp.) worldwide. We studied the feeding behavior of P. citri on grapevine leaves and whole plants infected with GLRaV-3 and on artificial feeding membranes using DC-electrical penetration graphs (EPGs). P. citri ingested from phloem sieve elements, but it also spent long intervals in the xylem. Waveforms, not described before for mealybugs, were characterized, some of them resembling those of aphids: 1) one new pattern occurring within the phloem phase, named E23, correlated with honeydew excretion and positive ninhydrine reaction and therefore was associated with sap ingestion from the phloem sieve elements; and 2) an extracellular waveform, named G, also possibly associated with ingestion in artificial membranes, which probably represented xylem ingestion. The potential drops (pd) of P. citri showed two distinct phases (pd1 and pd2). The occurrence of pds was, on average, less frequent than in aphids (0.14/min), but they lasted much longer (32.5 s). The temporal analysis of 20 EPG recordings on detached leaves lasting 20 h showed great variability among individuals. Only 11/20 mealybugs reached the phloem phase, and ingestion from the phloem sieve elements (E23) was the predominant phloem-related activity. However, the G pattern was even more frequent, and most insects (16/20) showed xylem ingestion activities with an average duration of 8.7 h. This work represents the first step to identify specific stylet activities associated with the acquisition and inoculation of GLRaV-3 by P. citri. © 2010 Entomological Society of America.
de Blas E.,University of Vigo |
Rodriguez-Alleres M.,University of Vigo |
Almendros G.,CSIC - Center for Environmental Sciences
Geoderma | Year: 2010
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.
Ochoa-Hueso R.,CSIC - Center for Environmental Sciences |
Manrique E.,CSIC - Center for Environmental Sciences
Environmental Pollution | Year: 2011
We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha -1 yr-1 in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. β-carotene/chlorophylls increased with 20-50 kg N ha-1 yr-1 (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha-1 yr-1. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes. © 2010 Elsevier Ltd. All rights reserved.
Rincon A.,CSIC - Center for Environmental Sciences |
Pueyo J.J.,CSIC - Center for Environmental Sciences
Forest Ecology and Management | Year: 2010
We investigated the diversity and structure of the ectomycorrhizal (EM) fungal community associated with post-fire regenerated Pinus pinaster Ait., and the influence of fire severity and site slope on EM assemblage patterns. Seedlings were sampled in the first autumn and in both spring and autumn of the second growing season after fire, in a total of three samplings. EM percentages per seedling were assessed, morphotypes described, and tentative identification of EM types performed by restriction fragment length polymorphism (RFLP) and sequencing of nrDNA internal transcribed spacer (ITS) region. Seedlings were highly mycorrhizal in all samplings, independently of the factors studied. A total of 45 EM types were identified, and richness and diversity significantly increased from the first to the second autumn after fire. Neither fire severity nor slope had a significant effect on fungal richness and diversity. Overall EM community composition was similar in all samplings, although fire severity, site slope and elapsed time after fire caused evident shifts in presence or in relative frequencies of a number of EM types. No significant effect of fire severity or slope on EM assemblage patterns was detected in the first two samplings after fire. However, a significant effect of fire severity was observed at the end of the second growing season. The harvest of burned wood did not significantly affect EM fungal assemblages although the slope did. We conclude that there was a high potential of active EM inoculum in soil immediately after fire colonizing post-fire natural regenerated P. pinaster seedlings with high EM percentages, and that factors defining burn intensity, such as fire severity and topography, directly influenced the species composition and assemblage patterns of EM fungal communities, triggering replacements and succession of EM fungal species. © 2010 Elsevier B.V.
Soliveres S.,Rey Juan Carlos University |
Soliveres S.,CSIC - Center for Environmental Sciences |
DeSoto L.,University of Valladolid |
Maestre F.T.,Rey Juan Carlos University |
Olano J.M.,University of Valladolid
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2010
Plant-plant interactions are largely influenced by both environmental stress and ontogeny. Despite the effects of each of these factors on the overall outcome of these interactions has received considerable attention during the last years, the joint effects of both factors as drivers of such outcome are poorly understood. We used the combination of spatial pattern analysis, fruit production surveys, carbohydrate assays, sowing experiments and dendrochronological techniques to explore the interaction between Stipa tenacissima (nurse) and Lepidium subulatum (protégée) in two different slope aspects. This battery of techniques allows us to study the effects of the nurse plant during the whole life cycle of the protégée, and to assess the role of spatio-temporal variability in abiotic stress as a modulator of ontogenetic shifts in plant-plant interactions. Spatial pattern analyses suggested a net facilitative effect of S. tenacissima on L. subulatum. This effect was particularly important during the germination, shifting to competition (growth reduction) early after establishment. Competition was gradually reduced as the shrub aged, suggesting niche differentiation. The magnitude of competition was reduced under low rainfall levels in south-facing slopes, whereas this response was observed due to other abiotic factors in north-facing slopes. Our results highlight the crucial effect that positive interactions at early life-stages have to determine the long-term outcome of a given plant-plant interaction, and the existence of multiple shifts between facilitation and competition along different life-stages of the protégée. They also show how these ontogenetic shifts are modulated by abiotic factors, which differ among slope aspects. These findings may help to refine conceptual and theoretical models about shifts between facilitation and ontogeny under current climate change scenarios. © 2010 Rübel Foundation, ETH Zürich.