Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought   总被引：1，自引：0，他引：1  

David TS  Henriques MO  Kurz-Besson C  Nunes J  Valente F  Vaz M  Pereira JS  Siegwolf R  Chaves MM  Gazarini LC  David JS 《Tree physiology》2007,27(6):793-803

In the Mediterranean evergreen oak woodlands of southern Portugal, the main tree species are Quercus ilex ssp. rotundifolia Lam. (holm oak) and Quercus suber L. (cork oak). We studied a savannah-type woodland where these species coexist, with the aim of better understanding the mechanisms of tree adaptation to seasonal drought. In both species, seasonal variations in transpiration and predawn leaf water potential showed a maximum in spring followed by a decline through the rainless summer and a recovery with autumn rainfall. Although the observed decrease in predawn leaf water potential in summer indicates soil water depletion, trees maintained transpiration rates above 0.7 mm day(-1) during the summer drought. By that time, more than 70% of the transpired water was being taken from groundwater sources. The daily fluctuations in soil water content suggest that some root uptake of groundwater was mediated through the upper soil layers by hydraulic lift. During the dry season, Q. ilex maintained higher predawn leaf water potentials, canopy conductances and transpiration rates than Q. suber. The higher water status of Q. ilex was likely associated with their deeper root systems compared with Q. suber. Whole-tree hydraulic conductance and minimum midday leaf water potential were lower in Q. ilex, indicating that Q. ilex was more tolerant to drought than Q. suber. Overall, Q. ilex seemed to have more effective drought avoidance and drought tolerance mechanisms than Q. suber.  相似文献   

Wheat and barley cultivars show plant traits acclimation and increase grain yield under simulated shade in Mediterranean conditions     

M. Guadalupe Arenas‐Corraliza  M. Lourdes Lpez‐Díaz  Víctor Rolo  Gerardo Moreno 《Journal of Agronomy and Crop Science》2021,207(1):100-119

Agroforestry systems are reported as climate‐resilient productive systems, but it is yet unclear how tree shade affects crops performance. The aim of this work was to assess how the phenology, plant traits and grain yield of wheat and barley were affected by shade. In an open greenhouse experiment, we cultivated in pots nine cultivars differing in precocity for each species and imposed three artificial shading levels (S0 ~ 0%, S1 ~ 25%, S2 ~ 50%) at the start of cereal booting. Our results showed that shade speeded up first growth stages in both species, until the starting of milk development. Barley showed consistent phenological responses to the three irradiance levels among cultivars, but not wheat that showed larger phenological differences among cultivars at moderate shade. Deep shade prolonged the time needed for wheat grain ripening. Both species increased grain yield by 15%–20% with shade, driven by shade‐acclimations of plant traits that differed among species. For wheat, grain yield was determined by the assemblage of traits that contribute to yield, such as grain weight, precocity and non‐photochemical quenching, while, for barley, SPAD value, precocity to reach phenological stages, grains per spike and plant height had the strongest influence. These traits varied widely among cultivars and seem of interest to identify best suited cultivars for shading conditions of Mediterranean agroforestry systems.  相似文献   

Carbon storage in the different compartments of two systems of shrubs of the southwestern Iberian Peninsula     

J. C. Alías  M. García  T. Sosa  C. Valares  N. Chaves 《Agroforestry Systems》2015,89(4):575-585

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Mammal population losses and the extinction crisis   总被引：1，自引：0，他引：1  

Ceballos G  Ehrlich PR 《Science (New York, N.Y.)》2002,296(5569):904-907

The disappearance of populations is a prelude to species extinction. No geographically explicit estimates have been made of current population losses of major indicator taxa. Here we compare historic and present distributions of 173 declining mammal species from six continents. These species have collectively lost over 50% of their historic range area, mostly where human activities are intensive. This implies a serious loss of ecosystem services and goods. It also signals a substantial threat to species diversity.  相似文献   

Coastal ecosystem-based management with nonlinear ecological functions and values   总被引：4，自引：0，他引：4  

Barbier EB  Koch EW  Silliman BR  Hacker SD  Wolanski E  Primavera J  Granek EF  Polasky S  Aswani S  Cramer LA  Stoms DM  Kennedy CJ  Bael D  Kappel CV  Perillo GM  Reed DJ 《Science (New York, N.Y.)》2008,319(5861):321-323

A common assumption is that ecosystem services respond linearly to changes in habitat size. This assumption leads frequently to an "all or none" choice of either preserving coastal habitats or converting them to human use. However, our survey of wave attenuation data from field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes reveals that these relationships are rarely linear. By incorporating nonlinear wave attenuation in estimating coastal protection values of mangroves in Thailand, we show that the optimal land use option may instead be the integration of development and conservation consistent with ecosystem-based management goals. This result suggests that reconciling competing demands on coastal habitats should not always result in stark preservation-versus-conversion choices.  相似文献   

Furuncular myiasis caused by Dermatobia hominis in five cats and efficacy of topical fluralaner for its treatment     

Diefrey Ribeiro Campos  Rayane Christine Pereira de Assis  Jéssica Karoline de Oliveira Chaves  Gabriela Pereira Salça de Almeida  Emily Andressa Santos Lima  Juliana de Moraes Intrieri  Fabio Barbour Scott 《Veterinary dermatology》2021,32(5):438-e117

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Sustainability of regulated deficit irrigation in a mid-maturing peach cultivar     

Jordi Marsal  Jaume Casadesus  Gerardo Lopez  Merce Mata  Joaquim Bellvert  Joan Girona 《Irrigation Science》2016,34(3):201-208

The level of irrigation restriction to apply in a deficit irrigation (DI) programme for sustainable peach (‘Baby gold 6’) production was investigated. The experiment involved four irrigation treatments over five consecutive seasons (2007–2011). They were full irrigation (control), reducing irrigation by 20 % during the first half of stage III (DI-80 %), withholding irrigation until reaching a light stress level (DI-L) and withholding irrigation until reaching a moderate stress level (DI-M). The withholding of irrigation in both DI-L and DI-M was applied only during stage II and postharvest periods and was based on midday stem water potential thresholds (Ψ _stem). For the DI-L treatment ?1.5 MPa was used in both periods, and for DI-M ?1.8 and ?2.0 MPa were used during stage II and postharvest, respectively. Average Ψ _stem values during DI periods were approximately ?1.4 and ?1.2 MPa for DI-M and DI-L, respectively. The pre-defined thresholds required to trigger irrigation were rarely reached. No significant differences between treatments were found in terms of yield in any experimental year. However, DI-M and to a lesser extent DI-L had lower final fruit fresh mass at harvest related to lower Ψ _stem after three consecutive years of the experiment (during 2010 and 2011). Therefore, in terms of fruit size, DI was not sustainable. Rather than lowering Ψ _stem thresholds, we recommend discontinuing DI after 3-year application.  相似文献   

Characterization of under-utilized fruits by molecular markers. A case study of loquat     

María L. Badenes  Teresa Canyamás  Carlos Romero  Jose Martínez-Calvo  Edgardo Giordani  Gerardo Llácer 《Genetic Resources and Crop Evolution》2004,51(3):335-341

The usefulness of RAPD markers for genotyping a minor fruit species such as loquat has been tested in order to assess their ability for identifying accessions and to provide a set of markers suitable for use by different groups of scientists and curators. Twenty-nine polymorphic markers selected from a previous study of 33 accessions were tested in 46 new accessions added to the collection. Using the same PCR standard conditions, only 20 markers out of 29 selected in the previous study gave consistent amplifications in the new set of plant material. The rest required optimization of reaction conditions. This fact pointed out that RAPD markers were sensitive to the experimental conditions, hence a standard technique did not guarantee reproducibility. To overcome this problem markers for plant fingerprinting should be selected after comparison across accession sets. Only those markers reproducible with different sampling and checked in several sets of accessions are suitable for germplasm fingerprinting. In the present study we propose 31 RAPDs for fingerprinting loquat that accomplished these characteristics.The markers obtained were sufficient for determining origin and relationships of cultivars, for identifying synonyms and derived varieties from bud-sports. All bud sports were identical for all RAPDs selected.  相似文献   

Response of Tribolium castaneum (Coleoptera, Tenebrionidae) to Salpichroa origanifolia Withanolides.   总被引：1，自引：0，他引：1  

Graciela Mareggiani  María I Picollo  Adriana S Veleiro  María C Tettamanzi  Miriam O V Benedetti-Doctorovich  Gerardo Burton  Eduardo Zerba 《Journal of agricultural and food chemistry》2002,50(1):104-107

Biological effects on Tribolium castaneum larvae were evaluated for three withanolides isolated from Salpichroa origanifolia (Solanaceae), (20S,22R,24S,25S,26R)-5alpha,6alpha:22,26:24,25-triepoxy-26-hydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide A, 1), (20S,22R,24S,25S,26R)-22,26:24,25-diepoxy-5alpha,6beta,26-trihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide C, 2), and (20S,22R,24S,25S,26R)-5alpha,6alpha:22,26:24,25-triepoxy-15,26-dihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide G, 3), and for several chemically modified analogues. The compounds were incorporated into the larval diet at concentrations of 500 and 2000 ppm. Salpichrolide C (2) produced a significant delay in the development of neonate larvae to adults at the highest concentration (2000 ppm); development delays and lethal effects were produced by salpichrolides A (1) and G (3) at both concentrations assayed. The size of surviving adults was used as a criterion for assessing feedant deterrent effects; the results suggest that these compounds act as feeding inhibitors. Influence of chemical modifications in development delay was analyzed.  相似文献   

The amphibian chytrid fungus along an altitudinal transect before the first reported declines in Costa Rica     

Robert Puschendorf  Federico Bolaños  Gerardo Chaves 《Biological conservation》2006,132(1):136-142

Amphibian populations have declined and disappeared in protected and apparently undisturbed areas around the world, especially in montane areas of the tropics. The amphibian chytrid fungus, Batrachochytrium dendrobatidis has been implicated in many of these declines. In Costa Rica most declines occurred in the highlands. We examined an amphibian collection made in Braulio Carrillo National Park in 1986 for the amphibian chytrid fungus B. dendrobatidis, prior to the well documented amphibian declines in Monteverde, along an altitudinal transect from 100 to 2600 m elev. Skin from the pelvic patch of 202 specimens corresponding to 30 species was examined histologically to determine whether the disease was present in the highlands of the park before amphibian populations declined. For comparison, in 2002 we collected and examined 18 specimens of seven species of Eleutherodactylus and Craugastor from two other lowland Caribbean sites. The chytrid fungus was present in almost all altitudes in 1986, including lower areas. The pathogen was also found in both species that later declined and in species that did not do so. We detected chytrid fungus on amphibians collected at almost all altitudes in 1986, including those sampled at 280 m. B. dendrobatidis was abundant in frogs collected in the 2002 survey, and seems to be endemic in most of Costa Rica. More retrospective museum surveys are needed in order to determine whether it can be found in the area before 1986.  相似文献