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T. Morán-López R. Poyatos P. Llorens S. Sabaté 《European Journal of Forest Research》2014,133(2):369-382
Drought-induced decline is affecting Pinus sylvestris populations in southern Europe, with very little impact on the more drought-tolerant Quercus pubescens. Although multiple studies have investigated interspecific differences in water use and growth strategies, the link between these two processes and how they vary within drought-exposed populations remains poorly understood. Here, we analysed tree ring and sap flow data from P. sylvestris and Q. pubescens stands in the Pyrenees in order to (1) evaluate differences in climate–growth responses among species, (2) disentangle the role of past growth trends and water use strategies in individual trees drought sensitivity and (3) assess whether such intraspecific patterns vary between species. Both species have suffered recent climatic constraints related to increased aridity. However, the effects of past growth trends and current water use traits on drought sensitivity varied among them. Initially, fast-growing ‘drought-sensitive’ pines displayed a higher gas exchange potential but were more sensitive to evaporative demand and soil moisture. They also showed lower water use efficiency for growth (WUEBAI) and current growth decline. In contrast, initially, slow-growing ‘drought-tolerant’ pines showed the opposite water use traits and currently maintain the highest growth rates. In comparison, neither current WUEBAI nor recent growth trends varied across Q. pubescens climate–growth groups. Nonetheless, ‘drought-sensitive’ oaks showed the lowest gas exchange potential and the highest growth rates under milder conditions. Our results show a strong effect of past growth trends and current water use strategies on tree resilience to increased aridity, which is more evident in P. sylvestris. 相似文献
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Noblin X Rojas NO Westbrook J Llorens C Argentina M Dumais J 《Science (New York, N.Y.)》2012,335(6074):1322
Various plants and fungi have evolved ingenious devices to disperse their spores. One such mechanism is the cavitation-triggered catapult of fern sporangia. The spherical sporangia enclosing the spores are equipped with a row of 12 to 13 specialized cells, the annulus. When dehydrating, these cells induce a dramatic change of curvature in the sporangium, which is released abruptly after the cavitation of the annulus cells. The entire ejection process is reminiscent of human-made catapults with one notable exception: The sporangia lack the crossbar that arrests the catapult arm in its returning motion. We show that much of the sophistication and efficiency of the ejection mechanism lies in the two very different time scales associated with the annulus closure. 相似文献
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The physiological responses to water deficits of Scots pine (Pinus sylvestris L.) and pubescent oak (Quercus pubescens Willd.) were studied under Mediterranean mountain climate. Minimum leaf water potentials were ?3.2 MPa for oak and ?2.1 MPa for pine, with higher predawn values for pubescent oak. Relative sap flow declined in both species when vapour pressure deficit (D) went above ca. 1.2 kPa, but stomatal control was stronger for pine during the 2003 summer drought. P. sylvestris plant hydraulic conductance on a half-total leaf area basis (k L,s?1) was 1.2–2.6 times higher than the values shown by Q. pubescens, and it showed a considerably steeper decrease during summer. Leaf-level gas exchange was positively related to k L,s?1 in both species. Scots pine was more vulnerable to xylem embolism and closed stomata to prevent substantial conductivity losses. The results of this study confirm that pubescent oak is more resistant to extreme drought events. 相似文献
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Radial variation in sap flux density across the sapwood was assessed by the heat field deformation method in several trees of Quercus pubescens Wild., a ring-porous species. Sapwood depths were delimited by identifying the point of zero flow in radial patterns of sap flow, yielding tree sapwood areas that were 1.5-2 times larger than assumed based on visual examinations of wood cores. The patterns of sap flow varied both among trees and diurnally. Rates of sap flow were higher close to the cambium, although there was a significant contribution from the inner sapwood, which was greater (up to 60% of total flow) during the early morning and late in the day. Accordingly, the normalized difference between outer and inner sapwood flow was stable during the middle of the day, but showed a general decline in the afternoon. The distribution of sap flux density across the sapwood allowed us to derive correction coefficients for single-point heat dissipation sap flow measurements. We used daytime-averaged coefficients that depended on the particular shape of the radial profile and ranged between 0.45 and 1.28. Stand transpiration calculated using the new method of estimating sapwood areas and the radial correction coefficients was similar to (Year 2003), or about 25% higher than (Year 2004), previous uncorrected values, and was 20-30% of reference evapotranspiration. We demonstrated how inaccuracies in determining sapwood depths and mean sap flux density across the sapwood of ring-porous species could affect tree and stand transpiration estimates. 相似文献
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F. San Roman DVM PHD M. P. Llorens MD PHD M. T. Peña DVM F. A. Garcia DVM PHD D. Prandi DVM 《Veterinary radiology & ultrasound》1990,31(5):235-238
This study describes a method of using a conventional x-ray device and film-positioning system for dental radiography in dogs. This system is economical, safe and results in high quality dental radiographs. 相似文献
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Silvia Martínez‐Llorens Ana Tomás Vidal Miguel Jover Cerdá 《Aquaculture Research》2012,43(11):1697-1709
The economic profitability of fish meal replacement by soybean meal and pea‐rice concentrate mixture, was analysed considering the economic conversion ratio (ECR) and the economic profit index (EPIst) as a proposal for evaluating the economic profitability in diets for sea bream. The optimal fish meal levels for minimizing the ECR were 33% (when soybean meal was included) and 14% (in the case of pea‐rice concentrate mixture) and for maximizing the EPIst, optimal fish meal levels were 31% and 28.8%, respectively, considering the current market price of fish meal and vegetal ingredients. The EPIst, seems to be a better index than the ECR to estimate diet profitability, because it considers weight increment, feed conversion ratio, diet cost and fish sale price. A sensibility analysis was conducted, considering variations in the price of fish meal and vegetal ingredients. Finally, several multiple regressions were developed for estimating the optimal level of fish meal with each vegetable ingredient and the expected value of the economic profit as a function of the market price of both fish meal and plant protein. When fish meal prices increase, the highest beneficial level of the inclusion fish meal and the highest economic profit would be achieved with pea‐rice mixture. 相似文献
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J. Velazco‐Vargas A. Tomás‐Vidal M. Hamdan F.J. Moyano López M. Jover Cerda S. Martínez‐Llorens 《Aquaculture Nutrition》2014,20(5):520-531
This study investigates the effect of digestible protein levels in experimental diets for meagre (Argyrosomus regius). A group of 253 fish, 52 g of mean weight, was distributed in 12 tanks, three replicates per treatment. Four isolipidic diets (170 g kg?1 crude lipid) with different digestible protein levels (350 g kg?1, 430 g kg?1, 490 g kg?1 and 530 g kg?1) were formulated using commercial ingredients. The trial lasted 62 days. Meagre fed diets 430, 490 and 530 g kg?1 obtained higher TGC (2.47, 2.57, 2.69 × 10?3, respectively) than fish fed diet 350 g kg?1 (2.14 × 10?3). Group of fish fed diet with 350 g kg?1 DP showed the lowest ammonia excretion level. According to the in vitro digestibility trial diets with 350 and 430 g kg?1 DP released less amino acids in comparison with diet with 49% DP, although in vivo digestibility test did not show significant differences among diets 430, 490 and 530 g kg?1 DP. Using the quadratic regression, optimal digestible protein intake according to the ECR for rearing juvenile meagre was recorded in 0.8 g DP/100 g fish and day. 相似文献
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Vibrio vulnificus biotype 2 is subdivided into two main serovars, serovar E, able to infect fish and humans, and serovar A, only virulent for fish. Serovar E emerged in 1976 as the causative agent of a haemorrhagic septicaemia (warm‐water vibriosis) affecting eels cultured in brackish water. Serovar A emerged in 2000 in freshwater‐cultured eels vaccinated against serovar E, causing warm‐water vibriosis with fish showing a haemorrhagic intestine as the main differential sign. The aim of the present work was to compare the disease caused by both serovars in terms of transmission routes, portals of entry and host range. Results of bath, patch‐contact and oral‐anal challenges demonstrated that both serovars spread through water and infect healthy eels, serovar A entering mainly by the anus and serovar E by the gills. The course of the disease under laboratory conditions was similar for both serovars in terms of transmission and dependence of degree of virulence on water parameters (temperature and salinity). However, the decrease in degree of virulence in fresh water was significantly greater in serovar E than in serovar A. Finally, both serovars proved pathogenic for tilapia, sea bass and rainbow trout, but not for sea bream, with significant differences in degree of virulence only in rainbow trout. In conclusion, serovar A seems to represent a new antigenic form of V. vulnificus biotype 2 with an unusual portal of entry and is better adapted to fresh water than serovar E. 相似文献