Assessor científic de l'article “Regreso al futuro”

Claramunt B (2008) Assessor científic de l'article “Regreso al futuro” National Geographic vol. 23 núm. 6.

Classification of hyperspectral images compressed through 3D-JPEG2000

Blanes I., Zabala A., Moré G., Pons X., Serra-Sagristà J. (2008) Classification of hyperspectral images compressed through 3D-JPEG2000. Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). 5179 LNAI: 416-423.
Link
Doi: 10.1007/978-3-540-85567-5-52

Abstract:

Classification of hyperspectral images is paramount to an increasing number of user applications. With the advent of more powerful technology, sensed images demand for larger requirements in computational and memory capabilities, which has led to devise compression techniques to alleviate the transmission and storage necessities. Classification of compressed images is addressed in this paper. Compression takes into account the spectral correlation of hyperspectral images together with more simple approaches. Experiments have been performed on a large hyperspectral CASI image with 72 bands. Both coding and classification results indicate that the performance of 3d-DWT is superior to the other two lossy coding approaches, providing consistent improvements of more than 10 dB for the coding process, and maintaining both the global accuracy and the percentage of classified area for the classification process. © 2008 Springer-Verlag Berlin Heidelberg.

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Production of undersized offspring in a solitary bee

Bosch J. (2008) Production of undersized offspring in a solitary bee. Animal Behaviour. 75: 809-816.
Link
Doi: 10.1016/j.anbehav.2007.06.018

Abstract:

As predicted by Conditional Sex Allocation Theory, females of the solitary bee Osmia cornuta exposed to scarce floral resources biased their progeny sex ratio towards males, the least costly sex, and produced smaller-than-average females. Surprisingly, nesting females also produced a number of 'tiny' offspring, which contrasted with regular-sized offspring within the same nest. Developmental and wintering mortality are strongly size dependent in O. cornuta, and a high proportion of tiny offspring did not survive. This result is in disagreement with Optimal Allocation Theory, according to which resources should be allocated in portions that maximize fitness returns. I ask why did O. cornuta females build tiny provisions and why did they lay female eggs (with lower survival probability than male eggs) on these provisions. I argue that egg maturation rates and selective pressure to avoid kleptoparasitism and provision desiccation in cells left unsealed for long periods may impose a limit to the time available for cell provisioning. Under low food availability, this limit will be reached before provision sizes resulting in maximum fitness returns are attained. I also argue that the decision to fertilize an egg (and thus produce a female) is made at the beginning of the cell-provisioning process, so that females cannot adjust offspring sex to provision size. At the same time, altering the female-male cell sequence within a nest would result in fratricide because of protandric emergence. I provide evidence supporting these ecological and physiological constraints on resource allocation decisions in O. cornuta. © 2007 The Association for the Study of Animal Behaviour.

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Life Cycle Ecophysiology of Osmia Mason Bees Used as Crop Pollinators

Bosch J., Sgolastra F., Kemp W.P. (2008) Life Cycle Ecophysiology of Osmia Mason Bees Used as Crop Pollinators. Bee Pollination in Agricultural Ecosystems. : 0-0.
Link
Doi: 10.1093/acprof:oso/9780195316957.003.0006

Abstract:

Several solitary bee species in the genus Osmia have been studied as potential pollinators of fruit trees and other early-blooming crops. Methods to manage large populations in agro-ecosystems have been developed for at least three species. This chapter reviews current knowledge on the life cycle of Osmia and emphasizes the need to establish a solid ecophysiological basis to develop adequate rearing methods for these species. Two phenological events - the timing of adult diapause in the autumn, and the timing of emergence in the spring - require particular attention when managing Osmia populations. The timing of adult diapause is critical because prewintering temperatures have a profound effect on fat body depletion, winter survival, and vigor at emergence. Timing of emergence and its synchronization with bloom of the target crop is important to maximize pollination and production of bee progeny. Both events can be adjusted with proper temperature management. © 2008 by Oxford University Press, Inc. All rights reserved.

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Development and improvement of broad based sorghum populations with farmers in Burkina Faso [Création et amélioration de populations de sorgho à base large avec les agriculteurs au Burkina Faso]

Brocke K.V., Trouche G., Zongo S., Abdramane B., Barro-Kondombo C.P., Weltzien E., Chantereau J. (2008) Development and improvement of broad based sorghum populations with farmers in Burkina Faso [Création et amélioration de populations de sorgho à base large avec les agriculteurs au Burkina Faso]. Cahiers Agricultures. 17: 146-153.
Link
Doi: 10.1684/agr.2008.0174

Abstract:

This study presents a strategy for sorghum conservation and enhancement by assembling a high number of interesting and important traits within a population by participatory recurrent selection. The specific objective is to present a methodology which respects farmers' needs and preferences in all population development stages. This work includes the choice of crossing parents and the management of populations in farmers' fields. Four populations were developed, each derived from eight to fifteen local varieties and three to four improved sorghum lines. Each population was sown for two to three subsequent generations in the target region. The key elements of this recombination and adaptation phase were farmers' management of the populations in their fields, the identification of male sterile plants during flowering by the farmer, as well as harvest, evaluation (using evaluation sheets) and preference classification of male sterile panicles. The final choice of panicles which form the new population results from the partitioning of roles between the farmers, farmer organisations and breeders.

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Post-dispersal seed predation in Pinus halepensis and consequences on seedling establishment after fire

Broncano M.J., Rodrigo A., Retana J. (2008) Post-dispersal seed predation in Pinus halepensis and consequences on seedling establishment after fire. International Journal of Wildland Fire. 17: 407-414.
Link
Doi: 10.1071/WF07095

Abstract:

In the present study, we analyse the spatiotemporal patterns of seed predation and the consequences of this predation in the establishment of new Pinus halepensis individuals. Rodents were the main predators of P. halepensis seeds in burned areas, while predation by ants was considerably lower. Concerning spatiotemporal patterns of seed predation, the results obtained indicate that, although there were some small differences among distances or among seasons, removal of P. halepensis seeds was consistently very high in all situations, whether close to or far from the unburned margins, in pine or mixed forests, in different sites and in all sampling periods throughout the year. We analysed the role of seed predation on the modulation of post-fire regeneration of P. halepensis. Just after fire, no differences in seedling density were found between plots with or without rodent exclusion, probably owing to the high density of seeds on the ground and the low density of rodents affected by fire. One year after fire, when rodent populations had recovered in burned areas and seeds were much less abundant, the combination of addition of seeds and rodent exclusion led to an increase in pine seedling establishment. © IAWF 2008.

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European BVOC emissions: A model comparison, and future emission trends from European forests. BG0064

Keenan T, Niinemets U, Gracia C, Noe S, Peñuelas J, Sabaté S (2008) European BVOC emissions: A model comparison, and future emission trends from European forests. BG0064 EGU2008-A-04247 BG4.1-1FR3P-0064.

Random sampling, abundance-extinction dynamics and niche-filtering immigration constraints explain the generation of species richness gradients

Carnicer J., Brotons L., Sol D., De Cáceres M. (2008) Random sampling, abundance-extinction dynamics and niche-filtering immigration constraints explain the generation of species richness gradients. Global Ecology and Biogeography. 17: 352-362.
Link
Doi: 10.1111/j.1466-8238.2007.00380.x

Abstract:

Aim: The paradigm that species' patterns of distribution, abundance and coexistence are the result of adaptations of the species to their niches has recently been challenged by evidence that similar patterns may be generated by simple random processes. We argue here that a better understanding of macroecological patterns requires an integration of both ecological and neutral stochastic approaches. We demonstrate the utility of such an integrative approach by testing the sampling hypothesis in a species-energy relationship of forest bird species. Location: A Mediterranean biome in Catalonia, Spain. Methods: To test the sampling hypothesis we designed a metacommunity model that reproduces the stochastic sampling from a regional pool to predict local species richness variation. Four conceptually different sampling procedures were evaluated. Results: We showed that stochastic sampling processes predicted a substantial part (over 40%) of the observed variation in species richness, but left considerable variation unexplained. This remaining variation in species richness may be better understood as the result of alternative ecological processes. First, the sampling model explained more variation in species richness when the probability that a species colonises a new locality was assumed to increase with its niche width, suggesting that ecological differences between species matter when it comes to explaining macroecological patterns. Second, extinction risk was significantly lower for species inhabiting high-energy regions, suggesting that abundance-extinction processes play a significant role in shaping species richness patterns. Main conclusions: We conclude that species-energy relationships may not simply be understood as a result of either ecological or random sampling processes, but more likely as a combination of both. © 2008 The Authors Journal compilation © 2008 Blackwell Publishing Ltd.

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Habitat invasions by alien plants: A quantitative comparison among Mediterranean, subcontinental and oceanic regions of Europe

Chytrý M., Maskell L.C., Pino J., Pyšek P., Vilà M., Font X., Smart S.M. (2008) Habitat invasions by alien plants: A quantitative comparison among Mediterranean, subcontinental and oceanic regions of Europe. Journal of Applied Ecology. 45: 448-458.
Link
Doi: 10.1111/j.1365-2664.2007.01398.x

Abstract:

1. Although invasions by alien plants are major threats to the biodiversity of natural habitats, individual habitats vary considerably in their susceptibility to invasion. Therefore the risk assessment procedures, which are used increasingly by environmental managers to inform effective planning of invasive plant control, require reliable quantitative information on the extent to which different habitats are susceptible to invasion. It is also important to know whether the levels of invasion in different habitats are locally specific or consistent among regions with contrasting climate, flora and history of human impact. 2. We compiled a database of 52 480 vegetation plots from three regions of Europe: Catalonia (Mediterranean-submediterranean region), Czech Republic (subcontinental) and Great Britain (oceanic). We classified plant species into neophytes, archaeophytes and natives, and calculated the proportion of each group in 33 habitats described by the European Nature Information System (EUNIS) classification. 3. Of 545 alien species found in the plots, only eight occurred in all three regions. Despite this large difference in species composition, patterns of habitat invasions were highly consistent between regions. None or few aliens were found in environmentally extreme and nutrient-poor habitats, e.g. mires, heathlands and high-mountain grasslands. Many aliens were found in frequently disturbed habitats with fluctuating nutrient availability, e.g. in man-made habitats. Neophytes were also often found in coastal, littoral and riverine habitats. 4. Neophytes were found commonly in habitats also occupied by archaeophytes. Thus, the number of archaeophytes can be considered as a good predictor of the neophyte invasion risk. However, neophytes had stronger affinity to wet habitats and disturbed woody vegetation while archaeophytes tended to be more common in dry to mesic open habitats. 5. Synthesis and applications. The considerable inter-regional consistency of the habitat invasion patterns suggests that habitats can be used as a good predictor for the invasion risk assessment. This finding opens promising perspectives for the use of spatially explicit information on habitats, including scenarios of future land-use change, to identify the areas of highest risk of invasion. © 2007 The Authors.

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Hundred of the most invasive alien species in Europe, In: DAISIE Handbook

Vilà M, Basnou C, Gollasch S, Josefsson M, Pergl J, Scalera R (2008) Hundred of the most invasive alien species in Europe, In: DAISIE Handbook Springer Dordrecht-Heidelberg ISBN 978-3-540-99500-5

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