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81.
82.
Bonhoeffer et al. (Reports, 26 November 2004, p. 1547) presented evidence for positive epistasis in a clinical data set of HIV-1 mutants and corresponding fitness values. We demonstrate that biases in the original and simulated data sets may lead to erroneous evidence for epistasis. More rigorous statistical tests must be used to account for such biases before one can infer epistasis. 相似文献
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84.
Latorre R Arencibia A Gil F Rivero M Henry RW Ramírez G Váquez JM 《American journal of veterinary research》2006,67(5):756-761
OBJECTIVE: To correlate anatomic features of the equine tarsus identified in plastinated sections with images obtained via magnetic resonance imaging (MRI). ANIMALS: 4 horses. PROCEDURE: MRI (1.5-Tesla magnet) of the tarsus was performed on the pelvic limbs of 4 clinically normal horses following euthanasia. After imaging, tarsocrural joint spaces and vasculature were injected with colored latex. Sagittal and transverse sections of the tarsi were plastinated to facilitate interpretation of MR images. RESULTS: Relevant anatomic structures were identified and labeled on the plastinated tissue slices and corresponding MR images. Results indicated high correlations between MRI findings and those of plastinated sections. CONCLUSIONS AND CLINICAL RELEVANCE: The data obtained provided certain reference standards for normal anatomic structure sizes and positions in the equine tarsus. This information may aid future physiologic or clinical studies of this joint. 相似文献
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86.
V. Ramón Vallejo Athanasios Smanis Esteban Chirino David Fuentes Alejandro Valdecantos Alberto Vilagrosa 《New Forests》2012,43(5-6):561-579
Reforestation efforts in dryland ecosystems frequently encounter drought and limited soil productivity, although both factors usually interact synergistically to worsen water stress for outplanted seedlings. Land degradation in drylands (e.g. desertification) usually reduces soil productivity and, especially, soil water availability. In dry sub-humid regions, forest fires constitute a major disturbance affecting ecosystem dynamics and reforestation planning. Climate change projections indicate an increase of drought and more severe fire regime in many dryland regions of the world. In this context, the main target of plantation technology development is to overcome transplant shock and likely adverse periods, and in drylands this is mostly related to water limitations. In this paper, we discuss some selected steps that we consider critical for improving success in outplanting woody plants, both under current and projected climate change conditions including: (1) Plant species selection, (2) Improved nursery techniques, and (3) Improved planting techniques. The number of plant species used in reforestation is increasing rapidly, moving from a reduced set of well-known, easy-to-grow, widely used species, to a large variety of promising native species. Available technologies allow for reintroducing native plants and recovering critical ecosystem functions for many degraded drylands. However, climate change projections introduce large uncertainties about the sustainability of current reforestation practices. To cope with these uncertainties, adaptive restoration approaches are suggested, on the basis of improved plant quality, improved techniques for optimizing rain use efficiency in plantations, and exploring native plant species, including provenances and genotypes, for their resilience to fire and water use efficiency. 相似文献
87.
Plant biomass, species diversity and net primary productivity are presented for herb layer of banj oak (Quercus leucotrichophora A. Camus)-chir pine (Pinus roxburghii Sarg.) mixed forest in Kumaun, central Himalaya, India. The species diversity declined from a maximum (3.56) in September to a minimum (2.11) in December. The monthly live shoots biomass exhibited a single peak growth pattern with highest live shoot biomass of 185 g·m-2 in August. The seasonal pattern showed that the maximum above-ground production (131 g·m-2) occurred during the rainy season and the minimum (1 g·m-2) during winter season. The below-ground production was maximum during winter season (84 g·m-2) and minimum during summer season (34 g·m-2). The annual net shoot production was 171 g·m-2 and total below-ground production was 165 g·m-2. Of the total input 61% was channeled to above-ground parts and 39% to below-ground parts. Transfer of live shoots to dead shoots compartments and that of dead shoots to litter compartments was 61% and 66%, respectively. The total dry matter disappearance was 61% of the total input within annual cycle. The herb layer showed a net accumulation of organic matter, indicating the seral nature of the community. 相似文献
88.
Ana Vasques Paula Maia Mariana Pedro Concei??o Santos V. Ramón Vallejo J. Jacob Keizer 《Annals of Forest Science》2012,69(4):499-507
? Context
Maritime Pine forests cover important mountain areas in Portugal and are known to be a particularly fire-prone forest type. Understory composition plays an important role in maintaining biodiversity and ecosystem services after recurrent wildfires.? Aims
This study aims to improve the knowledge on the germination ecology of understory species of Maritime Pine forests, focusing on the importance of seed provenance, including in relation to germination enhancement by heating.? Methods
The selected species were Cistus ladanifer L., Erica australis L., Erica umbellata L., Pterospartum tridentatum L. (Willk), and Genista triacanthos Brot. Seeds were collected from two or three distant populations. Besides a control treatment, two heating regimes were applied, i.e., 100°C during 5?min and 80°C during 30?min.? Results
Heating treatments significantly enhanced germination in four out of the five species. Differences between provenances were most evident for C. ladanifer and E. australis, especially following the heating treatments. Overall, the seeds from the southern provenances germinated better and, at the same time, were smaller.? Conclusion
The present results confirmed that seed provenance should not be ignored as a key factor in germination ecology, so that further work is needed to untangle the roles of environmental and genetic factors in the observed differences between provenances. 相似文献89.
José Ramón Arévalo Guacimara González-Delgado Beatriz Mora José María Fernández-Palacios 《Journal of Forest Research》2012,17(2):184-192
The laurel forest of Anaga is the most emblematic community of the Canarian Archipelago. Restoration programs are being developed
to increase laurel forest area on the island of Tenerife. Structural and spatial characteristics determine many aspects of
the community, including regeneration patterns, disturbance level, stand history. In spite of the importance of this information
for restoration, few quantitative studies have been conducted on laurel forest dynamics. We analyzed two stands of the Anaga
laurel forest of different aspect. The main difference between the two sites was the wind exposure, one leeward and the other
windward. Regeneration, spatial distribution of regeneration, tree species composition, asexual regeneration and environmental
parameters were analyzed in three 50 × 50 m plots at each site. Both sites differ in important aspects such as species richness,
species composition, asexual regeneration and dead tree composition, while they are not different in basal area, density,
density of regeneration and density of dead trees. Both sites have had similar management in the last century. Asexual regeneration
is able to maintain the present species composition, while sexual regeneration is able to offer future changes in the canopy
composition. Regeneration strategies and the effect of some environmental characteristics should be considered in restoration
programs. 相似文献
90.
Teresa Valor Míriam Piqué Bernat C. López José Ramón González-Olabarria 《Annals of Forest Science》2013,70(5):503-513