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71.
Marney E. Isaac Jean-Michel HarmandDidier Lesueur Joseph Lelon 《Forest Ecology and Management》2011,261(3):582-588
Acacia senegal, an important leguminous tree in arid and semi-arid environments, has shown promise as a multipurpose species, including gum production and soil fertility improvement, linked with N2-fixation capabilities. Of particular interest are ontogenetic and edaphic effects on A. senegal performance in natural populations. Our research objectives were to investigate the effect of tree age and site phosphorus conditions on (1) tree N2-fixation and (2) soil N and C dynamics in natural stands of A. senegal var. senegal, Baringo District, in the Rift Valley, Kenya. Sites consisted of A. senegal saplings (9 months) and mature A. senegal trees (7 years) along an edaphic gradient of soil P availability. A single-tree neighborhood approach was employed using a two by two factorial design: site conditions [high and low soil P contents] and tree age class [juvenile and mature]. Soil (N and C pools and fluxes) and plant metrics were quantified. A soil transfer experiment was also employed to confirm age and site effects on soil N mineralization. On the high soil P site, A. senegal had significantly lower foliar (15N levels than neighboring non-leguminous species (Balanites aegyptiaca), while foliar δ15N values in A. senegal on the low P site exhibited no significant difference with our reference plant, B. aegyptiaca. Across P sites, B. aegyptiaca had similar foliar δ15N values. These results indicate that the rate of N2-fixation of A. senegal trees, as determined with foliar 15N natural abundance methodology, increased with increasing soil P availability in these natural populations. However, N2-fixation rates declined with age. Although soil texture and soil CO2 efflux did not differ between sites or across ages, soils under mature A. senegal at the high P site exhibited significantly greater total N content and total C content in comparison to soils at the low P site and under juvenile plants. Furthermore, under mature A. senegal trees, soil N mineralization rates were significantly greater as compared to under saplings. Soil transplants confirmed that soil microbial activity may be stimulated under mature trees as N mineralization rates were 2-3 fold greater compared to under A. senegal saplings. Our findings suggest that tree age and soil P availability are important factors in the nitrogen budget of natural populations of A. senegal, determining N2-fixation rates, and potentially influencing soil total N and C pools and soil mineral N. This study provides information regarding the adaptation of A. senegal under differing edaphic conditions thus increasing accuracy of management support for A. senegal populations as productive agroforests. 相似文献
72.
A digital photographic method is presented which is able to reconstruct the profile of the stem on standing trees up to a height of 12 m and to provide a fine level of detail. The method uses two digital photographs taken at 90° to each other and does not require special illumination conditions. A method is proposed to perform the data acquisition process from the two photographs and to transform the stem dimensions and 3-D position from pixels to units of length. The accuracy of this method for measuring tree shape was tested by comparing the results with those obtained from a laser system. The comparison showed that the photographic method provides a good assessment of standing tree shape. 相似文献
73.
Thomas Giordanengo Jean-Paul Charpentier Jean-Michel Roger Sylvie Roussel Loïc Brancheriau Gilles Chaix Henri Baillères 《Annals of Forest Science》2008,65(8):803-803
74.
Perrine Tabarant Cécile Villenave Jean-Michel Risède Jean Roger-Estrade Marc Dorel 《Biology and Fertility of Soils》2011,47(3):341-347
Nematodes are major pests for crops, including banana. Environmentally friendly methods for managing plant-parasitic nematodes
have to be developed, such as organic material application. Our study focuses on the impacts of several organic amendments
on banana plants, considering mainly their effect on soil nitrogen supply and soil microbial biomass, and the consequences
on plant-parasitic nematode impacts on the plants. A microcosm experiment for 13 weeks was conducted to evaluate four organic
materials: sugarcane bagasse, sugarcane sludge, plant residues, and sewage sludge, compared to a control without organic amendment.
Input of organic materials led to an important change on nitrogen resource, and plants grew better when the N availability
was the highest, but better growth conditions did not necessarily reduce parasitic nematodes impacts on the roots. Damage
on the roots depended on plant-parasitic nematode abundance. Three of four tested amendments exhibited a regulator effect
on plant-parasitic nematode populations (bagasse, sugarcane sludge, and plant residues). Root growth was not the explanatory
factor for this regulation. Only sugarcane sludge led to an overall positive effect on the plant, increasing its growth and
reducing its parasitism pressure. The other organic materials exhibited an antagonism between the promoted plant growth and
the reduced nematode populations. 相似文献
75.
Holger Wernsd?rfer Antoine Colin Jean-Daniel Bontemps Hélène Chevalier Gér?me Pignard Sylvain Caurla Jean-Michel Leban Jean-Christophe Hervé Meriem Fournier 《Annals of Forest Science》2012,69(7):829-844
? Context
Forest resource projections are required as part of an appropriate framework for sustainable forest management. Suitable large-scale projection models are usually based on national forest inventory (NFI) data. However, sound projections are difficult to make for heterogeneous resources as they vary greatly with respect to the factors that are assumed to drive forest dynamics on a large spatial scale, e.g. geographically varying growth conditions (here represented by NFI regions), tree species composition (here broadleaf-dominated, conifer-dominated and broadleaf-conifer mixed stands) and stand structure (here high forest, coppice forest and high-coppice forest mixture).? Question and objective
Our question was how does the variance of forest dynamics parameters (i.e. growth, felling and mortality, and recruitment processes) and that of 20-year forest resource projections partition between these factors (NFI region, tree species composition and stand structure), including their interactions. Our objective was to capitalise on the suitability of an existing multi-strata, diameter class matrix model for the purposes of making projections for the highly heterogeneous French forest resource.? Methods
The model was newly calibrated for the entire territory of metropolitan France based on most recent NFI data, i.e. for years 2006?C2008. The forest resource was divided into strata by crossing the factors NFI region, tree species composition and stand structure. The variance partitioning of the parameters and projections was assessed based on a model sensitivity analysis.? Results
Growth, felling and mortality varied mainly with NFI region and species composition. Recruitment varied mainly with NFI region and stand structure. All three factors caused variations in resource projections, but with unequal intensities. Factor impacts included first order and interaction effects.? Conclusions
We found, by considering both first order and interaction effects, that NFI region, species composition and stand structure are ecologically relevant factors that jointly drive the dynamics of a heterogeneous forest resource. Their impacts, in our study, varied depending on the forest dynamics process under consideration. Recruitment would appear to have a particularly great impact on resource changes over time. 相似文献76.
Vandeweerd JM Kirschvink N Clegg P Vandenput S Gustin P Saegerman C 《Veterinary journal (London, England : 1997)》2012,191(1):28-34
Evidence-based medicine (EBM) refers to the conscientious, explicit and judicious use of current best evidence from research for the care of an individual patient. The concept of EBM was first described in human medicine in the early 1990s and was introduced to veterinary medicine 10 years later. However, it is not clear that the EBM approach promulgated in human medicine can be applied to the same extent to veterinary medicine. EBM has the potential to help veterinarians to make more informed decisions, but obstacles to the implementation of EBM include a lack of high quality patient-centred research, the need for basic understanding of clinical epidemiology by veterinarians, the absence of adequate searching techniques and accessibility to scientific data bases and the inadequacy of EBM tools that can be applied to the busy daily practise of veterinarians. This review describes the development of EBM in the veterinary profession, identifies its advantages and disadvantages and discusses whether and how veterinary surgeons should further adopt the EBM approach of human medicine. 相似文献
77.
Alexandra Jullien Jean-Michel Allirand Amlie Mathieu Bruno Andrieu Bertrand Ney 《Field Crops Research》2009,114(2):188-197
Leaf mass per area (LMA) is a parameter the variability of which contributes to architectural plasticity. However its variations according to environment remain not completely understood. We hypothesise that LMA variations of winter oilseed rape (WOSR) follow an ontogenetic trajectory that can be modified by the environment. This was assessed at plant and leaf levels comparing four genotypes field-grown under different environmental conditions characterised by year and nitrogen nutrition. Leaves of the main stem of plants sampled between emergence and harvest were surfaced, oven-dried and weighed to calculate LMA of each individual leaf. At the plant level, LMA presented a common ontogenetic trajectory, which increases from seedling emergence to bolting and from then on decreases. Variations in LMA were related to the variations in plant demand, LMA decreased when demand increased. The trajectory was modified by low N nutrition that increased LMA but differently according to year and genotype, reflecting the plant plasticity. At the leaf level, variations for each individual leaf were related to the variations at the plant level. Plant plasticity and genotypic variability of the responses of LMA to N deficiency seemed to be related to differences in biomass allocation between leaves and stems. 相似文献
78.
Pierre Roudier Bruno Tisseyre Hervé Poilvé Jean-Michel Roger 《Precision Agriculture》2008,9(5):233-250
Site-specific management (SSM) is a common way to manage within-field variability. This concept divides fields into site-specific
management zones (SSMZ) according to one or several soil or crop characteristics. This paper proposes an original methodology
for SSMZ delineation which is able to manage different kinds of crop and/or soil images using a powerful segmentation tool:
the watershed algorithm. This image analysis algorithm was adapted to the specific constraints of precision agriculture. The
algorithm was tested on high-resolution bio-physical images of a set of fields in France. 相似文献
79.
80.
Among the sources of lignocellulosic biomass that could be considered as a feedstock for a biorefinery, hemp (Cannabis sativa) is known for the quality and relative abundance of its fibre. In this work, two variations of the Feedstock Impregnation Rapid and Sequential Steam Treatment (FIRSST) process are compared for the production of both fibres and biomolecules (including liquid fuels) as the valorization of the entire carbon content of biomass is needed to reach economical viability. In the first variation, the fibres were isolated via two specific and sequential steam treatments while in the second variation, fibres were isolated using only one steam treatment. Both processes allowed the isolation of a fibre that was comparable to kraft pulp while reducing the amounts of ashes along the process. Compositions of the residual solid fibre at different steps of the treatment were evaluated using ASTM and TAPPI standard methods. Carbohydrates were identified and quantified using HPLC with an anion exchange stationary phase. The qualities of the FIRSST and Kraft pulp produced were compared using standard ATPPC methods. Both pulps showed similar indexes. The two-steps FIRSST process has leaded to direct isolation of cellulose, hemicelluloses and lignin that could be suitable for the production of energy (biofuels) and high value chemicals, with small investments in terms of chemicals and energy. 相似文献