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101.
102.
Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. 相似文献
103.
104.
Hora RR Ionescu-Hirsh A Simon T Delabie J Robert J Fresneau D Hefetz A 《Die Naturwissenschaften》2008,95(1):55-60
In the ectatommine ant Ectatomma tuberculatum, the visual appearance of queens changes after mating and ovarian development in that their cuticle turns from shiny to matte.
In this study, we have shown that this change seems to be caused by 15-fold accumulation of hydrocarbons, in particular heptacosane
that covers the multiple grooves present on the cuticular surface creating a wax coat in mated fully fertile queens. Analyses
of the scrapped wax revealed that it is composed largely of heptacosane. Peak-by-peak comparison of the cuticular hydrocarbon
(CHC) composition of mated, virgin with developed ovaries and virgin with nondeveloped ovaries revealed significant differences
between the queen groups. Although the total amount of the CHC of virgin queens with developed ovaries was not higher than
virgin queens that did not have developed ovaries, the composition showed a shift toward the mated queen. While it is possible
that the large accumulation of hydrocarbons may give extra physical and chemical protection to queens, we propose that the
switch in the relative abundance of heptacosane and nonacosane and perhaps of other components is indicative of being a mating
and fertility cue. This is the first report in social insects where external chemical changes are accompanied by changes in
visual appearance. 相似文献
105.
Studies of the influence of parasites on host fitness generally conclude that parasites have a strong negative effect on their
hosts. In this study, we have investigated experimentally the role of Polymorphus minutus, an acanthocephalan parasite, on the salinity tolerance of the freshwater amphipod Gammarus roeseli, one of its intermediate hosts. Unexpectedly, P. minutus-infected gammarids were more tolerant to salinity stress than uninfected ones. The mean lethal salt concentrations for 50%
mortality of hosts tested were 17.3 (infected) and 9.7 g/L (uninfected). The parasitic load (one or two parasites per host)
did not affect the result. The size of hosts had no significant influence on the salinity tolerance of either infected or
uninfected gammarids. The mobility of all types of gammarid decreased when the salinity exceeded 9.0 g/L, but there was no
significant difference between infected and uninfected gammarids. We discuss the higher salinity tolerance of infected amphipods
in relation to O2 consumption and osmoregulation. Finally, we demonstrate that the salinity tolerance is enhanced in the parasitized amphipod
but without a significant change in behavior or an osmoregulatory adjustment. 相似文献
106.
Ploton P Pélissier R Proisy C Flavenot T Barbier N Rai SN Couteron P 《Ecological applications》2012,22(3):993-1003
Reducing Emissions from Deforestation and Forest Degradation (REDD) in efforts to combat climate change requires participating countries to periodically assess their forest resources on a national scale. Such a process is particularly challenging in the tropics because of technical difficulties related to large aboveground forest biomass stocks, restricted availability of affordable, appropriate remote-sensing images, and a lack of accurate forest inventory data. In this paper, we apply the Fourier-based FOTO method of canopy texture analysis to Google Earth's very-high-resolution images of the wet evergreen forests in the Western Ghats of India in order to (1) assess the predictive power of the method on aboveground biomass of tropical forests, (2) test the merits of free Google Earth images relative to their native commercial IKONOS counterparts and (3) highlight further research needs for affordable, accurate regional aboveground biomass estimations. We used the FOTO method to ordinate Fourier spectra of 1436 square canopy images (125 x 125 m) with respect to a canopy grain texture gradient (i.e., a combination of size distribution and spatial pattern of tree crowns), benchmarked against virtual canopy scenes simulated from a set of known forest structure parameters and a 3-D light interception model. We then used 15 1-ha ground plots to demonstrate that both texture gradients provided by Google Earth and IKONOS images strongly correlated with field-observed stand structure parameters such as the density of large trees, total basal area, and aboveground biomass estimated from a regional allometric model. Our results highlight the great potential of the FOTO method applied to Google Earth data for biomass retrieval because the texture-biomass relationship is only subject to 15% relative error, on average, and does not show obvious saturation trends at large biomass values. We also provide the first reliable map of tropical forest aboveground biomass predicted from free Google Earth images. 相似文献
107.
Bontemps Christophe Bougherara Douadia Nauges Céline 《Environmental Modeling and Assessment》2021,26(4):609-630
Environmental Modeling & Assessment - Even if there exists an extensive literature on the modeling of farmers’ behavior under risk, actual measurements of the quantitative impact of risk... 相似文献
108.
Daphné Durant Eric Kernéïs Jean-Marc Meynard Jean-Philippe Choisis Claude Chataigner Jean-Michel Hillaireau Christophe Rossignol 《Journal of Coastal Conservation》2018,22(6):1177-1190
Storm Xynthia crossed France’s western coast between 28th February and 1st March 2010. It hit the Vendée and Charente-Maritime departments hardest, as storm surge flooded up to 23,000 ha of coastal agricultural areas (i.e. polders), causing severe damage to farming operations. However, farm-level damage in the aftermath of seawater flooding is an issue that has rarely been explored in the literature. Here we investigated the effects of storm Xynthia on agriculture at the farm scale. We focused on the case study of Saint Laurent de la Prée research farm, a mixed crop–livestock system that was severely hit. All damages were described and economic losses were quantified for the years 2010 and 2011. The results show numerous consequences of the storm in terms of crop and fodder production losses, but also farm infrastructure repairs, crop restoration and animal health problems. Economic damage costs were high, reaching €71,720 in 2010 (€500/ha flooded) and €56,195 (€390/ha) in 2011 for the case study farm. The discussion highlights the farm-level impacts of seawater flooding and the crucial factors that can explain the damage caused to agriculture by storm events in coastal areas. The results are also discussed in the wider context of global warming which is expected to cause sea level rise and more frequent storm events in the future. The vulnerability of coastal agricultural areas to storms thus exposes broader issues of coastal flooding risk management and specifically the allied protection–remediation–adaptation measures. The conclusions underline the need for future research to address prospective scenarios and subsequent adaptive strategies. 相似文献
109.
The establishment of dominance hierarchies through aggressive interactions is very common in insect societies. In many cases,
it is also mediated through pheromone emissions that enable individuals to evaluate the reproductive quality and level of
aggressiveness of the dominant individual, thereby reducing the number and intensity of costly fights. Here, we studied these
processes in the primitively eusocial bee Bombus terrestris, using a paired bee system. Specifically, we investigated the behavioral, reproductive, and pheromonal correlates of dominance
establishment. Workers were shown to establish dominance hierarchies using overt aggression within 3–4 days. Thereafter, the
aggression drastically decreased, and dominance was maintained mostly by ritualized agonistic behavior. The behaviorally dominant
bee lost the ester compounds that workers produce in their Dufour's gland (the so-called “sterility signal”) concomitantly
with the development of her ovaries. The other bee announced as subordinate by continuously producing high amounts of those
esters. The hypothesis that sterility signaling serves as an appeasement signal to pacify the dominant bees is supported by
the negative correlation found between the proportion of these esters and the level of aggression that the subordinate received
from the dominant worker. Physical interactions, and presumably also the ensuing overt aggression between the bees, were essential
for the above pheromonal change to take place and enabled the dominant workers to develop their ovaries and to lay eggs. The
subordinate bee’s signaling of non-reproductive status may minimize energy expenditure in costly fights and help stabilize
the reproductive division of labor among workers. 相似文献
110.
Plant uptake of phosphorus and nitrogen recycled from synthetic source-separated urine 总被引:1,自引:0,他引:1
Christophe Bonvin Bastian Etter Kai M. Udert Emmanuel Frossard Simone Nanzer Federica Tamburini Astrid Oberson 《Ambio》2015,44(2):217-227
Urine contains about 50 % of the phosphorus (P) and about 90 % of the nitrogen (N) excreted by humans and is therefore an interesting substrate for nutrient recovery. Source-separated urine can be used to precipitate struvite or, through a newly developed technology, nitrified urine fertilizer (NUF). In this study, we prepared 33P radioisotope- and stable 15N isotope-labeled synthetic NUF (SNUF) and struvite using synthetic urine and determined P and N uptake by greenhouse-grown ryegrass (Lolium multiflorum var. Gemini) fertilized with these products. The P and N in the urine-based fertilizers were as readily plant-available in a slightly acidic soil as the P and N in reference mineral fertilizers. The ryegrass crop recovered 26 % of P applied with both urine-based fertilizers and 72 and 75 % of N applied as struvite and SNUF, respectively. Thus, NUF and urine-derived struvite are valuable N and P recycling fertilizers. 相似文献