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Soil acidification can be detrimental to root growth and nutrient uptake, and liming may alleviate such acidification. In
the following study, seedlings of sessile oak (Quercus petraea Liebl. M.) were grown in rhizotrons and subjected to liming
(L) or gypsum (G) treatments and compared with the control (C). In order to study and interpret the impact of these calcium
rich treatments on fine root development and tree growth, the following parameters were assessed: fine root biomass, fine
root length, seedling development (height, diameter, leaves), seedling biomass, nutrient content of roots and seedlings, bulk
soil and soil solution chemistry and rhizosphere soil chemistry. The results show that liming increased bulk soil pH, exchangeable
Mg, Ca and the Ca/Al molar ratio, and decreased exchangeable Al, mainly in the A-horizon. Gypsum had a similar but smaller
impact on exchangeable Al, Ca, H+ and the Ca/Al molar ratio in the A-horizon, but reacted with depth, so that exchangeable Mn, Mg and Ca were increased in
the B-horizon. In the rhizosphere, the general pattern was determined by the treatment effects of the bulk soil. Most elements
were more concentrated in the rhizosphere than in bulk soil, except for Ca which was less concentrated after liming or gypsum
application. In the B-horizon rhizosphere pH was increased by the treatments (L > G,C) close to the root tips. Furthermore,
the length of the zone with a positive root-induced pH increase was greater for the limed roots as compared with both the
other treatments. Fine root growth was stimulated by liming (L > G,C) both in terms of biomass and length, whereas specific
root length was not obviously affected apart from the indication of some stimulation after liming at the beginning. The live:dead
ratio of fine roots was significantly higher in the limed rhizotrons as compared to the control (G not assessed), indicating
lower mortality (higher longevity). Shoot growth showed greater lime-induced stimulation (L > G,C) as compared to root growth.
As a result the shoot:root ratio was higher in the limed rhizotrons than in the control (L > G,C). Liming induced a higher
allocation of P, S, Mg, Ca and K to the leaves, stem and twigs. Gypsum showed similar effects, but was only significant for
S. Liming increased the foliar Ca/Al ratio by both increasing foliar Ca and decreasing foliar Al, whereas gypsum did not clearly
improve foliar nutrition. This study suggests that a moderate application of lime can be successful in stimulating seedling
growth, but that gypsum had no effect on seedling growth. It can be concluded that this lime-induced growth stimulation is
directly related to the improved soil fertility status, and the alleviation of Al toxicity and acid stress, resulting in better
foliar nutrition. The impact of liming on fine roots, as a consequence, was not limited to a stimulation of the total amount
of fine roots, but also improved the root uptake performance.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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A. Marmier H. Spohr D. J. Cooke S. Kerisit J. P. Brodholt P. B. Wilson 《Molecular simulation》2013,39(5):385-389
The high-throughput Condor environment now allows many simulations to be performed on related systems, whether the focus is on improving the statistics or on broadening the range of conditions under which these simulations run. We illustrate the scope of the approach by using equilibrium molecular dynamics (EMD) to calculate self-diffusivities of argon atoms diffusing through single wall carbon nanotubes (SWNT). The diameters of the tubes and their helicities were varied and different argon loadings were studied. We also considered the effect of the rigidity/flexibility of the tube on the diffusivity. We found that the helicity and flexibility of the tubes have almost no noticeable influences. The size of the pore had a small effect, but the diffusivity depended essentially on the fluid loading. 相似文献
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