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81.
Soil development with time was investigated on beach ridges with ages ranging from about 1380 to 6240 14C-years BP at the eastern coast of central Patagonia. The main pedogenic processes are accumulation of organic matter and carbonate leaching and accumulation within the upper part of the soils. Soil formation is strongly influenced by incorporation of eolian sediments into the interstitial spaces between the gravel of which the beach ridges are composed. Different amounts of eolian material in the soils lead to differentiation into Leptosols (containing ≤ 10% fine earth in the upper 75 cm) and Regosols (containing > 10% fine earth). Soil depth functions and chronofunctions of organic carbon, calcium carbonate, pH, Ca:Zr, Mg:Zr, K:Zr, Na:Zr, Fe:Zr, Mn:Zr, and Si:Al (obtained from X-ray fluorescence analysis) were evaluated. To establish soil chronofunctions mean values of the horizon data of 0–10 cm below the desert pavement were used, which were weighted according to the horizon thicknesses. The depth function of pH shows a decrease towards the surface, indicating leaching of bases from the upper centimeters. Chronofunctions of pH show that within 6000 radiocarbon years of soil development pH drops from 7.0 to 6.6 in the Leptosols and from 8.1 to 7.5 in the Regosols. The higher pH of the Regosols is due to input of additional bases from the eolian sediments. Chronofunctions of Ca:Zr and K:Zr indicate progressive leaching of Ca and K in the Regosols, showing close relationships to time (R2 = 0.972 and 0.995). Na leaching as indicated by decreasing Na:Zr ratios shows a strong correlation to time only in the Leptosols (R2 = 0.999). Both, Leptosols and Regosols show close relationships to time for Fe:Zr (R2 = 0.817 and 0.824), Mn:Zr (R2 = 0.940 and 0.803), and Si:Al (0.971 and 0.977), indicating enrichment of Fe and Mn and leaching of Si. Leaching of mobile elements takes place on a higher level in the Regosols than in the Leptosols from the beginning of soil formation. Hence, a significant part of the eolian sediments must have been incorporated into the beach ridges very soon after their formation. 相似文献
82.
Two strains of bacteria (Burkholderia sp., strain FeGL01, and Burkholderia caribiensis, strain FeGL03) were isolated from a Brazilian high phosphorus iron ore. The capacity of both strains to solubilize hydroxyapatite, Ca5(PO4)3(OH), was assessed in plate and batch cultures. In batch cultures, the concentration of solution-P showed two kinetics: an initial one, characterized by a continuously increasing kinetics and a second one, characterized by oscillatory kinetics. To understand the nature of these oscillations, phosphatic residues in the spent broth were collected before, during and after the oscillations, and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray chemical microanalyses (EDX) and X-ray diffraction (XRD). From these studies, it was found that drops in P concentration were related to the formation of an intermediate phosphate in the residues, identified as brushite, CaHPO4·2H2O. Later increase of available P in the solution was found to be a consequence of re-dissolution of brushite crystals previously formed. Re-crystallization of brushite was also detected in plate cultures after 12-14 days of incubation 相似文献
83.
V.J. Allison Z. Yermakov R.M. Miller J.D. Jastrow R. Matamala 《Soil biology & biochemistry》2007,39(2):505-516
Simultaneously assessing shifts in microbial community composition along landscape and depth gradients allows us to decouple correlations among environmental variables, thus revealing underlying controls on microbial community composition. We examined how soil microbial community composition changed with depth and along a successional gradient of native prairie restoration. We predicted that carbon would be the primary control on both microbial biomass and community composition, and that deeper, low-carbon soils would be more similar to low-carbon agricultural soils than to high carbon remnant prairie soils. Soil microbial community composition was characterized using phospholipid fatty acid (PLFA) analysis, and explicitly linked to environmental data using structural equations modeling (SEM). We found that total microbial biomass declined strongly with depth, and increased with restoration age, and that changes in microbial biomass were largely attributable to changes in soil C and/or N concentrations, together with both direct and indirect impacts of root biomass and magnesium. Community composition also shifted with depth and age: the relative abundance of sulfate-reducing bacteria increased with both depth and restoration age, while gram-negative bacteria declined with depth and age. In contrast to prediction, deeper, low-C soils were more similar to high-C remnant prairie soils than to low-C agricultural soils, suggesting that carbon is not the primary control on soil microbial community composition. Instead, the effects of depth and restoration age on microbial community composition were mediated via changes in available phosphorus, exchangeable calcium, and soil water, together with a large undetermined effect of depth. Only by examining soil microbial community composition shifts across sites and down the soil column simultaneously were we able to tease apart the impact of these correlates environmental variables. 相似文献
84.
概述了国内外对植物花粉萌发、花粉管生长的生理过程、植物体内的相关Ca2 离子通道和Ca2 泵的分类、信号转导、花粉极性生长的现象、Ca2 离子可能参于花粉萌发和极性生长的模式系统和机理。 相似文献
85.
不同浓度Ca~(2+)对三角帆蚌养殖水体微生物和浮游生物的影响 总被引:1,自引:0,他引:1
研究了不同Ca2+浓度条件下,三角帆蚌养殖水体中的细菌总量、致病性肠道菌和葡萄球菌及藻类的增长情况。研究结果表明:实验水体的细菌总量增长呈现出比较完整的逻辑斯谛增长特性,Ca2+对细菌总量的增长起着调控作用,Ca2+浓度越高,对于细菌的生长抑制就越明显。对于致病性肠道菌,10mg/L组Ca2+浓度有利于增长,20mg/L和30mg/L组在后期具有明显的抑制增长的作用。葡萄球菌在20mg/L的Ca2+浓度下增长最快,30mg/L组则明显抑制葡萄球菌的生长。在10 ̄30mg/L的Ca2+浓度范围内,水体中藻类的增长不受Ca2+浓度控制。 相似文献
86.
锰和钙处理对桃果实贮藏品质的影响 总被引:3,自引:0,他引:3
本试验以北京地区主栽桃品种"八月脆"和"丰白"为试验材料,研究了采前锰、钙和钙加锰处理对两个品种桃在(2±1)℃贮藏温度下贮藏品质的影响。结果表明,钙、锰和钙加锰处理均抑制了桃果实在贮藏过程中硬度、可滴定酸含量、Vc含量的下降,使可溶性固形物维持在一个较高水平,从而保持了果实的良好风味。同时,各处理也促进了贮藏期间桃果实红色的增加,保持了果实亮度,延迟了果实底色变黄时间,从而也提高了果实的外观品质。其中锰处理对果实红色的增加效应显著,而钙处理对可溶性固形物变化无明显影响。 相似文献
87.
[目的]明确钙对盾叶薯蓣产量和皂素含量的影响。[方法]用0、20、40、80、120mg/kg钙分别处理盾叶薯蓣的实生苗,测定盾叶薯蓣产量、皂素含量、叶片叶绿体Ca2+-ATPase的活性和土壤中有效钙含量。[结果]随钙肥用量的升高,盾叶薯蓣产量、皂素含量均呈先上升后下降的趋势。钙肥用量为80mg/kg时,单株平均产量最高,为38.967g/株;有效钙含量最低(10.721mg/100g);叶绿体Ca2+-ATPase活性最高[26.740μmol/(mg.h)]。钙肥用量为40mg/kg时,皂素含量最高,为2.56%。[结论]在一定的范围内,钙肥可明显提高盾叶薯蓣产量和皂素产量。Ca2+通过影响叶绿体Ca2+-ATPase的活性而影响Ca2+吸收,进而影响盾叶薯蓣产量,但是Ca2+-ATPase的活性变化与皂素含量未显示出相关性。 相似文献
88.
89.
硝酸钾和石灰氮打破苹果和葡萄自然休眠的试验研究 总被引:1,自引:0,他引:1
[目的]打破苹果、葡萄的自然休眠。[方法]用浓度为1%、3%、5%、7%和9%的硝酸钾涂抹苹果品种嘎拉的休眠芽,用浓度为2倍液(石灰氮与水的重量比为1∶2,下同)5、倍液和8倍液的石灰氮涂抹葡萄品种巨峰的休眠芽,研究不同浓度的硝酸钾、石灰氮打破果树自然休眠的效果。[结果]2006年试验发现,浓度为5%、7%的硝酸钾打破嘎拉休眠芽的效果最好,平均萌芽率分别为72.00%和69.33%;2007年试验发现,浓度为5%的硝酸钾打破嘎拉休眠芽的效果最好,平均萌芽率为78.33%。2年试验发现,浓度为5倍液的石灰氮打破巨峰休眠芽的效果最好。[结论]浓度为5%和7%的硝酸钾打破苹果自然休眠的效果最好,浓度为5倍液的石灰氮打破葡萄自然休眠的效果最好。 相似文献
90.
活化磷矿粉在砖红壤上的施用效果 总被引:13,自引:2,他引:13
砖红壤酸性强和活性铁、铝含量高,对磷固定强烈,磷肥有效性低.为了提高磷肥利用率,将高分子有机化合物与磷矿粉混合加工制成活化磷矿粉,分别施用于种植甘蔗的新垦砖红壤和种植大白菜的严重侵蚀砖红壤以及种植花生的水旱轮作熟化砖红壤,结果表明:施用活化磷矿粉的肥效至少与过磷酸钙相当,甚至优于过磷酸钙.因此,为了节省生产成本和改良土壤,活化磷矿粉值得在砖红壤区推广应用。 相似文献