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11.
This research examined nitrogen mineralization in the top 10 cm of soils with a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected, with the in situ core incubation method used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total Kjeldahl nitrogen (TKN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 > S2 > S3 > S4 > S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper ground. In the absence of fire for 3 to 6 years, the build-up of SOM and TKN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed. 相似文献
12.
含磷材料钝化修复重金属Pb、Cu、Zn复合污染土壤 总被引:10,自引:1,他引:9
运用2种含P材料即重过磷酸钙磷肥(TSP)和磷灰石矿尾料(PR)钝化修复Pb、Cu和Zn3种重金属并存的复合污染土壤,通过化学提取和土柱淋溶方法评价修复效果并探讨其可能存在的机理。土壤添加P材料4星期后,所有3种P处理(PR、TSP和PR+TSP)均有效地降低了毒性提取态的Pb和Cu,其分别下降了15%~70%和10%~18%;水提取态的Pb和Cu分别下降了16%~43%和46%~58%。添加含P材料对土壤中Zn的稳定化影响较小,甚至TSP处理使水提取态的Zn提高了15%。P处理抑制了Pb和Cu在土壤剖面的径向迁移,但对Zn的影响较小。Pb和Cu的固定可能主要是由于形成了磷酸盐沉淀,而Zn的稳定性可能与表面吸附或络合作用有关。P处理未明显改变土壤pH值,尽管总P有所增加,但未观察到其径向迁移的现象。P处理对于稳定P Pb和Cu很有效,对Zn稳定效果有限,甚至有被活化的可能,在实际应用中应关注这一现象。 相似文献
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从识别有机磷农药的酶及识别机理、酶的固定化技术、酶固定化载体等不同角度,综述了有机磷农药电化学酶传感器的研究概况,并展望了其发展前景。 相似文献
15.
Two experiments were carried out at Pegões (central Portugal) to determine the potential N mineralization in a pulse amended disturbed and undisturbed soil incubated at several temperatures, and to evaluate for 2 years the yield and N2 fixation capacity of sweet lupine (Lupinus albus L. cv. Estoril) inoculated with a mixture of rhizobia strains or nodulated by indigenous soil bacteria and submitted to conventional tillage or no-till practices. A completely randomized block design for soil mobilization with three replicates was used for the laboratory study, and completely randomized blocks for inoculation and tillage treatments with four replicates were used for the lupine yield and N2 fixation experiment. Residue N immobilization occurred immediately after mature residue return to the soil independent of temperature, and was greater at 7 °C especially in the disturbed topsoil. Greater immobilization was also observed by doubling the amount of mature residue incorporated in the soil. This was expected since soil microorganisms would be in direct contact with the fresh organic matter and would be provided with more organic carbon under these circumstances. Nitrogen mineralization proceeded after 5 days of amendment. Potential N mineralization was higher at 25 °C than at 18 or 7 °C, for both conventional and no-till practices. At 25 °C, 42% of buried residue-15N was released over 210 days, at a smaller rate than 18 °C (49%) over 81 days. Lupine yield and N2 fixation capacity were similar in plots that were not inoculated and those receiving the mixture of three rhizobia strains. White lupine had an efficient symbiosis with indigenous soil rhizobia at pod-filling (>99%, >100 kg N ha−1 year−1) which was not affected by tillage. At this stage, plant residue including visible roots and nodules accounted for a soil N input of +96 kg ha−1 year−1 (91% of crop N), showing the large soil N benefit by the crop at this stage. The lupine residue at pod-filling stage can be used as a green manure under the conditions of organic farming systems. The apparent N “harvest” index of the pulse at pod-filling was only 9% though at maturity phase it should result in a higher value and the legume will show a lower fertilizer N value. 相似文献
16.
温室条件下,向盆栽山毛榉幼苗中施加192g.m·^-2^15N示踪物,研究连续两个生长季沉积氮在森林土壤(含森林地被物)、沥出物、以及地上和地下部分生物量的分配。模拟了四种处理(栽培和非栽培)下的NH4^+和NO3^-沉积情况,每种处理各自标记为^15N-NH4^+或者^15N-NO3^-。在整个体系中施加15N的总回收率分别是,盆栽处理的^15N-NH4^+为67.3%~74.9%,非盆栽处理的^15N-NO3^-为85.3%~88.1%。两种^15N示踪物主要沉积在森林土壤(包括森林地被物)中,其中盆栽处理的森里土壤中^15N-NH4^+为34.6%~33.7%,^15N-NO3^-为13.1%~9.0%,说明异养微生物有很强的固氮作用。森林土壤微生物对^15N-NH4^+的固定能力比^15N-NO3^-的固定能力强三倍。^15N-NH4^+的优先异养利用造成土壤中^15N-NH4^+的沉积量是植物体保存量的两倍 而土壤中^15N-NO3^-的沉积量却低于植物体的。总之,植被-土壤系统中15N-NH4+的沉积量比^15N-NO3^-的沉积高了60%,说明了沉积氮的形式在森林生态系统中氮保存中的重要性。 相似文献
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不同条件下固定化菌株在土壤中的释放情况存在差异,本实验测定固定化枯草芽孢杆菌在不同条件下土壤中的释放及其降解特性。通过设定不同温度、水分、pH值测定固定化枯草芽孢杆菌在灭菌土壤中的释放情况,并分别用碱扩散法、碳酸氢钠抽提-钼锑抗比色法、乙酸铵抽提-火焰光度计法测定菌株的固氮、解磷、解钾性能。结果表明:固定化菌株在温度35℃和40℃、水分为50ml/100g、pH5-8时均能大量繁殖释放,固定化后在不同温度和水分条件下不影响其降解特性。该研究结果为固定化菌株在农业复合微生物肥料上的应用提供理论基础。 相似文献
20.
Sven Marhan Franziska Rempt Petra Högy Andreas Fangmeier Ellen Kandeler 《植物养料与土壤学杂志》2010,173(6):861-868
This study was conducted to improve our understanding of how earthworms and microorganisms interact in the decomposition of litter of low quality (high C : N ratio) grown under elevated atmospheric [CO2]. A microcosm approach was used to investigate the influence of endogeic earthworm (Aporrectodea caliginosa Savigny) activity on the decomposition of senescent Charlock mustard (Sinapis arvensis L.) litter produced under ambient and elevated [CO2]. Earthworms and microorganisms were exposed to litter which had changed in quality (C : N ratio) while growing under elevated [CO2]. After 50 d of incubation in microcosms, C mineralization (CO2 production) in the treatment with elevated‐[CO2] litter was significantly lower in comparison to the ambient‐[CO2] litter treatment. The input of Charlock mustard litter into the soil generally induced N immobilization and reduced N2O‐emission rates from soil. Earthworm activity enhanced CO2 production, but there was no relationship to litter quality. Although earthworm biomass was not affected by the lower quality of the elevated‐[CO2] litter, soil microbial biomass (Cmic, Nmic) was significantly decreased. Earthworms reduced Cmic and fungal biomass, the latter only in treatments without litter. Our study clearly showed that A. caliginosa used the litter grown under different [CO2] independent of its quality and that their effect on the litter‐decomposition process was also independent of litter quality. Soil microorganisms were shown to negatively react to small changes in Charlock mustard litter quality; therefore we expect that microbially mediated C and N cycling may change under future atmospheric [CO2]. 相似文献