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1.
The effect of soil burning on N and P availability and on mineralization and nitrification rates of N in the burned mineral soil was studied by combustion of soils in the laboratory. At a fire temperature of 600°C, there was a complete volatilization of NH4 and a significant increase of pH, from 7.6 in the unburned soil to 11.7 in the burned soil. Under such conditions ammonification and nitrification reactions were inhibited. Less available P was produced immediately after the fire at 600°C, as compared to P amount produced at 250°C. Burning the soils with plants caused a decrease in NH4-N and (NO2+NO3)-N concentrations in the soil as well as a reduction in ammonification and nitrification rates. Combustion of soil with plants contributed additional available P to the burned soil. The existence of a non-burned soil under the burned one played an important role in triggering ammonification and nitrification reactions.  相似文献   
2.
Nitrogen transformations in the soil, and the resulting changes in carbon and nitrogen compounds in soil percolate water, were studied in two stands of Norway spruce (Picea abies L.). Over the last 30 years the stands were repeatedly limed (total 6000 kg ha–1), fertilized with nitrogen (total about 900 kg ha–1), or both treatments together. Both aerobic incubations of soil samples in the laboratory, and intact soil core incubations in the field showed that in control plots ammonification widely predominated over nitrification. In both experiments nitrogen addition increased the formation of mineral-N. In one experiment separate lime and nitrogen treatments increased nitrification, in the other, only lime and nitrogen addition together had this effect. In one experiment immobilization of nitrogen to soil microbial biomass was lower in soil only treated with nitrogen. Soil percolate water was collected by means of lysimeters placed under the humus layer and 10 cm below in the mineral soil. Total N, NH4-N and NO3-N were measured, and dissolved organic nitrogen was fractioned according to molecular weight. NO3-N concentrations in percolate water, collected under the humus layer, were higher in plots treated with N-fertilizer, especially when lime was also added. The treatments had no effect on the N concentrations in mineral soil. A considerable proportion of nitrogen was leached in organic form.  相似文献   
3.
刘美  马志良 《应用生态学报》2021,32(6):2045-2052
本文研究了青藏高原东部窄叶鲜卑花高寒灌丛生长季前期、生长季后期和非生长季3个生育期的土壤氮转化速率对模拟增温的响应,分析全球气候变暖对高寒灌丛土壤氮循环过程的影响。结果表明: 模拟增温使高寒灌丛土壤温度显著升高1.2 ℃,土壤水分显著降低2.5%。高寒灌丛生长季土壤净氮矿化(氨化和硝化)速率显著高于非生长季,但土壤净氮固持速率显著低于非生长季。土壤氮矿化在生长季前期以硝化作用为主,在生长季后期和非生长季以氨化作用为主。模拟增温对高寒灌丛土壤氮转化过程的影响在不同时期存在显著差异。模拟增温显著增加了生长季前期土壤净氨化、净硝化、净氮矿化、净氮固持速率和非生长季土壤净硝化、净氮矿化速率,并显著降低了生长季后期土壤净硝化、净氮矿化、净氮固持速率和非生长季土壤净氨化速率。但模拟增温对高寒灌丛非生长季净氮固持速率和生长季后期净硝化速率的影响不显著。未来气候变暖将显著改变青藏高原东部高寒灌丛土壤氮转化,进而加速高寒灌丛土壤氮循环过程。  相似文献   
4.
不同改良方法对盐碱土壤氮素营养状况的影响   总被引:5,自引:0,他引:5  
采用浅耕翻、施用磷石膏、施用糠醛渣、施用有机肥、建植星星草人工草地或星星草 羊草人工草地等不同改良方法对盐碱土壤氮素营养影响的研究结果表明,不同改良方法与浅耕翻相比能不同程度地提高土壤全氮含量、碱解氮含量、氨化强度、固氮强度、蛋白酶活性、脲酶活性、硝酸还原酶活性和亚硝酸还原酶活性.其中,浅耕 有机肥 星星草 羊草处理对所测定盐碱土壤氮素营养及相关酶活性指标增加明显,同时,盐碱土壤氮素营养各指标间存在着一定的相关关系.  相似文献   
5.
精氨酸氨化方法的干扰因素分析   总被引:2,自引:0,他引:2  
精氨酸氨化方法的干扰因素分析林启美(中国农业大学土壤和水科学系,北京100094)TheInterferingFactorsofArginineAmmonificationMethod.LinQimei(DepartmentofSoilandWate...  相似文献   
6.
Direct groundwater inputs are receiving increasingattention as a potential source of nutrients and otherdissolved constituents to the coastal ocean. Seepageinto St. George Sound, Florida was measuredextensively from 1992 to 1994 using seepage meters. Spatial and temporal variations were documented alonga 7-km stretch of coastline and up to 1 km from shore. Measurements were made at 3 transects perpendicular toshore and 1 transect parallel to shore. The generalresults indicated that seepage decreased with distancefrom shore (2 of 3 transects), and substantialtemporal and spatial variability was observed inseepage flow from nearshore sediments. In addition,trends in mean monthly integrated seepage rates weresimilar to precipitation patterns measured at a nearbycoastal weather station. Based on these measurements, weestimate that the magnitude of groundwater seepage intothe study area is substantial, representing from 0.23 to4.4 m3 sec-1of flow through the sediments, approximately equivalentto a first magnitude spring. Although it is unknown howrepresentative this region is with respect to globalgroundwater discharge, it demonstrates thatgroundwater flow can be as important as riverine andspring discharge in some cases. Our subsurfacedischarge rates suggest groundwater is an importanthydrologic source term for this region and may beimportant to the coastal biogeochemistry as well.  相似文献   
7.
海岸带地区的固氮、氨化、硝化与反硝化特征   总被引:11,自引:2,他引:9  
徐继荣  王友绍  孙松 《生态学报》2004,24(12):2907-2914
海岸带是海洋环境中受人类活动影响最大、生物地球化学循环最为活跃的地区。这一地区氮的生物地球化学循环包括 :生物固氮、有机氮的氨化、氮的硝化、反硝化等 4个主要过程。概括性地介绍了有关这四个过程的发生机制、环境影响因素及研究方法等方面的研究动态、进展、存在的科学问题与今后的研究方向。过去十几年来 ,固氮主要集中在对束毛藻属的研究上 ,其间有两个重要发现 ,一是生物固氮在海洋氮循环中的作用远比人们以前的想象要重要得多 ;二是蓝细菌已经在海洋中存在了 2 0亿年 ,它们有可能调节大气中的 CO2 ,进而影响全球气候。由于有机物的结构千差万别 ,含氮有机物的氨化过程可能是一个简单的矿化反应 ,也有可能是一系列复杂的代谢过程 ,在水解酶的作用下含氮有机物降解为下一级化合物。硝化过程分两步进行 ,氨的硝化为反硝化细菌提供了重要的硝酸盐来源 ,通常采用同位素方法来研究硝化过程。发生在沉积物中的反硝化过程是氮循环的关键步骤 ,反硝化过程一方面减少了海水中初级生产者可利用的氮 ,另一方面产生了终结产物 N2 和 N2 O,而 N2 O是一种温室气体 ,可能影响全球气候变化  相似文献   
8.

Distribution and diversity of nrfA gene encoding dissimilatory nitrite reduction to ammonium (DNRA) in the sediments of the Colne River, North Essex, UK, were investigated. Sequencing cloned nrfA fragments amplified from environmental DNA enabled structure analysis of the bacterial community responsible for this pathway. The DNA was extracted from the sediment samples at different depths from the estuary ranging from freshwater to seawater regions, and amplified using specific PCR primer pairs targeting for the nrfA gene. Analysis of the nrfA clones showed two distinct clusters corresponding to their origins, namely, divided into the stable sites (marine and freshwater regions) and the unstable sites (brackish water region), where the tidal rise and fall constantly disturbs the environmental conditions. In addition, the nrfA clones from the deeper layer of the sediment formed a more homogenous community than those from the surface layer of the sediment. This may be due to more isolated and anaerobic conditions kept in the deeper sediment less influenced by the overlying water and other environmental factors. Most of the nrfA clones from the Colne estuarine sediments formed several distinct clusters including known nitrate ammonifiers such as Aeromonas, Shewanella, Desulfovibrio and Sulfurospillum. One of which was, however, related to Bacteroides but still quite divergent (~70% identity) and the rest forming unknown clusters of supposedly uncultured members of bacteria. This is the first trial to describe the nrfA partial sequences derived from a natural environment, with reference to their habitat-specific community structure.  相似文献   
9.
Abstract Clostridium butyricum strains DSM 552 (ATCC 19398) and ATCC 8260 grow with nitrite and hydroxylamine, but not with nitrate as the sole nitrogen source. Nitrite is largely converted to extracellular ammonium. The nitrite reductases are neither repressed by NH4+ nor induced by NO2, and are located in the cytoplasm. Methyl viologen and ferredoxin, but not NADH, serve as electron donors. No evidence for a nitrate reductase was found in either strain.  相似文献   
10.
Abstract Competition for nitrate between nitrate ammonifying enterobacteria and a denitrifying pseudomonad was studied in electron acceptor-limited chenostats. In pure cultures, using different carbon and energy sources, the C/N-ratio needed for denitrification is far lower than that required for nitrate ammonification. In mixed cultures of Citrobacter freundii and Pseudomonas stutzeri , competing for nitrate with l -lactate as electron donor, the nitrate ammonifying organism dominated at dilution rates of D ≤ 0.14 h−1. Competition for both nitrate and l -lactate at a dilution rate of D = 0.05 h−1 always resulted in the coexistence of both species. Using glucose as additional carbon source, the final ratio of nitrate ammonifying and denitrifying organism depended on the C/N-ratio as well as on the dilution rate. The results of the study are discussed with respect to field data.  相似文献   
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