生物炭对水稻土Olsen-P的影响

生物炭如何影响土壤磷素的有效性目前尚不清楚。本研究以稻草和白杨树枝为原料,采用室内培养方法,研究了300℃、450℃和600℃制备的生物炭在5、15和40g/kg施用量下对水稻土Olsen-P的影响。与树枝炭相比,稻草炭显著提高了水稻土Olsen-P含量;3种温度制备的稻草炭对水稻土Olsen-P的影响不存在显著差异;3种施用量稻草炭均显著提高了水稻土Olsen-P含量。生物炭制备原料和施用量均显著影响土壤磷素的有效性,不同温度制备的生物炭对土壤磷素的有效性影响不显著。     

深圳市抛石填海强夯地基的瑞雷波法检测

介绍了瑞雷波勘探的基本原理和工作方法及瑞雷波勘探在抛石填海强夯地基检测中的实际应用。瑞雷波法能全面、直观和快速地检测强夯地基的加固效果，缩短地基检测周期。     

BP神经网络在不同植被产流产沙分析中的应用

以甘肃省西峰市南小河沟小流域径流场为研究对象，利用BP神经网络对4种植被类型的径流小区（农田、林地、人工草地和天然荒坡）进行了产流产沙量模拟和预测。其模拟产流量的相对误差分别为0．2％～5．7％，0．1％～2．5％，0．7％～2.9％和0．1％～3％；模拟产沙量的相对误差分别为0．1％～3．2％，0．2％～3．1％，0．6％～4．2％和0．2％～2．7％。预测农地、林地、草地和天然荒坡产沙量最大相对误差分别为-11％，14％，-14．6％，18％，产流量最大相对误差分别为10．9％，27．3％，15％，26．3％。结果表明，BP神经网络预测产流产沙的效果较好，对径流小区运用神经网络进行蓄水拦沙指标分析是可行的。     

南通市沙土区几种水土保持工程技术措施

针对沿海平原沙土区土质沙松、土颗粒间凝聚力小 ,河堤边坡水土流失严重的现象 ,研制、开发了一系列的水土保持工程技术 ,在河堤坡岸保护中发挥了重要作用     

RNA沉默—新型的植物病毒病害防治策略

植物RNA沉默(RNAsilencing)是植物本身固有的一种抗病毒防御系统,是对病毒在复制过程中形成双链RNA(dsRNA)的特殊反应。RNA沉默介导的dsRNA干涉病毒侵染转基因抗病毒有其不足,几种体外生产dsRNA的抗病毒体系能弥补这一不足,它们与转基因表达病原RNA不同,但仍然依赖RNA沉默机制来获取病原抗性。综述了近年来发展起来的各种启动RNA沉默的dsRNA产生策略、抗病状况和存在的问题及发展前景     

陇东地区油松人工林碳密度及其影响因素

[目的]分析陇东地区人工林碳密度及其影响因素,为黄土丘陵区生态环境评价提供理论依据。[方法]采用样地调查与生物量实测方法,对陇东地区油松人工林碳密度进行了估算,并分析生态因素对油松人工林生态系统碳密度的影响。[结果]油松林各器官碳含量变化范围为48.58%~53.54%,各器官碳密度按从高到低的大小顺序依次为:树干树枝树根树叶树皮果实;灌木层叶、茎、根的碳含量分别为43.93%,45.62%,42.38%;草本层地上部分和地下部分碳含量为43.04%,39.77%;枯落物层未分解和半分解层碳含量为43.79%,38.83%;植被层碳密度按从高到底的大小顺序为:乔木层草本层灌木层。土壤层(0—100cm)碳含量随着土壤深度的增加而降低,且不同土壤层碳密度存在显著差异,以50—100cm碳密度最高。油松林生态系统平均碳密度为52.86t/hm2,其空间分布排序为土壤层(75.15%)植被层(24.14%)枯落物层(0.71%)。[结论]油松人工林生态因子中,林分平均树高、平均胸径、郁闭度均与各层碳密度呈现极显著正相关性,林分枯落物未分解干质量与各层碳密度呈现显著正相关性。平均树高、平均胸径、郁闭度、枯落物未分解干质量是油松人工林生态系统碳密度的主要生态因子。     

上海郊区河流沉积物N、P释放的初步研究

A laboratory study was conducted to observe the release of nitrogen and phosphorus from the sedimentsunder both anaerobic and aerobic conditions. The samples used were five creek sediments and a fish-pondsediment (as a comparison) obtained from suburban Shanghai. High loads of nitrogen and phosphoruswere found in the creek sediments. Total nitrogen of the sediments ranged from 1.17 to 5.95 g kg^-1; totalphosphorus from 608.63 to 2 033.95 mg kg^-1. Making up more than 90% of the total nitrogen, organicnitrogen was the dominant nitrogen fraction in the sediments; where as inorganic phosphorus was the dominant phosphorus fraction, which made up more than 85 percent of the total phosphorus. Cabound phosphorus fraction dominated inorganic phosphorus, which occupied more than 50% of the total. A large amount of ammonium was released from the sediments under both aerobic and anaerobic conditions, and the anaerobic releases were slightly greater than the aerobic. In addition, ammonium contents in the aerobic waters decreased sharply after reaching the peaks because of strong nitrification, compared with the relatively maintained ammonium peaks in the anaerobic waters. Anaerobic phosphate releases were much greater than the aerobic and the released ortho-phosphate was mainly from Fe-bound phosphorus. Ammonium and ortho-phosphate releases from the sample of the dredged creek were the lowest, showing that creek dredging could effectively remove contaminants from the surface of sediments and weaken the release potentials of nitrogen and phosphorus. Ammonium and ortho-phosphate releases from the fish-pond sediment were greater than those from the creek sediments though its total nitrogen and phosphorus were not the highest, which was probably due to the larger amount of biologically degraded organic matter in the fish-pond sediment.     

增硝营养对水稻不同生育时期生长及氮素吸收同化的影响

The effect of nitrate （NO3^-） on rice （Oryza sativa L.） growth as well as N absorption and assimilation during different growth stages was examined using three typical rice cultivars. Dry weight, yield, N uptake, nitrate reductase activity （NRA） in leaves, and glutamine synthetase activity （GSA） in roots and leaves during their entire growth periods, as well as the kinetic parameters of ammonium （NH4^＋） uptake at the seedling stage, were measured with solution culture experiments. Results indicated that addition of NH4^＋-N and NO3^-N at a ratio of 75：25 （NH4^＋＋NO3^- treatment） when compared with that of NH4^＋-N alone （NH4^＋ treatment） increased the dry weight of ‘Nanguang＇ cultivar by 30% and ‘Yunjing 38＇ cultivar by 31%, and also increased their grain yield by 21% and 17%, respectively. For the four growth stages, the total N accumulation in plants increased by an average of 36% for ‘Nanguang＇ and 31% for ‘Yunjing 38＇, whereas the increasing effect of NO3^- in the ‘4007＇ cultivar was only found at the seedling stage, in the NH4^＋＋NO3^- treatment compared to the NH4^＋ treatment, NRA in the leaves increased by 2.09 folds, and GSA increased by 92% in the roots and 52% in the leaves of the three cultivars. NO3^- supply increased the maximum uptake rate （Vmax） in the ‘Nanguang＇ and ‘Yunjing 38＇ cultivars, reflecting that the NO3^- itself, not the increasing N concentration, increased the uptake rate of NH4^＋ by rice. There was no effect on the apparent Michaelis-Menten constant （Kin） of the three cultivars. Thus, some replacement of NH4^＋ with NO3^-could greatly improve the growth of rice plants, mainly on account of the increased uptake of NH4^＋ promoted by NO3^-, and future studies should focus on the molecular mechanism of the increased uptake of NH4^＋ by NO3^-.     

转基因棉花对土壤生态环境的影响

总结了转基因棉花在生态安全性方面的研究进展,重点介绍了转基因棉花对土壤生态环境的影响,包括：外源基因表达产物在土壤中的富集;外源基因表达产物对土壤生物的影响：外源基因在土壤生态系统中的水平转移。认为目前对转基因棉花的土壤生态学过程的研究较少,尚难以确定转基因棉花对土壤生态环境的影响程度。并由此介绍了Biolog系统和DNA指纹技术在土壤生态安全性研究中的应用。     

液体培养研究不同土壤中硝化活性

A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)2SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered.