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991.
以温州生态园的规划建设实践为例,以国外类似建设经验为参照,阐述了我国城市生态公园建设的一般原则和方法,探讨了城市生态公园规划的基本思路和规划理念,并且对我国城市生态公园规划建设中的相关问题提出了解决策略。 相似文献
992.
[目的]对上海市地面沉降进行验证与预测,为地下工程建设和地下水开采格局的科学调整提供参考。[方法]基于地下水抽灌量、地面沉降和土层分层变形等长期监测数据,研究地面沉降量与地下水开采量、土层分层变形量之间的相关性,并结合上海市地面沉降特性及原因,建立考虑地下水开采量和第4含水层变形量的地面沉降多项式分布滞后模型(PDL模型)。[结果]①上海市累计地下水开采量、第4含水层累计变形量与累计地面沉降量之间均具有高度的正相关性,但由于砂土蠕变、弱透水层释水缓慢等原因,地面沉降相对于地下水开采量和第4含水层变形都有着一定的滞后性;②采用考虑滞后效应的多项式分布滞后模型预测地面沉降,其计算结果相对误差较小、拟合效果较好;③若以当前采灌格局及第4含水层变形量作为参考进行预测,地面沉降在2019—2024年间将会发生稳定的轻微回弹现象。[结论]上海市地面沉降与地下水开采量和土层变形量之间有着较高的相关性,且控制地下水开采能够有效缓解地面沉降的发展。 相似文献
993.
施氮水平对小麦子粒蛋白质组分和加工品质的影响 总被引:13,自引:3,他引:13
选用两个优质小麦品种烟农15号和济麦19号,研究了施氮水平对小麦子粒蛋白质组分和加工品质的影响。田间试验设4个施氮水平,即N.0、120、240和360.kg/hm2。结果表明,施用氮肥对子粒发育前期清蛋白和球蛋白含量有明显的提高效应,但随子粒灌浆充实,这种效应逐渐削弱,到成熟期,施氮处理虽能提高子粒清蛋白和球蛋白的含量,但不同施氮水平间无明显差异。施用氮肥还能显著地提高子粒醇溶蛋白和麦谷蛋白的含量,尤其是子粒麦谷蛋白的含量,使子粒麦谷蛋白/醇溶蛋白比值提高。试验还表明,施用氮肥能明显提高子粒湿面筋含量,延长面团形成时间、面团稳定时间和断裂时间。综合分析看出,子粒醇溶蛋白和麦谷蛋白的含量以及麦谷蛋白/醇溶蛋白比值是影响小麦加工品质的重要因素,可以作为小麦品质育种中亲本及后代材料的选择、评价和优质栽培技术评价的依据。 相似文献
994.
Qiangqiang Rong Jingtao Liu Yanpeng Cai Zhaohua Lu Zhenzhen Zhao Wencong Yue Jiangbao Xia 《Journal of Soils and Sediments》2016,16(3):864-877
Purpose
As a useful comprehensive index for reflecting nutrient cycling in soils, nitrogen (N) and phosphorus (P) stoichiometry is subject to influences of many external environmental and biological factors. Studies on such influences were limited, and the influential mechanism remains unclear. The purpose of this research is to investigate soil N and P stoichiometric variations and analyze “fertile island” effects of Tamarix chinensis Lour. (T. chinensis) in the coastal wetland of Laizhou Bay in China.Materials and methods
Soil samples beneath clusters and communities of T. chinensis were collected respectively in July 2012. Amounts of ammonium, nitrate, and available phosphorus in the soil samples were measured through the corresponding standard methods for material measuring.Results and discussion
In general, there were significant vertical variations in soil N and P stoichiometry beneath clusters and communities of T. chinensis. A downtrend was observed for N and P contents with the increase in soil depth. On the contrary, the N/P ratio revealed a trend of going up first and then dropping off along with the increase of the soil depth. Comparatively, the horizontal variations in the soil N and P stoichiometry beneath a single cluster of T. chinensis were greater in the topsoil than those in the subsoil. The N and P contents gradually decreased from the canopy center to the outside. On the contrary, an opposite trend was found for the N/P ratio. For the horizontal variations beneath T. chinensis communities, there were no significant differences for either N and P contents or N/P ratios.Conclusions
Similar to the ecosystems in arid and semi-arid areas, vegetations in many semi-humid areas could also form fertile islands and exert significant influences on the soil nutrient cycle. The formation of fertile islands beneath a single cluster of T. chinensis could have significant influence on soil N and P stoichiometry. Under the influence of fertile islands beneath T. chinensis, the limiting element of the biogeochemical processes in the coastal wetland of Laizhou Bay might change from N to P. However, the influences of fertile island effects on soil N and P stoichiometry beneath T. chinensis communities were relatively small, illustrating that the influences of fertile island effects was not significant at the community level. Thus, the impacts of environmental factors on soil N and P stoichiometry might be greater than that of the fertile island effects in the wetland on a larger scale.995.
996.
Sang S Zou M Xia Z Lao A Chen Z Ho CT 《Journal of agricultural and food chemistry》2001,49(10):4780-4783
Three new spirostanol saponins have been isolated from the seeds of Allium tuberosum. On the basis of acid hydrolysis and comprehensive spectroscopic analysis, their structures were established as tuberoside J, (25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside; tuberoside K, (25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside; and tuberoside L, 27-O-beta-D-glucopyranosyl-(25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-D-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside. 相似文献
997.
Completion of the agronomic evaluations of Medicago ruthenica [(L.) Ledebour] germplasm collected in Inner Mongolia 总被引:3,自引:0,他引:3
Because Medicago ruthenica [(L.) Ledebour] is a potential new forage legume, we collected 90 accessions in Inner Mongolia in 1991. The 40 accessions evaluated in this study (E2) trace to 13 collection sites ranging from 40° 40 (N) × 111° 15 (E) to 42° 55 (N) × 122° 20 (E) and to altitudes ranging from 175 to 1493 m. Nineteen of these accessions were collected from new or under-represented sites in generally milder and drier climates (temperate desert steppes), compared to the 50 accessions evaluated earlier (E1). All accessions were evaluated at Beltsville, MD (USA) on a B and K deficient Iuka sandy loam (coarse-loamy, siliceous, acid, thermic, Aquic Udigluvent; pH 6.4) in two-year studies. Significant variation was noted in E1 and E2 for dry matter yield, growth habit, leaf shape, and plant height and width. Upright growth habit and leaf narrowness, and procumbency and yield were positively correlated in both evaluations, but no particular leaf shape or growth habit was correlated with tolerance to winter conditions. In E2, leaf:stem ratios of four M. ruthenica accessions and a cultivated alfalfa (M. sativa L.) check were not significantly different, but M. ruthenica was significantly more tolerant of potato leafhopper (Empoasca fabae Harris) feeding than was M. sativa. Second-year alfalfa dry matter yield was about five times larger than that of M. ruthenica. Many of the highest yielding accessions were collected near cultivated fields and/or buildings. Although data for both evaluations demonstrated the same basic trends, there were sufficient deviations to emphasize the value of evaluating the entire germplasm collection. 相似文献
998.
999.
本文研究了用氨气敏电极-标准加入法测定土壤脲酶活性的新方法。该法使样品液和标准溶液均处于同一条件下测定,消除了土壤中基体对测定的影响,提高了方法的准确性。方法简便、快速,结果可靠,应用于不同土壤样品中脲酶活性的测定,相对标准偏差为1.78%-3.94%,回收率在98.3%-101.8%之间。 相似文献
1000.