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81.
近年来,国内出现了不少基于城市老街区改造为商业街区的项目。通过对佛山岭南天地项目中有代表性的广场、街道、建筑等节点进行调研,选取开放空间的3个特色要素——空间形态和尺度,传统装饰元素,植物和水景布置,探析"新天地"模式中开放空间营造的特色手法,包括保持街巷形态和宜人尺度,增强街区公共属性;保护传统建筑构件,利用传统材料、技术;保留古树,并结合植物和水景布置,形成多层次的景观系统等。 相似文献
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Dense planting and less basal nitrogen (N) fertilization have been recommended to further increase rice (Oryza sativa L.) grain yield and N use efficiency (NUE), respectively. The objective of this study was to evaluate the integrative impacts of dense planting with reduced basal N application (DR) on rice yield, NUE and greenhouse gas (GHG) emissions. Field experiments with one conventional sparse planting (CK) and four treatments of dense planting (increased seedlings per hill) with less basal N application were conducted in northeast China from 2012 to 2013. In addition, a two-factor experiment was conducted to isolate the effect of planting density and basal N rate on CH4 emission in 2013. Our results show that an increase in planting density by about 50% with a correspondingly reduction in basal N rate by about 30% (DR1 and DR2) enhanced NUE by 14.3–50.6% and rice grain yield by 0.5–7.4% over CK. Meanwhile, DR1 and DR2 reduced GWP by 6.4–12.6% and yield-scaled GWP by 7.0–17.0% over CK. According to the two-factor experiment, soil CH4 production and oxidation and CH4 emission were not affected by planting density. However, reduced basal N rate decreased CH4 emission due to it significantly reduced soil CH4 production with a smaller reduction in soil CH4 oxidation. The above results indicate that moderate dense planting with less basal N application might be an environment friendly mode for rice cropping for high yield and NUE with less GHG emissions. 相似文献
85.
花生在生产过程中产生大量副产物,其营养价值较高,是重要的饲料加工原料。文章主要针对花生生产过程中副产物营养价值及在畜牧生产中的利用进行综述。 相似文献
86.
[目的]比较分析制备胃膜素的2种方法,优化制备方法,为工业化规模生产提供试验依据。[方法]以猪胃黏膜为材料,采用单产工艺和联产工艺提取胃膜素,比较分析2种制备方法所得胃膜素的性状、得率、总氮含量和还原性物质含量的差异。[结果]2种方法提取的胃膜素在黏度、酸度、干燥失重和炽灼残渣等方面差异不大,总氮含量和还原性物质含量也无明显差异,均符合国家标准。单产工艺胃膜素得率较高,平均达3.5%,联产工艺得率偏低,仅有1.7%,但联产工艺可以得到副产品胃蛋白酶。[结论]单产工艺的得率高于联产工艺,联产工艺可以同时得到副产品。 相似文献
87.
Ragweed (Ambrosia artemisiifolia L.) is a noxious plant that not only is a troublesome agronomic weed that causes economic damage to agricultural crops but also − and even more importantly − causes severe health problems due to its severe allergenicity. The pollen of invasive ragweed has become a major allergenic risk factor in urban areas in newly occupied regions. Many urban areas prohibit herbicide application; thus, mowing is the most widely used control measure. Counting pollen is labour intensive; therefore, pollen production data are mainly based on estimations. Field experiments were conducted to determine the effects of different mowing scenarios, plant density and cutting height on the biomass, pollen production and seed production of common ragweed plants. Ragweed plants were mown twice: just before the flowering of terminal racemes (BBCH 59) and when the flowers of the re-sprouting lateral shoots reached BBCH 59. A 1- to 3-cm cutting height produced the greatest pollen reduction compared to that of intact control plants (94%) based on a season-long pollen collection. The number of female flowers also significantly decreased (97%). Compared to the control, the onset of pollen discharge was delayed by 5 weeks and the length of the pollen discharge period decreased from 9 to 4 weeks. The season-long unique and reproducible pollen production data can be integrated with airborne pollen modelling and population management strategies. 相似文献
88.
NO emissions from soils and ecosystems are of outstanding importance for atmospheric chemistry. Here we review the current knowledge on processes involved in the formation and consumption of NO in soils, the importance of NO for the physiological functioning of different organisms, and for inter- and intra-species signaling and competition, e.g. in the rooting zone between microbes and plants. We also show that prokaryotes and eukaryotes are able to produce NO by multiple pathways and that unspecific enzymo-oxidative mechanisms of NO production are likely to occur in soils. Nitric oxide production in soils is not only linked to NO production by nitrifying and denitrifying microorganisms, but also linked to extracellular enzymes from a wide range of microorganisms.Further investigations are needed to clarify molecular mechanisms of NO production and consumption, its controlling factors, and the significance of NO as a regulator for microbial, animal and plant processes. Such process understanding is required to elucidate the importance of soils as sources (and sinks) for atmospheric NO. 相似文献
89.
利用浙江省67个县市的农业经济截面数据,以环境负荷量为因变量,以肉产量和耕地面积为自变量构建模型,对家畜养殖生产的环境效应进行研究。结果表明,2013年绍兴市区、衢州市区、龙游县和江山县的环境负荷量超过警戒值,金华市区、德清县和淳安县的环境负荷量超过适宜值;家畜养殖生产存在着环境负效应,并受到耕地资源的约束,其环境负荷量与肉产量正相关,与耕地面积负相关。 相似文献
90.
旨在维护国家稳定,为预判粮食生产前景、提高粮食生产效率、保障粮食安全提供理论依据。利用湖南省统计数据,运用灰色关联分析法筛选关联性较强的影响因素,并建立GM(1,N)预测模型预测粮食产量。2008—2017年与湖南省粮食产量关联度最大的影响因素是粮食作物播种面积和农业机械总动力;科技因素是影响2008—2017年湖南省粮食产量的主要因素,其次是自然因素,社会因素;2018—2027年湖南省粮食产量有较小波动,且农业机械总动力和财政农业支出影响较大;农业机械总动力在前后十年对粮食产量都有较重要的影响,越来越占据主导地位。粮食产量受国家政策的影响,受农业机械总动力影响最大,维持产量水平需高度重视农业机械化水平,稳步提高粮食作物播种面积。 相似文献