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991.
992.
Context
Eco-environmental effects of urbanization are a focus in landscape ecology.Objective
The influences of population, economic and spatial development during the urbanization process in Beijing City, China on net primary productivity (NPP) were analyzed. The responding mechanism of NPP in different urbanization stages was also examined to develop advice about eco-environmental sustainability of urban development.Methods
Using the Carnegie Ames Stanford Approach model, we estimated NPP. Using linear regression and polynomial regression analysis, we analyzed NPP responses to stages of urbanization.Results
High NPP areas were located in northeast Yanqing, northwest Miyun, northern Huairou and Pinggu. The distribution of NPP generally occurred in the following order from high NPP to low NPP: outer suburbs, inner suburbs, encircled city center, and inner city. Because of the heat island effect in winter, the estimated NPP in the encircled city center and inner city was higher in 2009 than in 2001. There was a negative correlation between NPP and both economic and spatial urbanization, but an increase in population did not necessarily lead to an immediate decrease in NPP. An analysis of NPP dynamics in five kinds of urban development zones showed that urbanization resulted in a lasting and observable loss of NPP over time and space, although there was some promotion of NPP in highly urbanized zones.Conclusion
There are three stages in the response of NPP to urbanization: damage stage, antagonistic stage, and coordination stage. The stage threshold depends on local eco-environmental management and urban planning interventions.993.
【目的】研究棉花合理的化肥减施量和有机肥替代量,筛选化肥减施与有机肥替代最佳模式,为新疆南部棉区棉花化肥减施增效技术提供理论依据。【方法】采用田间试验,以不施肥和无机复混肥为对照,分析化肥有机替代比例(20%、40%、100%)对棉花产量构成的影响。【结果】施肥可改善棉花产量构成,提高棉花产量。与无机肥处理(CF)比较,化肥减量20%下施用400 kg有机肥、化肥减量40%下施用800方有机肥处理,通过提高棉花单铃重和衣分,改善棉花产量构成,显著提高棉花产量。处理3、处理4处理棉花产量分别为423.50和403.76 kg/667m 2,比空白处理(CK)增产27.70%、21.75%,比CF处理增产5.81%、0.88%。【结论】新疆南部棉区棉花种植以化肥减量20%、化肥减量40%,即每667 m2基施有机肥400 kg,无机复混肥65.39 kg,追施尿素22.35 kg(每667 m2基肥施用有机肥800 kg,无机复混肥49.04 kg,追肥尿素16.76 kg)较为适宜。处理3、处理4模式(20%、40%的化肥减量)可以推广应用。 相似文献
994.
为充分利用西藏油菜地方种质资源,对收集到的52份油菜种质资源的12个主要农艺性状进行了遗传多样性分析、主成分分析和聚类分析。结果表明,52份油菜种质资源具有丰富的遗传多样性,12个农艺性状中单株产量的变异系数最高,为76%;主成分分析将12个农艺性状归为4个主成分,累计贡献率为74.989%;聚类分析将52份供试材料划分为3个类群,第Ⅰ类群包含31份材料,第Ⅱ类群包含14份材料,第Ⅲ类群包含7份材料。 相似文献
995.
沼泽小叶桦嫩枝扦插试验 总被引:3,自引:1,他引:3
沼泽小叶桦属于嫩枝扦插难生根树种,采用ABT生根粉可有效促进其生根。研究表明,ABT生根粉浓度与浸泡时间的最佳组合为ABT生根粉50mg/L,浸泡15min,沼泽小叶桦生根率达到51%。浓度与浸泡时间有一定的互补作用,即高浓度、短时间与低浓度、较长时间2种组合处理有相似的促根作用。 相似文献
996.
改良剂对铅锌尾矿砂重金属形态的影响 总被引:4,自引:0,他引:4
采用改良剂(有机肥、泥炭、土壤)与铅锌尾矿砂混合的试验方法,通过改进BCR法连续提取As、Zn、Pb、Cu的化学形态,评价改良剂对尾矿砂中As、Zn、Pb和Cu的移动性和生物有效性的影响,降低铅锌尾矿砂的重金属污染风险.结果表明,尾矿砂中As、Zn、Pb和Cu总量高,分别为255.44、9 445.67、1 296.02和61.93 mg/kg,重金属主要以残渣态>可氧化态>可还原态>弱酸提取态的形式存在.改良剂与铅锌尾矿砂混合后,As、Zn、Pb、Cu的总量、弱酸提取态所占比例得到降低,其中有机肥和泥炭能显著提升重金属的可氧化态所占比例,使重金属稳定性得到增加,达到降低重金属危害的目的. 相似文献
997.
AIM: To investigate the influence of Streptococcus pneumoniae on the apoptosis of alveolar epithelial cell and the modulation of caspases-3 on apoptosis. METHODS: A study was undertaken to determine whether Streptococcus pneumoniae infection induced the apoptosis of A549 and facilitated the expression of pro-inflammative cytokine. After inhibited by siRNA, the expression of caspase-3 and apoptosis grade in A549 were determined. RESULTS: Streptococcus pneumoniae contributed to alveolar epithelial cell apoptosis in a time-dependent manner. Streptococcus pneumoniae facilitated the expression of caspase-3 and IL-6 in A549, while depressed IL-10 concentration in culture medium. SiRNA directly decreased the expression of caspase-3 to rescue A549 from apoptosis but not affected IL-6 and IL-10 concentration. CONCLUSION: caspase-3 gene silencing rescues epithelial cells from apoptosis initiated by Streptococcus pneumoniae infection. 相似文献
998.
CHEN Ning HUANG Di LI Zhuo-ran SHENG Dan ZHAO Juan YE Jing LIU Xin PEI Ai-ping 《园艺学报》2010,26(12):2493-2496
AIM: To establish an animal model of acute renal failure (ARF) according to the clinical manifestations by reducing renal blood flow.METHODS: Renal ischemia in rabbits was induced by the ligation of bilateral renal arteries incompletely for 20 min and then the ligation was released. Before and after incomplete ligation of bilateral renal arteries, and after resuming renal blood flow, the urine volume, serum creatinine, electrolytes and blood gas analysis in the experimental animals were determined. One kidney of each rabbit was harvested at different stages for pathological examination.RESULTS: After reducing renal blood flow, the urine volume of the rabbit decreased (P<0.05) and the serum levels of creatinine increased significantly (P<0.01). At the same time, the level of serum K+ appeared an elevated trend. pH and HCO-3 in the arterial blood decreased, and the negative value of BE increased markedly, indicating that metabolic acidosis developed. After resuming the kidney perfusion, the urine volume of the rabbits increased to normal, the level of serum creatinine also decreased to normal as the renal reflow recovery for 1 h, but metabolic acidosis remained continuously. The level of serum K+ decreased for a while and elevated again. No obvious pathological changes of the kidney were observed under microscope at the stage of ischemia for 20 min, reflow for 1 h and 5 h.CONCLUSION: Incomplete ligation of bilateral renal arteries develops multiple clinical manifestations and characteristics of functional ARF. This animal model of ARF is helpful for relevant purposes of teaching and research. 相似文献
999.
为研究醋糟作为粗纤维饲料在生长獭兔饲粮中的适宜添加比例,选择90日龄健康的生长獭兔180只,随机分成6组,分别饲喂6种不同比例醋糟替代谷草与小米壳(对照组、7%、14%、21%、28%和35%)的饲粮。结果表明:35%组有提高试验兔生产性能的趋势,其次是21%组;各组间屠宰率无显著差异。粗蛋白消化率以对照组最高,极显著高于5个试验组;酸性洗涤纤维、中性洗涤纤维及木质素的消化率均以21%组最高。不同醋糟比例的试验饲粮对试验兔皮张面积、腹部被毛密度、臀部绒毛长度及枪毛比例无显著影响,臀部绒毛密度以7%组最小,其他组间差异不显著。因此在獭兔日粮中添加21%的醋糟效果最好。 相似文献
1000.