西南山地丘陵区农村居民点用地适宜性评价与分区优化

农村居民点是中国农村人口的主要聚居形式。以西南山区丘陵区的重庆市丰都县兴义镇为例,运用ArcGIS空间分析、数理统计、SPSS聚类分析等多种研究方法,构建了农村居民点用地布局影响评价体系。在评价结果基础上对兴义镇农村居民点用地进行分区优化。(1)通过单因素量化分析和综合评价法分析可知,兴义镇农村居民点用地布局综合适宜度0~45.52,其中高度适宜性区域面积占兴义镇土地总面积的25.16%,中度适宜区面积占29.49%,低度适宜区面积占29.09%,不适宜区面积占16.26%。(2)利用聚类分析法划分出了4个类型区域:即适度挖潜区、重点发展区、限制扩建区和优先整治区,各区农村居民点面积分别为:113.30,188.59,104.01和41.72 hm²。(3)针对各类型区的具体特征,提出了相应的优化方案。     

边坡土壤含水率对不同植被土壤抗剪强度的影响

边坡土壤含水率是影响边坡稳定性的重要因素。本文通过直剪试验,研究边坡土壤含水率对不同植被类型土壤抗剪强度的影响。试验结果显示,天然含水率时,草地土壤抗剪强度高于裸地;随着含水率的增加,土壤抗剪强度及其指标（粘聚力和内摩擦角）基本呈现先增大后减小的趋势,其中裸地土壤抗剪强度在含水率约为10％时达到峰值,草地土壤达到抗剪强度峰值时的含水率约为12％,且草地土壤峰值时的抗剪强度值明显大于裸地;峰值过后含水率继续增加到饱和含水率的过程中,草地土壤抗剪强度减小的幅度小,受含水率变化的影响小。由此表明,边坡植被能显著减弱土壤含水率的增加对土壤抗剪强度的影响,增强边坡土体的稳定性。     

不同品质类型小麦优质高产群体氮效率的差异

为给小麦分类栽培措施的确定提供依据,于2000～2002年在扬州选用5个不同品质类型小麦品种,通过不同类型小麦氮肥运筹调控试验,研究了小麦优质高产群体与普通群体的氮效率差异.结果表明,同一品种不同群体类型间氮肥农学效率、氮肥吸收效率表现为强筋和中筋小麦优质高产群体高于普通群体,而弱筋小麦优质高产群体略低于普通群体;氮素利用效率则表现为强筋小麦优质高产群体低于普通群体,中筋小麦两者之间相近,弱筋小麦优质高产群体高于普通群体;不同群体的氮收获指数差异表现为优质高产群体与普通群体相比互有高低;不同类型专用小麦的各氮效率指标与籽粒产量及蛋白质含量之间表现出不同的相关性.     

不同培养基对两种乳酸菌复合系生长的影响

采用两组乳酸菌复合系,以MRS改良培养基为对照,初步研究以玉米面、玉米蛋白及马铃薯淀粉作为培养基成分时,乳酸菌复合系的生长情况,并筛选两组复合菌系生长最适的培养基．结果表明：复合系LBC-8在玉米面、玉米蛋白与葡萄糖7：3配比培养基中生长最适;复合系LBC-8和SFC-2的pH值下降程度,OD600nm的增加幅度,玉米面与葡萄糖培养基中较马铃薯淀粉与酵母粉培养基中明显;两组复合系分别在马铃薯淀粉与酵母粉3：7和5：5配比中生长菌落数最多,分别为5．0×10^7CFU／mL、3．4×10^7CFU／mL．     

不同林龄白桦次生林降雨水化学特征研究

通过对不同林龄白桦次生林林外降雨、穿透雨、树干茎流和枯透水中的Cl~-,NO_3~-N,Na~+,K~+,Ca2-,Mg~(2+)等进行测定,以研究4个林龄之间降水化学性质的差异.结果表明:林外降雨中Ca~(2+)的含量最高,Na~+含量最低,养分元素平均含量(以mg/L计)排列顺序为:Ca~(2+)>Cl~->K~+>NO_3~--N>Mg~(2+)>Na~+,各元素在林外降雨中的季节变化较大.变化幅度最小的是Cl~-;穿透雨中NO_3~--N,Ca~(2+)含量在25 a白桦次生林中最低,Cl~-,Mg~(2+)含量在38 a中最低,而Na~+,K~+含量在56 a中最低;树干茎流中Cl~-,NO_3~--N,K~+含量在38 a白桦次生林中最低,而Na~+,Ca~(2+),Mg~(2+)含量在56 a中最低;枯透水中Cl~-,NO_3~--N,Na~+,K~+含量在25 a白桦次生林中最低,Mg~(2+)含量在38 a中最低,而Ca~(2+)含量在56 a中最低.     

河北省梨树褐斑病菌对不同机制杀菌剂的敏感性及其与戊唑醇敏感性的关系

为明确河北省梨树褐斑病菌(Septoria piricola Desm)对戊唑醇和双胍三辛烷基苯磺酸盐、吡唑醚菌酯、环丙唑醇等不同作用机制杀菌剂的敏感性及交互抗性,采用室内菌丝生长速率法和田间小区试验分别测定了不同杀菌剂对11个地市分离到的133株病菌菌株的毒力,以及对梨树褐斑病的防治效果,研究了病菌对戊唑醇与对双胍三...     

碳酸丙烯酯固化剂对酚醛树脂固化性能的影响

在自制的酚醛树脂（PF树脂）中加入不同固化剂,考察固化剂对酚醛树脂固化时间的影响,筛选出固化速度最快的固化剂碳酸丙烯酯,同时研究了碳酸丙烯酯用量与树脂固化时间、适用期、胶合强度之间的关系,并优化出添加最佳用量的碳酸丙烯酯优化树脂的热压工艺．结果表明,当碳酸丙烯酯用量为树脂胶液量的2％时,酚醛树脂的固化时间缩短了64．4％,适用期240min．利用添加2％碳酸丙烯酯的酚醛树脂,通过不同热压工艺生产胶合板,当热压时间为1．0min·mm-1时,热压温度从105℃降到95℃;当热压温度为105℃时,热压时间从1．0min·mm-1缩短至0．7min·mm-1,两者均可减少能耗,降低生产成本．差示扫描量热法分析结果表明,添加2％碳酸丙烯酯的酚醛树脂固化起始温度为49．6℃,峰顶温度为109．2℃,固化温度较低．     

同异分析法在山东小麦新品种(系)综合评价中的应用

采用同异分析法,对山东省区试8个小麦新品种(系)的13个主要性状指标进行了综合分析和评价。结果表明,烟2415、山农D642、10-7的联系度值较高,排在前3位,与田间实际观察结果基本吻合。同异分析方法是对新品种(系)进行评价分析的一种新方法,该方法和常用的方差分析相比,运算简便,易于掌握,评价更全面、更合理,用于评价小麦新品种(系)切实可行。     

Use of tissue and sediment‐based threshold concentrations of polychlorinated biphenyls (PCBs) to protect juvenile salmonids listed under the US Endangered Species Act

• 1. Under the Endangered Species Act, the National Marine Fisheries Service has authority to protect listed species from any adverse actions that may jeopardize the population's ability to recover and increase to sustainable levels. Listed salmon species in the northwest United States are known to travel through urban areas in their migration from river to ocean. Species such as the chinook salmon (Oncorhynchus tshawytscha) often spend several weeks in these urban estuaries where they can be highly exposed to urban‐related contaminants that reside in the sediments and accumulate in their prey species. The concern is that these contaminants are bioaccumulated to levels that may impact the ability of individual salmon to grow and mature normally. This paper provides a framework for determining the tissue and sediment concentrations of polychlorinated biphenyls (PCBs) that are likely protective against adverse effects in listed salmonid species.
• 2. The relevant ecotoxicological literature was examined and 15 studies were selected that met the pre‐established criteria outlined here. For each study, the lowest tissue concentration (residue) of total PCBs associated with a biological response was selected. The tissue concentration associated with the 10th percentile of these 15 studies was chosen to represent the residue effect threshold (RET) above which wild juvenile salmonids would be expected to exhibit adverse sublethal effects from accumulated PCBs. This value (2.4 μg PCBs g^?1 lipid) is expressed in terms of the lipid‐normalized concentration because of the large effect lipid can have on the expressed toxicity and the substantial variability in lipid content observed in salmonids over their life cycle.
• 3. A sediment concentration that is expected to produce the RET was then determined using the biota‐sediment accumulation factor approach. The sediment effect threshold, which varies with the total organic carbon content in sediment, is the level above which adverse effects may be expected in juvenile salmonids due to accumulation of PCBs from environmental exposure. Bioaccumulation of PCBs was examined in one river system as a model for determining an appropriate bioaccumulation factor for wild juvenile chinook salmon.
• 4. Evaluation of exposure to potentially deleterious concentrations of PCBs based on tissue residues is the preferred approach; however, the sediment effect threshold may also be used in cases where bioaccumulation has been characterized in an estuary. The threshold values presented here are intended as interim guidelines that should be modified as more data become available. Additionally, because of the uncertainty around many of the factors and assumptions that comprise the single threshold effect values, it is recommended that future studies be employed to help determine a range of acceptable values that would afford protection under various environmental and biological conditions.

Published in 2002 by John Wiley & Sons, Ltd.     

不同能量水平和采精频率对绒山羊种公羊精液品质的影响

为研究日粮不同能量水平对陕北白绒山羊种公羊体重、血清睾酮水平和精液品质的影响,选择12只健康的种公羊按随机区组设计分为4组,每组3个重复,每个重复1只羊。日粮按NRC(1981,2007)标准推荐量的85%、100%、115%和130%设置4个能量梯度。结果表明,各个试验阶段日粮能量水平对试验公羊的平均日增重影响极显著(P< 0.01)。Ⅰ组和Ⅱ组公羊在整个试验期体重呈现先减后增的趋势,Ⅲ组和Ⅳ组公羊体重呈现先增后减再增的趋势;5 d 2次频率下公羊的睾酮和射精量高于5 d 4次的频率。日粮能量水平对试验公羊的血清睾酮水平和有效精子数影响极显著(P< 0.01),对射精量和精子密度影响显著(P< 0.05)。射精量、精子密度和有效精子数均以Ⅲ组最好。采精频率和能量浓度只对睾酮水平有极显著的互作效应(P< 0.01)。综上所述,陕北白绒山羊种公羊代谢能(ME)需要以12.08 MJ/d为宜。