EFFECTS OF TIME STEP SIZE IN IMPLICIT DYNAMIC ROUTING1

ABSTRACT The effects of the size of the Δt time step used in the integration of the implicit difference equations of unsteady open-channel flow are determined for numerous typical hydrographs with durations in the order of days or even weeks. Truncation errors related to the size of the Δt time step cause a numerical distortion (dispersion and attenuation) of the computed transient. The magnitude of the distortion is related directly to the size of the time step, the length of channel reach, and the channel resistance and inversely to the time of rise of the hydrograph. The type of finite difference expression which replaces spatial derivatives and non-derivative terms in the partial differential equations of unsteady flow has an important influence on the magnitude of the numerical distortion, as well as the numerical stability of the implicit difference equations. Time step sizes in the range of 3 to 6 hrs generally tend to minimize the combination of required computation time and numerical distortion of transients having a time of rise of the order of several days.     

Absence of sex-differential brood raising by workers in Diacamma sp. from Japan

To optimally allocate resources between workers, reproductive females, and males, ant workers have to be able to identify the sex of larvae and raise them differently. The ability of workers to discriminate between the sexes in the brood was tested in colonies of queenless ponerine ants, Diacamma sp., from Japan. The ratio of male eggs in the egg pile was increased experimentally. This manipulation resulted in a corresponding increase in the ratio of adult males, suggesting that Diacamma workers do not raise the sexes differently. Received: 4 November 1997 / Accepted after revision: 14 March 1998     

Queen control of egg fertilization in the honey bee

The study investigated the precision with which honey bee queens can control the fertilization of the eggs they lay. Because males and workers are reared in different-sized cells, the honey bee is one of the few Hymenoptera in which it is possible for the experimenter to know which type of egg a queen “intends” to lay. Eggs were collected from both worker and drone (male) cells from four honey bee colonies. Ploidy of the embryo was determined using polymorphic DNA microsatellites. All 169 eggs taken from worker cells were heterozygous at at least one microsatellite locus showing that the egg was fertilized. All 129 eggs taken from drone cells gave a single band at the B124 locus, strongly suggesting haploidy. These data show that honey bee queens have great, and quite possibly complete, ability to control the fertilization of the eggs they lay. Data from the literature suggest that in two species of parasitoid Hymenoptera (Copidosoma floridanum, Colpoclypeus florus) females have great, but not complete, ability to control fertilization. Received: 23 December 1997 / Accepted after revision: 17 May 1998     

Energy use and allocation in the Florida harvester ant, Pogonomyrmex badius: are stored seeds a buffer?

Limitation of a necessary resource can affect an organism’s investment into growth and reproduction. Pogonomyrmex harvester ants store vast quantities of seeds in their nests that are thought to buffer the ants when external resources are not available. This research uses externally controlled food availability to examine how resource shortage affects colony investment, resource use, and resource distribution within the nest. Colonies were either starved or supplemented with resources for 2 months, beginning at the onset of reproductive investment and ending immediately before nuptial flights. Fed colonies invested more in overall production, proportionally more in reproduction relative to growth and in female reproductives relative to males. Stored seeds in starved colonies did not buffer production in this study. However, worker fat reserves were depleted in starved colonies, indicating that fat reserves fuel the spring bout of production. In starved colonies, worker fat reserves were depleted evenly throughout the nest, distributing the burden of starvation on all workers regardless of caste and age. A reallocation of diploid eggs into female workers rather than reproductives best explains the observed change in sex ratio investment between treatments. The redistribution of resources into growth relative to reproduction in starved colonies is consistent with life history theory for long-lived organisms, switching from current to future reproduction when resources are scarce.     

典型氢氧化细菌固碳特性种间差异及胞外有机物对固碳过程影响

化能自养细菌对全球CO₂固定具有重要的意义.研究了4种典型氢氧化细菌（HOB,分别是Alcaligenes hydrogenophilus DSM 2625、Pelomonas saccharophila DSM 654、Variovorax paradoxus DSM 30034和Acidovorax facilis DSM 649）的固碳特性及其种间差异性,并探究了胞外游离有机碳（EFOC）对不同种类HOB固碳效率差异性的影响.结果表明：①不同HOB自养培养过程中表观固碳量随时间呈显著差异性,其中,DSM 2625生长速度较快,其平均固碳量分别是DSM 654、DSM 649和DSM 30034的6.30、8.76和7.02倍.②不同HOB之间cbbL基因转录量与 表观固碳量的相关系数为0.980 （p<0.05）,cbbL基因转录量是造成不同菌种之间表观固碳效率差异的关键因素.③HOB细胞蛋白质含量与cbbL基因丰度和转录量之间也存在显著正相关,相关系数分别为0.999（p<0.01）和0.976（p<0.05）,即化能自养细菌CO₂同化途径所固定的有机碳进一步参与细胞蛋白质的合成,进而影响其生长速度和表观固碳效率.④HOB在自养培养过程中产生的EFOC对cbbL基因转录效率产生反馈抑制作用,且不同HOB之间,EFOC/TOC比例越低,表观固碳效率越高.     

基于产业投资视角的乡村旅游发展区域差异与形成机制

乡村旅游发展区域差异是乡村旅游投资空间不均衡的外在表现。新时代乡村振兴背景下乡村旅游投资不断增长,正加速影响乡村旅游发展空间格局与区域差异。在对比认识浙晋乡村旅游发展差异基础上,深入剖析了乡村旅游投资系统作用区域乡村旅游发展差异的深层机理。结果发现：（1）以乡村旅游精品线路为表征的浙晋乡村旅游发展水平和市场成熟度差异显著。（2）在乡村旅游投资“自然—产业—社会”环境中,产业基础环境对区域乡村旅游发展差异贡献最突出,是区域差异形成的核心要素,自然生态环境是基础,社会文化环境则发挥积极促进作用。（3）乡村旅游发展区域差异是不同乡村旅游投资环境引起区域乡村旅游投资收益预期和回报水平与乡村旅游发展路径及模式差异的结果。基于此,提出新时代乡村旅游投资IE-maps模式,以期促进区域乡村旅游协调发展和乡村振兴战略实施。     

中国公众环境意识的时空差异及影响因素分析

建设生态文明是中华民族永续发展的千年大计,引导和培育公众牢固树立环境保护意识是构建生态环境治理全民行动体系的根本保障。本文以2003年和2013年中国综合社会调查（CGSS）数据为基础,评估了全国28个省（市、自治区）（不含新疆、西藏、海南及港澳台地区）的公众环境意识,综合运用空间自相关分析、标准差椭圆分析和空间计量模型等方法,揭示了中国公众环境意识的时空差异特征,甄别了主要影响因素及其作用。结果表明：（1）2003—2013年中国公众环境意识水平基本维持不变,环境付费能力大幅下降,但公众对环境意识的关注程度有所提高;（2）中国公众环境意识的总体空间演化形态表现为整体分布规模略微缩小,省域公众环境意识空间差异显著,中西部地区环境意识有所增强,东部地区公众环境意识处于较高水平;（3）公众环境意识水平存在显著的空间正相关性,空间集聚程度不断加剧;空间局部特征以高—高型和低—低型最为显著,各省份空间相似度较高;（4）人口密度、工业污染治理投资、教育经费投入、地区环境污染程度及地区城市设施水平等因素均对公众环境意识产生显著影响。     

淮河流域新型城镇化水平的空间差异及其影响因素分析

以淮河流域31个地级市为研究对象,从人口、经济、生活和环境四个方面构建了新型城镇化水平的综合评价指标体系,利用熵值法对其综合城镇化水平及其子系统水平进行评价.结果表明,淮河流域地区新型城镇化发展水平存在较强的空间依赖性,即一个地区城镇化水平的提高通过空间溢出促进周边地区的城镇化发展,地区产业结构的变化是决定其新型城镇化水平的主要因素,尤其是第三产业发展对其影响极大.     

Differences in Evaporation Between a Floating Pan and Class A Pan on Land1

Abstract: Research was conducted to develop a method for obtaining floating pan evaporation rates in a small (less than 10,000 m²) wetland, lagoon, or pond. Floating pan and land pan evaporation data were collected from March 1 to August 31, 2005, at a small natural wetland located in the alluvium of the Canadian River near Norman, Oklahoma, at the U.S. Geological Survey Norman Landfill Toxic Substances Hydrology Research Site. Floating pan evaporation rates were compared with evaporation rates from a nearby standard Class A evaporation pan on land. Floating pan evaporation rates were significantly less than land pan evaporation rates for the entire period and on a monthly basis. Results indicated that the use of a floating evaporation pan in a small free‐water surface better simulates actual physical conditions on the water surface that control evaporation. Floating pan to land pan ratios were 0.82 for March, 0.87 for April, 0.85 for May, 0.85 for June, 0.79 for July, and 0.69 for August.     

基于大田试验的铅镉复合污染土壤中甜糯玉米低积累特性

为筛选适合在铅（Pb）、镉（Cd）复合污染土壤种植的低积累特性甜糯玉米品种,选取39个玉米品种,通过大田试验,研究其籽粒和秸秆对Pb和Cd的富集特性和差异.将玉米产量、富集系数和基于土壤Pb和Cd风险阈值的方法作为筛选低积累玉米品种的评价指标.结果表明,不同品种玉米的产量、籽粒和秸秆的Pb和Cd含量之间存在显著差异（P<0.05）.籽粒对Pb和Cd的富集系数分别为0.00003~0.00230和0.01~0.15,秸秆对Pb和Cd的富集系数分别为0.003~0.065和0.64~4.28.通过对不同玉米富集系数的聚类分析,综合不同品种玉米的土壤Pb和Cd风险阈值得出,惠甜5号、新美甜818和玉糯9号可在Pb和Cd含量超风险管制值的耕地安全生产,天贵糯937和金萬糯2000可在Cd含量超风险筛选值的耕地安全生产.惠甜5号、新美甜818和玉糯9号作为Pb和Cd复合低积累品种,适宜在广西铅镉复合污染土壤上推广种植,天贵糯937和金萬糯2000作为籽粒低积累、秸秆Cd高积累品种,建议将其作为植物修复资源加以利用.