Heterogeneity in the local employment multipliers in the United States

Recent studies have found evidence of a local employment multiplier’s effect. For the most part, these studies provide an average estimate for all labor markets. In this paper, we examine how the average local employment multiplier, the effect of an exogenous increase in employment in the tradable sector on total employment, depends on the characteristics of the local labor market. Specifically, we estimate the average multipliers for coastal, noncoastal, large, and small metropolitan statistical areas (MSAs) across different time periods using the data of 333 US MSAs. Overall, we find a reduced form of local employment multiplier ranging from 1.38 to 2.24, which is within the range of typically estimated local employment multipliers. In addition, the characteristics of the local labor market matter. The local multipliers appear larger in noncoastal and large MSAs. For small and coastal metros, the multiplier is closer to 1.5 than to 2.0 while in the case of large and noncoastal metros, it is closer to 2.0 than to 1.5. The local multipliers are also sensitive to the time period considered.     

Determinants of entry: Evidence from new manufacturing firms in the U.S

The objective of this paper is to estimate the relationship between agglomeration economies and the birth of new firms in U.S. manufacturing sectors during 2004–2012. I examine the variations in Marshallian factors across MSAs and across counties within MSAs. My findings support the existence of Marshallian agglomeration forces: input sharing, labor market pooling, and knowledge spillovers, with input–output linkages particularly important. I then examine the variations in Marshallian factors across regions and find regional differences are not very strong. In addition, large-sized firms appear to be more responsive to a supplier-customer relationship. Moreover, my empirical results provide evidence that firms in highly concentrated industries react more to input linkage and labor pooling.     

恢复系南34恢复谱、恢复力、恢复性的初步研究

通过恢复系南34与35个滇Ⅰ型不育系组配的35个滇型杂交粳稻新组合在不同海拔种植试验，结果表明：恢复系南34对滇Ⅰ型不育系的恢复谱广、恢复力强、恢复性稳定。     

Effects of Increasing Temperatures on Spikelet Fertility in Different Rice Cultivars based on Temperature Gradient Chamber Experiments

Spikelet sterility in rice (Oryza sativa L.) induced by high temperatures is a major concern given global warming predictions. We studied differences among eight rice cultivars in spikelet fertility at five different temperature levels in temperature gradient chamber (TGC) experiments. Six japonica and two indica cultivars were exposed to high‐temperature gradients in TGCs during the 2005 flowering season. Spikelet sterility increased with temperature in TGCs and differed among cultivars because of both variations in temperature tolerance and timing of heading. The correlation between spikelet fertility of individual panicles and both air temperature and panicle temperature during flowering was analyzed to compare tolerances among cultivars. The temperature (T₇₅) at which spikelet fertility was 75 % of maximum ranged from 34 to 39 °C air temperature and differed significantly among cultivars. Indica varieties had higher T₇₅ values than japonica varieties. The T₇₅ values based on panicle temperature also differed among cultivars, but the difference between indica and japonica varieties were less significant. We concluded that the higher temperature tolerances of indica cultivars in our experiments could be attributed to lower spikelet temperatures, and cultivars with similar spikelet temperatures still had different heat tolerances due to differences in pollination ability.     

湖北中稻抽穗开花期高温热害风险分析及区划

为探究湖北中稻抽穗开花期高温热害发生风险变化特征,基于湖北18个农业气象站中稻生育期观测资料和1960—2019年气象资料以及2016—2017年荆州大田高温控制试验资料,采用数理统计、相关分析等方法,从产量致灾角度探究中稻花期高温热害指标,分析中稻高温热害年际变化、空间分布特征并对其风险进行区划,结果表明：（1）≥35℃高温危害积温与关键产量构成因素（结实率）的（负）相关性较高温日数更好。（2）1960—2019年湖北中稻花期高温热害强度呈先降后升的年代变化,尤其自21世纪初以来,高温热害呈现频率增高、强度加大、范围更广的特点,在空间上以鄂东地区的强度、频率增幅最大,其次是江汉平原和鄂西南,鄂西北增幅较小。（3）高风险区为鄂西北部、长江三峡河谷以及鄂东一带,低风险区为鄂西南中高山及江汉平原大部地区,其余为中风险区,1990—2019年较1960—1989年高温热害风险明显增强。     

Cytogenetics and morphology of the pentaploid hybrid between Brassica napus and Orychophragmus violaceus and its progeny

A pentaploid hybrid plant (2n= 50, AACCO) between Brassica napus (AACC) and Orychophragmus violaceus (OO) showed matroclinous morphology and some patroclinous characters. Cloned progenies were mixoploid, consisting of various cells with 38–53 chromosomes, half of the cells with 50 chromosomes. The 50 chromosomes were mainly paired as 25 bivalents and segregated as 25:25 or 22:28; many other segregations were observed in some cells. Progenies produced by selfing had 38–47 chromosomes. Plants with 38 chromosomes were cytologically stable; in all other plants the chromosome number of individual cells varied between the genotype-specific maximum number and 38, indicating loss of chromosomes during mitosis. The mixoploid plants with 44 chromosomes mainly produced two kinds of mixoploid progenies with 44 and 41 chromosomes, respectively. All plants with 2n= 38 had the same morphology as the parental B. napus and were normal in fertility. These chromosome pairings and segregations in the pentaploid and its progeny support the hypothesis that O. violaceus is a natural polyploid species with a basic chromosome number of 3.     

Diverse Retail Structure and Christaller's Separation Principle in Medium-Sized Metropolitan Areas

Standardized features dominate the retail landscape of the United States and are the physical components of retail districts. This study tests the hypothesis that standardized building blocks have failed to produce the same retail structure in all metropolitan statistical areas (MSAs). Ninety-two medium-sized MS As are analyzed to determine if the arrangement and strength of their retail districts differ. The relationship between functional and spatial aspects of retail structure in central place theory provides a basis for testing the hypothesis of diversity. Christaller's separation principle provides a plausible conceptual framework for diverse retail structure if each MSA is analyzed as an isolated region. Five types of retail structure are analyzed using data obtained from the Census of Population and the Census of Retail Trade. The types are identified by performing a serial iterative partition cluster procedure on prioritized metropolitan sales variables. The statistical significance of the types is tested with Mann-Whitney U-tests of functional variables not used in the cluster analysis. Verification confirms five distinctive types. Monocentric and polycentric retail structures exist but decentralized retail structure is even more common in medium-sized MSAs. The distribution of types of retail structure follows regional pattern that indicate historical and political factors as contributing causes.     

Chromosomal and genic structure of Brassicoraphanus related to seed fertility and the presentation of an instance of improvement of its fertility

Summary In order to elucidate the mechanism of low fertility of Brassicoraphanus, i.e., amphidiploids between Brassica japonica Sieb. and Raphanus sativus L., the chromosome number of 253 plants was studied during the 3rd–9th generations for their seed fertility. Meiotic irregularity showed no connection with degree of sterility. Brassicoraphanus consisted of euploids (2n=38), hyperploids (2n=39–43) and hypoploids (2n=34–37) with white or yellow flowers. The number of plants was highest in euploids and became lower as the chromosome number diverged from the euploid number. Further, seed fertility was highest and the range of its variation widest in euploids. The seed fertility of aneuploids became lower and its variation narrower in proportion to the number of chromosomes additional to or missing from the euploid number. Yellow-flowered plants were superior in seed fertility to white-flowered plants. Seed fertility of plants is primarily affected by their chromosome numbers and secondarily modified by genic effects. As a whole, seed fertility of Brassicoraphanus increased gradually and its variation widened with the advance of generations. This was explained mainly by the increase of balanced combinations of genes.     

Independent and Combined Effects of High Temperature and Drought Stress During Grain Filling on Plant Yield and Chloroplast EF‐Tu Expression in Spring Wheat

High temperature and drought stress are among the two most important environmental factors influencing crop growth, development and yield processes. These two stresses commonly occur in combination. Objectives of this research were to investigate the independent and combined effects of high temperature and drought stress during grain filling on physiological, vegetative and yield traits and expression of a chloroplast protein synthesis elongation factor (EF‐Tu) of wheat (Triticum aestivum L.). Two spring wheat cultivars (Pavon‐76 and Seri‐82) were grown at control temperatures (CT; day/night, 24/14 °C; 16/8 h photo/dark period) from sowing to heading. Thereafter, one half of the plants were exposed to high temperature stress (HT; 31/18 °C in Exp. 1 and 34/22 °C in Exp. 2), drought stress (withholding water), or a combination of both HT and drought stress. There were significant influences of HT and/or drought stress on physiological, growth and yield traits. There was no cultivar or cultivar by temperature or cultivar by drought interaction effects on most traits. The decreases in leaf photosynthesis were greater at HT compared with drought alone throughout the stress period, and the combination of HT and drought had the lowest leaf photosynthetic rates. Overall, HT or drought had similar effects (about 48–56 % decrease) on spikelet fertility, grain numbers and grain yield. High temperature decreased grain numbers (by 56 % averaged across both experiments) and individual grain weight (by 25 %), while, respective decreases due to drought were 48 % and 35 %. This suggests that the grain numbers were more sensitive to HT and grain weights to drought for the range of temperatures tested in this research. The interaction between HT and drought stress was significant for total dry weights, harvest index and spikelet fertility, particularly when HT stress was severe (34/22 °C). The combined effects of HT and drought were greater than additive effects of HT or drought alone for leaf chlorophyll content, grain numbers and harvest index. High temperature stress and the combination of HT and drought stress but not drought stress alone resulted in the overexpression of EF‐Tu in both spring wheat cultivars.     

Comparison of soil and sediment properties of a loamy sand soil

Ten 25 m² runoff plots at the Hilton experimental site, east Shropshire, UK, have been used to compare the physicochemical properties of loamy sand plot soils and sediment eroded from the plots over one year. Sediment contained more sand (2 mm–60 μm) and less clay (< 2 μm), silt (2–60 μm) and coarse fraction (> 2 mm) than soil. Erosion rates increased with slope and proportionally more silt and particularly clay were eroded on steeper slopes. Selective clay depletion has serious implications for soil structure and fertility. Correlations existed between the organic matter contents and particle size distributions of soil and sediment, but the sediment had less organic matter and lower pH values than soil. Sediment also contained lower concentrations of calcium, iron, potassium, magnesium, manganese and phosphorus than soil. Relationships between erosion and soil textural change appear to be partly technique-dependent, which suggests more uniformity in approach would be beneficial in studies on the effects of erosion on soil fertility.     

Nitrogen Uptake by Rice (Oryza sativa L.) Exposed to Low Water Temperatures at Different Growth Stages

The responses of nitrogen (N) uptake by rice (Oryza sativa L.) to low water temperatures at different growth stages were examined during a 3‐year field trial in northern Japan. Cool irrigation water was applied at two to three temperature levels (16–25 °C) for 20–34 days during the vegetative stage and then during reproductive growth. We measured the N uptake rate, N content and canopy radiation interception during both growth stages. Exposure to low water temperature during either the vegetative or the reproductive growth stage slowed N uptake, and the magnitude of the decrease differed between the growth stages; the decrease was greater during vegetative growth than during reproductive growth. Consequently, total N uptake at maturity was most strongly reduced by low water temperature during vegetative growth and was not affected by low water temperature during reproductive growth, even though N distribution to the panicle was greatly reduced. The variations in N uptake during the growing season among growth stages and years were explained better by the amount of canopy radiation capture than by the number of degree‐days based on water temperature. This strong dependency on canopy radiation capture improves our understanding of the factors responsible for variations in N uptake under different levels of water temperature, and this knowledge will provide an opportunity to simplify the modelling of N uptake.     

Is low-input management system a good selection environment to screen winter wheat genotypes adapted to organic farming?

The move toward resilient and productive agriculture requires, among other innovations, the design of new sustainable farming systems in which the variety plays a main role. Plant breeding strategies adapted to organic farming conditions have to deal with limiting factors. Whereas in north-west France, it is known that trials carried out under high-input management do not give a good prediction of genotype performance in organic conditions, less is known about the relative stability of wheat genotypes between low-input (LI) and organic cropping systems. A retrospective analysis of 34 winter wheat trials conducted from 2004 to 2011 was performed to determine whether data obtained on genotypes grown under LI conditions can be used to predict genotype performance in organic (ORG) target conditions. Every year, ORG and LI (no fungicide or growth regulators, N balance sheet-60 kgN/ha, weed control with herbicides) trials including 25–30 genotypes describing a large range of genetic diversity were sown in three different agro-climatic regions across north-west France. Genotype performance in ORG management system was reduced from 25 to 40 % for yield and from 10 to 22 % for grain protein content. Estimates of genotypic values appeared to be more precise under LI than ORG conditions. Because of high genetic correlations between LI and ORG conditions, the relative efficiency of indirect selection from LI to ORG conditions was approximately 1. Spearman’s rank correlations were high (Rs = 0.54–0.92) and genotype rank inversions generally had a minor extent. However, in 2005 and 2010, almost 50 % of the lines had to be retained in LI to keep 80 % of the top 20 % of genotypes in organic conditions. Compared with previous results from high-input conditions, LI management provided a better prediction of genotype performance under ORG conditions but crossover genotype × management interactions could be observed between both systems. Overall, combining information provided from both LI and ORG crop management systems appears to be a good process for building efficient and adapted breeding schemes for ORG farming conditions.     

高粱A2型胞质在中国的研究与利用

高粱A2型质核互作雄性不育系是美国高粱育种家舍尔茨教授于1976年创制,1979年引入中国。它的细胞质来自埃塞俄比亚,细胞核产自印度。A2型不育性是由一对细胞核基因和细胞质基因共同作用。不育系的基因型是S2（ms2 ms2）,其保持系的基因型是F2（ms2 ms2）,恢复系的基因型是F2或S2（Ms2 Ms2）。对A1型不育系恢复或保持,大多对A2型也恢复或保持,少数恢复系呈保持型,说明A2具有更广泛的保持源。温度是影响育性的主要因子,在自然条件下,A2不育系雌蕊败育轻或不败育,雄蕊遇高温可散出花粉,使不育系产生少量自交结实。A2型胞质主要农艺性状的杂种优势和配合力与A1胞质无明显差异。山西省农科院1987年育成了第一个在生产中可以利用的A2细胞质雄性不育系V4A,并组配出A2型杂交种——晋杂12。该杂交种于1997年获山西省科技进步二等奖。以A2V4为母本组配并经省级审定杂交种5个。因此,该不育系的创制,于1998年获国家发明三等奖。原四平市农科院,用A2TAM428与南133组配成四杂25号,于2002年获吉林省科技进步二等奖。吉林省农科院用A2型不育系培育出吉杂80、吉杂83、吉杂96、吉杂97,辽宁农科院育出辽杂10等在生产中大面积推广。文中讨论了非迈罗胞质的育性反应及利用问题。     

花生新品种龙花163丰产性和稳产性分析

摘要：通过对2005-2006年福建省花生区域试验资料进行了丰产性和稳产性分析,结果表明：龙花163两年区试平均荚果产量居第一,平均产量分别为265.5kg/666.7m2和271.5kg/666.7m2,分别比对照泉花10号增产15.7%和16.3%,丰产性和稳产性都高于其它品种,适宜在我省大部分地区种植,在环境条件和栽培技术好的地方种植产量潜力更大。     

Retail Trade on the U.S.‐Mexico Border During the NAFTA Implementation Era

ABSTRACT When NAFTA was implemented in 1994, there was a general expectation that it would hurt U.S. retailers along the U.S.‐Mexico border. This paper asks whether there was a significant change in the pattern of retail trade in border MSAs in the years surrounding NAFTA's implementation. Data from MSAs in the four border states are analyzed. After controlling for other potential influences on retail trade, there remained a statistically significant change in the pattern of retail trade between 1992 and 1997. The changes cannot be unquestionably attributed to NAFTA but do suggest that NAFTA had a negative influence on retail sales on the U.S. side of the border.     

Consistent Variation Across Soil Types in Salinity Resistance of a Diverse Range of Chickpea (Cicer arietinum L.) Genotypes

Chickpea is considered sensitive to salinity, but the salinity resistance of chickpea germplasm has rarely been explored. This study aimed to (i) determine whether there is consistent genetic variation for salinity resistance in the chickpea minicore and reference collections; (ii) determine whether the range of salinity resistance is similar across two of the key soil types on which chickpea is grown; (iii) assess the strength of the relationship between the yield under saline conditions and that under non‐saline conditions; and (iv) test whether salinity resistance is related to differences in seed set under saline conditions across soils and seasons. The seed yield of 265 chickpea genotypes in 2005–2006 and 294 cultivated genotypes of the reference set in 2007–2008 were measured. This included 211 accessions of the minicore collection of chickpea germplasm from the International Crops Research Institute for the Semi‐Arid Tropics (ICRISAT). The experiments were conducted in a partly controlled environment using a Vertisol soil in 2005–2006 and an Alfisol soil in 2007–2008, with or without 80 mm sodium chloride (NaCl) added prior to planting. In a separate experiment in 2006–2007, 108 genotypes (common across 2005–2006 and 2007–2008 evaluations) were grown under saline (80 mm NaCl) and non‐saline conditions in a Vertisol and an Alfisol soil. In 2005–2006 in the Vertisol and 2007–2008 in the Alfisol, salinity delayed flowering and maturity, and reduced both shoot biomass and seed yield at maturity. There was a large variation in seed yield among the genotypes in the saline pots, and a small genotype by environment interaction for grain yield in both soil types. The non‐saline control yields explained only 12–15 % of the variation of the saline yields indicating that evaluation for salinity resistance needs to be conducted under saline conditions. The reduction in yield in the saline soil compared with the non‐saline soil was more severe in the Alfisol than in the Vertisol, but rank order was similar in both soil types with a few exceptions. Yield reductions due to salinity were closely associated with fewer pods and seeds per pot (61–91 %) and to lesser extent from less plant biomass (12–27 %), but not seed size. Groups of consistently salinity resistant genotypes and the ones specifically resistant in Vertisols were identified for use as donor sources for crossing with existing chickpea cultivars.     

Growth and dynamics in populations of echinocardium cordatum living in the North Sea off the Dutch North coast

Numerical densities and size distributions in populations of the spatangoid Echinocardium cordatum were followed at 19 fixed sampling stations with sandy sediments at depths of 6 to 18 m off the west-Frisian islands of Texel and Terschelling.Recruitment was irregular with some recruitment occurring during half of the years and successful year classes developing during only 3 of the years in the 10 year period of observation (1972–1982). Annual mortality of the strong year class born in 1972 was rather regular in the ages of 1 to 7 years, averaging ∼27% in the 2 areas, but was followed by catastrophic mortality at most stations during the severe winter 1979.Growth was rapid. A mean length of 2 to 2.5 cm was reached after 2 growing seasons and 4 cm after 4 or 5 growing seasons.     

宁南黄土丘陵区旱作苜蓿地土壤肥力特征分析

为了阐明宁南黄土丘陵区旱作苜蓿地土壤肥力的变化特征,采用算术均数赋值法将因子分析法、相关分析法、灰色关联法、变异系数法4种赋权方法相结合,对宁南半干旱黄土丘陵区旱作苜蓿地土壤肥力因子的权重进行计算。土壤肥力因子权重计算结果表明：研究区苜蓿地土壤肥力因子权重排序为有机质>速效氮>全量氮>土壤pH>速效磷≈全量磷>速效钾,土壤有机质、速效氮、全量氮、土壤pH的权重值相对较高,是该区旱作苜蓿地最为关键的肥力指标。利用改进的内梅罗综合指数法得到的苜蓿地土壤综合肥力指数在0.549~0.873之间,土壤肥力水平一般。退耕还林还草旱作苜蓿后,研究区水土流失明显得到控制,不同坡位苜蓿地土壤肥力指数差异逐渐减小;不同旱作年限苜蓿地土壤综合肥力指数排序为：7年生>3年生>19年生。     

A decade of Tropical Legumes projects: Development and adoption of improved varieties,creation of market‐demand to benefit smallholder farmers and empowerment of national programmes in sub‐Saharan Africa and South Asia

This article highlights 12 years (2007–2019) of research, achievements, lessons learned, challenges and gaps in discovery‐to‐delivery research in legumes emanating from three projects, collectively called Tropical Legumes (TL) with a total investment of about US$ 67 million funded by the Bill & Melinda Gates Foundation. These projects were implemented by three CGIAR centres (ICRISAT, CIAT and IITA) together with 15 national agricultural research system partners in sub‐Saharan Africa and South Asia. The TL projects together with some of their precursors and complementary projects from other agencies, facilitated the development of 266 improved legume varieties and the production of about 497,901 tons of certified seeds of the target legume crops in the focus countries. The certified seeds have been planted on about 5.0 million ha by more than 25 million smallholder farmers in the 15 countries and beyond, producing about 6.1 million tons of grain worth US$ 3.2 billion. Furthermore, the projects also trained 52 next generation scientists that included 10 women, by supporting 34 Masters degrees and 18 PhD degrees.     

华南主要露地蔬菜土壤的供氮指标

本文依托测土配方施肥田间试验的数据,开展露地蔬菜土壤供氮指标研究,旨为华南菜田土壤养分丰缺指标体系建设提供参考。以蔬菜不施氮肥处理与完全施肥处理的相对产量的50%、75%、90%和95%为指标,建立华南菜田土壤碱解氮丰缺指标,根据土壤碱解氮含量划分的极缺、缺、中等、高和极高5级水平的土壤供氮指标分别为小于42、42~97、97~164、164~194和大于194 mg?kg-1。针对目前逐渐采用土壤硝态氮作为土壤供氮指标的需求,建立了碱解氮-硝态氮和碱解氮-无机氮的转换方程,分别为：y硝态氮 = 0.4012x碱解氮 - 1.3695和y无机氮= 0.4955x碱解氮 + 2.0736,二者均达到极显著水平。由该方程计算得出,当蔬菜相对产量为50%、75%、90%和95%时,并对所建立的丰缺指标进行不同形态氮的指标值转换。土壤硝态氮的丰缺指标转换值为：11mg?kg-1、34mg?kg-1、66mg?kg-1和82mg?kg-1;无机氮的丰缺指标转换值为：17mg?kg-1、46mg?kg-1、86mg?kg-1和105mg?kg-1。