长春地区大豆田蓟马种类鉴定及黄蓟马种群动态

为了在大豆生产中更好地防治蓟马类害虫,于2017年长春地区的大豆田中调查蓟马种类及消长动态。结果发现,大豆田有1亚目2科5属6种蓟马,横纹蓟马(Aeolothrips fasciatus)、黄蓟马(Thrips flavus)、豆喙蓟马(Mycterothrips glycines)、齿裂绢蓟马(Hydatothrips dentatus)、烟蓟马(Thrips tabaci)和花蓟马(Frankliniella intonsa)。根据成虫特征编写了本地区大豆田蓟马种类识别检索表。调查发现,黄蓟马是本地区的优势种,发生高峰期为盛花期至始粒期。初步明确了该虫在大豆植株上的垂直分布规律:即主要分布于大豆植株上层叶片的第1叶位到第5叶位,主要在叶背面活动,成虫、若虫在各个物候期虫口数量与大豆叶位之间的关系以逻辑斯蒂模型拟合度较佳。     

Quality traits related to lipid component in hemp(Cannabis Sativa L.) germplasm

In order to accelerate breeding progress of oil-used hemp, 8 quality traits related to lipid component were measured and analyzed in 55 representative hemp germplasms. Results showed that linolenic acid content had the highest variance coefficient of 51.67% as well as protein content had minimum variance coefficient of 4.07%. Correlation analysis showed that total oil content was significantly positively correlated to linolenic acid, while significantly negatively correlated with oleinic acid. Protein content was significantly positively correlated with linolenic acid but significantly negatively with stearic acid. Both total oil and protein content were closely correlated with other traits. The first 3 PCs from principal component analysis of 8 traits accounted for 83.53% contribution. All hemp germplasms were classified into 3 groups at the level of euclidian distance D=8.5 using cluster analysis. The above analysis and classification may provide a reliable theoretical basis and technological guidance for germplasms utilizing and accelerating breeding process.     

马边大风顶国家级自然保护区物种多样性新记录

为了更全面地了解马边大风顶自然保护区的物种资源情况,本研究调查了马边大风顶自然保护区从2016年至今红外相机数据中发现的保护区新物种记录,共计8种,包括1种国家二级保护动物(灰林鸮),4种国家"三有"物种(褐头鸫、棕朱雀、丘鹬、橙色小鼯鼠),1种IUCN红色名录中易危物种(褐头鸫)。建议应对这些动物分布区(如中等海拔地区(2 100 m～2 600 m)进行集中研究,如探究其生境适宜性及日常行为,加强对它们的监测和保护。     

乌海市几种灌木与土壤养分聚集的关系

植被与土壤资源的空间格局关系可以为植被恢复提供重要信息,对内蒙古乌海市周边地区的不同灌木与不同土壤养分（全氮、全磷、有机质）的空间聚集关系进行研究。在乌海市周边选取9个包含锦鸡儿属Caragana灌木或沙蒿Artemisia desertorum的植被群,在尺度为5 m×5 m样方中建立坐标系,记录每株灌木坐标点,并从坐标原点在样方范围内沿4个方向隔100 cm采集1份土样,测定土样中全氮、全磷和有机质质量分数,将灌木坐标点和每种养分质量分数前20%的土样坐标点代入点格局模型进行分析。结果表明:在草原化荒漠区域,狭叶锦鸡儿Caragana stenophylla（r=250 cm）,锦鸡儿Caragana sinica（r=230 cm）和柠条锦鸡儿Caragana korshinskii（r=150 cm）与全氮的关联尺度相对于沙蒿（r=100 cm或r=75 cm）较大;与全磷存在聚集关系的仅有草原化荒漠区域的锦鸡儿（r=50 cm）;在荒漠草原毛刺锦鸡儿Caragana tibetica（r=45 cm）与有机质存在聚集关系;而沙蒿在荒漠草原（r=190 cm）或草原化荒漠（r=200 cm）均能聚集有机质。将点格局模型运用到灌木与土壤养分的空间关系分析中,得到的关联尺度一定程度可以反映灌木的根冠范围,揭示灌木与土壤养分的空间格局关系。     

协青早B//协青早B/东乡野生稻BC1F5群体产量性状QTL分析

两年同地种植协青早B//协青早B/东乡野生稻BC1F5群体的202个株系,利用含149个DNA标记的连锁图谱,检测到23个产量性状QTLs,包括每株穗数2个、每穗实粒数4个、每穗总粒数6个、结实率5个、千粒重4个和单株产量2个;有9个QTLs的增效等位基因来自东乡野生稻,包括每株穗数2个、每穗实粒数1个、每穗总粒数5个和千粒重1个,其中6个与前人应用野栽群体检测到的产量性状QTLs位于相似区间。这23个QTLs分布于除第11染色体外的所有水稻染色体中,其中18个形成8个QTL簇,含增效等位基因来自野生稻的2个、来自协青早B的4个,以及效应方向发生变化的2个。这些结果为东乡野生稻增产等位基因的发掘提供了基础。     

长期施肥对黑土氮素矿化与硝化作用特征的影响

采用培养试验研究了长期施肥对黑土矿化与硝化作用特征的影响。结果表明,黑土的矿化作用和硝化作用都较强,长期施肥对黑土矿质态氮量有显著影响,施用化肥能够增加矿质态氮量,在施用NPK肥基础上增施有机肥,矿质态氮量进一步增加,表明在土壤管理上如果增加有机肥的施用,可以提高土壤的供氮能力。长期施肥黑土的硝化率与施N肥相关性较好,其次是施用PK肥。有机肥与无机肥配施可使土壤硝化率显著提高;硝化率高低取决于黑土可矿化态氮素含量和土壤pH。     

基于改进K-means算法的冬小麦覆盖度提取研究

为快速、精准地提取冬前分蘖期冬小麦覆盖度,提出了一种基于改进K-means算法的冬小麦覆盖度提取方法。首先将冬小麦图像转换到Lab色彩空间,其次利用蜉蝣算法（Mayfly Algorithm, MA）获取K-means最优初始聚类中心,并用马氏距离代替欧氏距离进行算法改进,最后利用分割得到的二值图像计算冬小麦覆盖度。结果显示,该方法的平均分割精度和平均处理时间分别为94.66%和2.03 s,与过绿指数（excess green,EXG）自适应阈值分割和基于粒子群优化算法（particle swarm optimization,PSO）的K-means(PSO-K-means)分割相比,分割精度分别提高了12.04%和4.18%,处理时间分别减少了2.26和2.94 s。该方法分割效果优于EXG和PSO-K-means分割方法,可用于提取冬小麦覆盖度。     

胶体态及溶解态有机质对土壤镉吸附的影响

为研究外源细颗粒态有机质对土壤重金属吸附特征的影响,以紫色土坡耕地、冬水田和水旱轮作田土壤为对象,通过吸附动力学试验和等温吸附试验,探索猪粪源胶体态有机质（COM,10~0.45 μm）和溶解态有机质（DOM,<0.45 μm）及其不同初始浓度对土壤镉（Cd）吸附行为的影响。结果表明：准二级动力学方程能更好地描述3种利用方式土壤对Cd的动态吸附（R²>0.90）,Langmuir模型能更好地拟合Cd的等温吸附（R²>0.95）,供试土壤对Cd的吸附均为强烈的非线性（Freundlich模型非线性指数<0.42）化学吸附。3种利用方式土壤对Cd的吸附强度顺序为水旱轮作田>冬水田>坡耕地,Cd吸附强度与土壤pH、有机质和粉粒含量正相关。猪粪源DOM比COM更能抑制土壤Cd的吸附,且二者均对水旱轮作田土壤吸附Cd的影响最明显。猪粪源COM和DOM初始添加浓度（0~100 mg·L^-1,以C计）对土壤Cd吸附量的影响呈现较快（<30 mg·L^-1,以C计）降低和平稳非显著增加的特征。对于重金属污染的耕地土壤,在施用外源有机肥时,应同时注重外源DOM和COM对土壤中重金属的潜在活化效应,尤其是降雨径流中重金属的动态变化。     

The role of time preferences in contract breach: Evidence from Chinese poultry farmers participating in contract farming

Farmers’ contract breach behavior is cited as one of the major stumbling blocks in the sustainable expansion of contract farming in many developing countries. This paper examines farmers’ contract breach decisions from the perspective of time preferences. The empirical analysis is based on a household survey and economic field experiments of poultry households participating in contract farming conducted in Jiangsu Province, China. A discounted utility model and a maximum likelihood technique are applied to estimate farmers’ time preferences and the effect of time preferences on contract breach in the production and sales phases are explored with a bivariate probit model. The results show that, on average, the poultry farmers in the sample are generally present biased and impatient regarding future utility. The regression results show that farmers with a higher preference for the present and a higher discount rate are more likely to breach contracts, and time preferences play a greater role in the production phase than in the sales phase. When considering heterogeneity, specific investments and transaction costs promote contract stability only for farmers with a low degree of impatience. Moreover, compared with large-scale farmers, small-scale farmers’ contract breach decisions are more significantly affected by their time preferences. These results have implications for contract stability policies and other issues that are impacted by the linking of behavioral preferences to agricultural decisions.