冬小麦拔节期灌溉防霜冻效果研究

以矮抗58为研究对象,在冬小麦拔节期设置灌溉与未灌溉两种水分处理,通过对无霜冻年份(2012年)和晚霜冻年份(2013年)的对比试验,分析晚霜冻害对冬小麦群体密度、干物质积累、产量及其构成要素的影响,探讨拔节期灌溉的防霜效果。研究结果表明:1)孕穗-抽穗期发生晚霜冻害可使冬小麦群体密度下降、产量显著降低。2012年的产量整体高于2013年的,且2012年未灌溉处理的产量显著高于2013年灌溉处理的(P0.05);受霜冻影响,2013年灌溉与未灌溉的成熟期密度分别比抽穗期下降11.8%和14.8%,地上部分总干物质重先显著下降而后逐渐恢复,和抽穗期相比其下降幅度分别为18.5%(灌溉)和33.7%(未灌溉)。2013年成熟期叶片干重占地上部分总干物质重比例为43.5%(灌溉)和41.0%(未灌溉),显著高于2012年的16.3%(灌溉)和4.1%(未灌溉)。2)无论是否有霜冻害发生,拔节期灌溉均可显著提高产量,灌溉处理产量分别比未灌溉处理的偏高16.3%(2012年)和24.5%(2013年)。霜冻年份拔节期灌溉处理可显著降低穗粒数损失和抽穗期以后叶面积指数的衰减速度。3)2013年灌溉处理较2012年灌溉处理减产23.6%,未灌溉处理较2012年未灌溉处理减产32.9%。拔节期灌溉能够有效减少霜冻造成的产量损失,但这主要是由水分增加所引起,抽穗期的冬小麦抗霜能力并没有提高。     

ENSO and Sea Surface Temperature Anomalies in Association with Canadian Wheat Yield Variability

Interannual variations of spring wheat yields in Canadian agricultural regions are analyzed, together with the associated sea surface temperature (SST) anomalies in the northern hemisphere tropics and extratropics, from 1961 to 2015. The cubic trend is calculated and used to represent the trend related to advances in agricultural technology over this time period. The correlations between Canadian wheat yields at regional scales and the tropical El Niño–Southern Oscillation (ENSO) variability are not robust at any stage of the evolution of ENSO. Based on the power spectrum and cross-spectrum analysis, the most prominent yield variance is found in the Canadian Prairies, with a significant power peak of 4.5 years but does not co-vary significantly with interannual ENSO variability. ENSO weakly affects temperature and precipitation anomalies in the Canadian Prairie Region in summer—two important agroclimatic conditions for crop growth—and hence insignificantly impacts wheat yields. This indicates that there would be little benefit to including tropical ENSO indices in the operational wheat yield forecasting system. For Canadian wheat yield forecasting, attention should be paid to the preceding winter and spring SST anomalies in the northern extratropics. The SST anomalies associated with yields in the Canadian Prairie region and Central Region are generally stronger than those associated with yields in the Canadian Pacific Coast Region and eastern Maritime Region. In association with the Prairie Region and Central Region yields, SST shows pronounced anomalies in the mid-high latitudes of the North Pacific from winter to summer. The non-linearity of the SST anomalies associated with the Canadian yields is also clearly evident. Stronger (weaker) SST anomalies in the extratropical North Pacific correspond to low wheat yields in the Prairie (Central) Region, while weaker (stronger) SST anomalies correspond to high yields in the Prairie (Central) Region.     

全球视野下崩岗侵蚀地貌及其研究进展

典型的崩岗具有“圆形露天剧场”般的沟头,发育在深厚的红色花岗岩风化壳上,通常包括集水坡面、崩壁、崩积体、沟道、洪积扇5个地貌组成部分;崩壁自上而下可分为表土层、风化红粘土层(红土层)、风化砂质红粘土层(砂土层)、风化粗碎屑层(碎屑层)。中国的崩岗与马达加斯加的lavaka属于同类地貌,两者具有地貌学上的可比性。崩岗群是劣地的表现形式之一,但与欧洲的badland有不同的侵蚀过程,也不同于意大利和巴西的两种沟谷侵蚀地貌calanchi和vocoroca。崩岗主要发育在华南和东南热带和亚热带湿润季风气候区中等偏缓的丘陵坡地上,由沟谷侵蚀发展而成,是沟谷侵蚀的高级阶段。崩岗沟道侵蚀产沙量占崩岗沟谷流域侵蚀产沙量的一半以上,其中沟道沟壁崩塌侵蚀产沙量与沟床下切侵蚀产沙量又各占崩岗沟道侵蚀产沙量的一半左右。野外人工模拟降雨试验是研究崩岗流域侵蚀、产流和产沙过程的有效手段。崩岗流域侵蚀产沙量可以通过崩岗沟谷和洪积扇地形测量加以估算。     

Fuzzy logic modeling of the resistivity parameter and topography features for aquifer assessment in hydrogeological investigation of a crystalline basement complex

A linguistic fuzzy logic system (LFLS)-based expert system model has been developed for the assessment of aquifers for the location of productive water boreholes in a crystalline basement complex. The model design employed a multiple input/single output (MISO) approach with geoelectrical parameters and topographic features as input variables and control crisp value as the output. The application of the method to the data acquired in Khondalitic terrain, a basement complex in Vizianagaram District, south India, shows that potential groundwater resource zones that have control output values in the range 0.3295–0.3484 have a yield greater than 6,000 liters per hour (LPH). The range 0.3174–0.3226 gives a yield less than 4,000 LPH. The validation of the control crisp value using data acquired from Oban Massif, a basement complex in southeastern Nigeria, indicates a yield less than 3,000 LPH for control output values in the range 0.2938–0.3065. This validation corroborates the ability of control output values to predict a yield, thereby vindicating the applicability of linguistic fuzzy logic system in siting productive water boreholes in a basement complex.     

Estimation of rice grain yield from dual-polarization Radarsat-2 SAR data by integrating a rice canopy scattering model and a genetic algorithm

Fast and accurate estimation of rice yield plays a role in forecasting rice productivity for ensuring regional or national food security. Microwave synthetic aperture radar (SAR) data has been proved to have a great potential for rice monitoring and parameters retrieval. In this study, a rice canopy scattering model (RCSM) was revised and then was applied to simulate the backscatter of rice canopy. The combination of RCSM and genetic algorithm (GA) was proposed for retrieving two important rice parameters relating to grain yield, ear length and ear number density, from a C-band, dual-polarization (HH and HV) Radarsat-2 SAR data. The stability of retrieved results of GA inversion was also evaluated by changing various parameter configurations.Results show that RCSM can effectively simulate backscattering coefficients of rice canopy at HH and HV mode with an error of <1 dB. Reasonable selection of GA’s parameters is essential for stability and efficiency of rice parameter retrieval. Two rice parameters are retrieved by the proposed RCSM-GA technology with better accuracy. The rice ear length are estimated with error of <1.5 cm, and ear number density with error of <23 #/m². Rice grain yields are effectively estimated and mapped by the retrieved ear length and number density via a simple yield regression equation. This study further illustrates the capability of C-band Radarsat-2 SAR data on retrieval of rice ear parameters and the practicability of radar remote sensing technology for operational yield estimation.     

新疆巴楚气象因子对棉花发育期及产量的影响分析

利用巴楚国家基本气候站1961—2013年53 a的气温、降水量等资料,结合1981—2013年的棉花发育期、单位面积产量,采用线性倾向估计计算、检验方法、气候趋势系数和气候倾向率方法,对1961年以来巴楚气候变化特征、1981年以来棉花发育期、产量进行分析,探讨了巴楚近期气候变化对棉花生产的影响。结果表明:近53 a来,巴楚年和各季平均气温、平均最高气温、平均最低气温总体呈线性上升趋势,其中年平均最低气温的升温率最明显;各季节中春、秋季平均最低气温的升温率最大;年、各季节降水量呈明显的增多趋势,季节中夏季降水量的增幅最大,为3.25 mm/10 a;初霜日的变化呈推后趋势(1.2 d/10 a)、而终霜日呈提前趋势(-2.4d/10 a),使无霜期明显延长(1.1 d/10 a)。近33 a来,巴楚县棉花各发育期均表现出不同程度的提前趋势,其中现蕾期的提前趋势最明显,为4.8 d/10 a(P0.01);棉花停止生长期呈延迟趋势,延迟幅度为3.7 d/10 a(P0.01)。初、终霜冻日、无霜期与棉花产量总体呈正相关,初霜日推后、终霜日提前、无霜期延长,棉花产量增多。     

竖井地基的粘弹—粘塑性固结及有限元解

用1个带双屈服面的粘弹-粘塑性模型来描述软土的流变性状，并结合Biot固结理论对软土地基的固结沉降进行有限元分析。对竖井预固结地基进行计算，以预压所产生的沉降量及所引起的附加有效应力分别大于设计载荷所引起的最终沉降量和附加应力为终止预压的依据，计算取得了合理结果。     

Effect of hot dry summer tropical climate on forage intake and milk yield in Holstein–Friesian and indigenous zebu cows in Sudan

The effects of dry summer ambient temperature on some physiological and productive responses were studied in an exotic European breed (Holstein–Friesian) and a local zebu breed (Butana ecotype) of cattle in Sudan. Rectal temperature and respiration rate were positively correlated, and dry matter intake and milk yield were negatively correlated with variation in ambient temperature. However, significant adverse effects on high ambient temperature were only observed in the exotic breed.     

玉米潜在产量与积温关系模型及其应用

依据于物质积累的基本规律,用包括早、中、晚熟和紧凑、平展两类株型的10个玉米杂交种在北京、延庆、泰安、公主岭、石河子5个不同气候类型地区的试验观察数据,模拟出玉米的标准生长函数W=[1+e~(3.56-13.52μ)]~(-1)。据此建立潜在生物量与品种所需积温的关系:B_(max)/kg·亩~(-1) =100+1.1∑T_m。用此模式估算了不同熟性品种的潜在产量,讨论了模拟结果在气候变化影响评价中的应用。