郯麦98对播种期变化的响应

播种期调整被广泛用于作物适应气候变化, 但播种期调整对作物生长发育过程的影响仍需探讨。基于2017—2022年华北平原北部冬小麦郯麦98的播种期调整大田试验资料, 分析播种期变化对郯麦98的生长发育、产量形成和品质影响。结果表明: 播种期推迟使郯麦98的生长季缩短、有效穗数和籽粒产量减少, 9月30日—10月30日播种期的籽粒产量减少率达569.71 kg·hm-2·(10 d)-1, 但对穗粒数、穗粒重无显著影响。播种期推迟还影响郯麦98成熟期地上干物质分配, 茎秆随播种期推迟呈减少趋势, 为2.44%·(10 d)-1; 而穗部呈增加趋势, 为2.44%·(10 d)-1。播种期变化对郯麦98的叶片光合特性和籽粒品质影响不显著。研究结果可为华北平原北部冬小麦播种期调整提供依据。     

A comparative analysis of three habitat suitability models for commercial yield estimation of Tapes philippinarum in a North Adriatic coastal lagoon (Sacca di Goro, Italy)

Habitat Suitability (HS) models have been extensively used by conservation planners to estimate the spatial distribution of threatened species and of species of commercial interest. In this work we compare three HS models for the estimation of commercial yield potential and the identification of suitable sites for Tapes philippinarum rearing in the Sacca di Goro lagoon (Italy) on the basis of six environmental factors. The habitat suitability index (HSI) is based on expert opinion while the habitat suitability conditional (HSC) is calibrated on observational data. The habitat suitability mixed (HSM) model is a two-part model combining expert knowledge and regression analysis: the first component of the model uses logistic regression to identify the areas in which clams are likely to be present; the second part applies the same parameter-specific suitability functions of the HSI model only in the areas previously identified as productive by the logistic component.The HS models were validated on an independent data set and estimates of potential yield of the Goro lagoon were compared. The effectiveness of the three approaches is then discussed in terms of predicted yield and identification of suitable sites for farming.     

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。     

Can channel banks be the dominant source of fine sediment in a UK river?: an example using 137Cs to interpret sediment yield and sediment source

Cultivated fields have been shown to be the dominant sources of sediment in almost all investigated UK catchments, typically contributing 85 to 95% of sediment inputs. As a result, most catchment management strategies are directed towards mitigating these sediment inputs. However, in many regions of the UK such as the Nene basin there is a paucity of sediment provenance data. This study used the caesium‐137 (¹³⁷Cs) inventories of lake and floodplain cores as well as the ¹³⁷Cs activities of present day sediment to determine sediment provenance. Sediment yields were also reconstructed in a small lake catchment. Low ¹³⁷Cs inventories were present in the lake and floodplain cores in comparison to the reference inventory and inventories in cores from other UK catchments. Caesium‐137 activities in the present day sediments were low; falling close to those found in the channel bank catchment samples. It was estimated that 60 to 100% of the sediment in the Nene originated from channel banks. Pre‐1963 sediment yields were approximately 11.2 t km^?2 yr^?1 and post‐1963 was approximately 11.9 t km^?2 yr^?1. The lack of increased sediment yield post‐1963 and low sediment yield is unusual for a UK catchment (where a yield of 28 to 51 t km^?2 yr^?1 is typical for a lowland agricultural catchment), but is explained by the low predicted contribution of sediment from agricultural topsoils. The high channel bank contribution is likely caused by the river being starved of sediment from topsoils, increasing its capacity to entrain bank material. The good agreement between the results derived using cores and recently transported sediments, highlight the reliability of ¹³⁷Cs when tracing sediment sources. However, care should be taken to assess the potential impacts of sediment particle size, sediment focusing in lakes and the possible remobilization of ¹³⁷Cs from sedimentary deposits. Copyright © 2016 John Wiley & Sons, Ltd.     

Suspended sediment transport in a highly erodible catchment: The River Isábena (Southern Pyrenees)

Understanding and quantifying sediment load is important in catchments draining highly erodible materials that eventually contribute to siltation of downstream reservoirs. Within this context, the suspended sediment transport and its temporal dynamics have been studied in the River Isábena (445 km², south-central Pyrenees, Ebro basin) by means of direct sampling and turbidity recording during a 3-year dry period. The average flood-suspended sediment concentration was 8 g l^− 1, with maximum instantaneous values above 350 g l^− 1. The high scatter between discharge and suspended sediment concentrations (up to five orders of magnitude) has not permitted the use of rating curve methods to estimate the total load. Interpolation techniques yielded a mean annual sediment load of 184,253 t y^− 1 for the study period, with a specific yield of 414 t km^− 2 y^− 1. This value resembles those reported for small torrents in nearby mountainous environments and is the result of the high connectivity between the badland source areas and stream courses, a fact that maximises sediment conveyance through the catchment. Floods dominated the sediment transport and yield. However, sediment transport was more constant through time than that observed in Mediterranean counterparts; this can be attributed to the role of base flows that entrain fine sediment temporarily stored in the channel and force the river to carry high sediment concentrations (i.e., generally in the order of 0.5 g l^− 1), even under minimum flow conditions.     

黄河内蒙古段支流“十大孔兑”侵蚀产沙的时空变化及其成因

“十大孔兑”来沙造成黄河干流强烈淤积.为了通过流域治理来减轻泥沙灾害,研究“十大孔兑”侵蚀产沙过程具有重要意义.基于1960—2005年的河流输沙量、径流量和降雨量资料,运用统计方法进行了研究.结果表明:“十大孔兑”输沙量高度集中于几个大水大沙年份,其余年份对46年总输沙量的贡献很小.最大1年、最大3年、最大5年和最大10年的累积输沙量分别占到46年总输沙量的21.26%、37.18%、47.92%和69.29%.1960—1991年和1992—2005年两个时段相比,后一时段输沙量年均值减少了37%.这一差异可以用暴雨特征的差异和下垫面(如植被)的变化来解释.1991年以后,年降水量无明显变化,但最大1日降雨量在p<0.10的水平上呈现减小的趋势.虽然20世纪90年代西柳沟并未大规模实施水土保持治理,但由于农村富余劳动力转移,对土地的压力减轻,对植被的破坏大大减弱,使得植被逐渐恢复,NDVI呈增大趋势,因而侵蚀产沙减弱.“十大孔兑”产沙模数具有明显的空间分异特征,从西向东增大,在西柳沟达到最大值,然后再减小.流域自然地理因素具有明显的变化,从西向东,沙尘暴频率减小,降雨量增大.沙丘类型也发生了变化,由以流动沙丘为主变为以半固定沙丘为主,进入河道风沙的输沙强度减小.另一方面,水力驱动的侵蚀和泥沙输移从西向东增强.上述两种作用叠加的结果,在区域中部西柳沟附近出现了侵蚀产沙的峰值区.     

小麦单产的遥感—气象综合模式研究

本文以北京顺义县为例,以气象因子与垂直植被指数(PVI)作为参数,用灰色模型G(0,2)和逐段订正模型即阶乘模型,建立冬小表遥感信息-气象因子综合模型。计算结果表明,改进后的综合模型其平均精度比单纯的遥感信息模型提高近7％,个别年份达到10％以上。     

Prediction of sediment yield by coupling Kalman filter with instantaneous unit sediment graph

An instantaneous unit sediment graph (IUSG) model in conjunction with Kalman filter was investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. The state vector of the watershed sediment yield system was constituted by the IUSG and then the sediment yield was estimated by the IUSG model using Kalman filter. The initial values of the state vector were assumed as the average of the IUSG values and the initial sediment yield estimated from the average IUSG. The IUSG model using Kalman filter with a recursive algorithm accurately predicted sediment yield from watershed W‐5, Mississippi. The filter allowed the IUSG to vary in time, increased the accuracy of the IUSG model, and reduced physical uncertainty of the sediment yield process in the watershed. Copyright © 1999 John Wiley & Sons, Ltd.