不同施肥与耕作模式下紫色土坡地产流特征

为了明确施肥与耕作对坡地产流特征的影响,以"冬小麦—夏玉米"种植模式为研究对象,设置对照(T0)、复合施用化肥与农家肥(T1)、单施化肥(T2)、单施化肥增加施肥量(T3)、单施化肥横坡垄作(T4)5种处理,采用径流小区观测法,对紫色土坡地2008—2012年产流特征进行了研究。结果表明,紫色土区产流降雨主要集中在5—9月,6月是产流降雨的峰值期,径流量与降雨量表现出相对一致的规律,产流量变化范围为9.57~100.36mm,径流系数变化范围为0.05~0.19;不同处理年均径流量和年均径流系数依次表现为:T0T3T2T1T4,施肥处理比对照处理径流量减少25.90%~47.50%,T4比T2减少25.46%,年降雨量与年径流量呈幂函数关系;方差分析表明,不同处理间年径流系数、年径流量差异达到显著水平,施肥、耕作和降雨是影响产流的主要因素。     

中国新疆绿洲地区多时空尺度上土壤盐分变化特征及其相关驱动因素研究

Located in the inland arid area of central Asia, salt-affected farmlands take up one third of the total irrigated land area in Xinjiang of Northwest China. Spatio-temporal variability of soil salinity and the underlying mechanism are fundamental problems challenging the sustainability of oasis agriculture in China. In this study, the data of total dissolved solids(TDS) measured for soil samples collected from 27 representative study areas in the oasis areas of Xinjiang were analyzed and the coefficient of variation(CV) and stratification ratio(SR) of TDS were used to describe the lateral and vertical soil salinity variations, respectively. Weekly, monthly,and annual changes in soil salinity were also summarized. Results showed that the top(0–20 cm) soil salinity was highly variable(CV 75%) for most studied areas. Lateral variation of soil salinity was significantly correlated with the sampling interval; as a result, a maximum sampling interval of 0.9 m was found for reducing evaluation uncertainty. The top 0–20 cm soil salt accounted for about25.2% of the total salt in the 0–100 cm soil profile. The stratification ratio values(the ratio of TDS at the 20–40 cm depth to that at the 0–20 cm depth) were mostly smaller than 1 and on average 0.92, illustrating that the top 0–20 cm soil contained slightly more salt and a considerable amount of salt still existed in subsurface and deep horizons. Irrigation reduced top soil salinity by 0.52 g kg-1, or14.6%, within the first week. On average, the relative range of soil salinity, calculated to indicate monthly changes in soil salinity, was58.2% from May to September. A 27-year experiment indicated that cultivation increased soil salinity by 44.4% at a rate of 0.14 g kg-1year-1. At small spatio-temporal scales, soil salinity variation was mainly affected by anthropogenic factors, such as irrigation and land use. However, natural factors, including groundwater, topography, and climate conditions, mainly influenced soil salinity variation at large spatio-temporal scales. This study displayed the highly variable nature of soil salinity in space and time. Those driving factors identified in this study could provide guidelines for developing sustainable agriculture in the oasis areas and combating salinization in arid regions of China.     

源于松针的可溶性有机物对土壤多环芳烃吸附和解吸行为的影响研究

Study of the relationship between plant litter-derived dissolved organic matter（DOM） and organic pollutant transport in soil is important for understanding the role of forest litter carbon cycling in influencing pollutant behaviour and fate in forest soil.With the aim of providing insight into the capacity of plant litter-derived DOM to influence sorption and desorption of selected polycyclic aromatic hydrocarbons（PAHs） on soil, batch experiments were carried out with application of a sorption-desorption model incorporating DOM effects. Freshly fallen pine（Pinus elliottii） needles were used as the source of organic matter. Input of the pine needle litter-derived DOM was found to significantly decrease desorption hysteresis as well as soil adsorption capacity of phenanthrene（PHE） and fluoranthene（FLA）. Addition of 1 728 mg L-1dissolved organic carbon（DOC） lowered the organic carbon-normalized sorption distribution coefficient of PHE from 7 776 to 2 541 L kg-1C and of FLA from 11 503 to 4 368 L kg-1C. Decreases of the apparent sorption-desorption distribution coefficients of PHE and FLA with increased DOC concentration indicated that DOM favored desorption of PAHs from soil. Increases in the fraction of apparently dissolved PAHs were attributable to the dissolved PAH-DOM complexes, accounting for the dissolved proportions of 39% to 69% for PHE and 26% to 72% for FLA in the sorption and desorption processes as the concentration of the added DOM solution rose from 0 to 1 728 mg L-1. Our results suggest that pine needle litterderived DOM can have a substantial effect of inhibiting PAHs sorption and promoting PAHs desorption, thus leading to enhanced leaching in soil, which should be taken into account in risk assessment of PAHs accumulated in forest soil.     

阜新煤矿区次生裸坡土壤抗冲性动态变化

为探讨煤矿区次生裸坡的稳定性,采用径流含沙量和土壤抗冲系数分析方法,对阜新孙家湾煤矸石山的6个典型坡面的表层土壤进行了抗冲性试验。结果表明,矿区次生裸坡不同坡向、不同坡位的径流含沙量和土壤抗冲系数存在较大差异,且均存在一定的动态变化规律。在土壤冲刷过程中,初始径流含沙量均较大,之后呈规律性骤减,并逐渐趋于稳定。与对照样地相比,矿区次生裸坡的总径流含沙量虽少,但衰减速度较快,至冲刷第2min后基本趋于稳定。不同样地径流含沙量与时间之间显著服从于幂函数关系土壤抗冲系数的变化是随着冲刷时间的延长呈现出先缓慢后快速增大趋势,且前10min的抗冲系数表现为:矿区次生裸坡>对照样地。不同样地的土壤抗冲系数与时间之间显著服从于指数函数关系。     

昆明市云龙水库径流区氮磷非点源污染负荷分析

云龙水库是昆明市最大的城市集中式饮用水源地。水源区农业非点源污染是影响水库水质的主要来源,因此分析水库径流区氮磷非点源污染负荷与来源构成,可为饮用水源区水质保护提供科学依据。采用输出系数模型法,对昆明市云龙水库径流区氮、磷负荷的产生量与入库量进行了估算。结果表明:(1)云龙水库径流区氮、磷非点源污染负荷产生量分别为2079.8和454.32t/a,入库量分别为207.98和24.73t/a。(2)从不同乡镇分析,撒营盘镇的氮、磷负荷产生量最高,云龙乡和茂山镇产出量较低,其余乡镇产生量相近。(3)从不同污染源类型分析,该区非点源污染的主要污染源为农村生活污染和畜禽粪便污染。     

不同作物类型下蒸散发时间尺度扩展方法对比

该文的目的是评价由瞬时潜热通量经过时间尺度扩展方法计算日蒸散发量的可靠性。为此,采用蒸发比法、改进的蒸发比法、正弦关系法及作物系数法等4种常用的蒸散发时间尺度扩展方法,针对位于华北平原的高营站和位于东北平原的通榆站的5种典型下垫面类型,分别对瞬时潜热通量进行时间尺度扩展,估算日蒸散发量,并与通量站采用涡度相关系统观测的日蒸散发量进行对比。结果表明,尽管4种方法在总体上具有一致性,但改进的蒸发比法的模拟精度最高(相对均方根误差20%左右),更适合于估算中国北方典型农田的日蒸散发量。然而,4种方法均存在系统误差,从而导致采用上午时段瞬时通量估算的日蒸散发量系统偏小,而采用下午时段估算的日蒸散发量系统偏大。     

云蒙湖流域非点源磷污染时空变化研究

运用输出系数模型,在GIS & RS支持下,对云蒙湖流域非点源磷污染进行了时空动态模拟.结果表明,1986-2010年,云蒙湖流域非点源磷污染负荷量明显增加,1986、1995与2010年TP负荷量分别为100.98,123.57,144.36 t;从空间分布来看,TP高负荷区主要分布于流域的河谷低平地带,主要是由于该区集中了大部分农业耕作区,化肥施用量高;从土地利用类型来看,耕地非点源污染TP逐年增加,其贡献率也逐年增加,由1986年的89.5％,1995年91.35％上升至2010年92.02％,林地、草地TP变化较小,贡献率呈减小趋势,居民用地TP增加幅度大,但由于面积较小,其贡献率较小;对于子流域而言,耕地面积比例高的子流域,TP负荷强度增加程度较大,TP负荷强度较大的子流域逐渐由中东部地区向全流域扩展.     

基于浸入边界法的翼型俯仰振摆动态特性

为了探究翼型振摆运动时的动态特性以及升力波动形成机制,采用基于浸入边界法的自编求解器,对NACA0012翼型在1000雷诺数作不同起始攻角、不同振摆频率、不同振摆幅值的俯仰振摆运动进行了直接数值模拟,并分析了升力系数的波动特性和其与流场演变的相关性.结果表明:翼型的高频振摆(2.92 Hz)较低频振摆(1.46 Hz)...     

结蜡厚度与土壤总传热系数相关性影响研究

针对铁大线低输量运行开展了管道结蜡的预测及与土壤总传热系数相关性影响研究,给出了铁大线低输量运行条件下的经济结蜡厚度以及结蜡厚度与土壤总传热系数的相关式,确定了各站间的总传热系数和管道的安全最低输量,提高了管道在综合处理工艺条件下的热力校核的准确性,为铁大线低输量运行热力系统改造节约了费用.     

Higher crop performance of rice hybrids than of elite inbreds in the tropics: 2. Does sink regulation,rather than sink size,play a major role?

Higher harvest index, widely reported as a main trait supporting major improvements in rice yield potential, also supports the higher performance of hybrids over inbreds. Although higher sink size is generally claimed for being the driver of higher grain filling in hybrid rice, it is relevant to question whether efficient sink regulation, that is timing and magnitude of the successive sink activities over crop growth from early stage, plays a role in supporting higher harvest index and is a key feature ensuring higher performance of hybrid rice. The partitioning coefficient (PC), as the increase in dry matter of one single organ over that of shoot, was calculated over short and successive periods to quantify the dynamics of dry matter partitioning. Four hybrid and four inbred genotypes of similar crop duration were grown under the same cropping management on the IRRI farm during a wet and a dry seasons. While PC to blade and sheath was similar for both plant types in both seasons at the early stage, PC to culm of hybrids was higher than that of inbreds, and PC to blade was lower, in the late vegetative and early reproductive phases. During the late reproductive phase, PC to panicle of hybrids was higher than that of inbreds, and PC to culm was lower whereas culm elongation was similar for both plant types. During grain filling, PC to culm was significantly more negative with hybrids which indicated stronger remobilization with hybrids. Specific culm length before anthesis, as low as 40 cm g⁻¹, accounted for storage ability, and at maturity, as high as 130 cm g⁻¹, for remobilization ability. Sink strength index, as a better indicator of dry matter partitioning efficiency than harvest index, and unfilled grain size, as an indicator of assimilate wastage, were suggested as key indices to account for the better sink regulation in hybrid rice and to improve screening protocols for increasing yield potential and tolerance to lodging.