陕西关中地区生态需水量的初步估算

生态需水量的计算是水资源优化配置的前提和基础。通过分析生态需水的概念和分类,将陕西关中地区的生态需水划分为3类:河道外的生态需水、河道内的生态需水和城市生态需水。详细界定了3种生态需水的内涵和计算方法。植被生态需水量的计算采用直接计算法,即各种植被面积和植被蒸散发量的乘积求和;人工水域生态需水量的计算采用多年平均蒸发量与降水量的差值乘以水域面积;河流基本生态基流量以早期未遭到人类破坏的河流(渭河1963-1983年)最小月平均实测径流量的多年平均值作为基准;河流输沙需水量以多年平均输沙量与多年最大月平均含沙量的平均值的比值来计算。结合现有的数据,对关中地区的生态需水量进行了估算,现状水平年(2005年)生态需水量是45.73×108m3。由于生态需水是一定经济技术条件下的产物,可以根据现状水平年生态需水量来计算其他年份的生态需水量。     

毛乌素沙地不同水分梯度根系垂直分布与土壤水分关系的研究

通过对毛乌素沙地不同水分梯度根系垂直分布的研究表明:不同水分梯度根系分布随土壤深度的增加呈指数形式下降,不同梯度由于土壤水分、植被根系类型的差异,不同水分梯度植被根系的空间分布也有差异,不同梯度根量随土壤垂直深度的模拟方程分别为:y=9.5736e-0.1341x,R2=0.8859(I);y=16.246e-0.2037x,R2=0.9301(II);y=32.001e-0.1904x,R2=0.9544(III);y=28.336e-0.1993x,R2=0.9484(IV)。不同水分梯度土壤含水率变化程度不同,同一水分梯度各层土壤含水率变化幅度亦有差异,0.1m土壤含水率变异系数最大,随着土壤深度增加变异系数减小,根据土壤含水率变异系数分析我们将各层土壤水分垂直变化划分为活跃层(0-0.1m)、次活跃层(0.2-0.6m)、相对稳定层(1m)(I、II、III);而对IV梯度划为活跃层(0-0.1m、1m)、相对稳定层(0.3m)。根系生物量垂直分布与其对应土壤含水率有明显相反的关系,土壤含水率的变化与根系生物量的变化趋于相反,当土壤含水率增大时相应区域根系生物量减小;反之则增加。随水分梯度的增加各梯度最高水分利用层逐渐向表层发展,从第I梯度0.4m的6.84到第IV梯度0.1m的14.33。     

Seasonal patterns in water uptake for Medicago sativa grown along an elevation gradient with shallow groundwater table in Yanchi county of Ningxia,Northwest China

Lucerne(Medicago sativa L.) is a deep-rooted perennial leguminous forage with high evapo-transpiration rate exceeding the annual precipitation in semi-arid areas of Northwest China.Groundwater might be the potential water sources of lucerne in the area with shallow groundwater table.In this study,stable isotopic compositions of oxygen and hydrogen(δ18O and δD) of different water sources and xylem sap were analyzed to determine the seasonal(April,June,July and August) and topographic(three slope positions) variations in water sources for lucerne growing in Ningxia eastern semi-arid area adjacent to Mu Us Desert characterized by shallow groundwater table.Iso Source software was used to calculate the probable contribution of different water sources to the total plant water uptake.Stomatal conductance,stem water potential,carbon isotope discrimination(?~(13)C) of whole plant were also determined for evaluating the water status of lucerne growing at different slope positions.The results showed that soil water content increased as the elevation decreased.Oxygen compositions of soil water in the 0–40 cm profile fluctuated considerably.Soil water δ~(18)O values in deep profile(3.5 m) were similar to those in groundwater,implying the recharge of groundwater to this soil layer.Highest water utilization rate from deep soil profile(below 350 cm) was recorded for lucerne grown at the slope position 1(groundwater table depth of 3.5–3.9 m) in April,June and July.The lucernes at slope position 2(groundwater table depth of 5.8–6.4 m) and slope position 3(groundwater table depth 7.1–8.3 m) mostly used water from deep soil layers(below 350 cm) during dry period,and turned to use water from superficial soil layer in wet period.Higher yield,?~(13)C value of whole plant and stomatal conductance were observed for lucerne grown at the slope position 1 than those at other slope positions.These results indicated that groundwater is a significant water source for transpiration of lucerne grown in Ningxia semi-arid area with shallow groundwater table where lucerne grassland is suggested to be established so as to obtain better yield performance.     

不同覆盖种植方式与平衡施肥对旱地春玉米产量及水分利用效率的影响

采用田间试验方法,研究了不同覆盖种植方式与平衡施肥对旱地春玉米产量及其水分利用效率的影响。结果表明, 三种覆盖种植方式中,全膜双垄沟播种植方式有利于玉米碳水化合物的合成,增加玉米干物质积累量,N、P、K平衡施肥干物质积累量增加效果明显;与全膜双垄沟播相比,半膜覆盖和裸地种植玉米籽粒产量分别减产8.5%～17.6%和61.1%～95.3%,水分利用效率分别降低3.5%～15.1%和52.8%～60.2%;N、P₂O₅和K₂O的用量分别为225、120、60 kg·hm^-2时,F₁N₁处理玉米籽粒产量和水分利用效率最高。研究表明,在玉米全膜双垄沟播栽培技术条件下,平衡施肥可显著提高玉米籽粒产量和水分利用效率。     

干旱、半干旱区平原水库对坝后盐渍化的影响

为了农业灌溉,干旱、半干旱区修建大量的平原水库,坝基多位于第四纪松散深厚覆盖层上,深厚覆盖层地基上平原水库的渗漏引起坝后地下水位抬升,造成水库下游大面积土地盐渍化,使许多土地减产甚至弃耕。通过对代表性平原水库的监测,分析水库对坝后地下水临界水位的影响程度,进而分析防渗措施的型式。利用有限元计算了深厚覆盖层透水坝基垂直防渗墙和水平铺盖时,坝基渗流量与防渗体尺寸的关系,并联合坝后排水体进行综合控制地下水临界水位,推导出控制地下水临界水位的水库防渗体尺寸计算公式。结合工程实例计算表明,选择合理的防渗体型式并结合排渗体联合控渗,可以从源头上控制坝基的渗漏量,使坝后地下水位控制在临界水位以下,防治坝后土壤的次生盐渍化问题。     

Allelopathic potential of itchgrass (Rottboellia exaltata L. f.) powder incorporated into soil

Itchgrass ( Rottboellia exaltata L. f.) is a widespread weed in northern Thailand. The farmers in this area have been using itchgrass as a mulching material in order to control other weeds in vegetable fields. Laboratory experiments were undertaken to investigate the phytotoxic activity of itchgrass powder incorporated into soil in order to evaluate the allelopathic activity in the field. The phytotoxic activity on the growth of radish seedlings ( Raphanus sativa L. var. radicula ), used as a test plant, was more pronounced in the root than in the shoot growth. The phytotoxic activity was found to be similar for the soils incorporated with the shoot or the root powder of itchgrass. The growth of the radish seedlings grown in sea sand and watered with soil water obtained from the soil previously incorporated with itchgrass powder showed a similar inhibition to those planted in the treated soil. The phytotoxic activity on the growth of the radish seedlings in the soil incorporated with the powder decreased over time. It is suggested that itchgrass releases phytotoxic compound(s) into soil water and the concentration of the active compound(s) in the soil water decreases over time.     

新疆博斯腾湖水环境问题研究

博斯腾湖是塔里木河流域4大源流--开都河的尾闾湖,孔雀河的源地.位于焉耆盆地东南,是我国最大的一个十分特殊,而又非常重要的内陆淡水湖泊.湖水清澈、水温适中(18.2～19.7 ℃),水生生物资源丰富.湖区西岸大片沼泽湿地是我国优质芦苇生产基地.博斯腾湖不仅对焉耆盆地和孔雀河流域环境具有调节作用,更为重要的是对当地的经济社会环境的可持续发展、对区域环境友好建设具有直接的影响.基于物质和能量的守恒理论,消耗品必须有出处,废弃物必须有去处.河流和气流在给博斯腾湖带来各种径流的同时,也带来了自然和人类活动产生的废弃物,导致湖泊生态功能受损.为适应变化着的湖泊环境,人类曾采取了一些限制自我行为的措施,收到了一定的成效.通过分析博斯腾湖水污染现状、机理,提出进一步适应和改善博斯腾湖水环境的措施.