A meta-analysis of global crop water productivity of three leading world crops (wheat,corn, and rice) in the irrigated areas over three decades

ABSTRACT

The overarching goal of this study was to perform a comprehensive meta-analysis of irrigated agricultural Crop Water Productivity (CWP) of the world’s three leading crops: wheat, corn, and rice based on three decades of remote sensing and non-remote sensing-based studies. Overall, CWP data from 148 crop growing study sites (60 wheat, 43 corn, and 45 rice) spread across the world were gathered from published articles spanning 31 different countries. There was overwhelming evidence of a significant increase in CWP with an increase in latitude for predominately northern hemisphere datasets. For example, corn grown in latitude 40–50° had much higher mean CWP (2.45?kg/m³) compared to mean CWP of corn grown in other latitudes such as 30–40° (1.67?kg/m³) or 20–30° (0.94?kg/m³). The same trend existed for wheat and rice as well. For soils, none of the CWP values, for any of the three crops, were statistically different. However, mean CWP in higher latitudes for the same soil was significantly higher than the mean CWP for the same soil in lower latitudes. This applied for all three crops studied. For wheat, the global CWP categories were low (≤0.75?kg/m³), medium (>0.75 to <1.10?kg/m³), and high CWP (≥1.10?kg/m³). For corn the global CWP categories were low (≤1.25?kg/m³), medium (>1.25 to ≤1.75?kg/m³), and high (>1.75?kg/m³). For rice the global CWP categories were low (≤0.70?kg/m³), medium (>0.70 to ≤1.25?kg/m³), and high (>1.25?kg/m³). USA and China are the only two countries that have consistently high CWP for wheat, corn, and rice. Australia and India have medium CWP for wheat and rice. India’s corn, however, has low CWP. Egypt, Turkey, Netherlands, Mexico, and Israel have high CWP for wheat. Romania, Argentina, and Hungary have high CWP for corn, and Philippines has high CWP for rice. All other countries have either low or medium CWP for all three crops. Based on data in this study, the highest consumers of water for crop production also have the most potential for water savings. These countries are USA, India, and China for wheat; USA, China, and Brazil for corn; India, China, and Pakistan for rice. For example, even just a 10% increase in CWP of wheat grown in India can save 6974 billion liters of water. This is equivalent to creating 6974 lakes each of 100?m³ in volume that leads to many benefits such as acting as ‘water banks’ for lean season, recreation, and numerous ecological services. This study establishes the volume of water that can be saved for each crop in each country when there is an increase in CWP by 10%, 20%, and 30%.     

两种沉水植物对黄颡鱼(Pseudobagrus fulvidraco)夏花培育水体主要水质因子的影响

以黄颡鱼夏花培育水体为实验用养殖污水,伊乐藻、轮叶黑藻作为净化水质的沉水植物材料,建立封闭型(非换水)和交换型(定期换水)的两种鱼草共生的生态系统并与传统的商业性养殖系统模式作同步比较,分析了养鱼水体水质主要因子的变化及对鱼存活率的影响．实验结果如下：1．作为实验组的鱼草共生系统两种水体水质优良,鱼类生长良好,交换型水体中D0值≥8．0,NH4—N≤0．34,COD≤18mg/L,悬浮物≤12mg/L夏花成活率为93．3％;封闭型水体中D0值≥7．5,总NH4—N≤0.92,COD≤28mg/L,悬浮物毒20mg/L夏花成活率为60．0%．2．作为对照组有色无草的封闭系统中水质逐渐恶化,鱼类生长受到抑制甚至生存也不能保障,其中,D0值≥2．5,NH4-N≤3.22,COD≤88mg/L,悬浮物≤55mg/L,夏花成活率仅为6．7％;交换系统中D0值≥4．0,总NH4—N≤2．41,COD≤66mg/L,悬浮物≤51mg/L,即使定期换水夏花成活率也仅达66．7％;研究结果表明：鱼草共生系统中栽培伊乐藻、轮叶黑藻等沉水植物可有效地净化水质,不仅确保了夏花生产良性运行,还节约了水资源并达到无污染排放．     

2007-2019年太湖藻型和草型湖区叶绿素a变化特征及影响因子

基于太湖31个站点的逐月监测数据,分析了2007-2019年太湖藻型湖区和草型湖区的叶绿素a变化特征,并分析研究不同环境因子对不同类型湖区叶绿素a的影响.结果表明,近年来太湖不同类型湖区的总磷浓度和叶绿素a浓度变化基本一致,均呈波动上升趋势.不同类型湖区的总磷浓度拐点均为2015年,叶绿素a浓度拐点均为2016年.最低月平均水温、前冬积温、年平均水温、年均风速与藻型湖区和草型湖区叶绿素a浓度均呈显著相关.沉水植物分布面积与草型湖区叶绿素a浓度之间呈显著相关.湖西区年内和年度降雨剧烈变化,湖西区年降雨量与不同类型湖区当年叶绿素a浓度的关系不明显,5日极端降雨量与不同类型湖区下年度叶绿素a浓度均呈显著正相关.太湖蓝藻水华强度在短期内可能仍会处于较高水平,迫切需要高度重视高温时段太湖蓝藻打捞处置工作,保障饮用水安全;同时,要进一步加强湖西区强降雨期间的非点源污染防控措施研究,推动入湖污染通量稳步降低,并探索东西山之间及东茭咀附近水域沉水植物生态修复技术,降低风浪扰动作用,尽快恢复相关重要水域的沉水植物.     

鄱阳湖湿地典型中生植物水分利用来源的同位素示踪

水分是维持植物生长、决定种群分布的关键因子,研究植物水分利用来源是揭示水文过程与植被演替作用机制的基础,作为中国最大的淡水湖泊系统,鄱阳湖水文情势的显著改变已直接影响到湿地生态系统的水分补给来源.本文通过测定降水、土壤水、地下水、湖水和植物茎水中δ¹⁸O、δD同位素组成,识别鄱阳湖湿地典型中生植被——茵陈蒿（Artemisia capillaris）群落的土壤水分补给来源,并应用直接对比法和IsoSource多源混合模型估算优势种茵陈蒿的主要吸水区间及水源利用比例.结果发现：（1）与降水同位素相比,湖水和湿地土壤水同位素较为富集,地下水同位素较少发生分馏;（2）湿地地下水主要受历史长期降水和湖水共同补给,土壤水在雨季4—6月和秋季9—10月主要受降水补给,夏季7—8月深层土壤水受湖水侧向入渗和地下水的共同补给,并在蒸发作用下水分向浅层土壤传输;（3）茵陈蒿主要利用0~80 cm深度的土壤水,且能够在不同土层水源间灵活转换.当土壤含水量较高时（4—5月）,主要利用0~40 cm浅层土壤水,利用率约49%~68%;当浅层土壤含水量较低时（6—8月）,主要利用40~80 cm深层土壤水,利用率高达74%~95%;当植物进入生长后期（9—10月）,主要利用0~15 cm表层土壤水,利用率介于41%~70%.总体发现,湖水是鄱阳湖湿地中生植物群落土壤水分的重要补给来源,优势种茵陈蒿能够响应土壤含水量的变化改变吸水深度,具有较强的干旱适应能力.研究结果可为鄱阳湖湿地植被生态系统演变和科学保护提供理论参考.     

三峡水库消落区植物群落演变趋势及优势植物适应策略

三峡水库周期性蓄水显著改变了消落区植物群落组成及多样性,植物群落的演变过程能反映和影响整个消落区生态系统的变化,但目前还缺乏长期连续的观测数据记录,因而本研究基于2009—2021年6月的固定样方长时间序列监测数据和优势植物叶片功能性状数据,分析了消落区3个高程(145～155、155～165和165～175m)区域植物群落多样性和优势植物重要值的变化趋势,通过冗余分析和蒙特卡罗检验揭示了水库运行特征参数和气象因子对消落区植物特征的影响。研究发现:1)消落区3个高程区域,优势植物差异明显,145～155和155～165 m区域以狗牙根、香附子和苍耳等为主,165～175 m区域以狗牙根、野胡萝卜和鬼针草等为主。145～155 m区域植物群落Shannon-Wiener多样性指数(1.47±0.47)和Pielou均匀度指数(0.67±0.07)显著低于165～175 m区域。2)2009—2021年期间,高程145～155和155～165 m区域Shannon-Wiener多样性指数和Pielou均匀度指数呈波动下降趋势,优势植物狗牙根和香附子的重要值呈增加趋势。3) RDA分析表明,...     

能动断层的概念及其演化

对能动断层概念史的研究,可以揭示出能动断层的核心意义以及与活动断层的区别和联系。能动断层的鉴定以确定未来地表或近地表断层错断可能性为目的,与地震地面运动相比是一种不可设计的厂址评价要素。因此,在厂址适宜性评价中意义重大。     

Impact factors on distribution and characteristics of natural plant community in reclamation zones of Changjiang River estuary

To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness (MA), species diversity (H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance (D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels (R = 0.55, p < 0.05), soil moisture (R = 0.53, p < 0.05), soil salinity (R = 0.43, p < 0.05) and reclamation time (R = 0.40, p < 0.05).     

ESTIMATE OF METHANE EMISSIONS FROM RICE FIELDS IN CHINA BY CLIMATE-BASED NET PRIMARY PRODUCTIVITY

1INTRODUCTIONIrrigated ricefieldsarecharacterizedbylargespatialandtemporalvariationsin CH4 emissiontotheatmo-sphere.Accordingly,thereisagreatuncertaintyintheestimate ofCH4 emissionsfromricefields.GreateffortshavebeenmadetoestimatetheCH4 emissionsfromricefieldsandseveralapproacheshavebeendeveloped.TherepresentativemethodsincludetheIPCC(Inter-governmentPanelofClimateChange)region-specificemissionfactormethodandthemodelcalculationmethod.Toimprovethecalculationaccuracy,theIPCCmethodreq…     

稻壳灰加筋土力学性能研究

稻壳灰与土体混合应用,一方面废弃资源再利用,环保,又可增强土体强度。通过三轴试验,研究不同比例稻壳灰混合黏土及其加筋土应力-应变性能、强度特性以及不同应变水平下模量、偏应力及加筋强度比等土体变化特征。试验结果表明,随稻壳灰比例增加,混合土最大干密度显著减小,最优含水率显著增加。添加不同比例稻壳灰对加筋土抗剪强度有较大影响,10%～15%稻壳灰比例下,加筋稻壳灰混合土初始切线模量和应力峰值达到最大,抗剪强度较优。与土工织物加筋稻壳灰混合土相比,土工格栅加筋稻壳灰混合土偏应力及抗剪强度更大,土工格栅层数对土体抗剪强度增大效果更明显,对应的应力-应变曲线拐点也更突出。试样弹性模量与稻壳灰比例及筋材种类、层数有关,加入稻壳灰后,土体弹性模量增长显著,土工格栅加筋稻壳灰混合土较优比例下可增加1.5倍多,稻壳灰及筋材均能有效提高土体强度。随加筋层数增加,稻壳灰混合土加筋强度比明显增大,与围压关系较小。     

雪宝顶区块流域钙华形成的生物作用研究

钙华不仅具有重要的景观旅游价值,而且对确定区内碳酸盐沉积特征、环境演化规律及同期环境生物的作用与贡献有重要的研究意义。本文在对比国内外典型钙华特征的基础上,以黄龙和九寨沟为例,对雪宝顶区块流域内钙华的沉积特征、环境化学与生物作用进行阐述,指出了雪宝顶区块流域冷水型钙华的形成与演化是化学沉积-溶解作用、生物沉积与溶蚀作用等共同作用的结果,并受非生物、生物因素影响。在雪宝顶冷水型钙华的形成过程中,微生物协同参与了钙华的沉积与溶蚀过程,通过自身新陈代谢促活动促使使钙离子结晶,并诱导晶型变化;其他生物体如植物、藻类等或以间接的方式促进或加快了钙华形成,或为钙华生长提供模板和体量。