Reflections on food security under water scarcity

Forecasts on population growth and economic development indicate that there will be substantial increases in food demand for the forthcoming decades. We focus here on the water requirements of food production, on the issue of whether there would be enough water to produce sufficient food in the future, and we offer options to face this challenge based on recent trends observed in some agricultural systems. Given the competition for water faced by the agricultural sector, and the uncertainties associated with climate change, improving the efficiency of water use in both rain-fed and irrigated systems is the main avenue to face the challenge. In rain-fed agriculture, managing the risk associated with rainfall variability is a promising option to increase productivity. In irrigated systems, a case study on the improvements in water productivity in Andalusia, Spain, is used to illustrate some of the opportunities to make progress. Progress in reducing irrigation water use in recent decades has been substantial, but decreasing the consumptive use of crops is a much more difficult challenge. The need for more research and technology transfer on improving water-limited crop production is highlighted, and emphasis is placed on interdisciplinary approaches to gain the insight needed to achieve new breakthroughs that would help in tackling this complex problem.     

The water footprint of Tunisia from an economic perspective

This paper quantifies and analyses the water footprint of Tunisia at national and sub-national level, assessing green, blue and grey water footprints for the period 1996–2005. It also assesses economic water and land productivities related to crop production for irrigated and rain-fed agriculture, and water scarcity. The water footprint of crop production gave the largest contribution (87%) to the total national water footprint. At national level, tomatoes and potatoes were the main crops with relatively high economic water productivity, while olives and barley were the main crops with relatively low productivity. In terms of economic land productivity, oranges had the highest productivity and barley the lowest. South Tunisia had the lowest economic water and land productivities. Economic land productivity was found to explain more of the current production patterns than economic water productivity, which may imply opportunities for water saving. The total blue water footprint of crop production represented 31% of the total renewable blue water resources, which means that Tunisia as a whole experienced significant water scarcity. The blue water footprint on groundwater represented 62% of the total renewable groundwater resources, which means that the country faced severe water scarcity related to groundwater.     

Differential response of wild and cultivated wheats to water deficits during grain development: changes in soluble carbohydrates and invertases

Wheat, staple food crop of the world, is sensitive to drought, especially during the grain-filling period. Water soluble carbohydrates (WSCs), stem reserve mobilization and higher invertase activity in the developing grains are important biochemical traits for breeding wheat to enhance tolerance to terminal drought. These traits were studied for three accessions of Triticum dicoccoides(a tetraploid wheat progenitor species) - acc 7054 (EC 171812), acc 7079 (EC 171837) and acc 14004 (G-194-3 M-6 M) selected previously on the basis of grain filling characteristics. Check wheat cultivars- PBW-343 (a popular bread wheat cultivar for irrigated environments) and C-306 (widely adapted variety for rain-fed agriculture) were also included in this set. Analysis of variance revealed significant genotypic differences for the content of water soluble carbohydrates, activity of acid invertase and alkaline invertase. Acc 7079 was found to be a very efficient mobilizer of water soluble carbohydrates (236.43 mg g^-1 peduncle DW) when averaged over irrigated and rain-fed conditions. Acid invertase activity revealed marked genotypic differences between wild and cultivated wheats. Alkaline invertase activity was highest in Acc 7079 when pooled across both the environments. On the whole, acc 7079 qualifies as a suitable donor for enhancing tolerance of bread wheat to terminal drought. The association of physio-biochemical differences observed with grain filling attributes on one hand and molecular markers on the other could be of use in improving wheat for water stress conditions.     

Current Productivity and Prehistoric Use of Piñon (Pinus edulis,Pinaceae) in the Dolores Archaeological Project Area,Southwestern Colorado

The possible contribution of pinon (Pinus edulis) seed to the diet of an Anasazi population is investigated using present data on seed productivity and archaeological data on resource use. Annual estimates of total productivity for a 135.7 sq km study area in Montezuma County, Colorado, vary by a factor of 141 in a sample spanning 5 yr. Trees greater than about 25 cm (basal diameter) are usually monoecious and produce significantly more cones per tree but fewer good seeds per cone than smaller, usually dioecious specimens. Archaeological data suggest that piñon seed was a relatively unimportant food item after the initial period of Anasazi colonization of the Dolores River valley about a.D. 600. Use of piñon seed as food was inversely related to degree of agricultural intensification and use of piñon for fuel.     

Foliar pathogenesis and plant water relations: a review

As the world population grows, there is a pressing need to improve productivity from water use in irrigated and rain-fed agriculture. Foliar diseases have been reported to decrease crop water-use efficiency (WUE) substantially, yet the effects of plant pathogens are seldom considered when methods to improve WUE are debated. We review the effects of foliar pathogens on plant water relations and the consequences for WUE. The effects reported vary between host and pathogen species and between host genotypes. Some general patterns emerge however. Higher fungi and oomycetes cause physical disruption to the cuticle and stomata, and also cause impairment of stomatal closing in the dark. Higher fungi and viruses are associated with impairment of stomatal opening in the light. A number of toxins produced by bacteria and higher fungi have been identified that impair stomatal function. Deleterious effects are not limited to compatible plant-pathogen interactions. Resistant and non-host interactions have been shown to result in stomatal impairment in light and dark conditions. Mitigation of these effects through selection of favourable resistance responses could be an important breeding target in the future. The challenges for researchers are to understand how the effects reported from work under controlled conditions translate to crops in the field, and to elucidate underlying mechanisms.     

基于遥感和地面数据的景观尺度生态系统生产力的模拟

描述了一个反映系统碳循环和水循环的景观尺度生态系统生产力过程模型(EPPML)．该模型以遥感图像作为数据源,从中获取影响植被生产力的重要变量——叶面积指数(LAI);主要对景观尺度生态系统的净初级生产力(NPP)和蒸散量的空间分布格局和时间动态进行模拟;用地理信息系统(GIS)手段对空间数据进行处理、分析和显示,从而实现将植物生理生态研究的结果从小尺度向中尺度进行拓展和转换．本研究用EPPML对1995年长白山自然保护区的植被生产力进行了模拟,结果表明,EPPML可以比较准确地模拟该保护区主要植被的NPP．NPP的模拟值年均为0．680kgC·m^-2,变幅为0．105—1．241kgC·m^-2(82.1％),其中阔叶红松林的年NPP最高(1．084kgC·m^-2)．NPP年总量为1．332×10^6tC,以阔叶红松林和云冷杉林最高,分别为0．540×10^6tC和0．428×10^6tC．NPP的季节变化呈明显的单峰型,7月最大(6．13gC·m^2·d^-1)．NPP在夏季积累最多(0．465kgC·m^-2),春季次之,冬季最少。     

Agronomic improvements can make future cereal systems in South Asia far more productive and result in a lower environmental footprint

South Asian countries will have to double their food production by 2050 while using resources more efficiently and minimizing environmental problems. Transformative management approaches and technology solutions will be required in the major grain‐producing areas that provide the basis for future food and nutrition security. This study was conducted in four locations representing major food production systems of densely populated regions of South Asia. Novel production‐scale research platforms were established to assess and optimize three futuristic cropping systems and management scenarios (S2, S3, S4) in comparison with current management (S1). With best agronomic management practices (BMPs), including conservation agriculture (CA) and cropping system diversification, the productivity of rice‐ and wheat‐based cropping systems of South Asia increased substantially, whereas the global warming potential intensity (GWPi) decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were achieved. In comparison with S1, S4, in which BMPs, CA and crop diversification were implemented in the most integrated manner, achieved 54% higher grain energy yield with a 104% increase in economic returns, 35% lower total water input, and a 43% lower GWPi. Conservation agriculture practices were most suitable for intensifying as well as diversifying wheat–rice rotations, but less so for rice–rice systems. This finding also highlights the need for characterizing areas suitable for CA and subsequent technology targeting. A comprehensive baseline dataset generated in this study will allow the prediction of extending benefits to a larger scale.     

三江平原粮食作物生产水足迹时空特征及影响因素

水足迹是评价人类活动对水资源开采和水环境污染程度的重要方法,对农作物生长过程的绿水足迹、蓝水足迹和灰水足迹进行量化和分析,可以为农业用水综合评价和用水管理提供指导。以三江平原为研究区域量化粮食作物生产水足迹的时空特征,揭示粮食生产对区域水资源的占用情况,并分析水足迹的影响因素。结果表明:(1)三江平原粮食生产水足迹总量在2005-2018年间呈显著增加趋势,其中绿水足迹、蓝水足迹和灰水足迹在水足迹总量中的占比历年平均为28%、8%和64%;(2)粮食生产水足迹空间差异明显,在地市尺度,佳木斯市水足迹最高,占三江平原总量的47%,在县区尺度,富锦市、依兰县和桦南县是水足迹热点地区;(3)只考虑蓝水足迹,粮食生产给三江平原水资源造成轻度压力,而同时考虑蓝水和灰水足迹,粮食生产给三江平原水资源造成重度压力;各地市间水资源压力有较大差异,其中佳木斯市负担了该区域将近一半的粮食产量,水资源压力最高,鹤岗市则水资源压力最低;(4)降雨量、灌溉水利用效率、化肥施用量、粮食种植结构和作物单产水平等都会影响粮食作物生产水足迹,其中蓝水足迹响应种植结构的变化最敏感,灰水足迹响应化肥施用量的变化最敏感,而水足迹总量响应作物单产水平的变化最敏感。因此,建议减少化肥施用量、提高作物单产水平和优化作物种植结构纳入区域水资源可持续管理之中。     

有机农业与可持续发展

从国内外有机农业研究与生产发展状况出发,阐述了我国绿色食品研究的目标、生产中坚持的原则;结合国外有机农业和可持续农业的争论,论证了“替代农业”的理论和实践意义．与常规农业高强度农业生产方法相比。有机农业生产方式能够培肥土壤,对环境的影响很小．有机农业为代表的“替代农业”的研究与实践已近一个世纪,我国的绿色食品事业的发展已历时十几年．讨论有机农业“环境友好”和对人体健康为主要宗旨的食品生产方式,以及维持农业系统的可持续性问题,对我国绿色食品产业的发展具有积极的指导作用。     

Energy balance, metabolism, hydration, and performance during strenuous hill walking: the effect of age.

We aimed to examine the effect of age on energy balance, metabolism, hydration, and performance during 10 days of strenuous hill walking. Seventeen male subjects were divided into two groups according to their age. The nine subjects in group 1 constituted the younger group (age 24 +/- 3 yr), whereas eight older subjects were in group 2 (age 56 +/- 3 yr). Both groups completed 10 consecutive days of high-intensity hill walking. Mean (range) daily walking distances and ascent were 21 km (10-35 km) and 1,160 m (800-2,540 m), respectively. Energy intake was calculated from weighed food intake, and energy expenditure was measured by the doubly labeled water method. Blood and urine were sampled on alternative days to determine any changes in metabolism and hydration during the 10 days. Subjects also completed a battery of tests that included muscular strength (handgrip), jump performance, cognitive processing time, and flexibility. The younger group remained hydrated, whereas the older group became progressively dehydrated, indicated by a near twofold increase in urine osmolality concentration on day 11. This increased urine osmolality in the older group was highly correlated with impairment in vertical-jump performance (r = -0.86; P < 0.05) and decreased cognitive processing time (r = 0.79; P < 0.05). Despite energy expenditure of approximately 21 MJ/day, body mass was well maintained in both groups. Both groups displayed a marked increase in fat mobilization, reflected in significantly lowered prewalk insulin concentrations and elevated postwalk glycerol and nonesterified fatty acid concentrations. Despite the dehydration and impaired performance in the older group, blood glucose concentrations were well maintained in both groups, probably mediated via the increased mobilization of fat.     

Plankton dynamics in a high mountain lake (Las Yeguas,Sierra Nevada,Spain). Indirect evidence of ciliates as food source for zooplankton

A detailed sampling programme during the ice-free season (July–September) in the oligotrophic lake Las Yeguas (Southern Spain) has shown a well-defined time lag between phytoplankton and zooplankton maximum standing stocks, the former displaying a peak (23 μgC l^-1) just after the ice-melting, and the latter by the end of September (80 μgC l^-1). A ratio of autotrophs to heterotrophs lower than 1 which lasted more than two thirds of the study period may suggest a high algal productivity per unit of biomass. The estimated strong top-down regulation of phytoplankton by zooplankton indicates an efficient utilization of resources. A comparative analysis between the available food supply and the critical food concentration that is necessary to maintain the population of Daphnia pulicaria (which constitutes up to 98% of the heterotrophic biomass) proves this species to be food-limited in the lake under study. To explain the dominance (and development) of such large-bodied cladoceran population, we discuss the possibility of the utilization of naked protozoan ciliates (Oligotrichidae) as a complementary high quality food source, and the exploitation of benthic resources through a coupled daily migration behaviour.     

Changes in the Potential Multiple Cropping System in Response to Climate Change in China from 1960–2010

The multiple cropping practice is essential to agriculture because it has been shown to significantly increase the grain yield and promote agricultural economic development. In this study, potential multiple cropping systems in China are calculated based on meteorological observation data by using the Agricultural Ecology Zone (AEZ) model. Following this, the changes in the potential cropping systems in response to climate change between the 1960s and the 2010s were subsequently analyzed. The results indicate that the changes of potential multiple cropping systems show tremendous heterogeneity in respect to the spatial pattern in China. A key finding is that the magnitude of change of the potential cropping systems showed a pattern of increase both from northern China to southern China and from western China to eastern China. Furthermore, the area found to be suitable only for single cropping decreased, while the area suitable for triple cropping increased significantly from the 1960s to the 2000s. During the studied period, the potential multiple cropping index (PMCI) gap between rain-fed and irrigated scenarios increased from 18% to 24%, which indicated noticeable growth of water supply limitations under the rain-fed scenario. The most significant finding of this research was that from the 1960s to the 2000s climate change had led to a significant increase of PMCI by 13% under irrigated scenario and 7% under rain-fed scenario across the whole of China. Furthermore, the growth of the annual mean temperature is identified as the main reason underlying the increase of PMCI. It has also been noticed that across China the changes of potential multiple cropping systems under climate change were different from region to region.     

The influence of floodplain habitat on the quantity and quality of riverine phytoplankton carbon produced during the flood season in San Francisco Estuary

Primary productivity, community respiration, chlorophyll a concentration, phytoplankton species composition, and environmental factors were compared in the Yolo Bypass floodplain and adjacent Sacramento River in order to determine if passage of Sacramento River through floodplain habitat enhanced the quantity and quality of phytoplankton carbon available to the aquatic food web and how primary productivity and phytoplankton species composition in these habitats were affected by environmental conditions during the flood season. Greater net primary productivity of Sacramento River water in the floodplain than the main river channel was associated with more frequent autotrophy and a higher P:R ratio, chlorophyll a concentration, and phytoplankton growth efficiency (α^B). Total irradiance and water temperature in the euphotic zone were positively correlated with net primary productivity in winter and early spring but negatively correlated with net primary productivity in the late spring and early summer in the floodplain. In contrast, net primary productivity was correlated with chlorophyll a concentration and streamflow in the Sacramento River. The flood pulse cycle was important for floodplain production because it facilitated the accumulation of chlorophyll a and wide diameter diatom and green algal cells during the drain phase. High chlorophyll a concentration and diatom and green algal biomass enabled the floodplain to export 14–37% of the combined floodplain plus river load of total, diatom and green algal biomass and wide diameter cells to the estuary downstream, even though it had only 3% of the river streamflow. The study suggested the quantity and quality of riverine phytoplankton biomass available to the aquatic food web could be enhanced by passing river water through a floodplain during the flood season.     

Late Quaternary environmental and climate history of Rauer Group, East Antarctica

The Rauer Group is an archipelago in Prydz Bay, East Antarctica. The ice-free islands and the surrounding shallow marine areas provide valuable archives for the reconstruction of the late Pleistocene and Holocene environmental and climatic history of the region. Two sediment records from two marine inlets of Rauer Group have been studied for their sedimentological, geochemical, and biological characteristics. Radiocarbon ages from one of the inlets indicate ice-free conditions within the last glacial cycle, probably during the second half of Marine Isotope Stage 3. Subsequent ice sheet coverage of Rauer Group during the Last Glacial Maxiumum (LGM) can be inferred from a till layer recovered in one of the basins. The inlets became ice-free prior to 11,200 cal yr BP, when biogenic sedimentation started. Deglacial processes in the catchments, however, influenced the inlets until ~ 9200 cal yr BP as evidenced by the input of minerogenic material. Marine productivity under relatively open water conditions indicates an early Holocene climate optimum until 8200 cal yr BP, which is followed by a cooler period with increased sea ice. Warmer conditions are inferred for the mid Holocene, when both basins experienced an input of freshwater between ~ 5700-3500 cal yr BP, probably due to ice-sheet melting and increased precipitation on the islands. Neoglacial cooling in the late Holocene since c. 3500 cal yr BP is reflected by an increase in sea ice in both inlets.     

辽西人工林气候生产力分析

采用6种方法计算了辽西地区的人工林气候生产力。结果表明,辽西平均人工林生产潜力为8．8t·hm^-2．年^-1,其分布趋势从东南向西北逐渐降低,与降雨量分布一致。针对地区特点,生态地区法、层次递推法和综合模型是适宜的气候生产力计算模型。对比分析表明。辽西现实人工林生产力水平处于极低水平。提高人工林质量,挖掘生产潜力是今后人工林发展的关键．     

绿肥在我国旱地农业生态系统中的服务功能及其应用

旱地农业分布面积广、增产潜力大,在保障我国粮食安全方面占有重要地位,但也面临着水资源短缺、土壤贫瘠、水土流失严重和不可再生资源利用效率低等问题。绿肥不仅具有提高土壤质量、调节土壤养分和增强土壤水分蓄纳能力,从而改善作物生长环境,促进作物持续高产稳产的作用,而且在增加农田生态系统生物多样性、提高地表覆盖度、减少养分向环境中的无效损失、增强农田系统气体调节功能、提高病虫草害的生物防控等方面也具有显著的生态效益。在全球气候变化加剧、生态环境恶化和农产品需求改变等新形势下,以肥用为主要目的的传统绿肥种植应用技术已不能满足当前农业发展的需求,需要加强旱地绿肥种质资源的选育工作,通过研制新的适应新形势的全国绿肥区划,构建适应不同区域的绿肥种植模式,优化和研发适应现代化生产水平的耕作栽培技术,探究绿肥综合效益评价体系,为旱地农业区改善生态环境、提高经济效益,构建资源节约、生态保育型的绿肥应用模式,充分挖掘绿肥效益提供科学依据和技术支撑。     

虚拟水在农业生态系统中的作用与贡献分析

水是农业生态系统中最重要的组成要素之一,也是粮食生产的一个重要安全保证,在确保粮食资源持续供应增长人口的需求中起到了根本的作用.文中分析了虚拟水的政策内涵,并依据对我国过去20年粮食生产与进口替代趋势的分析和国内外的粮食生产条件,估算出1980～2000年,小麦进口每年有10.2×10⁹ m³水和27.7×10⁶ hm²土地输入,玉米进口约有0.3×10⁹m³水和1.6×10⁶ hm²土地被间接利用.这对缓解我国农业用水和耕地资源紧张状况,灵活利用粮食贸易进口,解决粮食生产中的用水困境,利用虚拟水进口来补偿水资源的贡献率,具有重要的现实意义.     

Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural production?

A fundamental shift has taken place in agricultural research and world food production. In the past, the principal driving force was to increase the yield potential of food crops and to maximize productivity. Today, the drive for productivity is increasingly combined with a desire for sustainability. For farming systems to remain productive, and to be sustainable in the long-term, it will be necessary to replenish the reserves of nutrients which are removed or lost from the soil. In the case of nitrogen (N), inputs into agricultural systems may be in the form of N-fertilizer, or be derived from atmospheric N₂ via biological N₂ fixation (BNF).Although BNF has long been a component of many farming systems throughout the world, its importance as a primary source of N for agriculture has diminished in recent decades as increasing amounts of fertilizer-N are used for the production of food and cash crops. However, international emphasis on environmentally sustainable development with the use of renewable resources is likely to focus attention on the potential role of BNF in supplying N for agriculture. This paper documents inputs of N via symbiotic N₂ fixation measured in experimental plots and in farmers' fields in tropical and temperate regions. It considers contributions of fixed N from legumes (crop, pasture, green manures and trees), Casuarina, and Azolla, and compares the relative utilization of N derived from these sources with fertilizer N.     

青铜时代中晚期辽西地区农业活动特征

辽西地区城子山遗址和夏家店遗址农作物种子遗存研究显示,城子山地区青铜时代中期以旱作农业种植为主.粟的栽培比例要明显高于黍.青铜时代晚期的夏家店地区属半农半牧区,存在黍与粟为主的旱作农业种植,但黍的栽培比例要远高于青铜时代中期的城子山地区.干旱化可能是导致夏家店地区青铜时代晚期黍栽培比例升高的主要原因.城子山和夏家店地区农业种植结构在青铜时代晚期可能已有所不同,但这2个地区农业种植的差异究竟从何时开始,仍是一个需要继续深入研究的问题.     

Water-use efficiency and transpiration efficiency of wheat under rain-fed conditions and supplemental irrigation in a Mediterranean-type environment

Growth and water use were measured in wheat (Triticum aestivum L.) grown in northern Syria in a typical Mediterranean climate over five seasons 1991/92–1995/96. Water use was partitioned into transpiration (T) and soil evaporation (E_s) using Ritchie's model, and water-use efficiency (WUE) and transpiration efficiency (TE) were calculated. The aim of the study was to examine the influence of irrigation and nitrogen on water use, WUE and TE. By addition of 100 kg N ha^-1, E_s was reduced from 120 mm to 101 mm under rain-fed conditions and from 143 mm to 110 mm under irrigated conditions, and T was increased from 153 mm to 193 mm under rain-fed conditions and from 215 mm to 310 mm under irrigated conditions. Under rain-fed conditions, about 35% of evapotranspiration (ET) may be lost from the soil surface for the fertilized crops and 44% of ET for the unfertilized crops. Transpiration accounted for 65% of ET for the fertilized crops and 56% for the unfertilized crops under rain-fed. As a result of this, WUE was increased by 44% for dry matter and 29% for grain yield under rain-fed conditions, and by 60% for dry matter and 57% for grain yield under irrigated conditions. Transpiration efficiency for the fertilized crops was 43.8 kg ha^-1 mm^-1 for dry matter and 15 kg ha^-1 mm^-1 for grain yield, while TE for the unfertilized crops was 33.6 kg ha^-1 mm^-1 and 12.2 kg ha^-1 mm^-1 for dry matter and grain yield, respectively. Supplemental irrigation significantly increased post-anthesis water use, transpiration, dry matter and grain yield. Water-use efficiency for grain yield was increased from 9.7 to 11.0 kg ha^-1 mm^-1 by supplemental irrigation, although WUE for dry matter was not affected by it. Irrigation did not affect transpiration efficiency for grain yield, but decreased transpiration efficiency for dry matter by 16%. This was associated with higher harvest index as a result of good water supply in the post-anthesis period and increased transpiration under irrigated conditions.