西北地区不同土壤水分处理对温室大棚番茄产量和耗水的影响

根据番茄的生长发育特点,分别以50%、60%、75%田间持水量作为苗期、花期、结果期的土壤水分下限,按照不同的土壤水分上限设置不同的灌水量处理。对番茄不同生育期的灌水量、耗水量、产量、水分利用效率及其关系进行了研究。结果表明,灌水控制上限和下限之间存在交互效应,番茄灌水量、耗水量与其具有显著的正相关性;当灌水控制下限一定时,耗水强度和耗水模数随灌水控制上限的减小呈降低趋势;番茄苗期、花期和结果期的灌水控制上、下限(占田持)分别控制在50%～65%、60%～75%和75%～85%为宜。

施氮量对黄土旱塬区冬小麦产量和土壤水分动态的影响

为了探明施氮量对黄土旱塬区冬小麦(Triticum aestivum L.)籽粒产量和麦田土壤水分动态的影响规律,以抗旱性冬小麦品种长武58为供试材料,于2006～2008年连续两个年度在陕西省长武县对不同施氮量条件下麦田土壤贮水量动态、耗水规律、小麦产量和夏闲期降水补给率等特征进行研究。结果表明,麦田土壤贮水量随季节和降水明显变化,同一生育时期2.7m土层的土壤贮水量基本随施氮量的增加而减少。偏旱年每公顷施氮300kg和平水年每公顷施氮225kg均能够获得当年最大的籽粒产量和水分利用效率。每公顷施氮75kg和225kg均能在夏闲期获得较大的降水补给率。每公顷施氮225kg更有利于黄土旱塬区冬小麦的高产和稳产。

沙地小叶杨和柠条细根分布与土壤水分消耗的关系

以生长在陕北水蚀风蚀交错带沙地上的人工小叶杨(Populus simonii)和柠条(Caragana korshinkii)为研究对象,采用剖面法调查2个树种的细根分布特征,通过2年土壤水分定位观测研究,初步分析沙地小叶杨和柠条细根分布与土壤水分消耗的关系。结果表明:1)沙地小叶杨和柠条随土层深度增加,细根表面积密度逐渐减小,0~100cm土层分别集中了整个剖面细根总量的63%和95%;2)小叶杨和柠条林地剖面土壤水分与细根垂直分布密切相关,小叶杨和柠条林地土壤水分特征类似,可分为3个层次:0~50 cm土层为速变层,50~200 cm土层为缓变层,200cm以下土层为缓慢衰减层;3)2年观测期内,小叶杨和柠条林地总蒸散量接近,与同期降水量基本持平,而裸沙地土壤储水量增加;4)小叶杨和柠条细根趋于浅表化的分布特征是对沙地浅层土壤经常获得雨水补给适应的结果。研究结果可为水蚀风蚀交错带沙区防护林建设提供理论依据。

黄土塬区旱作农田长期定位施肥对冬小麦水分利用的影响

对长期定位施肥试验第22年度的测定数据进行了分析,探讨了旱地施肥对冬小麦水分利用的影响。试验结果表明,测定年份冬小麦的耗水深度受播种前雨季降雨入渗深度的影响位于地下200 cm左右。长期单施磷肥处理,播种期土壤有效贮水量与不施肥的对照接近,而单施氮肥,氮磷配施和氮磷钾配施均显著低于对照;在施P2O590 kg/hm2配施氮肥或施N 90 kg/hm2配施磷肥,随着施氮量或施磷量从0增加到180 kg/hm2,播种期土壤有效贮水量均逐渐降低,但前者作物的土壤水分消耗表现出降低趋势,而后者表现出增加趋势。与对照相比,各施肥处理均提高了土壤有效底墒的利用率。氮磷配施比单施磷肥降低了土壤供水占作物耗水的比例,使得作物生长和产量的形成对当季降水的依赖性增加。与对照相比,氮磷配施及氮磷钾配施显著提高了冬小麦收获指数、产量和水分利用效率,而单施磷肥和氮肥使收获指数、产量和水分利用效率显著降低。施P2O590 kg/hm2的条件下,不同施氮量之间收获指数差异较小,而产量和水分利用效率均高于单施磷肥;施N 90 kg/hm2的条件下,不同施磷量作物的收获指数、产量和水分利用效率均得到提高。

丘陵半干旱区春小麦耗水特征与水分高效利用

该文利用Penman-Monteith公式和田间灌溉试验，对丘陵半干旱区春小麦的需水耗水特征进行了计算分析，并利用旱棚和田间试验、数理统计和系统分析等方法，对冬灌和涌流灌溉的节水效果、喷灌制度和喷灌水量分布、水肥耦合互馈作用、有限水量的最优分配等进行了综合研究.通过模拟寻优得出了春小麦不同产量水平下的水肥管理优化方案.以Jensen模型为基础，利用动态规划确定了不同初始土壤含水量和可利用灌溉水量下的最优分配决策.

农业经济用水量与我国农业战略节水潜力

在分析我国农业水资源利用现状基础上,从保障粮食安全和最大用水综合效益出发,提出了"农业经济用水量"的概念,分析了其内涵,提出了基于宏观水资源合理配置的"农业经济用水量"研究的理论基础及其相应技术基础,并从战略层面对我国未来可实现的农业经济用水量及其节水潜力进行了初步分析,为缓解我国农业用水与工业用水、生态用水之间的矛盾提供了有益的探索。

黄土高原半干旱区苜蓿草地土壤干燥化特征与粮草轮作土壤水分恢复效应

实地测定了黄土高原半干旱区固原不同生长年限苜蓿草地和连作8a苜蓿草地翻耕轮作不同年限粮食作物后深层土壤水分特征,分析了苜蓿草地土壤干燥化特征和粮草轮作对土壤水分的恢复效应。结果表明:(1)苜蓿连作1a、5a、8a和12a等4类苜蓿草地0~1000cm土层平均土壤湿度值为6.6%,平均土壤水分过耗量702.8mm,平均土壤干燥化速率147.1 mm/a,达到强烈干燥化程度,苜蓿连作5a土壤干层深度超过1000cm,苜蓿连作8a土壤干层深度超过1360cm,苜蓿草地合理利用年限为7a。(2)连作8a苜蓿草地翻耕并轮作4~7a和25a粮食作物等5类粮田0~1000cm土层土壤湿度介于6.74%~11.95%,土壤贮水量恢复值介于210.6~887.3mm,平均土壤水分恢复速率为80.8mm/a。轮作6a后粮田土壤干层轻度恢复程度以上深度达到1000cm。通过粮草轮作使苜蓿草地土壤湿度恢复到当地土壤稳定湿度需要13a以上。黄土高原半干旱区适宜的粮草轮作模式为:7a苜蓿→13a粮食作物。

半干旱区柠条林利用土壤水分深度和耗水量

植物根系利用土壤水分深度和耗水量是研究植物与土壤水关系的基础。以柠条为对象,采用中子仪,对撂荒地和柠条林地土壤水分进行长期定位观测和分析。结果表明,2002年内,随着时间推移,柠条利用土壤水分深度从播种时的2cm左右,迅速增加到9月1日的90cm,10月15日的110cm,11月1日的170cm,到11月15日柠条利用土壤水分深度为220cm;除丰水年(2年生)柠条土壤储水量增加了122.8mm外,随着林龄的增加和降雨量等的变化,植物利用土壤水分的深度和耗水量增加,土壤储水量下降。到2004年生长季末,3年生柠条林地100cm土层出现土壤干层,5年生柠条林地剖面60—300cm土层出现土壤干层。此时需要采取措施,控制柠条生长、密度和耗水量,实现土壤水资源的可持续利用。

土壤干湿交替对玉米生长速度及其耗水量的影响

在盆栽条件下研究了干湿交替对玉米生长速率、叶片水势、渗透势、气孔导度、相对生长速率和耗水量的影响。结果表明玉米在 3～ 7叶期经历土壤水分缓慢亏缺 ,再进行复水的干湿交替后玉米叶片渗透调节能力明显增加 ,叶片生长表现出补偿效应 ,每次干湿交替后生长速率迅速下降的叶水势趋于下降 ,气孔导度对土壤水分变化非常敏感 ,并在干旱—复水过程中具有后效作用 ,蒸腾耗水量随干—湿交替而具有下降趋势 ,初步证明可在节水灌溉条件下人为控制不同生育时期的供水时间形成干湿交替 ,促进渗透调节能力增强和补偿生长来实现作物高产、高效、优质的目的

黄土高原灌木林地水分环境特性研究

通过对黄土高原试验示范区的多年定位观测试验 ,并结合调查数据 ,分析了该区灌木林地的土壤水分循环过程 ,大气降水分配特点 ,揭示了灌木林蒸腾耗水特征 ,以及土壤水分动态趋势 ,总结了沙棘、柠条灌木林地土壤水分平衡规律 ,从而为黄土高原绿化、灌木林的合理布局和经营提供了一定的科学依据。

Impacts of land use change and climate variations on annual inflow into Miyun Reservoir,Beijing, China

The Miyun Reservoir, the only surface water source for Beijing city, has experienced water supply decline in recent decades. Previous studies suggest that both land use change and climate contribute to the changes of water supply in this critical watershed. However, the specific causes of the decline in the Miyun Reservoir are debatable under a non-stationary climate in the past 4 decades. The central objective of this study was to quantify the separate and collective contributions of land use change and climate variability to the decreasing inflow into the Miyun Reservoir during 1961–2008. Different from previous studies on this watershed, we used a comprehensive approach to quantify the timing of changes in hydrology and associated environmental variables using the long-term historical hydrometeorology and remote-sensing-based land use records. To effectively quantify the different impacts of the climate variation and land use change on streamflow during different sub-periods, an annual water balance model (AWB), the climate elasticity model (CEM), and a rainfall–runoff model (RRM) were employed to conduct attribution analysis synthetically. We found a significant (p  <  0.01) decrease in annual streamflow, a significant positive trend in annual potential evapotranspiration (p  <  0.01), and an insignificant (p  >  0.1) negative trend in annual precipitation during 1961–2008. We identified two streamflow breakpoints, 1983 and 1999, by the sequential Mann–Kendall test and double-mass curve. Climate variability alone did not explain the decrease in inflow to the Miyun Reservoir. Reduction of water yield was closely related to increase in actual evapotranspiration due to the expansion of forestland and reduction in cropland and grassland, and was likely exacerbated by increased water consumption for domestic and industrial uses in the basin. The contribution to the observed streamflow decline from land use change fell from 64–92 % during 1984–1999 to 36–58 % during 2000–2008, whereas the contribution from climate variation climbed from 8–36 % during the 1984–1999 to 42–64 % during 2000–2008. Model uncertainty analysis further demonstrated that climate warming played a dominant role in streamflow reduction in the most recent decade (i.e., 2000s). We conclude that future climate change and variability will further challenge the water supply capacity of the Miyun Reservoir to meet water demand. A comprehensive watershed management strategy needs to consider the climate variations besides vegetation management in the study basin.

Interactions spatiales et auto-organisation des végétations semi-arides

Les recherches récapitulées dans cette thèse de doctorat ont porté sur les causes de l’organisation spatiale des végétations périodiques. Ces structures paysagères aux motifs réguliers, tachetés, tigrés ou labyrinthiques, d’échelle décamétrique à hectométrique, couvrant des étendues considérables sur au moins trois continents, constituent un cas d’école dans l’étude des processus endogènes présidant à l’hétérogénéité du couvert végétal. Ces structures prennent place sur un substrat homogène, mis à part la rétroaction du couvert lui-même, et sont marquées par des écotones abrupts et la persistance d’une proportion considérable de sol nu. Plusieurs modèles ont mis en avant l’existence possible d’un phénomène d’auto-organisation du couvert, qui verrait une structure d’ensemble émerger des interactions locales entre individus. Ces modèles se basent sur le jeu simultané de la consommation de la ressource (compétition) et de l’amélioration de l’un ou l’autre des éléments du bilan de la même ressource par le couvert (facilitation). La condition à l’existence d’une structure d’ensemble spatialement périodique et stable réside dans une différence entre la portée de la compétition (plus grande) et celle de la facilitation. L’apparition de ces structures est modulée par le taux de croissance biologique, qui est le reflet des contraintes extérieures telles que l’aridité, le pâturage ou la coupe de bois. Le modus operandi des interactions spatiales supposées entre individus reste largement à préciser.

Nos recherches ont été menées au sud-ouest de la République du Niger, à l’intérieur et dans les environs du parc Régional du W. Trois axes ont été explorés :(i) Une étude de la dépendance spatiale entre la structure de la végétation (biovolumes cartographiés) et les paramètres du milieu abiotique (relief, sol), sur base d’analyses spectrales et cross-spectrales par transformée de Fourier (1D et 2D). (ii) Une étude diachronique (1956, 1975 et 1996) à large échelle (3000 km²) de l’influence de l’aridité et des pressions d’origine anthropique sur l’auto-organisation des végétations périodiques, basée sur la caractérisation de la structure spatiale des paysages sur photos aériennes via la transformée de Fourier en 2D. (iii) Trois études portant sur les interactions spatiales entre individus :En premier lieu, via l’excavation des systèmes racinaires (air pulsé) ;Ensuite, par un suivi spatio-temporel du bilan hydrique du sol (blocs de gypse) ;Enfin, via le marquage de la ressource par du deutérium.

Nous avons ainsi pu établir que les végétations périodiques constituent bien un mode d’auto-organisation pouvant survenir sur substrat homogène et modulé par les contraintes climatiques et anthropiques. Un ajustement rapide entre l’organisation des végétations périodiques et le climat a pu être montrée en zone protégée. La superficie et l’organisation des végétations périodiques y ont tour à tour progressé et régressé en fonction d’épisodes secs ou humides. Par contre, en dehors de l’aire protégée, la possibilité d’une restauration du couvert semble fortement liée au taux d’exploitation des ressources végétales. Ces résultats ont d’importantes implications quant à la compréhension des interactions entre climat et écosystèmes et à l’évaluation de leurs capacités de charge. La caractérisation de la structure spatiale des végétations arides, notamment par la transformée de Fourier d’images HR, devrait être généralisée comme outil de monitoring de l’état de ces écosystèmes. Nos études portant sur les modes d’interactions spatiales ont permis de confirmer l’existence d’une facilitation à courte portée du couvert végétal sur la ressource. Cependant, cette facilitation ne semble pas s’exercer sur le terme du bilan hydrique traditionnellement avancé, à savoir l’infiltration, mais plutôt sur le taux d’évaporation (deux fois moindre à l’ombre des canopées). Ce mécanisme exclut l’existence de transferts diffusifs souterrains entre sols nu et fourrés. Des transferts inverses semblent d’ailleurs montrés par le marquage isotopique. L’étude du bilan hydrique et la cartographie du micro-relief, ainsi que la profondeur fortement réduite de la zone d’exploitation racinaire, jettent de sérieux doutes quant au rôle communément admis des transferts d’eau par ruissellement/diffusion de surface en tant que processus clé dans la compétition à distance entre les plantes. L’alternative réside dans l’existence d’une compétition racinaire de portée supérieure aux canopées. Cette hypothèse trouve une confirmation tant par les rhizosphères excavées, superficielles et étendues, que dans le marquage isotopique, montrant des contaminations d’arbustes situés à plus de 15 m de la zone d’apport. De même, l’étude du bilan hydrique met en évidence les influences simultanées et contradictoires (facilitation/compétition) des ligneux sur l’évapotranspiration.

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This PhD thesis gathers results of a research dealing with the causes of the spatial organisation of periodic vegetations. These landscape structures, featuring regular spotted, labyrinthine or banded patterns of decametric to hectometric scale, and extending over considerable areas on at least three continents, constitute a perfect study case to approach endogenous processes leading to vegetation heterogeneities. These patterns occur over homogeneous substratum, except for vegetation’s own feedbacks, and are marked by sharp ecotones and the persistence of a considerable amount of bare soil. A number of models suggested a possible case of self-organized patterning, in which the general structure would emerge from local interactions between individuals. Those models rest on the interplay of competitive and facilitative effects, relating to soil water consumption and to soil water budget enhancement by vegetation. A general necessary condition for pattern formation to occur is that negative interactions (competition) have a larger range than positive interactions (facilitation). Moreover, all models agree with the idea that patterning occurs when vegetation growth decreases, for instance as a result of reduced water availability, domestic grazing or wood cutting, therefore viewing patterns as a self-organised response to environmental constraints. However the modus operandi of the spatial interactions between individual plants remains largely to be specified.

We carried out a field research in South-West Niger, within and around the W Regional Park. Three research lines were explored: (i) The study of the spatial dependency between the vegetation pattern (mapped biovolumes) and the factors of the abiotic environment (soil, relief), on the basis of spectral and cross-spectral analyses with Fourier transform (1D and 2D). (ii) A broad scale diachronic study (1956, 1975, 1996) of the influence of aridity and human induced pressures on the vegetation self-patterning, based on the characterisation of patterns on high resolution remote sensing data via 2D Fourier transform. (iii) Three different approaches of the spatial interactions between individuals: via root systems excavation with pulsed air; via the monitoring in space and time of the soil water budget (gypsum blocks method); and via water resource labelling with deuterated water.

We could establish that periodic vegetations are indeed the result of a self-organisation process, occurring in homogeneous substratum conditions and modulated by climate and human constraints. A rapid adjustment between vegetation patterning and climate could be observed in protected zones. The area and patterning of the periodic vegetations successively progressed and regressed, following drier or wetter climate conditions. On the other hand, outside protected areas, the restoration ability of vegetation appeared to depend on the degree of vegetation resource exploitation. These results have important implications regarding the study of vegetation-climate interactions and the evaluation of ecosystems’ carrying capacities. Spatial pattern characterisation in arid vegetations using Fourier transform of HR remote sensing data should be generalised for the monitoring of those ecosystems. Our studies dealing with spatial interaction mechanisms confirmed the existence of a short range facilitation of the cover on water resource. However, this facilitation does not seem to act through the commonly accepted infiltration component, but rather on the evaporative rate (twice less within thickets). This mechanism excludes underground diffusive transfers between bare ground and vegetation. Inverse transfers were even shown by deuterium labelling. Water budget study and micro-elevation mapping, along with consistent soil shallowness, together cast serious doubts on the traditional mechanism of run-off/diffusion of surface water as a key process of the long range competition between plants. An alternative explanation lies in long range root competition. This hypothesis find support as well in the excavated root systems, shallow and wide, as in isotopic labelling, showing contaminations of shrubs located up to 15 m of the irrigated area. Water budget study also evidenced simultaneous contradictory effects (facilitation/competition) of shrubs on evapotranspiration.

Los grandes sistemas de abastecimiento de agua en el litoral de Alicante

El litoral de Alicante ha sufrido grandes transformaciones territoriales desde las décadas de 1960 y 1970 a raíz de la actividad turística. Uno de los servicios que necesita esta actividad, entre otros, es el abastecimiento de agua potable. En este sentido, por su papel estratégico, el suministro de agua en alta es decisivo para abastecer a los municipios turístico-residenciales. El objetivo de este estudio es conocer y analizar los diferentes sistemas de abastecimiento de agua en alta en la costa de Alicante, sus características, infraestructuras, recursos hídricos disponibles y medidas de gestión llevados a cabo. Algunas de las conclusiones extraídas son el papel estratégico que ejercen en el territorio, especialmente con el agua, un recurso escaso y de vital importancia para la orla costera alicantina, sobre todo en los meses estivales.

Arsenic behaviour from groundwater and soil to crops:impacts on agriculture and food safety

High levels of As in groundwater commonly found in Bangladesh and other parts of Asia not only pose a risk via drinking water consumption but also a risk in agricultural sustainability and food safety. This review attempts to provide an overview of current knowledge and gaps related to the assessment and management of these risks, including the behaviour of As in the soil-plant system, uptake, phytotoxicity, As speciation in foods, dietary habits, and human health risks. Special emphasis has been given to the situation in Bangladesh, where groundwater via shallow tube wells is the most important source of irrigation water in the dry season. Within the soil-plant system, there is a distinct difference in behaviour of As under flooded conditions, where arsenite (AsIII) predominates, and under nonflooded conditions, where arsenate (AsV) predominates. The former is regarded as most toxic to humans and plants. Limited data indicate that As-contaminated irrigation water can result in a slow buildup of As in the topsoil. In some cases the buildup is reflected by the As levels in crops, in others not. It is not yet possible to predict As uptake and toxicity in plants based on soil parameters. It is unknown under what conditions and in what time frame As is building up in the soil. Representative phytotoxicity data necessary to evaluate current and future soil concentrations are not yet available. Although there are no indications that crop production is currently inhibited by As, long-term risks are clearly present. Therefore, with concurrent assessments of the risks, management options to further prevent As accumulation in the topsoil should already have been explored. With regard to human health, data on As speciation in foods in combination with food consumption data are needed to assess dietary exposure, and these data should include spatial and seasonal variability. It is important to control confounding factors in assessing the risks. In a country where malnutrition is prevalent, levels of inorganic As in foods should be balanced against the nutritional value of the foods. Regarding agriculture, As is only one of the many factors that may pose a risk to the sustainability of crop production. Other risk factors such as nutrient depletion and loss of organic matter also must be taken into account to set priorities in terms of research, management, and overall strategy.

A case for facade integrated solar thermal systems.

This paper explores the potential for façade located solar thermal collectors. Building typologies with limited roof space area are highlighted. A relationship exists between hot water consumption and the solar collector area; hence, a literature review of the hot water consumption of different building typologies is conducted. The review showed that there is a paucity of information on the hot water consumption of buildings, primarily attributed to the difficulty in quantifying it. The hot water consumption is typically describedusing liters per capita per day (Lcd) units, with a broad range of values existing, dependent, primarily on the building's function and location. Asimulation-based study is conducted to size solar thermal systems for different buildings and their associated hot water loads. High solar fractions,for buildings with high levels of hot water consumption, could only be achievedby using significantly largercollector surface areas. As a result, façade located solar thermal collectors are required for certain high-rise buildings that aim to provide for their hot water needs using a considerable portion of solar energy.