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Xu M.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Advances in Meteorology | Year: 2017

Changes in permafrost and glaciers influence water balance in mountain regions of arid northwest China. Terrestrial water storage change (TWSC) is an important factor in the water cycle. In this study, we used Gravity Recovery and Climate Experiment (GRACE) satellites data to retrieve the TWSC in Tien Shan and Qi Lian Mountains. Variation of seasonal TWSC was obvious. However, the seasonal and annual differences reflected the imbalance of water resource distribution in two mountains. The TWSC decreased in the Tien Shan Mountains but increased in the Qi Lian Mountains during 2003 to 2010. Permafrost and glaciers play an important role in the water cycle in arid mountain regions. Demands for water for agriculture need more groundwater extraction for irrigation and glacial melt feeding the rivers which leads to the state of loss of TWSC in Tien Shan Mountains. Increase and thickening of the active layer of permafrost could lead to more infiltration of surface water into the groundwater, which result in increasing water storage and changes in the regional water balance. According to water balance, precipitation and evaporation changed little in short time, and TWSC changed obviously, whereas runoff showed an increasing trend in the Tien Shan Mountains and a decreasing trend in the Qi Lian Mountains. © 2017 Min Xu.

Human life and the entire ecosystem of South East Asia depend upon the monsoon climate and its predictability. More than 40% of the earths population lives in this region. Droughts and floods associated with the variability of rainfall frequently cause serious damage to ecosystems in these regions and, more importantly, injury and loss of human life. The headwater areas of seven major rivers in SE Asia, i.e. Yellow River, Yangtze, Mekong, Salween, Irrawaddy, Brahmaputra and Ganges, are located in the Tibetan Plateau. Estimates of the Plateau water balance rely on sparse and scarce observations that cannot provide the required accuracy, spatial density and temporal frequency. Fully integrated use of satellite and ground observations is necessary to support water resources management in SE Asia and to clarify the roles of the interactions between the land surface and the atmosphere over the Tibetan Plateau in the Asian monsoon system. The goal of this project is to: 1. Construct out of existing ground measurements and current / future satellites an observing system to determine and monitor the water yield of the Plateau, i.e. how much water is finally going into the seven major rivers of SE Asia; this requires estimating snowfall, rainfall, evapotranspiration and changes in soil moisture; 2. Monitor the evolution of snow, vegetation cover, surface wetness and surface fluxes and analyze the linkage with convective activity, (extreme) precipitation events and the Asian Monsoon; this aims at using monitoring of snow, vegetation and surface fluxes as a precursor of intense precipitation towards improving forecasts of (extreme) precipitations in SE Asia. A series of international efforts initiated in 1996 with the GAME-Tibet project. The effort described in this proposal builds upon 10 years of experimental and modeling research and the consortium includes many key-players and pioneers of this long term research initiative.

Agency: European Commission | Branch: FP7 | Program: MC-IAPP | Phase: FP7-PEOPLE-2011-IAPP | Award Amount: 1.59M | Year: 2012

Slow time-dependent movements caused by creep of natural geomaterials affect the performance of infrastructure and cause high maintenance and repair costs, and the partial closures of infrastructure networks during the repair work have significant economic and social impact. Although the phenomenon of creep is well-known for being a major design issue, there is currently no accepted consensus on the best way to model creep. Reliable calculation tools are either missing or - due to their scientific nature - out of reach for the engineer in charge. If as a consequence creep is underestimated in design, structures will possibly be damaged so that they will not reach their design life. On the other hand, if creep is overestimated, unnecessary countermeasures such as soil improvement, deep foundations, or additional structural reinforcement will take up additional resources. For sustainable building processes it is therefore imperative to adequately incorporate creep behaviour in analyses and design. The research topic of this Marie Curie action is creep behaviour of geomaterials and its incorporation in geotechnical design; the project aims at establishing a consensus in creep modelling. The project shall supply tools and knowledge needed in creep analysis. Past research in the field of creep behaviour of soils has concentrated mainly on soft silts and clays. Different theoretical frameworks and numerical models were proposed. Yet, creep is likewise observed in geomaterials such as peat, sand, rock fills, and warm permafrost. Key questions formulated by industry and academia are therefore: Can existing creep concepts be adopted equally for those materials? Can different creep concepts be unified? Of the alternatives proposed, which work best at both element level and real geotechnical problem level? This project intends to answer these questions by combining the practical experience gathered by industry with the theoretical concepts worked out by academia.

Agency: European Commission | Branch: FP7 | Program: CSA-CA | Phase: SPA.2012.1.3-02 | Award Amount: 2.78M | Year: 2013

CORE-CLIMAX will coordinate the identification of available physical measurements, which can be reconciled with previously existing data records, to form long time series. It will help to substantiate how GMES observations and products can contribute to climate change analyses, by establishing the extent to which GMES observations complement existing Climate Data Records (CDR). With GCOS, GMES and ESA CCI projects, and EUMETSAT including its Satellite Application Facility (SAF) network, coordination will also take place with specific efforts to be undertaken by new FP7 GMES projects to further upgrade their product catalogues to include this climate relevant validation and information and lay the observational basis for service activities. CORE-CLIMAX will identify the integration of ECVs into the reanalysis chain by proposing a feedback mechanism ensuring that the results of the re-analysis process get appropriately reflected into updates of the ECVs. Together with intercomparing different reanalyses, CORE-CLIMAX will contribute to establish a European truly coupled gridded re-analysis which incorporates full exchanges and interactions between atmosphere, ocean, land, including the hydrological cycle. Specific objectives: 1 Coordinate with GMES ongoing activities and contribute to the formulation of the GMES climate service theme (GCOS, FP7 GMES and climate change projects, ESA CCI projects, EUMETSAT including its SAF network and EUMETNET as part of the European Meteorological Infrastructure) 2 Propose a structured process for delivering ECVs through the stepped and quality controlled elaboration of CDR, the latter being derived from prioritisation of the most appropriate input data sets; 3 Propose a validation process aiming at qualifying the accuracy of the climate variables; 4 Propose a feedback mechanism ensuring that the results of the re-analysis process get appropriately reflected into updates of the CDR; 5 Propose a process to compare reanalyses.

Nevo E.,Haifa University | Chen G.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Plant, Cell and Environment | Year: 2010

Drought and salinity are the major abiotic stresses that dramatically threaten the food supply in the world. Tribe Triticeae, including wheat and barley, possesses tremendous potential for drought and salt tolerance that has been extensively and practically identified, tested, and transferred to wheat cultivars with proven expression of tolerance in experimental trials. Triticum dicoccoides and Hordeum spontaneum, the progenitors of cultivated wheat and barley, have adapted to a broad range of environments and developed rich genetic diversities for drought and salt tolerances. Drought- and salt-tolerant genes and quantitative trait loci (QTLs) have been identified in T. dicoccoides and H. spontaneum and have great potential in wheat and barley improvement. Advanced backcross QTL analysis, the introgression libraries based on wild wheat and wild barley as donors, and positional cloning of natural QTLs will play prevailing roles in elucidating the molecular control of drought and salt tolerance. Combining tolerant genes and QTLs in crop breeding programs aimed at improving tolerance to drought and salinity will be achieved within a multidisciplinary context. Wild genetic resistances to drought and salinity will be shifted in the future from field experiments to the farmer. © 2010 Blackwell Publishing Ltd.

He M.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Dijkstra F.A.,University of Sydney
New Phytologist | Year: 2014

Summary: Climate change scenarios forecast increased aridity in large areas worldwide with potentially important effects on nutrient availability and plant growth. Plant nitrogen and phosphorus concentrations (plant [N] and [P]) have been used to assess nutrient limitation, but a comprehensive understanding of drought stress on plant [N] and [P] remains elusive. We conducted a meta-analysis to examine responses of plant [N] and [P] to drought manipulation treatments and duration of drought stress. Drought stress showed negative effects on plant [N] (-3.73%) and plant [P] (-9.18%), and a positive effect on plant N : P (+ 6.98%). Drought stress had stronger negative effects on plant [N] and [P] in the short term (< 90 d) than in the long term (> 90 d). Drought treatments that included drying-rewetting cycles showed no effect on plant [N] and [P], while constant, prolonged, or intermittent drought stress had a negative effect on plant [P]. Our results suggest that negative effects on plant [N] and [P] are alleviated with extended duration of drought treatments and with drying-rewetting cycles. Availability of water, rather than of N and P, may be the main driver for reduced plant growth with increased long-term drought stress. © 2014 The Authors.

Li X.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Science China Earth Sciences | Year: 2014

Uncertainty is one of the greatest challenges in the quantitative understanding of land-surface systems. This paper discusses the sources of uncertainty in land-surface systems and the possible means to reduce and control this uncertainty. From the perspective of model simulation, the primary source of uncertainty is the high heterogeneity of parameters, state variables, and near-surface atmospheric states. From the perspective of observation, we first utilize the concept of representativeness error to unify the errors caused by scale representativeness. The representativeness error also originates mainly from spatial heterogeneity. With the aim of controlling and reducing uncertainties, here we demonstrate the significance of integrating modeling and observations as they are complementary and propose to treat complex land-surface systems with a stochastic perspective. In addition, through the description of two modern methods of data assimilation, we delineate how data assimilation characterizes and controls uncertainties by maximally integrating modeling and observational information, thereby enhancing the predictability and observability of the system. We suggest that the next-generation modeling should depict the statistical distribution of dynamic systems and that the observations should capture spatial heterogeneity and quantify the representativeness error of observations. © 2013, Science China Press and Springer-Verlag Berlin Heidelberg.

Wang X.M.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Chinese Science Bulletin | Year: 2013

Sandy desertification is both an inherently interesting bioscience and geoscience topic and an important topic from the perspectives of the ecological environment and food security. It has therefore increasingly attracted the attention of the public, in addition to researchers, government officials, and international organizations. This paper reviews the development of knowledge on sandy desertification, research progress in understanding the physical and biological processes involved in sandy desertification, and the significance of wind activity in determining the increases and decreases in sandy desertification. Based on this review of current research on the mechanisms and processes of sandy desertification, combining geological and biological sciences appears likely to improve our understanding of this complex system, thereby providing a more holistic understanding of sandy desertification at a range of temporal and spatial scales. © 2013 The Author(s).

Cheng G.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Jin H.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Hydrogeology Journal | Year: 2013

The areal extent of permafrost in China has been reduced by about 18. 6 % during the last 30 years. Due to the combined influences of climate warming and human activities, permafrost has been degrading extensively, with marked spatiotemporal variability. Distribution and thermal regimes of permafrost and seasonal freeze-thaw processes are closely related to groundwater dynamics. Permafrost degradation and changes in frost action have extensively affected cold-regions hydrogeology. Progress on some research programs on groundwater and permafrost in two regions of China are summarized. On the Qinghai-Tibet Plateau and in mountainous northwest China, permafrost is particularly sensitive to climate change, and the permafrost hydrogeologic environment is vulnerable due to the arid climate, lower soil-moisture content, and sparse vegetative coverage, although anthropogenic activities have limited impact. In northeast China, permafrost is thermally more stable due to the moist climate and more organic soils, but the presence or preservation of permafrost is largely dependent on favorable surface coverage. Extensive and increasing human activities in some regions have considerably accelerated the degradation of permafrost, further complicating groundwater dynamics. In summary, permafrost degradation has markedly changed the cold-regions hydrogeology in China, and has led to a series of hydrological, ecological, and environmental problems of wide concern. © 2012 Springer-Verlag Berlin Heidelberg.

Zhao W.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Liu B.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Agricultural and Forest Meteorology | Year: 2010

Rainfall pulses can significantly drive the evolution of the structure and function of desert ecosystems, and understanding the mechanisms that underlie the response of desert plants to rainfall is the key to understanding the responses of desert ecosystems to global climatic change. The present study was carried out at the desert-oasis ecotone in the middle of China's Heihe River Basin. We measured sap flow in the branches and stems of desert shrubs (Nitraria sphaerocarpa and Elaeagnus angustifolia) using sap flow gauges, and studied the response of sap velocity to rainfall pulses using the " threshold-delay" model. The results showed that the response of sap flow began about 1. h earlier after rainfall, and that sap velocity increased two to threefold, compared to its pre-rainfall value. The sap velocity increased significantly, then decreased gradually, with increasing rainfall. The response of sap flow differed significantly between rainfall, species, position within species during pulse duration, and the interactive effects also differed significantly (P<0.0001). The response pattern followed the threshold-delay model, with lower thresholds of ≤5.2 and 1. mm of rainfall for the stems and branches, respectively, demonstrating the importance of small rainfall events (<5. mm) for plant growth and survival in desert regions. © 2010 Elsevier B.V.

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