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Physical mechanism of the rapid increase in intense and long-lived extreme heatwaves in the Northern Hemisphere since 1980

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Science China Earth Sciences 2024年第7期67卷 2103-2121页

作者： Yuqing WANG Wen ZHOU Chunzai WANG Key Laboratory of Polar Atmosphere-ocean-ice System for Weather and Climate of the MOE Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric SciencesFudan UniversityShanghai 200438China Key Laboratory for Polar Science of the MNR Polar Research Institute of ChinaShanghai 201209China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Global Ocean and Climate Research Center South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China

Since 1980,both the intensity and duration of summer heatwaves in the middle and high latitudes of the Northern Hemisphere have significantly increased,leading this region to become a critical area for a significant increase in the frequency of intense and long-lived extreme heatwaves.We found that stronger and more persistent high-pressure systems and lower soil moisture before the events were the main drivers of intense and long-lived extreme heatwaves in western Europe and the middle and high latitudes of North America.However,in eastern Europe and Siberia,lower cloud cover before events is also a main driver of this type of extreme heatwave,in addition to the above drivers.These factors are coupled with each other and can change heatwave intensity and duration by influencing surface radiation processes during events.Using the self-organizing map classification method,we found that 6 weather patterns with increased frequency,intensity,and duration were the main dynamic reasons leading to the increase in intense and long-lived extreme heatwaves after 1980.In addition,the decrease in summer average soil moisture in most areas of the mid-high latitudes of the Northern Hemisphere and the decrease in average cloud cover in eastern Europe and Siberia are found to be the main thermodynamic reasons leading to the increase in these extreme heatwaves.

关键词： High intensity Long duration Extreme heatwaves High pressure system soil moisture Cloud cover

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soil moisture controls the spatio-temporal pattern of soil respiration under different land use systems in a semi-arid ecosystem of Delhi,India

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Ecological Processes 2020年第1期9卷 172-184页

作者： Archana Meena M.Hanief J.Dinakaran K.S.Rao Department of Botany University of RajasthanJaipurRajasthan 302004India Department of Botany Baba Ghulam Ghulam Shah Badshah UniversityRajouriJammu and Kashmir 185234India Department of Botany Bhaskaracharya College of Applied SciencesUniversity of DelhiDwarkaDelhi 110007India Department of Botany University of DelhiDelhi 110007India

Background:soil respiration(S_(R))is a critical process for understanding the impact of climatic conditions and land degradation on the carbon cycle in terrestrial ecosystems.We measured the S_(R) and soil environmental factors over 1 year in four land uses with varying levels of disturbance and different vegetation types viz.,mixed forest cover(MFC),Prosopis juliflora(Sw.)forest cover(PFC),agricultural field(AF),and vegetable field(VF),in a semi-arid area of Delhi,India.Our primary aim was to assess the effects of soil moisture(S_(M)),soil temperature(S_(T)),and soil microbial activity(S_(MA))on the S_(R).Methods:The S_(R) was measured monthly using an LI-6400 with an infrared gas analyser and a soil chamber.The S_(M) was measured using the gravimetric method.The S_(T)(10 cm)was measured with a probe attached to the LI-6400.The S_(MA) was determined by fluorescein diacetate hydrolysis.Results:The S_(R) showed seasonal variations,with the mean annual S_(R) ranging from 3.22 to 5.78μmol m^(−2) s^(−1) and higher S_(R) rates of~15-55%in the cultivated fields(AF,VF)than in the forest sites(MFC,PFC).The VF had significantly higher S_(R)(P0.05).Contrasting results were observed in the VF,which showed high S_(R) during summer(May;11.21μmol m^(−2) s^(−1))and a significant exponential relationship with the S_(T)(R^(2)=0.52;P<0.05).The S_(R) was positively related to the SMA(R2=0.44-0.5;P<0.001).The interactive equations based on the independent variables S_(M),S_(T),and S_(MA) explained 91-95%of the seasonal variation in S_(R) with better

关键词： soil respiration soil moisture soil microbes soil temperature Precipitation Land use change Semi-arid ecosystems

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Spatial distribution of supra-permafrost groundwater in the Qinghai-Tibet Engineering Corridor using inversion models

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Advances in Climate Change Research 2024年第1期15卷 31-41页

作者： Yu GAO Ming-Tang CHAI Wei MA Yu-Tao GAO State Key Laboratory of Frozen soils Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 73000China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China School of Civil and Hydraulic Engineering Ningxia UniversityYinchuan 750021China

Supra-permafrost groundwater(SPG)is a key factor that causes damage to highways and railways in the Qinghai-Tibet Engineering Corridor(QTEC).It is difficult to monitor SPG in the field due to their complex formation mechanisms and movement characteristics.Traditional single-site field monitoring studies limit the spatial and temporal precision of SPG spatial distribution.To determine the moisture content of shallow soils and the SPG distribution along the QTEC,this work employed the temperature vegetation dryness index and remote sensing models for groundwater table distribution models.The accuracies of the models were validated using mea-surements obtained from different sites in the corridor.In the permafrost zones of the QTEC,72%,22%and 6%of the SPG were located at depths of 0.5-1,1 m,respectively.Meanwhile,79.4%of the area along the Qinghai-Tibet Highway(QTH)(Xidatan-Tanggula)section contained SPG.In these sections with SPG,37.9%have an SPG table at depths of 0.5-0.8 m.This study preliminarily explored the SPG distribution in the QTEC with a 30 m resolution.The findings can help improve the spatial scale of SPG research,provide a basis for the analysis of the hydrothermal mechanisms,and serve as a guide in the assessment of operational risks and road structure designs.

关键词： Dryness index Landsat soil moisture Groundwater level Qinghai-Tibet Engineering Corridor

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Global Change in Agricultural Flash Drought over the 21st Century

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Advances in Atmospheric Sciences 2024年第2期41卷 209-220,I0002-I0019页

作者： Emily BLACK National Centre for Atmospheric Science Fairbairn House71-75 Clarendon RoadLeedsLS29PHU.K Department of Meteorology Brian Hoskins BuildingUniversity of ReadingWhiteknights campusReadingRG66ETU.K.

Agricultural flash droughts are high-impact phenomena, characterized by rapid soil moisture dry down. The ensuing dry conditions can persist for weeks to months, with detrimental effects on natural ecosystems and crop cultivation. Increases in the frequency of these rare events in a future warmer climate would have significant societal impact. This study uses an ensemble of 10 Coupled Model Intercomparison Project(CMIP) models to investigate the projected change in agricultural flash drought during the 21st century. Comparison across geographical regions and climatic zones indicates that individual events are preceded by anomalously low relative humidity and precipitation, with long-term trends governed by changes in temperature, relative humidity, and soil moisture. As a result of these processes, the frequency of both upperlevel and root-zone flash drought is projected to more than double in the mid-and high latitudes over the 21st century, with hot spots developing in the temperate regions of Europe, and humid regions of South America, Europe, and southern Africa.

关键词： flash drought climate change soil moisture agricultural drought CMIP

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Patterns and drivers of seasonal water sources for artificial sand-fixing plants in the northeastern Mu Us sandy land,Northwest China

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Pedosphere 2024年第1期34卷 63-77页

作者： Yanwu PEI Laiming HUANG Ming'an SHAO Jiao WANG Yinglong ZHANG Yellow River Delta Modern Agricultural Engineering Laboratory Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Natural Resources and Environment Northwest Agriculture and Forestry UniversityYangling 712100China State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences of Chinese Academy of SciencesBeijing 100085China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Shenmu Ecological Association Shenmu 719399China

Understanding plant water-use patterns is important for improving water-use efficiency and for sustainable vegetation restoration in arid and semi-arid regions. However, seasonal variations in water sources and their control by different sand-fixing plants in water-limited desert ecosystems remain poorly understood. In this study, stable isotopic ratios of hydrogen(δ^(2)H) and oxygen(δ^(18)O) in precipitation, soil water, groundwater, and xylem water were determined to document seasonal changes in water uptake by three representative plant species(Pinus sylvestris var. mongolica Litv., Amygdalus pedunculata Pall., and Salix psammophila) in the northeastern Mu Us sandy land, Northwest China. Based on the depth distribution and temporal variation of measured gravimetric soil water content(SWC), the soil water profile of the three species stands was divided into active(0.01 g g^(-1)45%) layers. Annually, P. sylvestris, A. pedunculata, and S. psammophila obtained most water from deep(59.2%±9.7%, moist layer and groundwater),intermediate(57.4%±9.8%, stable and moist layers), and shallow(54.4%±10.5%, active and stable layers) sources, respectively. Seasonally, the three plant species absorbed more than 60% of their total water uptake from the moist layer and groundwater in the early(June) dry season;then, they switched to the active and stable layers in the rainy season(July–September) for water resources(50.1%–62.5%). In the late(October–November) dry season, P. sylvestris(54.5%–66.2%) and A. pedunculata(52.9%–63.6%) mainly used water from stable and moist layers, whereas S. psammophila(52.6%–70.7%) still extracted water predominantly from active and stable layers. Variations in the soil water profile induced by seasonal fluctuations in precipitation and groundwater levels and discrepancies in plant phenology, root distribution, and water demand are th

关键词： desert ecosystem MixSIAR model plant water uptake soil moisture stable isotopes vegetation restoration water-use efficiency

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soil CO_2 flux in relation to dissolved organic carbon,soil temperature and moisture in a subtropical arable soil of China

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Journal of Environmental Sciences 2003年第5期15卷 715-720页

作者： LOUYun-sheng LIZhong-pei ZHANGTao-lin CollegeofNaturalResourcesandEnvironmentalSciences NanjingAgriculturalUniversityNanjing210095China InstituteofsoilScience ChineseAcademyofSciencesNanjing210008China

soil CO 2 emission from an arable soil was measured by closed chamber method to quantify year round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. soil CO 2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red soil, the Chinese Academy of Sciences, in a subtropical region of China. soil CO 2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2 23 kgCO 2/(m 2·a) for average annual soil CO 2 flux. Regressed separately, the reasons for soil flux variability were 86 6% from soil temperature, 58 8% from DOC, and 26 3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85 2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2 49 kgCO 2/(m 2·a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO 2 flux from arable soil in subtropical regions of China.

关键词： soil CO 2 flux soil temperature DOC soil moisture arable soil

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soil-moisture dynamics and tree-water status in a Picea crassifolia forest, Qilian Mountains, China

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Research in Cold and Arid Regions 2020年第1期12卷 34-46页

作者： Hu Liu Lin Li SiJia Wang QiYue Yang WenZhi Zhao Linze Inland River Basin Research Station Chinese Ecosystem Research NetworkLanzhouGansu 730000China Key Laboratory of Ecohydrology of Inland River Basin Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China University of Chinese Academy of Sciences Beijing 100029China

Landscapes of the mountainous regions in northwestern China comprise a unique pattern of vegetation,consisting of a mosaic of grassland and shrub-forest.Forests generally self-organize into ordered structures and coalesce into blocks on north-facing slopes or stripes along southeast-facing slopes,with Picea crassifolia being the most representative and dominant tree species.We investigated the tree-water status and soil-moisture dynamics at a forest site(Guantan)of the Qilian Mountains in northwest China.The 30-minute-interval measurements of tree-sap flow during the growing season of 2008 are presented,and the potential functional relations between tree transpiration and environmental factors are evaluated.soil moisture and solar energy were identified as the most influential factors,explaining more than 70%of the variance in sap flow.Based on field measurements obtained at the forest site,a stochastic model of soil-moisture dynamics was tested;and the steady-state probability density functions(PDFs)of the long-term soil-moisture dynamics and static tree-water stress were estimated using the validated model and parameters.We found that the model reproduced measured soil moisture well,despite all the simplifying assumptions.The generated PDF of long-term soil moisture was relatively open,with middle to low average values;and the calculated density of the static tree-water stress at the forest site was largely concentrated between 0 and 0.6,suggesting a moderate water-stress situation in most cases.We argue that both water and energy are limiting factors for vegetation at the forest site.In addition,the tradeoff between reduced evapotranspiration(ET)from limited solar energy and increased soil-moisture availability may create a stressed but tolerable environment and,in turn,produce a relatively constant ecological niche favorable to Picea crassifolia growth.

关键词： sap flow soil moisture stochastic modeling semiarid alpine ecosystem

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Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis seedling to changes of soil moisture and temperature

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Journal of Environmental Sciences 2004年第4期16卷 666-669页

作者： XUZhen-zhu ZHOUGuang-sheng LIHui LaboratoryofQuantitativeVegetationEcology InstituteofBotanyChineseAcademyofSciencesBeijing100093China

Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soil moisture levels and 3 temperature levels was conducted in order to improve the understanding how leaf photosynthetic parameters will respond to climatic change. The results indicated that soil drought and high temperature decreased the photochemical efficiency of photosystem(F v/F m), the overall photochemical quantum yield of PSII(yield), the coefficient of photochemical fluorescence quenching(q\-P), but increased the coefficient of non-photochemical fluorescence quenching(q\-N). Severe soil drought would decrease F v/F m and yield by 3.12% and 37.04% under 26℃ condition, respectively, and 6.60% and 73.33% under 32℃ condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of soil drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought.

关键词： chlorophyll fluorescence nitrogen level Leymus chinensis soil moisture soil temperature

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soil moisture Effects on Sand Saltation and Dust Emission Observed over the Horqin Sandy Land Area in China

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Journal of Meteorological Research 2014年第3期28卷 444-452页

作者：李晓岚张宏升 Laboratory for Climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic SciencesSchool of Physics Peking University

In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity initiating the motion of surface particles, namely, the threshold friction velocity, is estimated to be 0.34, 0.40, and 0.50 m s？1 under the very dry, dry, and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission fl ux during the wet event is smaller, but the saltation activities of sand particles （d≧50 μm） are stronger. The size distributions of airborne dust particles （0.1≦d≦20 μm） show that concentrations of the fi ner dust particles （0.1≦d≦0.3 μm） have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have a larger size, and hence more potential saltating particles are available. This explains the occurrence of stronger saltation processes observed under wet soil conditions.

关键词： soil moisture sand saltation dust emission Horqin Sandy Land area

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Interrelationship of soil moisture and temperature to sylvatic plague cycle among prairie dogs in the Western United States

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Integrative Zoology 2021年第6期16卷 852-867页

作者： Cassandra D.PAULING Deborah L.FINKE Deborah M.ANDERSON Department of Veterinary Pathobiology University of MissouriColumbiaMissouriUSA Division of Plant Sciences University of MissouriColumbiaMissouriUSA

Plague,caused by Yersinia pestis,is a flea-borne disease that is endemic in areas throughout the world due to its successful maintenance in a sylvatic cycle,mainly in areas with temperate climates.Burrowing rodents are thought to play a key role in the enzootic maintenance as well as epizootic outbreaks of plague.In the United States,prairie dogs(Cynomys),rodents(Muridae),and ground squirrels(Spermophilus)are susceptible to infection and are parasitized by fleas that transmit plague.In particular,prairie dogs can experience outbreaks that rapidly spread,which can lead to extirpation of colonies.A number of ecological parameters,including climate,are associated with these epizootics.In this study,we asked whether soil parameters,primarily moisture and temperature,are associated with outbreaks of plague in black-tailed prairie dogs and Gunnison’s prairie dogs in the Western United States,and at what depth these associations were apparent.We collected publicly available county-level information on the occurrence of population declines or colony extirpation,while historical soil data was collected from SCAN and USCRN stations in counties and states where prairie dogs have been located.The analysis suggests that soil moisture at lower depths correlates with colony die-offs,in addition to temperature near the surface,with key differences within the landscape ecology that impact the occurrence of plague.Overall,the model suggests that the burrow environment may play a significant role in the epizootic spread of disease amongst black-tailed and Gunnison’s prairie dogs.

关键词： plague prairie dogs soil moisture soil temperature sylvatic cycle Yersinia pestis

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