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The Limiting Effect of Deep Soil Water on Evapotranspiration of a Subtropical Coniferous Plantation Subjected to Seasonal Drought

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Advances in Atmospheric Sciences 2014年第2期31卷 385-395页

作者： TANG Yakun wen xuefa SUN Xiaomin ZHANG Xinyu WANG Huimin Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of Chinese Academy of Sciences

Seasonal drought is a common occurrence in humid *** year 2003 was the driest year during the period 1985-2011 in southeastern *** objective of this study was to elucidate the impact of the exceptional drought in 2003,compared with eddy flux measurements during 2004-11,on the dynamics of evapotranspiration （ET） and related factors,as well as their underlying mechanisms,in a subtropical coniferous plantation in southeastern *** was found that daily ET decreased from 5.34 to 1.84 mm during the intensive drought period and recovered to 4.80 mm during the subsquent recovering drought *** analysis indicated that ET was mainly determined by canopy conductance and deep soil water content （50 cm） during the intensive drought and recovering drought periods,*** canopy conductance offset the positive effect of air vapor pressure deficit on ET when suffering drought stress,while the canopy conductance enhanced the positive effect of air temperature on ET during the late growing *** the fine roots of this plantation are mainly distributed in shallow soil,and the soil water in the upper 40 cm did not satisfy the demand for ET,stomatal closure and defoliation were evident as physiological responses to drought stress.

关键词： ChinaFLUX evapotranspiration seasonal drought subtropical coniferous plantation

Progress in watershed geography in the Yangtze River Basin and the affiliated ecological security perspective in the past 20 years,China

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Journal of Geographical Sciences 2020年第6期30卷 867-880页

作者： GAO Yang JIA Junjie LU Yao SUN Xiaomin wen xuefa HE Nianpeng YANG Tiantian Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China College of Resources and Environment University of Chinese Academy of Sciences.Beijing 100049China School of Civil Engineering and Environmental Science.University of Oklahoma NormanOK 73019United States

Bibliometrics was used to statistically analyze key zones within the Yangtze River Basin(YRB)funded by the National Natural Science Foundation of China(NSFC)and national ministries over the past 20 *** study determined that funds that derived from national ministries have mainly focused on issues related to environmental pollution,ecological security,technological water regulations,and river basin ecosystems,which offer a better understanding of the national requirements and the scientific knowledge of the YRB in combination with data from the *** a background of bolstering the construction of green ecological corridors in the economic belt of the YRB,this study proposes future conceptual watershed research initiatives in this region as a study objective by reinforcing the implementation of the Chinese Ecosystem Research Network(CERN)and by emphasizing the use of new technologies,new methods,and new concepts for the prospective design of frontier research under the perspective of geoscience and earth system *** study promotes large-scale scientific field and research objectives based on big science and big data.

关键词： watershed physiography ecological security earth system science critical zone C-N-H20 coupling Yangtze River Basin

Short-term variations of vapor isotope ratios re- veal the influence of atmospheric processes

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Journal of Geographical Sciences 2011年第3期21卷 401-416页

作者： ZHANG Shichun SUN Xiaomin WANG Jianlin YU Guirui wen xuefa Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China Key Laboratory of Wetland Ecology and Environment Northeast Institute of Geography and Agroecology CAS Changchun 130012 China Qingdao Agricultural University Qingdao 266109 Shandong China

Stable isotopes of atmospheric water vapor reveal rich information on water movement and phase changes in the atmosphere. Here we presented two nearly continuous time-series of δD and δ18O of atmospheric water vapor （δv） measured at hourly intervals in surface air in Beijing and above a winter wheat canopy in Shijiazhuang using in-situ measurement technique. During the precipitation events, the δv values in both Beijing and Shijiazhuang were in the state of equilibrium with precipitation water, revealing the influence of precipitation processes. However, the δv departures from the equilibrium state were positively correlated with local relative humidity. Note that the δv tended to enrich in Beijing, but deplete in Shijiazhuang during the precipitation events, which mainly resulted from the influence of transpiration processes that enriched the δv in Shijiazhuang. On seasonal time-scale, the δv values were log-linear functions of water vapor mixing ratios in both Beijing and Shijiazhuang. The water vapor mixing ratio was an excellent predictor of the δv by the Rayleigh distillation mechanisms, indicating that air mass advection could also play an important role in determining the δv. On a diurnal time-scale, the δv reached the minimum in the early afternoon hours in Beijing which was closely related to the atmospheric processes of boundary layer entrainment. During the peak of growing season of winter wheat, however, the δv reached the minimum in the early morning, and increased gradually through the daytime, and reached the maximum in the late afternoon, which was responsible by the interaction between boundary layer entrainment and the local atmospheric processes, such as transpiration and dew formation. This study has the implications for the important role of vegetation in determining the surface δv and highlights the need to conduct δv measurement on short-term （e.g. diurnal） time scales.

关键词： stables isotopes atmospheric water vapor precipitation TDLAS

Hydrologic implications of the isotopic kinetic fractionation of open-water evaporation

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Science China Earth Sciences 2018年第10期61卷 1523-1532页

作者： Wei XIAO Yufei QIAN Xuhui LEE Wei WANG Mi ZHANG xuefa wen Shoudong LIU Yongbo HU Chengyu XIE Zhen ZHANG Xuesong ZHANG Xiaoyan ZHAO Fucun ZHANG Yale-NUIST Center on Atmospheric Environment & Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology(CICAEET) Nanjing University of Information Science & Technology School of Forestry and Environmental Studies Yale University Jiangsu Key Laboratory of Agricultural Meteorology Nanjing University of Information Science & Technology Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences

The kinetic fractionation of open-water evaporation against the stable water isotope H_2 ^(18)O is an important mechanism underlying many hydrologic studies that use ^(18)O as an isotopic tracer. A recent in-situ measurement of the isotopic water vapor flux over a lake indicates that the kinetic effect is much weaker(kinetic factor 6.2‰) than assumed previously(kinetic factor14.2‰) by lake isotopic budget studies. This study investigates the implications of the weak kinetic effect for studies of deuterium excess-humidity relationships, regional moisture recycling, and global evapotranspiration partitioning. The results indicate that the low kinetic factor is consistent with the deuterium excess-humidity relationships observed over open *** moisture recycling rate in the Great Lakes region derived from the isotopic tracer method with the low kinetic factor is a much better agreement with those from atmospheric modeling studies than if the default kinetic factor of 14.2‰ is used. The ratio of transpiration to evapotranspiration at global scale decreases from 84±9%(with the default kinetic factor) to 76±19%(with the low kinetic factor), the latter of which is in slightly better agreement with other non-isotopic partitioning results.

关键词： Kinetic fractionation factor Craig-Gordon model Moisture recycling Evapotranspiration partitioning Deuteriumexcess

Carbon sequestration potential and its eco-service function in the karst area, China

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Journal of Geographical Sciences 2017年第8期27卷 967-980页

作者： SONG Xianwei GAO Yang wen xuefa GUO Dali YU Guirui HE Nianpeng ZHANG Jinzhong College of Resources and Environment Southwest University Chongqing 400716 China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China

The karst critical zone is an essential component of the carbon （C） pool, constituting the global C cycle. It is referred to as one of the ＂residual land sink＂ that remains largely in- determinate. Karst area （2.2×10^7 km^2） comprises 15% of the world＇s land area, and karst area comprises 3.44~106 km^2 of area in China. Due to the complexity of karst structure and its considerable heterogeneity, C sequestration rate estimations contain large inaccuracies, especially in relation to the different methods used in calculations. Therefore, we reevaluated rock weathering-related C sink estimations in China （approximately 4.74 Tg C yr^-1）, which we calibrated from previous studies. Additionally, we stipulated that more comprehensive re- search on rock-soil-biology-atmosphere continuum C migration is essential to better under- stand C conversion mechanisms based on uncertainty analyses of C sink estimations. Moreover, we stressed that a collective confirmation of chemical methods and simulated models through a combined research effort could at least partially eliminate such uncertainty. Furthermore, integrated C cycling research need a long-term observation of the carbon flux of multi-interfaces. The enhanced capacity of ecosystem C and soil C pools remains an effective way of increasing C sink. Karst ecosystem health and security is crucial to human social de- velopment, accordingly, it is critical that we understand thresholds or potential C sink capacities in karst critical zones now and in the future.

关键词： karst karst critical zone carbon sink carbon sequestration rate China

A comparison between simulated and measured CO_2 and water flux in a subtropical coniferous forest

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Science China Earth Sciences 2006年第S2期49卷 241-251页

作者： GU Fengxue, CAO Mingkui, wen xuefa, LIU Yunfen & TAO Bo Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Graduate University of the Chinese Academy of Sciences, Beijing 100049, China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China Graduate University of the Chinese Academy of Sciences Beijing China

Using data from eddy covariance measurements in a subtropical coniferous forest, a test and evaluation have been made for the model of Carbon Exchange in the Vegetation-Soil-Atmosphere (CEVSA) that simulates energy transfers and water, carbon and nitrogen cycles based on ecophysiological processes. In the present study, improvement was made in the model in calculating LAI, carbon allocation among plant organs, litter fall, decomposition and evapotranspiration. The simulated seasonal variations in carbon and water vapor flux were consistent with the measurements. The model explained 90% and 86% of the measured variations in evapotranspiration and soil water content. However, the modeled evapotranspiration and soil water content were lower than the measured systematically, because the model assumed that water was lost as runoff if it was beyond the soil saturation water content, but the soil at the flux site with abundant rainfall is often above water saturated. The improved model reproduced 79% and 88% of the measured variations in gross primary production (GPP) and ecosystem respiration (Re), but only 31% of the variations in measured net ecosystem exchange (NEP) despite the fact that the modeled annual NEP was close to the observation. The modeled NEP was generally lower in winter and higher in summer than the observations. The simulated responses of photosynthesis and respiration to water vapor deficit at high temperatures were different from measurements. The results suggested that the improved model underestimated ecosystem photosynthesis and respiration in extremely condition. The present study shows that CEVSA can simulate the seasonal pattern and magnitude of CO2 and water vapor fluxes, but further improvement in simulating photosynthesis and respiration at extreme temperatures and water deficit is required.

关键词： ecosystem CO2 and water flux CEVSA eddy covariance subtropical coniferous forest.

Seasonal drought effects on carbon sequestration of a mid-subtropical planted forest of southeastern China

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Science China Earth Sciences 2006年第S2期49卷 110-118页

作者： SUN Xiaomin, wen xuefa, YU Guirui, LIU Yunfen & LIU Qijing Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique is made at the Qianyanzhou mid-subtropical planted forest as part of the ChinaFLUX network. Qianyanzhou planted forest is affected by typical subtropical continental monsoon climate. It has plentiful water and heat resource but is in inconsistency of its seasonal distribution in the mid-subtropical region, thus seasonal drought frequently occurs in this planted forest. In this study, seasonal drought effect on ecosystem carbon sequestration was analyzed based on net ecosystem productivity (NEP), ecosystem respiration (RE) and gross ecosystem productivity (GEP) at the month scale in 2003 and 2004. In this drought-stressed planted forest, ecosystem carbon sequestration showed a clear seasonality, with low rates during seasonal drought and in winter. The declining degree of ecosystem carbon sequestration under the seasonal drought condition was determined by the accumulation of soil moisture deficits and a co-occurrence of high temperatures. Different drought effects are expected for RE and GEP. The net effect of ecosystem carbon balance depends on how these two quantities are affected relatively to each other. Summer drought and heat wave are two aspects of weather that likely play an important part in the annual NEP of forest in this region.

关键词： seasonal drought subtropical planted forest eddy covariance ecosystem respiration gross ecosystem productivity.

Seasonal variations and environmental control of water use efficiency in subtropical plantation

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Science China Earth Sciences 2006年第S2期49卷 119-126页

作者： SONG Xia, YU Guirui, LIU Yunfen, SUN Xiaomin, LIN Yaoming & wen xuefa Institute of Geographysic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Graduate University of the Chinese Academy of Sciences, Beijing 100049, China Institute of Geographysic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China Graduate University of the Chinese Academy of Sciences Beijing China

To understand the seasonal variations of water use efficiency (WUE) of coniferous plantation in the subtropical monsoon area, the experiment was conducted in 2003 and 2004 which presented two distinguished climatic conditions (severe summer drought in 2003 and normal climatic condition in 2004). The water stress influenced WUE greatly, which caused a special seasonal WUE pattern. WUE reached the minimum in summer drought and the maximum in winter, which was contrary to the variation of gross primary production (GPP) and canopy evaporation (Fw). In winter, GPP and Fw increased along with the increasing of air temperature and vapor pressure deficit (VPD), with the similar increasing rate. However, in drought summer, there was an adverse trend among GPP/Fw and air temperature and VPD, and the decreasing rate of GPP was far larger than that of Fw. In summer, the conservation of WUE was changed because of the environmental factors, resulting in the decreasing WUE. The photosynthesis and transpiration of vegetation were mainly controlled by the environmental factors in winter, and the impact of stomatal regulation was relatively weak. In summer, Fw was mainly controlled by the stomatal closure and GPP by both environmental factors and stomatal closure.

关键词： water use efficiency gross primary production canopy evapotransplratlon canopy conductance eddy covariance.

Internet of Things to network smart devices for ecosystem monitoring

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Science Bulletin 2019年第17期64卷 1234-1245页

作者： Xin Li Ning Zhao Rui Jin Shaomin Liu Xiaomin Sun xuefa wen Dongxiu Wu Yan Zhou Jianwen Guo Shiping Chen Ziwei Xu Mingguo Ma Tianming Wang Yonghua Qu Xinwei Wang Fangming Wu Yuke Zhou Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100101 China State Key Laboratory of Remote Sensing Science Faculty of Geographical Science Beijing Normal University Beijing 100875 China State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy o f Sciences Beijing 100101 China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy o f Sciences Beijing 100101 China Key Laboratory of Remote Sensing of Gansu Province Heihe Remote Sensing Experimental Research Station Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China State Key Laboratory of Earth Surface Processes and Resource Ecology Faculty o f Geographical Science Beijing Normal University Beijing 100875 China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China Optoelectronics System Laboratory Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China Research Base of Karst Eco-environments at Nanchuan in Chongqing Ministry of Nature Resources School of Geographical Sciences Southwest University Chongqing 400715 China Ministry of Education Key Laboratory for Biodiversity Science and Engineering Monitoring and Research Center for Amur Tigers and Amur Leopards National Forestry and Grassland Administration & College of Life Sciences Beijing Normal University Beijing 100875 China

Smart, real-time, low-cost, and distributed ecosystem monitoring is essential for understanding and managing rapidly changing ecosystems. However, new techniques in the big data era have rarely been introduced into operational ecosystem monitoring, particularly for fragile ecosystems in remote *** introduce the Internet of Things(IoT) techniques to establish a prototype ecosystem monitoring system by developing innovative smart devices and using IoT technologies for ecosystem monitoring in isolated environments. The developed smart devices include four categories: large-scale and nonintrusive instruments to measure evapotranspiration and soil moisture, in situ observing systems for CO2 and d13 C associated with soil respiration, portable and distributed devices for monitoring vegetation variables, and Bi-CMOS cameras and pressure trigger sensors for terrestrial vertebrate monitoring. These new devices outperform conventional devices and are connected to each other via wireless communication networks. The breakthroughs in the ecosystem monitoring IoT include new data loggers and longdistance wireless sensor network technology that supports the rapid transmission of data from devices to wireless networks. The applicability of this ecosystem monitoring IoT is verified in three fragile ecosystems, including a karst rocky desertification area, the National Park for Amur Tigers, and the oasis-desert ecotone in China. By integrating these devices and technologies with an ecosystem monitoring information system, a seamless data acquisition, transmission, processing, and application IoT is created. The establishment of this ecosystem monitoring IoT will serve as a new paradigm for ecosystem monitoring and therefore provide a platform for ecosystem management and decision making in the era of big data.

关键词： Ecosystem monitoring Fragile ecosystem Internet of Things Wireless sensor network Smart device