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Grassland degradation in Northern Tibet based on remote sensing data

Journal of Geographical Sciences 2006年第2期16卷 165-173页

作者： GAO Qingzhu LI Yu＇e WAN Yunfan LIN Erda XIONG Wei jiangcun wangzha WANG Baoshan LI Wenfu Institute of Environment and Sustainable Development for Agriculture Chinese Academy of Agricultural SciencesBeijing 100081China Naqu Agriculture and Animal Husbandry Bureau Tibet Autonomous RegionNaqu 852100China

This study selected vegetation cover as the main evaluation index, calculated the grassland degradation index （GDI） and established the remote sensing monitoring and evaluation system for grassland degradation in Northern Tibet, according to the National Standard （GB19377-2003）, based on the remote sensing data such as NDVI data derived from NOAA/AVHRR with a spatial resolution of 8 km of 1981-2000, from SPOT/VGT with a spatial resolution of 1 km of 2001 and from MODIS with a spatial resolution of 0.25 km of 2002-2004 respectively in this area, in combination with the actual condition of grassland degradation. The grassland degradation processes and their responses to climate change during 1981-2004 were discussed and analyzed in this paper. The result indicated that grassland degradation in Northern Tibet is very serious, and the mean value of GDI in recent 20 years is 2.54 which belongs to the serious degradation grade. From 1981 to 2004, the GDI fluctuated distinctly with great interannual variations in the proportion of degradation degree and GDI but the general tendency turned to severe-grade during this period with the grassland degradation grade changed from light degraded to serious degraded in Northern Tibet. The extremely serious degraded and serious degraded grassland occupied 1.7% and 8.0% of the study area, the moderate and light degraded grassland accounted for 13.2% and 27.9% respectively, and un-degraded grassland occupied 49.2% of the total grassland area in 2004. The grassland degradation was serious, especially in the conjunctive area of Naqu, Biru and Jiali counties, the headstream of the Yangtze River lying in the Galadandong snow mountain and glaciers, the area along the Qinghai-Tibet highway and railway, and areas around the Tanggula and Nianqingtanggula snow mountains and glaciers. So the snow mountains and glaciers as well as their adjacent areas in Northern Tibet were sensitive to climate change and the areas along the vital communication l

关键词： grassland degradation temporal and spatial distribution remote sensing monitoring

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藏北地区生态与环境敏感性评价

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生态学报 2010年第15期30卷 4129-4136页

作者：高清竹段敏杰万运帆李玉娥郭亚奇江村旺扎中国农业科学院农业环境与可持续发展研究所北京100081 农业部农业环境与气候变化重点实验室北京100081 西藏自治区那曲地区草原站那曲852100

藏北地区自然条件极为严酷,生态与环境非常脆弱和敏感。采用地理信息系统手段与综合评价方法,对藏北地区主要生态与环境敏感性问题进行评估,分析了土壤侵蚀、沙漠化和草地退化等方面的敏感性空间分异规律,指出了今后生态与环境建设的优... 详细信息

藏北地区自然条件极为严酷,生态与环境非常脆弱和敏感。采用地理信息系统手段与综合评价方法,对藏北地区主要生态与环境敏感性问题进行评估,分析了土壤侵蚀、沙漠化和草地退化等方面的敏感性空间分异规律,指出了今后生态与环境建设的优先区域。结果表明:藏北地区土壤侵蚀敏感区占土地总面积的42.5%,主要分布于东中部区域;藏北地区沙漠化敏感区面积较大(占土地总面积的78.8%),主要分布在人类活动强度相对较低的西北部;藏北中东部和北部地区草地退化较为严重,尤其是藏北地区冰川与雪山及其周围等气候变化较为敏感区域和交通要道沿线等人类活动较为频繁区域的草地退化相对严重,对草地退化也比较敏感,是今后草地退化治理和恢复的优先区。

关键词：土壤侵蚀沙漠化草地退化综合评价地理信息系统藏北地区

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藏北地区草地退化的时空分布特征

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地理学报 2005年第6期60卷 965-973页

作者：高清竹李玉娥林而达江村旺扎万运帆熊伟王宝山李文福中国农业科学院农业环境与可持续发展研究所北京100081 西藏自治区那曲地区农牧局那曲852100

根据草地退化国家标准和藏北地区草地退化实际情况以及遥感数据特征,选择草地植被盖度为草地退化的遥感监测指标,建立藏北地区草地退化遥感监测和评价指标体系,并对藏北地区近24年的草地退化进行遥感监测和评价。结果表明:藏北地区草地... 详细信息

根据草地退化国家标准和藏北地区草地退化实际情况以及遥感数据特征,选择草地植被盖度为草地退化的遥感监测指标,建立藏北地区草地退化遥感监测和评价指标体系,并对藏北地区近24年的草地退化进行遥感监测和评价。结果表明:藏北地区草地退化现状(2004年)十分严重,重度和极重度退化草地面积分别占草地总面积的8.0%和1.7%,区域草地退化指数(GDI)为1.86,接近中度退化等级;其中藏北地区冰川与雪山及其周围等气候变化较为敏感区域和交通要道沿线等人类活动较为频繁区域的草地退化相对严重;从1981年到2004年的近24年以来,藏北地区及其各个区域草地退化较为严重,其草地退化等级分布比例和草地退化指数年际波动较大,草地退化等级在轻度退化至重度退化等级之间波动;近几年藏北全地区总体草地退化情况及中部、东部和北部地区的草地退化具有更加严重的趋势,而西部地区草地退化状况则略有减缓趋势。

关键词：草地退化遥感监测时空分布特征藏北地区

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藏北高原草地生态治理与畜牧业协同发展模式研究

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中国工程科学 2019年第5期21卷 93-98页

作者：干珠扎布胡国铮高清竹江村旺扎旦久罗布参木友巴桑旺堆杨富裕魏学红杨永平中国农业科学院农业环境与可持续发展研究所北京100081 那曲市草原站西藏那曲852000 西藏自治区农牧科学院拉萨850000 中国农业大学草地研究所北京100193 西藏农牧学院西藏林芝860000 中国科学院昆明植物研究所昆明650201

藏北高原是我国重要的生态安全屏障和高原特色畜牧业基地,而高寒草地退化严重制约着其生态和生产功能,给生态保护和畜牧业发展带来了挑战。本文在深入分析藏北高原生态治理与畜牧业发展状况的基础上,探讨了藏北高寒草地生态与生产功能... 详细信息

藏北高原是我国重要的生态安全屏障和高原特色畜牧业基地,而高寒草地退化严重制约着其生态和生产功能,给生态保护和畜牧业发展带来了挑战。本文在深入分析藏北高原生态治理与畜牧业发展状况的基础上,探讨了藏北高寒草地生态与生产功能的主要影响因素,提出了藏北高原草地生态治理与畜牧业协同发展的模式体系。研究表明,通过草地生态恢复、优化放牧管理方式、人工牧草种植、低海拔农区种草高海拔牧区养畜的“低草高牧”模式、冬季半舍饲养殖等一系列措施,能够推进高寒草地生态功能提升、促进草地畜牧业转型升级,实现“保护中发展”与“发展中保护”。相关研究将为治边稳藏、保障国家生态安全、增加牧民收入提供战略引导和科技支撑。

关键词：藏北高原生态修复草地畜牧业协同发展

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A review of tidal triggering of global earthquakes

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Geodesy and Geodynamics 2023年第1期14卷 35-42页

作者： Ruyu Yan Xiaodong Chen Heping Sun Jianqiao Xu jiangcun Zhou State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of Chinese Academy of Sciences Beijing 100049China

Earthquake prediction remains a challenging and difficult task for scientists all over the *** tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown that earthquakes are positively correlated with tides,and thus,tides provide a potential tool for earthquake prediction,especially for imminent *** this study,publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes,which were classified into three main types:tectonic,volcanic,and slow *** results reveal a high correlation between tectonic earthquakes and tides(mainly for semidiurnal and diurnal tides;14-day tides) before and after the occurrence of significant *** volcanic earthquakes,observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces,mostly those with semidiurnal and diurnal *** slow earthquakes,the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal *** conclusion,the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism,and thus,the prediction of these types of earthquakes should be ***,there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all *** main inadequacies are discussed in this paper from our point of view.

关键词： Tidal triggering Tectonic earthquakes Volcanic earthquakes Slow earthquakes Earthquake prediction

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Study on characteristics of long-term gravity changes at Wuhan station

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Chinese Science Bulletin 2008年第13期53卷 2033-2040页

作者： XU JianQiao ZHOU jiangcun LUO ShaoCong SUN HePing Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

We consider the characteristics of long-term changes in non-tidal gravity and their implication to the local perturbations in barometric pressure and water storage and to the local vertical crustal movement using the long-term continuous gravity observations from a superconducting gravimeter (SG) at Wu-han station,together with the co-site measurements from a Global Positioning System (GPS) receiver and an absolute gravimeter FG5. The observation results indicate that there are obvious seasonal variations in the long-term gravity changes measured with the SG. About 70 percent of the whole sea-sonal changes come from the contribution of the local disturbances in air pressure and water storage,while over 95 percent of the annual changes are attributed to the loading effects of these environmental perturbations. Due to the absence of direct measurements of the local water storage,especially those of the underground water,the global assimilating models of land water LaD (Land Dynamics) and GLDAS (Global Land Data Assimilation System) cannot virtually describe the real hydrologic distur-bances around the station. The resulting gravity changes,which are simulated theoretically by means of convolution integration of the loading Green’s functions and water models LaD and GLDAS,show significantly time delay of about 55 days from those measured with the SG. Compared with the meas-urements of the absolute gravity with the FG5,the long-term drift rate of the SG is determined as about 17.13 nms-2/a. From the co-site GPS measurements,it is found that the local crust is slowly subsiding at a rate of 3.71±0.16 mm/a,and the related gravity variation is estimated as 13.88±0.22 nms-2/a. In other words,the ratio of the changes in gravity and altitude related to the local vertical crustal movement is about -37.41 nms-2/cm. It implies that a considerable mass adjustment may be associated with the local vertical crustal movement,and its dynamic mechanism should be investigated further.

关键词：超导重力计潮汐引力气压水储存量

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Theoretical calculation of tidal Love numbers of the Moon with a new spectral element method

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Earth and Planetary Physics 2022年第3期6卷 241-247页

作者： BinBin Liao XiaoDong Chen JianQiao Xu jiangcun Zhou HePing Sun State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of the Chinese Academy of Sciences Beijing 100049China

The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial *** play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal *** this study,we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers:the spectral element ***,we explain the mathematical theory and advantages of this *** the basis of this new method,using 10 published lunar internal structure reference models,the lunar surface and lunar internal tidal Love numbers were calculated,and the influence of different lunar models on the calculated Love numbers was *** of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%,the influence on the maximum vertical displacement on the lunar surface could reach±8.5 mm,and the influence on the maximum gravity change could reach±6μ*** the influence on the Love numbers inside the Moon,different lunar models had a greater impact on the Love numbers h_(2) and l_(2) than on k_(2) in the lower lunar mantle and core.

关键词： lunar tidal Love numbers spectral element method solid lunar tides lunar internal structure reference models lunar tidal deformation theory

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Application of superconductive gravity technique on the constraints of core-mantle coupling parameters

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Science China Earth Sciences 2012年第2期55卷 513-520页

作者： CUI XiaoMing SUN HePing XU JianQiao ZHOU jiangcun Institute of Geodesy and Geophysics Chinese Academy of SciencesWuhan 430077China Key Laboratory of Dynamic Geodesy Chinese Academy of SciencesWuhan 430077China Graduate University of Chinese Academy of Sciences Beijing 100049China

The parameters, i.e. the Period and the Quality factor, of the Earth's free core nutation (FCN) are closely related to the dissipative coupling between the core and the mantle. Based on the FCN parameters obtained from the actual observations and theoretical simulation, significantly constrained in this study were several key parameters near the core-mantle boundary (CMB), related to the core and mantle coupling, including viscosity at the top of liquid core, conductivity at the bottom of the mantle, and dynamic ellipticity of the CMB. In order to choose high quality observations from global stations of the superconducting gravimeters (SG) on the Global Geodynamics Project (GGP) network, we adopted two criteria, the standard deviations of harmonic analysis on tidal observations and the quality of the FCN parameters calculated with the observations from single station. After the mean ocean tidal effects of the recent ocean tidal models were removed, the FCN parameters were retrieved by stacking the tidal gravity observations from the GGP network. The results were in a good agreement with those in the recent research by using the SG and/or the VLBI observations. Combined with an FCN theoretical model deduced by angular momentum method, the viscous and electromagnetic coupling parameters near the CMB were evaluated. Numerical results indicated that the viscosity at the top of the liquid core was in the range from 6.6×102 to 2.6×103 Pa·s, which was in good agreement with those obtained from the Earth's nutation, the FCN and variations in the length of day (LOD). The conductivity at the bottom of the mantle should be as large as 2.6×106-1.0×107 S m-1 to match the FCN quality factors from the actual observations. The dissipative coupling had a little influence of 1-2 sidereal days for the FCN period.

关键词： SG observations free core nutation core-mantle boundary viscosity conductivity dynamic ellipticity

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Co-seismic change in ocean bottom topography:Implication to absolute global mean sea level change

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Geodesy and Geodynamics 2019年第3期10卷 179-186页

作者： jiangcun Zhou Heping Sun Jianqiao Xu Xiaodong Chen Xiaoming Cui State Key Laboratory of Geodesy and Earth’s Dynamics Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhan430077China University of Chinese Academy of Sciences Beijing 100049China

Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level(RSL) change. However, the relative global mean sea level(GMSL) change is zero in that sea water mass is conserved. But the absolute GMSL change is not zero because earthquakes displace total ocean mass with respect to the Earth’s center of mass(CM) which remains unchanged after an earthquake. This displacement, i.e. the absolute GMSL change, may be detectable by altimetry since the satellites are orbiting around CM. In this paper, we proposed a method to estimate co-seismic absolute GMSL change caused by earthquakes based on the point dislocation theory for a spherically symmetric, non-rotating, elastic and isotropic(SNREI) *** change can be directly connected to the perturbation of ocean bottom topography. We first computed co-seismic displacements as well as the change in geo-potential and solved the sea level equation to validate the insignificance of the oceans’ feedback, i.e. the loading effect due to RSL change, to co-seismic displacements. The results imply that the loading effect due to RSL change is negligible on displacements while is considerable on geoid. We then computed the absolute GMSL change caused by co-seismic vertical and horizontal displacements by making use of the integrated Green’s function method. The numerical results show that a large earthquake may raise the absolute GMSL by magnitude of sub-millimeter and the recent three large events cause GMSL to rise about one millimeter, in which the contribution from horizontal displacement is non-negligible.

关键词： Point dislocation theory SNREI earth Sea level equation Absolute GMSL Ocean bottom topography

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Characteristics of tidal gravity changes in Lhasa,Tibet,China

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Chinese Science Bulletin 2012年第22期57卷 2586-2594页

作者： XU JianQiao CHEN XiaoDong ZHOU jiangcun SUN HePing State Key Laboratory of Geodesy and Earth＇s Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077China

Tidal gravity changes arise from the response of the solid Earth to the tidal forces of the Sun,Moon and planets close to the Earth,and are a comprehensive reflection of the structure and distribution of physical properties of the Earth's *** a result,observations of tidal gravity changes are the basis of studies on other global and/or regional dynamic *** characteristics of tidal gravity changes in the region of the Tibetan Plateau were investigated through continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa over a *** contrast measurements with a spring gravimeter LaCoste-Romberg ET20 at the same site,the gravity observations in Lhasa were scaled to the international tidal gravity reference in ***,the scale factor of the SG was determined accurately as-777.358 ± 0.136 nm s-2V-1,which is about 2.2% less than the value provided by the *** results indicate that the precision of the tidal gravity observations made with the SG in Lhasa was very *** standard deviation was 0.459 nm s-2,and the uncertainties of for the four main tidal waves (i.e.O 1,K 1,M 2 and S 2) were better than 0.006%.In addition,the observations of the diurnal gravity tides had an obvious pattern of nearly diurnal *** a result,it is affirmed that the Lhasa station can provide a local tidal gravity reference for gravity measurements on the Tibetan Plateau and its surrounding *** loading effects of oceanic tides on tidal gravity observations in Lhasa are so weak that the resulting perturbations in the gravimetric factors are less than 0.6%.However,the loading effects of the local atmosphere on either the tidal or nontidal gravity observations are significant,although no seasonal variations were *** removal of the atmospheric effects,the standard deviation of the SG observations in Lhasa decreased obviously from 2.009 to 0.459 nm *** removed the loading effects of ocea

关键词：超导重力仪潮汐变化拉萨国际重力潮汐基准青藏高原地区重力潮汐观测重力观测中国

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