Using gradually regression analysis to establish the driving force model of utilized change of cultivated land in Gonghe County, and using path analysis, correlation analysis, partial correlation analysis and system d...Using gradually regression analysis to establish the driving force model of utilized change of cultivated land in Gonghe County, and using path analysis, correlation analysis, partial correlation analysis and system dynamics method to inspect the effect of driving changing on cultivated land change under different change situations. Driving factors, action mechanism and process of utilized change of cultivated land were analyzed from the county territory scale level. At last, some corresponding policies and measures were put forward.展开更多
青海湖盆地因其独特的地理位置和气候环境,对气候变化响应敏感,是研究环境变化重要的场所。本研究在青海湖湖东沙地获取两个剖面,采用AMS14C测年,结合岩性、粒径组分和常量元素氧化物及其比值等多指标分析方法,重建了湖东沙地8.4 ka BP...青海湖盆地因其独特的地理位置和气候环境,对气候变化响应敏感,是研究环境变化重要的场所。本研究在青海湖湖东沙地获取两个剖面,采用AMS14C测年,结合岩性、粒径组分和常量元素氧化物及其比值等多指标分析方法,重建了湖东沙地8.4 ka BP以来的环境演变过程。结果表明:除少量沉积物处于中等化学风化阶段外,大部分沉积物处于物理风化和初级化学风化阶段,说明自8.4 ka BP以来研究区气候环境总体上相对寒冷干燥。在千年尺度上,研究区不同时间段的气候环境存在较大的差异。8.4—4.2 ka BP气候相对温暖湿润;其中,8.4—6.2 ka BP河湖相和风成相沉积互层,表明存在明显的百年尺度气候波动;6.2—4.2 ka BP化学风化和淋溶作用较强,表明季风降水较多,径流较强,发育了较为稳定的湖泊沉积环境。4.2 ka BP以来湖泊消失,化学风化和淋溶作用减弱,沉积物从砾石转变为砂质黄土,显示气候较为冷干且波动较大。对比分析表明,中晚全新世以来青海湖湖东沙地的气候变化特征与东亚季风边缘区其他区域基本一致,并主导了区域沉积环境的演变过程。展开更多
Branched glycerol dialkyl glycerol tetraethers （bGDGTs） are ubiquitous and abundant in soils, but their sources remain elusive. Recent studies demonstrate that the distributions of bGDGTs are sensitive to various en...Branched glycerol dialkyl glycerol tetraethers （bGDGTs） are ubiquitous and abundant in soils, but their sources remain elusive. Recent studies demonstrate that the distributions of bGDGTs are sensitive to various environmental factors. In an effort to understand how and to what extent soil moisture （expressed as soil water content （SWC） or mean annual precipita- tion （MAP）, pH and temperature may impact the distribution of bGDGTs, and to shed more light on the biological sources of bGDGTs in cold and arid regions, we investigated the distribution of bGDGTs as well as bacterial 16S rRNA gene and func- tional genes involved in the N cycle （including amoA, nirS and nirK） in 41 surface soil samples from around Lake Qinghai and east of Qaidam Basin on the Northeastern Qinghai-Tibetan Plateau. We found that lower soil moisture reduced the fractional concentrations of cyclic bGDGTs and thus the cyclisation ratio of branched tetraethers （CBT） index correlated negatively with SWC and MAP, suggesting that soil moisture is an important factor controlling bGDGT distributions in soils in this add and semi-add region. Two subgroups of bGDGTs were assigned on the basis of cluster analysis, and bGDGT indices behaved dif- ferently in the two groups, hinting at different biosynthetic mechanisms for bGDGTs under different environmental conditions. Real time PCR results showed that nirS and nirK genes correlated significantly with the concentration of bGDGTs, suggesting that the nirS- or nirK-encoding bacteria involved in denitrification might potentially be an additional biological source for soil bGDGTs （besides Acidobacteria）. Moreover, our results also support the application of new indices based on 5-methyl bGDGTs and 6-methyl bGDGTs in reconstructing past temperature and pH variations in this region.展开更多
基金Supported by the National Social Science Fund(06XMZ014)~~
文摘Using gradually regression analysis to establish the driving force model of utilized change of cultivated land in Gonghe County, and using path analysis, correlation analysis, partial correlation analysis and system dynamics method to inspect the effect of driving changing on cultivated land change under different change situations. Driving factors, action mechanism and process of utilized change of cultivated land were analyzed from the county territory scale level. At last, some corresponding policies and measures were put forward.
文摘青海湖盆地因其独特的地理位置和气候环境,对气候变化响应敏感,是研究环境变化重要的场所。本研究在青海湖湖东沙地获取两个剖面,采用AMS14C测年,结合岩性、粒径组分和常量元素氧化物及其比值等多指标分析方法,重建了湖东沙地8.4 ka BP以来的环境演变过程。结果表明:除少量沉积物处于中等化学风化阶段外,大部分沉积物处于物理风化和初级化学风化阶段,说明自8.4 ka BP以来研究区气候环境总体上相对寒冷干燥。在千年尺度上,研究区不同时间段的气候环境存在较大的差异。8.4—4.2 ka BP气候相对温暖湿润;其中,8.4—6.2 ka BP河湖相和风成相沉积互层,表明存在明显的百年尺度气候波动;6.2—4.2 ka BP化学风化和淋溶作用较强,表明季风降水较多,径流较强,发育了较为稳定的湖泊沉积环境。4.2 ka BP以来湖泊消失,化学风化和淋溶作用减弱,沉积物从砾石转变为砂质黄土,显示气候较为冷干且波动较大。对比分析表明,中晚全新世以来青海湖湖东沙地的气候变化特征与东亚季风边缘区其他区域基本一致,并主导了区域沉积环境的演变过程。
基金supported by the National Natural Science Foundation of China (Grant Nos. 41373072, 40873011 &41030211)the Shanghai Bureau of Science and Technology (Grant No. 13JC1405200)the Thousand Talents Program through the State Key Laboratory of Marine Geology at Tongji University (C. L. Zhang)
文摘Branched glycerol dialkyl glycerol tetraethers （bGDGTs） are ubiquitous and abundant in soils, but their sources remain elusive. Recent studies demonstrate that the distributions of bGDGTs are sensitive to various environmental factors. In an effort to understand how and to what extent soil moisture （expressed as soil water content （SWC） or mean annual precipita- tion （MAP）, pH and temperature may impact the distribution of bGDGTs, and to shed more light on the biological sources of bGDGTs in cold and arid regions, we investigated the distribution of bGDGTs as well as bacterial 16S rRNA gene and func- tional genes involved in the N cycle （including amoA, nirS and nirK） in 41 surface soil samples from around Lake Qinghai and east of Qaidam Basin on the Northeastern Qinghai-Tibetan Plateau. We found that lower soil moisture reduced the fractional concentrations of cyclic bGDGTs and thus the cyclisation ratio of branched tetraethers （CBT） index correlated negatively with SWC and MAP, suggesting that soil moisture is an important factor controlling bGDGT distributions in soils in this add and semi-add region. Two subgroups of bGDGTs were assigned on the basis of cluster analysis, and bGDGT indices behaved dif- ferently in the two groups, hinting at different biosynthetic mechanisms for bGDGTs under different environmental conditions. Real time PCR results showed that nirS and nirK genes correlated significantly with the concentration of bGDGTs, suggesting that the nirS- or nirK-encoding bacteria involved in denitrification might potentially be an additional biological source for soil bGDGTs （besides Acidobacteria）. Moreover, our results also support the application of new indices based on 5-methyl bGDGTs and 6-methyl bGDGTs in reconstructing past temperature and pH variations in this region.
