荒漠生态系统C、N、P生态化学计量研究进展

生态化学计量学是通过研究生物有机体主要元素含量及其比值的变化关系,揭示生态系统各组分间元素循环规律的一门学科,生态化学计量也是荒漠生态系统研究的重要内容。因此,综合掌握水分和养分限制环境下C、N、P生态化学计量的关系对揭示荒漠生态系统植物的限制性元素、土壤营养的供给能力、养分的有效性等都具有重要的意义。基于此,回顾和分析了国内外荒漠生态系统C、N、P生态化学计量最新研究和动态,分别从植物、凋落物、土壤、土壤微生物、土壤酶进行较为系统的评述,讨论了植物-土壤-微生物-酶四者的关系,提出了荒漠生态系统C、N、P生态化学计量的未来研究方向,期望为全面理解固沙植被的演变过程、稳定性维持机制及其科学管理提供理论指导。     

Relationship Between Land Cover Ratio and Urban Heat Island from Remote Sensing and Automatic Weather Stations Data

Urban heat island (UHI) effect has a close relation to land covers type. This paper investigates the relationship between land cover ratio and UHI in Guangzhou, south of China using remote sensing and automatic weather stations data. The temperature data were obtained by Automatic weather stations (AWS) of Guangzhou in October, 2004, at the same time with the CBERS remote sensing image acquired. Firstly, the hourly mean temperature was computed from hourly AWS data. Secondly, the CBERS remote sensing image was classified using support vector machine (SVM) and land covers classification were output. Thirdly, the classification result was overlapped with a round buffer with 1.5 KM radius centered on the AWS, and then the land cover ratio, Edge Density (ED) and Mean Fractal Dimension (MFRACT) of buffers were computed out. Finally, the correlation coefficient between hourly mean temperature and land cover ratio, ED and MFRACT was calculated. It concluded that UHI intensity was heavier during nighttime than daytime. Stations with higher vegetation ratio and higher ED had lower heat island effect. On the contrary, stations with higher impervious ratio and lower ED had more serious heat island effect. The positive–negative of correlation coefficient between hourly mean temperature and vegetation ratio during 11:00–17:00 h (local time) was opposite to that during other time. ED was negatively correlated with hourly mean temperature except during 11:00–17:00 h. On the contrary, MFRACT was positively correlated with hourly mean temperature. It implied that fragmentations of patches were favorable to UHI alleviation, and complexities of patch were unfavorable factors.     

Temporal and spatial dynamical simulation of groundwater characteristics in Minqin Oasis

Application scope of geostatistics has been gradually extended from original geologic field to soil science and ecological field, etc. and its successful application results have been widely demonstrated. But little information is reported as to the direct use of geostatistical method to work out the distribu- tion map of groundwater characteristics. In this paper the semivariogram of geostatistics, in combina- tion with GIS, was used to quantitatively study the spatial variation characteristics of groundwater table depth and mineralization degree and their relation to the landuse changes. F test of the used spherical model reached a very significant level, and the theoretical model can well reflect the spatial structural characteristics of groundwater table depth and mineralization degree and achieve an ideal result. This shows that the application of the method in the dynamical simulation of groundwater is feasible. And this paper also provides useful reference for the application of geostatistics in the study of the dy- namical variations of groundwater resources in the oasis.     

Geochemical processes in a Mediterranean Lake: a high-resolution study of the last 4,000 years in Zoñar Lake,southern Spain

High-resolution geochemical analysis of a 6-m-long sediment core from Zoñar Lake, southern Spain, provides a detailed characterization of major changes in lake and watershed processes during the last 4,000 years. Geochemical variables were used as paleolimnological indicators and complement Zoñar Lakes’s paleoenvironmental reconstruction based on sedimentological and biological proxies, which define periods of increasing allochthonous input to the lake and periods of dominant autochthonous sedimentation. Chemical ratios identify periods of endogenic carbonate formation (higher Ca/Al, Sr/Al and Ba/Al ratios), evaporite precipitation (higher S/Al, Sr/Al ratios), and anoxic conditions (higher Mo/Al, U/Th ratios and Eu anomaly). Higher productivity is marked by elevated organic carbon content and carbonate precipitation (Mg/Ca). Hydrological reconstruction for Zoñar Lake was based on sedimentological, mineralogical and biological proxies, and shows that lower lake levels are characterized by Sr-rich sediments (a brackish lake with aragonite) and S-rich sediments (a saline lake with gypsum), while higher lake levels are characterized by sediments enriched in elements associated with alumino-silicates (Al, K, Ti, Fe, trace and rare earth elements), reflecting fresher conditions. Geochemical indicators also mark periods of higher detrital input to the lake related to human activity in the watershed: (1) during the Iberian Roman Humid Period (650 BC–AD 300), around the onset of the Little Ice Age (AD 1400), during the relatively drier Post-Roman and Middle Ages (AD 800–1400), and over the last 50 years, due to mechanized farming practices. Heavy metal enrichment in the sediments (Cu and Ni) suggests intensification of human activities during the Iberian Roman Period, and the use of fertilizers during the last 50 years.     

A Long-Term Decrease of the Mid-Size Segmentation Lengths Observed in the He <Emphasis Type="SmallCaps">ii</Emphasis> (30.4 nm) Solar EUV Emission

Power spectra of segmentation-cell length (a dominant length scale of EUV emission in the transition region) from full-disk He?ii extreme ultraviolet (EUV) images observed by the Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during periods of quiet-Sun conditions for a time interval from 1996 to 2015 were analyzed. The spatial power as a function of the spatial frequency from about 0.04 to 0.27 (EIT) or up to 0.48 (AIA) Mm^?1 depends on the distribution of the observed segmentation-cell dimensions – a structure of the solar EUV network. The temporal variations of the spatial power reported by Didkovsky and Gurman (Solar Phys. 289, 153, 2014) were suggested as decreases at the mid-spatial frequencies for the compared spectra when the power curves at the highest spatial frequencies of 0.5 pix^?1 were adjusted to match each other. This approach has been extended in this work to compare spectral ratios at high spatial frequencies expressed in the solar spatial frequency units of Mm^?1. A model of EIT and AIA spatial responses allowed us to directly compare spatial spectral ratios at high spatial frequencies for five years of joint operation of EIT and AIA, from 2010 to 2015. Based on this approach, we represent these ratio changes as a long-term network transformation that may be interpreted as a continuous dissipation of mid-size network structures to the smaller-size structures in the transition region. In contrast to expected cycling of the segmentation-cell dimension structures and associated spatial power in the spectra with the solar cycle, the spectra demonstrate a significant and steady change of the EUV network. The temporal trend across these structural spectra is not critically sensitive to any long-term instrumental changes, e.g. degradation of sensitivity, but to the change of the segmentation-cell dimensions of the EUV network structure.     

常量元素氧化物含量及其比值揭示的中晚全新世以来玛曲高原的环境演变

对玛曲高原具有代表性的黄土-古土壤-风成砂剖面(OL剖面)常量元素氧化物含量及其比值的地球化学特征分析表明:(1)常量元素氧化物总含量为91.93%且SiO₂(67.93%) >Al₂O₃(11.2%) >Fe₂O₃(3.97%) >CaO(3.76%)>K₂O(2.16%) >Na₂O(1.81%) >MgO(1.1%);(2)玛曲高原处于较弱的脱Ca、Na初级风化阶段,并伴有碳酸盐的淋失;(3)玛曲高原的气候经历了冷干-凉润-温湿-凉干的冷暖旋回。依据常量元素氧化物含量及其比值揭示的环境特征并结合¹⁴C测年将玛曲高原中晚全新世以来的环境演变划分为4.6 ka BP以前的风沙活动强烈期、4.6～4.3 ka BP的风沙活动较弱期、4.3～0.3 ka BP的固结成壤期和0.3 ka BP至今的风沙活动增强期4个阶段。     

Comparison of the spatio-temporal dynamics of vegetation between the Changbai Mountains of eastern Eurasia and the Appalachian Mountains of eastern North America

The Changbai Mountains and the Appalachian Mountains have similar spatial contexts. The elevation, latitude, and moisture gradients of both mountain ranges offer regional insight for investigating the vegetation dynamics in eastern Eurasia and eastern North America. We determined and compared the spatial patterns and temporal trends in the normalized difference vegetation index (NDVI) in the Changbai Mountains and the Appalachian Mountains using time series data from the Global Inventory Modeling and Mapping Studies 3rd generation dataset from 1982 to 2013. The spatial pattern of NDVI in the Changbai Mountains exhibited fragmentation, whereas NDVI in the Appalachian Mountains decreased from south to north. The vegetation dynamics in the Changbai Mountains had an insignificant trend at the regional scale, whereas the dynamics in the Appalachian Mountains had a significant increasing trend. NDVI increased in 55% of the area of the Changbai Mountains and in 95% of the area of the Appalachian Mountains. The peak NDVI occurred one month later in the Changbai Mountains than in the Appalachian Mountains. The results revealed a significant increase in NDVI in autumn in both mountain ranges. The climatic trend in the Changbai Mountains included warming and decreased precipitation, and whereas that in the Appalachian Mountains included significant warming and increased precipitation. Positive and negative correlations existed between NDVI and temperature and precipitation, respectively, in both mountain ranges. Particularly, the spring temperature and NDVI exhibited a significant positive correlation in both mountain ranges. The results of this study suggest that human actives caused the differences in the spatial patterns of NDVI and that various characteristics of climate change and intensity of human actives dominated the differences in the NDVI trends between the Changbai Mountains and the Appalachian Mountains. Additionally, the vegetation dynamics of both mountain ranges were not identical to those in previous broader-scale studies.     

Distribution of the indigenous microorganisms and mechanisms of their orientational activation in Daqing Oilfield

The distribution of indigenous microorganisms was surveyed in Block 1 of Daqing Oilfield. Based on this survey, the indigenous microorganisms in the formation water were activated with different activator systems at the simulated stratum ecological environment. The changes of the number of bacteria of various physiological groups were determined during the process of activation. Also changes of pH value and composition of gas productions were analyzed at the end of culturing. The results showed that the selected block formation water contained a great number of saprophytic bacteria, hydrocarbon-oxidizing bacteria, fermentative bacteria, methane-producing bacteria and sulfate-reducing bacteria. Under the conditions that the growth of sulfate-reducing bacteria was controlled the block had the potential to enhance oil recovery by activating beneficial bacteria. The growth of sulfate-reducing bacteria can be inhibited through the activation of nitrate-reducing bacteria. The number of nitrate-reducing bacteria reached 10⁶–10⁷ cells/mL, but sulfate-reducing bacteria reached only 0–45 cells/mL in A system. Methane-producing bacteria can be activated by C, D activators. The relative content of biological methane in the light hydrocarbon gas reached 80% in C, D systems. B activator was conducive to the propagation of acid-producing bacteria, so that the pH value of the culture medium decreased from 7.5 to around 5.0. Hydrocarbon-oxidizing bacteria can be activated by various activator systems. There was low molecular light hydrocarbon in gas production according to the analysis of gas chromatograph. According to the content of methane and the number of methane-producing bacteria, methane only can be generated through activating methane-producing bacteria. By choosing different activator systems, various populations of indigenous microorganisms can be activated accordingly.     

长江三峡库区梯田稳定性分析与对策*──以鄂西秭归县为例

三峡库区历史上就是滑坡、崩塌作用强烈的地带,在调查分析秭归县滑坡、崩塌对梯田稳定性的影响的基础上,探讨了四种不稳定梯田培坎的特征、性质和现状,提出了利用优势植物固土护坎等相应的对策。     

基于学籍地址和地理编码的乡村小学教育资源空间可达性分析

基于“学籍信息中的家庭地址承载了学生空间位置”这一假设,通过学籍信息收集了湖南省株洲县小学生的家庭地址,借助高德开放平台提供的地理编码和POI搜索服务,获得到了株洲县小学生的空间位置和分布,并基于最短路径分析和高斯型两步移动搜索法分析了株洲县小学教育资源的空间可达性及其特征,尝试为区域教育资源的空间均衡性分析与规划配置提供新的数据源和方法借鉴。结果表明：① 基于学籍地址和地理编码技术能够较准确地获取株洲县小学生的空间分布。② 株洲县小学生就近入学距离的最大值、平均值和中位数分别为11.83 km、2.10 km和1.81 km,就近入学距离小于2.0 km的学生仅占55.46%,为株洲县兼顾公平和效率的教育资源配置工作带来了挑战。③ 株洲县北部城镇地区因学校数量较多,平均就近入学距离较小,教育资源的空间可达性普遍较高,且空间差异小,均衡性好;而东南部的乡村地区,平均就近入学距离较大,教育资源的空间可达性普遍较低,且空间差异大。④ 基于情景分析,在不造成局地生源稳定性问题的前提下,新增3所学校后,东南部地区的平均就近入学距离和教育资源的空间可达性有很大的改善,龙潭镇和龙门镇的平均入学距离由3784 m和3520 m降低到3116 m和2636 m,教育资源的空间可达性分别由0.0492和0.0982提高到0.0762和0.1496。