Impacts of soil conservation on groundwater recharge in the semi-arid Loess Plateau, China

Soil conservation measures undertaken to address land degradation can alter the hydrologic cycle by changing partitioning of water fluxes at the land surface. While effects on runoff are well documented, impacts of soil conservation activities on fluxes to groundwater are poorly understood. The goal of this study was to examine fluxes to groundwater in a semi-arid area of China’s Loess Plateau that has been subject to extensive soil conservation activities. Unsaturated zone pore-water pressures and concentrations of chloride show that impacts on deep drainage differ between ecological and structural soil conservation approaches. High matric potentials and low chloride beneath cultivated terrace and gulley sites are consistent with deep drainage occurring at these sites. Estimated recharge rates for dryland cultivated upland sites were approximately 55??0?mm/year (11??8% of mean annual rainfall) based upon chloride mass balance. In contrast, results suggest that mature tree and shrub plantations prevent deep drainage. Stable isotope signatures of unsaturated-zone moisture and groundwater indicate that focused infiltration through gullies and other topographic lows is likely to be the primary recharge mechanism. The results of this study highlight the potential for inadvertent effects of some soil conservation approaches on regional water resources.     

测井方法在山西宁武煤田马营堡井田勘探中的应用

马营堡井田基本构造形态为一单斜构造,区内不同岩性地层的电阻率、密度、声波时差及伽马值均有明显差异,其中煤层的电阻率、密度及声波时差曲线均表现出出高异常及自然伽马低异常;而砂岩随粒度的变细及泥质含量的增加,自然伽玛逐渐增大。依据该区岩性基本物性特征,确定了井田内新生界与基岩、下石盒子组与山西组分界及主采煤层4、9号等主要标志层的响应特征。这些地层标志在测井曲线上形态,可作为该区地层对比的重要依据。     

Surface atmospheric circulation patterns and associated minimum temperatures in the Maipo and Casablanca valleys, central Chile

This paper analyzes the influence of circulation anomalies on the magnitude of minimum air temperature (T _min) at a daily scale in two important agricultural valleys of Chile (Maipo and Casablanca) during the period 2001–2007. A statistical classification of synoptic fields was performed, resulting in eight circulation patterns (CPs, 84 % of explained variance). The corresponding anomalies of T _min (AT_min) of each CP were analyzed in order to understand their synoptic-scale forcing mechanisms. Results showed a direct association between AT_min and the synoptic structure. The average weakening in sea level pressure (SLP) yields positive AT_min, while negative AT_min is associated with a strengthening in SLP. In the latter case, it was also found that a synoptic structure (10.2 % of frequency) corresponding to a migratory high-pressure system passing eastward across the Andes led to the lowest AT_min and a higher probability of frost in both valleys (22 % on average) in winter and springtime.     

Using the Lund-Potsdam-Jena Model to Understand the Different Responses of Three Woody Plants to Land Use in China

In this study, the approach of conditional nonlinear optimal perturbation related to initial perturbation (CNOP-I) was employed to investigate the maximum variations in plant amount for three main woody plants (a temperate broadleaved evergreen, a temperate broadleaved summergreen, and a boreal needleleaved evergreen) in China. The investigation was conducted within a certain range of land use intensity using a state-of-the-art Lund-Potsdam-Jena dynamic global vegetation model (LPJ DGVM). CNOP-I represents a class of deforestation and can be considered a type of land use with respect to the initial perturbation. When deforestation denoted by the CNOP-I has the same intensity for all three plants, the variation in plant amount of the boreal needleleaved evergreen in northern China is greater than the variation in plant amount of both the temperate broadleaved evergreen and temperate broadleaved summergreen in southern China. As deforestation intensity increases, the plant amount variation in the three woody plant functional types carbon changes, in a nonlinear fashion. The impact of land use on plant functional types is minor because the interaction between climate condition and land use is not considered in the LPJ model. Finally, the different impacts of deforestation on net primary production of the three plant functional types were analyzed by modeling gross primary production and autotrophic respiration. Our results suggest that the CNOP-I approach is a useful tool for exploring the nonlinear and different responses of terrestrial ecosystems to land use.     

Reconstructing the landing trajectory of the CE-3 lunar probe by using images from the landing camera

An accurate determination of the landing trajectory of Chang'e-3(CE-3)is significant for verifying orbital control strategy, optimizing orbital planning, accurately determining the landing site of CE-3 and analyzing the geological background of the landing site. Due to complexities involved in the landing process, there are some differences between the planned trajectory and the actual trajectory of CE-3. The landing camera on CE-3 recorded a sequence of the landing process with a frequency of 10 frames per second. These images recorded by the landing camera and high-resolution images of the lunar surface are utilized to calculate the position of the probe, so as to reconstruct its precise trajectory. This paper proposes using the method of trajectory reconstruction by Single Image Space Resection to make a detailed study of the hovering stage at a height of 100 m above the lunar surface. Analysis of the data shows that the closer CE-3 came to the lunar surface, the higher the spatial resolution of images that were acquired became, and the more accurately the horizontal and vertical position of CE-3 could be determined. The horizontal and vertical accuracies were7.09 m and 4.27 m respectively during the hovering stage at a height of 100.02 m. The reconstructed trajectory can reflect the change in CE-3's position during the powered descent process. A slight movement in CE-3 during the hovering stage is also clearly demonstrated. These results will provide a basis for analysis of orbit control strategy,and it will be conducive to adjustment and optimization of orbit control strategy in follow-up missions.     

高精度磁测与四道γ能谱在金矿床上的应用—─以阿希金矿为例

对阿希金矿床高精度磁测结果分析，发现了环状磁异常，它是火山岩地区控矿构造—环状构造的反映。对该异常进行了延拓处理，得出其浅部为环状和放射状断裂，深部为南北向断裂。对该矿床又作了四道γ能谱测量，发现它可以清晰的划分矿化蚀变带与围岩的界线，其基本规律是：钾道和总道含量在矿化蚀变带上明显升高，而钍道则明显下降     

基于GPS的2021年玛多MW7.4地震同震静、动态形变场

利用青海省CORS网GPS连续观测数据获取2021年玛多M_W7.4地震的同震形变场以及震时地表运动状态。结果表明,断层南北两侧的近场测站分别展现出南东向和北西向运动,符合左旋走滑机制。同震形变集中在震中距300 km范围内,震中距150 km以内的站点均能反映出cm级的位移,最大水平向位移为28.3 cm(JDUO站)。高频GPS动态形变提取出的永久位移与静态解算结果相当,其动态波形最大峰值为49.9 cm(KANQ站)。依据震中距和波形初动时间估计得到地震波速为2.8~4.9 km/s,断层东端的站点估算速度大于其他站点,可能与此次破裂的方向性或者破裂传播速度有关。依据震级经验公式,动态波形估算震级在M6.8~7.6区间,拟合平均震级为M7.35±0.15。若在实时条件下,震后70 s内可得到稳定的震级。