Remote sensing and GIS based determination of groundwater dependent ecosystems in the Western Cape, South Africa

Finding the location of groundwater dependent ecosystems (GDEs) is important in determining the extent of restrictions that need to be placed upon the abstraction of groundwater. Remote sensing was combined with geographical information system (GIS) modelling to produce a GDE probability rating map for the Sandveld region, South Africa. Landsat TM imagery identified the areas indicating the probable presence of GDEs and GIS assisted in their delineation. Three GIS models were generated: a GIS model predicting landscape wetness potential (LWP model) based on terrain morphological features; the LWP model was modified to highlight groundwater generated landscape wetness potential (the resulting GglWP model); and a groundwater elevation model was interpolated, combining groundwater level measurements in boreholes in the region with digital elevation model data. Biomass indicators generated from Landsat were classified and combined with the GIS models, followed by field verification of riverine and wetland GDEs. The LWP model provided the most accurate results of the three models tested for GDEs in this region.

A New Method of Significance Testing for Correlation-Coefficient Fields and Its Application

Correlation-coefficient fields are widely used in short-term climate prediction research. The most frequently used significance test method for the correlation-coefficient field was proposed by Livezey, in which the number of significantcorrelation lattice(station) points on the correlation coherence map is used as the statistic. However, the method is based on two assumptions:(1) the spatial distribution of the lattice(station) points is uniform;and(2) there is no correlation between the physical quantities in the correlation-coefficient field. However, in reality, the above two assumptions are not valid.Therefore, we designed a more reasonable method for significance testing of the correlation-coefficient field. Specifically, a new statistic, the significant-correlation area, is introduced to eliminate the inhomogeneity of the grid(station)-point distribution, and an empirical Monte Carlo method is employed to eliminate the spatial correlation of the matrix.Subsequently, the new significance test was used for simultaneous correlation-coefficient fields between intensities of the atmospheric activity center in the Northern Hemisphere and temperature/precipitation in China. The results show that the new method is more reasonable than the Livezey method.     

新疆西天山金属矿床,成矿系列及形成演化规律

笔者根据对西天山北部大量矿床和矿点研究,在对西天山成矿类型及成矿控制因素分析的基础上,将该区金属矿床主要划分为３个成矿系列类型,即：①与中酸性、酸性花岗岩类有关的Ｃｕ－Ｆｅ－Ａｕ－ＭｏＯ－Ｗ－Ｓｎ－Ｐｂ－Ｚｎ成矿系列类型;②与基性－中性－酸性火山岩建造有关的Ｃｕ－Ｆｅ－Ａｕ成矿系列类型;③与沉积岩、热水沉积岩有关的层控Ｃｕ－Ｐｂ－Ｚｎ成矿系列类型。每个成矿系列类型具有不同的成矿特征和成矿背景。成矿     

Iron and Pyritization in Wetland Soils of the Florida Coastal Everglades

We explored environmental factors influencing soil pyrite formation within different wetland regions of Everglades National Park. Within the Shark River Slough (SRS) region, soils had higher organic matter (62.65 ± 1.88 %) and lower bulk density (0.19 ± 0.01 g cm^?3) than soils within Taylor Slough (TS; 14.35 ± 0.82 % and 0.45 ± 0.01 g cm^?3, respectively), Panhandle (Ph; 15.82 ± 1.37 % and 0.34 ± 0.009 g cm^?3, respectively), and Florida Bay (FB; 5.63 ± 0.19 % and 0.73 ± 0.02 g cm^?3, respectively) regions. Total reactive sulfide and extractable iron (Fe) generally were greatest in soils from the SRS region, and the degree of pyritization (DOP) was higher in soils from both SRS (0.62 ± 0.02) and FB (0.52 ± 0.03) regions relative to TS and Ph regions (0.30 ± 0.02 and 0.31 ± 0.02, respectively). Each region, however, had different potential limits to pyrite formation, with SRS being Fe and sulfide limited and FB being Fe and organic matter limited. Due to the calcium-rich soils of TS and Ph regions, DOP was relatively suppressed. Annual water flow volume was positively correlated with soil DOP. Soil DOP also varied in relation to distance from water management features and soil percent organic matter. We demonstrate the potential use of soil DOP as a proxy for soil oxidation state, thereby facilitating comparisons of wetland soils under different flooding regimes, e.g., spatially or between wet years versus dry years. Despite its low total abundance, Fe plays an important role in sulfur dynamics and other biogeochemical cycles that characterize wetland soils of the Florida coastal Everglades.     

Between-Population Differences in Multi-stressor Tolerance During Embryo Development in the American Horseshoe Crab, <Emphasis Type="Italic">Limulus polyphemus</Emphasis>

The American horseshoe crab, Limulus polyphemus, is found along the Atlantic and Gulf of Mexico coasts in genetically isolated populations. Eggs are laid in shoreline beaches that expose developing embryos to combinations of environmental stressors. Whether populations of L. polyphemus differ in multi-stressor tolerance had never been tested. We assessed the multi-stressor tolerance of L. polyphemus embryos from a population in Delaware Bay (DE) and determined whether these differed from the multi-stressor tolerance of embryos from a more southerly Florida Gulf Coast (FGC) population. We monitored the field sediment temperatures and determined multi-stressor tolerance of DE embryos, then compared these to published data for FGC embryos. For multi-stressor tolerance, we assessed development success of embryos in 2-week exposures to 36 full-factorial combinations of temperature (20, 25, 30, 35 °C), salinity (5, 15, and 34 ppt), and ambient O₂ (5, 13, and 21% O₂), followed by 2 weeks in recovery conditions. Sediment temperatures in the DE site ranged from 9.5 to 46 °C, with extended periods exceeding 35 °C. Development success was similar between the DE and FGC populations in 14 of 26 multi-stressor combinations. The DE embryos were generally more successful in conditions that included high temperature or moderate hyposalinity, whereas the FGC embryos were generally more successful in conditions that included extreme hyposalinity. This suggests that although multi-stressor tolerances are generally similar between the two populations, specific differences exist that correlate more with differences in nest microenvironment than latitude.     

Aftershock sequence simulations using synthetic earthquakes and rate-state seismicity formulation

We use an efficient earthquake simulator that incorporates rate-state constitutive properties and uses boundary element method to discretize the fault surfaces, to generate the synthetic earthquakes in the fault system. Rate-and-state seismicity equation is subsequently employed to calculate the seismicity rate in a region of interest using the Coulomb stress transfer from the main shocks in the fault system. The Coulomb stress transfer is obtained by resolving the induced stresses due to the fault patch slips onto the optimal-oriented fault planes. The example results show that immediately after a main shock the aftershocks are concentrated in the vicinity of the rupture area due to positive stress transfers and then disperse away into the surrounding region toward the background rate distribution. The number of aftershocks near the rupture region is found to decay with time as Omori aftershock decay law predicts. The example results demonstrate that the rate-and-state fault system earthquake simulator and the seismicity equations based on the rate-state friction nucleation of earthquake are well posited to characterize the aftershock distribution in regional assessments of earthquake probabilities.     

High-Frequency Rayleigh-Wave Method

High-frequency (≥2 Hz) Rayleigh-wave data acquired with a multichannei recording sys-tem have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave tech-niques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a nou-iuvasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.     

基于深度学习的区域生态安全时空模拟与预测

区域作为人类、自然、社会共同作用和互相影响的复杂系统,对区域进行生态量化建模与模拟仿真,是实现区域可持续发展战略的关键。传统机器学习方法对区域生态系统建模取得了一定的成果,但难以确定学习特征和实现时空模拟。深度学习不需事先确定训练特征,具有优异的特征学习能力,能够提高模型预测精度,因此利用深度学习进行建模具有显著优势。本文使用植被净初级生产力（NPP）、气溶胶光学厚度（AOD）和人口格网数据,充分利用深度学习的优点,采用最优深度神经网络时空模拟,得到了河南省2007-2014年3 km分辨率的生态赤字空间分布图和河南省2015-2020年的生态赤字时间预测结果并进行分析,为区域生态的科学管理和建设供科学依据和参考。