Assessing the ‘two water worlds’ hypothesis and water sources for native and exotic evergreen species in south‐central Chile

Recent studies using water‐stable isotopes (δ¹⁸O and δ²H) have suggested an ecohydrological separation of water flowing to streams or recharging groundwater and water used by trees, known as the ‘two water worlds’ (TWW) hypothesis. In this study, we measured water isotopic composition in precipitation [open field and throughfall, i.e. local meteoric water line (LMWL)] and the mobile water compartment (i.e. stream and soil solution), bulk soil water and xylem water over a period of 1.5 years in two headwater catchments: NF, covered with old growth native evergreen forest (Aetoxicon punctatum, Laureliopsis philippiana and Eucriphya cordifolia), and EP, covered with 4 and 16‐year‐old Eucalyptus nitens stands. Our results show that precipitation, stream and soil solution plot approximately along the LMWL, while xylem waters from all studied tree species plot below the LMWL, supporting the TWW hypothesis. However, we also found evidence of ecohydrological connectivity during the wet season, likely controlled by the amount of antecedent precipitation. These observations hold for all investigated tree species. On both sites, a different precipitation source for stream and xylem water was observed. However, in EP, bulk soil showed a similar precipitation source as xylem water from both E. nitens stands. This suggests that E. nitens may use water that is recharging the bulk soil compartment. We conclude that under a rainy temperate climate, the TWW hypothesis is temporal and does not apply during wet seasons. Copyright © 2016 John Wiley & Sons, Ltd.     

Large‐scale poroelastic fractured reservoirs modeling using the fast multipole displacement discontinuity method

An effective approach to modeling the geomechanical behavior of the network and its permeability variation is to use a poroelastic displacement discontinuity method (DDM). However, the approach becomes rather computationally intensive for an extensive system of cracks, particularly when considering coupled diffusion/deformation processes. This is because of additional unknowns and the need for time‐marching schemes for the numerical integration. The Fast Multipole Method (FMM) is a technique that can accelerate the solution of large fracture problems with linear complexity with the number of unknowns both in memory and CPU time. Previous works combining DDM and FMM for large‐scale problems have accounted only for elastic rocks, neglecting the fluid leak‐off from the fractures into the matrix and its influence on pore pressure and stress field. In this work we develop an efficient geomechanical model for large‐scale natural fracture networks in poroelastic reservoirs with fracture flow in response to injection and production operations. Accuracy and computational performance of the proposed method with those of conventional poroelastic DDM are compared through several case studies involving up to several tens of thousands of boundary elements. The results show the effectiveness of the FMM approach to successfully evaluate field‐scale problems for the design of exploitation strategies in unconventional geothermal and petroleum reservoirs. An example considering faults reveals the impact of reservoir compartmentalization because of sealing faults for both geomechanical and flow variables under elastic and poroelastic rocks. Copyright © 2015 John Wiley & Sons, Ltd.     

Modelling groundwater/surface water interaction in a managed riparian chalk valley wetland

Understanding hydrological processes in wetlands may be complicated by management practices and complex groundwater/surface water interactions. This is especially true for wetlands underlain by permeable geology, such as chalk. In this study, the physically based, distributed model MIKE SHE is used to simulate hydrological processes at the Centre for Ecology and Hydrology River Lambourn Observatory, Boxford, Berkshire, UK. This comprises a 10‐ha lowland, chalk valley bottom, riparian wetland designated for its conservation value and scientific interest. Channel management and a compound geology exert important, but to date not completely understood, influences upon hydrological conditions. Model calibration and validation were based upon comparisons of observed and simulated groundwater heads and channel stages over an equally split 20‐month period. Model results are generally consistent with field observations and include short‐term responses to events as well as longer‐term seasonal trends. An intrinsic difficulty in representing compressible, anisotropic soils limited otherwise excellent performance in some areas. Hydrological processes in the wetland are dominated by the interaction between groundwater and surface water. Channel stage provides head boundaries for broad water levels across the wetland, whilst areas of groundwater upwelling control discrete head elevations. A relic surface drainage network confines flooding extents and routes seepage to the main channels. In‐channel macrophyte growth and its management have an acute effect on water levels and the proportional contribution of groundwater and surface water. The implications of model results for management of conservation species and their associated habitats are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

PPP/SINS紧耦合系统仿真的研究与分析

在捷联惯导(SINS)和GPS卫星接收机进行紧耦合的研究中,采用差分定位进行紧耦合的方法比较成熟,而关于精密单点定位(PPP)与捷联惯导紧耦合的研究还比较少。本文对精密单点定位与捷联惯导紧组合系统进行了Matlab仿真,利用数学解析的方法产生机载运动轨迹,通过设置系统的参数,获得仿真SINS和GPS数据;然后,通过PPP/SINS紧组合系统的仿真程序解算,将定位结果与PPP的结果比较,表明PPP/SINS紧组合导航定位的结果比PPP的精度和可靠性好,而且收敛的速度更快,同时也验证了算法的正确性。最后,分析了不同等级惯导对定位精度的影响。     

基于遥感数据的哈尔滨土地利用/覆被变化研究

以哈尔滨市为例,基于Landsat数据,利用遥感技术和GIS技术对2000和2015年的遥感影像数据进行解译分类,通过对分类结果的统计分析,定量研究哈尔滨市15年间的土地利用变化过程,结果显示:哈尔滨市土地综合利用程度较高,区域内耕地面积减少;相反,城市建成区面积大幅增加,区域内绿地面积逐年减少,应注意生态环境维护保持。     

Accumulation by securitization: Commercial poaching,neoliberal conservation,and the creation of new wildlife frontiers

Part of a broader interest in the escalating securitization of conservation practice, scholars are beginning to take note of an emerging relationship between conservation–securitization, capital accumulation, and dispossession. We develop the concept of accumulation by securitization to better grasp this trend, positioning it in the critical literatures on neoliberal conservation, green grabbing, and conservation-security. The concept captures the ways in which capital accumulation, often tied to land and resource enclosure, is enabled by practices and logics of security. Security logics, moreover, increasingly provoke the dispossession of vulnerable communities, thereby enabling accumulation. We ground the concept by turning to the Greater Lebombo Conservancy (GLC) in the Mozambican borderlands. This is a new privately-held conservancy built as a securitized buffer zone to obstruct the movement of commercial rhino poachers into South Africa’s adjacent Kruger National Park. We show how wildlife tourism-related accumulation here is enabled by, and in some ways contingent upon, the GLC’s success in curbing poaching incursions, and, relatedly, how security concerns become the grounds upon which resident communities are displaced. In terms of the latter, we suggest security provides a troubling, depoliticized alibi for dispossession. Like broader neoliberal conservation and green grabbing, we illustrate how accumulation by securitization plays out within complex new networks of state and private actors. Yet these significantly expand to include including security actors and others motivated by security concerns.     

Geochemical and isotopic characterization of trace fossil infillings: New insights on tracemaker activity after the K/Pg impact event

Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ¹³C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ¹⁸O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures.     

A modeling study of effective radiative forcing and climate response due to tropospheric ozone

This study simulates the effective radiative forcing(ERF) of tropospheric ozone from 1850 to 2013 and its effects on global climate using an aerosol–climate coupled model, BCC AGCM2.0.1 CUACE/Aero, in combination with OMI(Ozone Monitoring Instrument) satellite ozone data. According to the OMI observations, the global annual mean tropospheric column ozone(TCO) was 33.9 DU in 2013, and the largest TCO was distributed in the belts between 30°N and 45°N and at approximately 30°S; the annual mean TCO was higher in the Northern Hemisphere than that in the Southern Hemisphere;and in boreal summer and autumn, the global mean TCO was higher than in winter and spring. The simulated ERF due to the change in tropospheric ozone concentration from 1850 to 2013 was 0.46 W m~(-2), thereby causing an increase in the global annual mean surface temperature by 0.36℃, and precipitation by 0.02 mm d~(-1)(the increase of surface temperature had a significance level above 95%). The surface temperature was increased more obviously over the high latitudes in both hemispheres, with the maximum exceeding 1.4?C in Siberia. There were opposite changes in precipitation near the equator,with an increase of 0.5 mm d~(-1)near the Hawaiian Islands and a decrease of about-0.6 mm d~(-1)near the middle of the Indian Ocean.     

The Upstream “Strong Signals” of the Water Vapor Transport over the Tibetan Plateau during a Heavy Rainfall Event in the Yangtze River Basin

A heavy rainfall event that occurred over the middle and lower reaches of the Yangtze River Basin(YRB) during July11–13 2000 is explored in this study. The potential/stream function is used to analyze the upstream "strong signals" of the water vapor transport in the Tibetan Plateau(TP). The studied time period covers from 2000 LST 5 July to 2000 LST 15 July(temporal resolution: 6 hours). By analyzing the three-dimensional structure of the water vapor flux, vorticity and divergence prior to and during the heavy rainfall event, the upstream "strong signals" related to this heavy rainfall event are revealed. A strong correlation exists between the heavy rainfall event in the YRB and the convective clouds over the TP. The "convergence zone" of the water vapor transport is also identified, based on correlation analysis of the water vapor flux two days and one day prior to, and on the day of, the heavy rainfall. And this "convergence zone" coincides with the migration of the maximum rainfall over the YRB. This specific coupled structure actually plays a key role in generating heavy rainfall over the YRB. The eastward movement of the coupled system with a divergence/convergence center of the potential function at the upper/lower level resembles the spatiotemporal evolution of the heavy rainfall event over the YRB. These upstream "strong signals" are clearly traced in this study through analyzing the three-dimensional structure of the potential/stream function of upstream water vapor transport.