中尺度涡影响下的南海西部活性铝分布

To understand the distribution of aluminum(Al) under the influence of mesocale eddies in the western South China Sea(SCS), sea level anomaly, geostrophic current, environmental parameters and reactive Al were investigated in the western SCS in August 2013. The highest reactive Al concentration((180±64) nmol/L) was observed in the surface waters, indicating a substantial atmospheric input. Vertically, the reactive Al decreased from the surface high concentration to the subsurface minima at the depth of chlorophyll a(Chl a) maxima and then increased again with depth at most of the stations. The average concentration of reactive Al in the upper 100 m water column was significantly lower in the cyclonic eddy((137±6) nmol/L) as compared with that in the noneddy waters((180±21) nmol/L). By contrast, the average concentrations of Chl a and silicate in the upper 100 m water column were higher in the cyclonic eddy and lower in the anticyclonic eddy. There was a significant negative correlation between the average concentrations of reactive Al and Chl a in the upper 100 m water column. The vertical distribution of reactive Al and the negative correlation between reactive Al and Chl a both suggest that the reactive Al in the upper water column was significantly influenced by biological removal processes. Our results indicate that mesoscale eddies could regulate the distribution of reactive Al by influencing the primary production and phytoplankton community structure in the western SCS.     

Reef building and carbonate production modes in the west-central Tethys during the Cenozoic

Changing components, rock textures, lithofacies, platform types and architecture throughout time are unique characteristics of carbonate rocks. Characterizing these attributes has been approached by 1) building reference models for specific Phanerozoic intervals, 2) recognizing the climatic impact in modulating carbonate production, and 3) analyzing the influence of changing bio-geochemical conditions. The reference-model approach is mostly based on biological evolution, the climatic-impact approach emphasizes temperature, and the bio-geochemical approach considers the changes in Mg/Ca ratios and Ca⁺⁺ concentrations in the oceans. To date, however, an analysis integrating all of these factors is still missing. The analysis presented here includes all these factors but also CO₂, which is fundamental for both photosynthesis and CaCO₃ precipitation.Here we analyze the waxing and waning of Cenozoic reef limestones from the central Tethys region through several steps: 1) on the basis of rock volume, rock textures, associated sediments and light-dependent skeletal components, as records of light penetration and wave energy (depth); 2) on global environmental conditions (δ¹³C, δ¹⁸O, pCO₂, temperature); and 3) on the basis of functionality, nutritional requirements and available resources.Through the Cenozoic, water motion, whether induced by surface or internal waves or by currents, increased as the thermal gradients strengthened, both with depth and with latitude. Active water motion is essential for plankton catchers such as corals, but less so for many larger benthic foraminifers (LBF). Pycnoclines in the meso-oligophotic zone would then favor the benthic plankton catchers such as corals, but would be detrimental for many LBF. Warm temperatures favored LBF. The Eocene LBF families predominated during lowering of atmospheric pCO₂ by using respiratory CO₂ to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence, whereas the Miocene families had to adapt to a progressive increase in turbulence. The eurythermal coralline red algae, however, became preponderant producers in the mesophotic zone during times when the δ¹³C was relatively high. This explains two apparent paradoxes: 1) corals thrive best when the Earth's high latitudes cool, and 2) the dominance of corals and LBF is inversely correlated, despite they both require tropical conditions and have similar trophic strategies (mixotrophy).     

Fluid flow characteristics of Bandanna Coal Formation: a case study from the Fairview Field,eastern Australia

Fluid flow characteristics of cleat systems in coalbed methane reservoirs are crucial in reservoir management and field development plans. This paper aims to evaluate the cleat system properties including cleat porosity, permeability, and aperture as well as the impact of permeability growth on production performance in the Bandanna Coal Formation of the Fairview Field, eastern Queensland. Owing to the presence of bad hole conditions and poor core recovery of the coal intervals, the petrophysical well logs and laboratory measurements cannot be used as a source of information for this purpose. Hence, a new approach is employed that utilises early water production data to measure water in place and absolute permeability of the coal. In addition, micro-computed tomography (CT) scan method is used to investigate the cleat system that is preserved in a core sample and results are compared with the ones obtained by analysis of production data. Cleat system evaluation by analysis of production data and micro-CT scan technique provides a comprehensive approach that brings confidence in measurements and helps to obtain cleat properties at the sufficient scale for reservoir engineering purposes. The necessary information including production data and core samples are collected from a dewatering well and the nearby observation well in the study area. Analysis of early water production data (single-phase flow) indicates that coal permeability is 189 mD and the average cleat porosity is approximately 5%. High cleat porosity describes the large volume of water produced over the life of the study well. The 3D model of the fossilised cleat system constructed by the micro-CT scan method reveals that coal is well-cleated and cleat spacing and mean cleat aperture are 4 and 0.136 mm, respectively. The average cleat porosity that is measured by the micro-CT scan method is 5.7%, which is fairly close to the cleat porosity measured by analysis of production data. Production data analysis indicates that effective permeability to gas starts to grow at the midlife of the well and it strongly controls the shape of the production profile. The results of this study help in future field development and infill drilling programs in the Fairview Field and provide important insights into cleat system of Bandanna Coal Formation.     

绿洲农户生产效率差异评价及改进策略——以张掖市制种玉米为例

绿洲农业是中国西北干旱区农业的精华,面临自然要素稀缺和生态环境脆弱的双重限制。基于制种玉米种植农户数据,在采用数据包络分析法（DEA）测算生产效率的基础上,依据测算结果对冗余投入要素进行改进模拟,得出以下结论：该地区制种玉米生产效率均值为0.863 3,且小规模农地效率值最高,大规模农地效率值最低。针对冗余投入要素的改进模拟后,提出了主要针对贡献率高的生产要素优化的建议。     

Contributions of climate change and human activities to ET and GPP trends over North China Plain from 2000 to 2014

Quantifying the contributions of climate change and human activities to ecosystem evapotranspiration (ET) and gross primary productivity (GPP) changes is important for adaptation assessment and sustainable development. Spatiotemporal patterns of ET and GPP were estimated from 2000 to 2014 over North China Plain (NCP) with a physical and remote sensing-based model. The contributions of climate change and human activities to ET and GPP trends were separated and quantified by the first difference de-trending method and multivariate regression. Results showed that annual ET and GPP increased weakly, with climate change and human activities contributing 0.188 mm yr–2 and 0.466 mm yr^–2 to ET trend of 0.654 mm yr^–2, and–1.321 g C m^–2 yr^–2 and 7.542 g C m^–2 yr^–2 to GPP trend of 6.221 g C m^–2 yr^–2, respectively. In cropland, the increasing trends mainly occurred in wheat growing stage; the contributions of climate change to wheat and maize were both negative. Precipitation and sunshine duration were the major climatic factors regulating ET and GPP trends. It is concluded that human activities are the main drivers to the long term tendencies of water consumption and gross primary productivity in the NCP.     

Seasonal variations in phytoplankton biomass and primary production in the Ethiopian Rift Valley lakes Ziway, Awassa and Chamo – The basis for fish production

Seasonal variations in the biomass (Chl a) and primary production (¹⁴C-method) of phytoplankton were studied during 12 months of 2005 in the three Ethiopian Rift Valley Lakes (ERVL) Ziway, Awassa and Chamo. Chl a showed an average value of 40, 20, and 30 mg m⁻³ for the three lakes, respectively. Integrated areal primary production for the total phytoplankton (g C m⁻² d⁻¹) varied 2-fold in the three lakes but on different levels, from 0.67–1.8 in L. Ziway, 1.8–4.6 in L. Awassa, and 1.0–2.6 in L. Chamo. The overall photosynthetic efficiency of utilizing photosynthetically active radiation by the phytoplankton on molar basis (mmol C mol of photons⁻¹) resulted in an average value of 1.4 for L. Ziway, 3.5 for L. Awassa and 1.6 for L. Chamo. Among the different factors regulating phytoplankton primary productivity, light penetration and nutrients were the most important in the three lakes. The seasonal variations of incident radiation (most values between 5 and 7 E m⁻² h⁻¹) and water temperature (most values between 22 and 24 °C) were small and unlikely to result in the marked differences in phytoplankton primary production. Although relative increase in nutrient concentrations occurred following the rainy periods, the major algal nutrients were either consistently low (nitrate and/or silicate) or high (phosphate and/or ammonium) and remained within a narrow range for most of the study period in all the three lakes. Consequently, phytoplankton biomass and primary production seem to be maintained more by nutrient regeneration or turnover (facilitated by high temperature) than by allochthonous nutrient input. This would be coupled with wind-induced mixing that would play an important role in determining hydrographic characteristics (water column structure) and the associated redistribution of nutrients and phytoplankton, the availability of light and subsequently the spatial (vertical) and temporal patterns of phytoplankton production in these three ERVL. Phytoplankton production (PP) is regarded as a good predictor of fish yield in lakes and seasonal measurements of PP is a prerequisite for good such estimates.     

全球变暖对淡水湖泊浮游植物影响研究进展

全球变暖对湖泊生态系统的影响已经成为近年来湖沼学领域的研究热点。本文首先列举了目前研究全球变暖对淡水湖泊浮游植物影响的常用方法：监测数据分析、时空转换、遥感信息提取、控制实验、模型预测和古湖沼学技术等。研究结果表明气候变暖导致的气温升高、湖泊热力分层提前破坏以及无冰期提前等因素可导致春季物候提前;在全球变暖大背景下浮游植物群落结构正朝着蓝藻占优的方向发展,但是不同地区以及不同物种对全球变暖的响应不一致。在营养盐充足的湖泊中,由于全球变暖延长了浮游植物生长季节等,从而能提高浮游植物初级生产力;但在贫营养湖泊中,浮游植物初级生产力与变暖趋势甚至可能呈负相关。由于生态系统往往是多因子的共同作用,这也使得全球变暖对浮游植物群落的影响效应复杂化,区分各因子的净影响份额是目前研究的一个难点;全球变暖引起的风场改变会促进浅水湖泊中营养盐从底泥的释放,同时也会增加水体中悬浮物的浓度而影响水下光场,因此开展气候变化对再悬浮及浮游植物群落结构的影响可能是将来研究的一个切入点。     

上海市上市企业总部的区位分布与影响机制

大企业总部在城市内部的分布既受城市发展的影响,又是重塑城市空间格局的重要力量。基于历年上海市上市公司数据,探讨上海市的上市公司总部区位分布特征及影响因素。上市企业总部在上海呈显著的中心型分布,多数总部集聚在中心区,且总部密度随到城市中心距离的增加而迅速降低。企业总部分布还呈现强烈的接近交通干道和开发区集聚的倾向。计量模型结果表明,企业所有制条件、上市时间、企业规模、行业类型显著影响上市企业总部的区位分布,通常国有企业、规模较大的企业和上市时间较早的企业更倾向于布局在中心城区区位条件更加优越的地区,形成总部分布的二元结构。市场化改革和规划下不同类型企业的主从秩序可以解释这种企业总部分布的核心边缘二元结构。     

农地边际化过程中农户土地利用行为变化及其对粮食生产的影响

认识农地边际化过程中农户土地利用行为的变化及其对粮食生产的影响,对正确判断中国的粮食生产形势,制订相关政策以确保粮食安全具有重要意义。基于湖北省咸宁市4县1市1区的23个村组、1252个农户家庭的调查数据,对1981年以来农户土地利用行为变化的特征及其对粮食生产的影响进行分析。结果表明：① 农户用于粮食生产的劳动力与土地面积明显下降,农户用地方式出现“省工性”变化,劳动力被农机要素替代,农业机械、化学肥料与农药等物质投入显著上升。② 主要粮食作物的劳动生产率、土地生产率与商品率分别提高了4.61%、29.69%与50.56%,但区域主要粮食作物的总产量与农户家庭平均粮食占有量却分别下降了10.49%与10.50%,区域粮食安全的保障能力出现弱化。③ 丘陵山区主要粮食作物的“三率”提高幅度高于平原地区,丘陵山区的水稻总产量与家庭占有量均略有提高,但平原地区却出现了明显下降。产粮重心在空间上出现从平原地区向丘陵山区倾斜的现象。④ 稳定主要粮食作物的用地规模,促进农户规模经营,提高土地产出效率,是应对农地边际化作用的关键。从事规模化与专业化粮食生产的农区与农户,应成为国家惠农政策与粮食安全政策重点扶持的对象。