微型生态系统中鲢、鳙下行影响的实验研究——1.浮游生物群落和初级生产力

在营养物供给量较大的实验条件下,鲢、鳙放养明显地改变了微型生态系统的群落结构、代谢和理化环境,以致实验后期鳙单养和鲢、鳙混养系统出现不同程度的富营养化。微型生态系统中浮游植物密度的增长不完全由营养级联效应所致,但初级生产力的组间差异可大致依据营养级联假说来解释。实验结果认为,以提高鱼产量为目标的鲢、鳙高密度放养,对加速营养物来源丰富的天然水域的富营养化起着重要的作用。     

Late Quaternary record of Indian summer monsoon-induced stratification and productivity collapse in the Andaman Sea

During each summer monsoon, the northeastern Indian Ocean receives a huge amount of rain and river discharge, resulting in strong stratification and prevalence of oligotrophic conditions. These water column changes impact upper ocean productivity which is reflected in the planktonic foraminifera distribution, providing an opportunity to study the effect of monsoon forcing and stratification history. Analogous to modern-day stratification, very intense water column stratification and productivity collapse were observed associated with Indian summer monsoon (ISM) evolution. This paper reports significant stratification events during MIS 3 (37.0 to 33 and 27 to 24 cal ka), Bølling/Allerød (B/A), early Holocene (10.0 to 8.0 cal ka) and mid-Holocene (7.0 to 5.0 cal ka) which slowly muted upwelling and productivity. The deglacial intensification of the ISM started in the early stages of the Bølling/Allerød (B/A) followed by slight weakening during the Younger Dryas and regained strength during the early Holocene, coinciding with the highest summer insolation at 30°N. A progressive decline in the abundances of productivity and salinity proxies from 4.2 to 2.0 cal ka suggests a gradual weakening of the ISM. The late Quaternary productivity variations in the Bay of Bengal and the Andaman Sea are primarily controlled by salinity-related stratification.     

Intense localized productivity in the Irish Sea

The variability of primary productivity in surface waters was continuously recorded during spatial and sectional surveys of the Irish Sea in the summer of 1977. Localized patches of intense productivity were found, not in the frontal region of the western Irish Sea, but farther east. Subsurface distributions of physical, chemical and biological characteristics through a latitudinal section of the Irish Sea are reported. These data showed that the productivity peaks occurred at the boundaries of a water type exhibiting properties uncharacteristic of Irish Sea waters.     

试用“稳定流”评价区域化探异常

出露地表或近地表的矿体,在遭受风化剥蚀作用时,稳定地向水系补充矿化物质,形成在矿体附近具有浓集中心,含量向下游逐渐衰减的水系沉积物异常,对这种异常的形成作用称之为“稳定流”。应用这一概念,可以筛选化探异常。进一步根据“稳定流”的长度和强度,还能够近似定量地推断未知矿化区面金属量(Ps)以及建立典型矿床水系沉积物元素分带序列,为寻找隐伏矿体,评价区域化探异常提供了一种新的方法。     

Increasing China’s Agricultural Labor Productivity: Comparison and Policy Implications from Major Agrarian Countries

China’s low agricultural labor productivity has become the key weakness of its agricultural competitiveness and sustainable development, and strategies for improving China’s agricultural labor productivity lack clear and consistent theory and empirical support. To address this issue, the current study uses the methods of convergence index, correlation coefficient, and nonparametric test, to analyze the characteristics and influencing factors of agricultural labor productivity among 32 major agrarian countries during 1961-2013. This analysis shows that the development gap among countries has been narrowing. The USA takes the leading position among all the countries, while some countries with scarce land like Japan have succeeded in achieving transcendence, and other countries like India have experienced relatively slow speed. The agricultural labor productivity is significantly driven by agricultural labor surplus, agricultural product processing, and agricultural industrial structure. The effects of land resource endowment, agricultural mechanization, and biochemical inputs have been declining and in some cases are no longer even significant. It is therefore necessary to shift attention to marketization, diversification, and high quality, instead of the former focus on agricultural intensification, concentration and large-scale operations, and this shift is probably more closely aligned with current practices. There are more people and less land in China, and the agricultural labor force in China still accounts for nearly 30% of the total population. Considering these national conditions, it is very important to simultaneously improve the efficiency of agricultural production of small farmers and promote the successful urbanization of the agricultural labor force. In the medium and long term, it is imperative to improve the competitiveness of Chinese agriculture by adopting related policy arrangements such as induced agricultural technological innovation, production factor substitution, and multifunctional agriculture development.     

皖江城市带植被NPP时空变化及其气候响应

针对现有植被净初级生产力研究对城市圈、城市带尺度缺乏关注的问题,基于MODIS遥感数据、地面气象资料等,利用改进的CASA模型,结合回归分析、相关分析等方法探究了2000—2013年皖江城市带植被NPP的时空变化及其对气候因子的响应,为区域生态环境质量评价提供参考。结果表明:近14年来,皖江城市带植被NPP总体呈增加趋势;不同土地利用类型NPP差异显著,林地草地耕地建设用地未利用土地水体;年NPP均值呈现由南部向西北部减少的空间分布特征;植被NPP年际变化率较小,介于±10gC·m-2·a-1范围内;温度是影响研究区植被NPP时空变化的主要气候因子。     

2000-2013年中国城市群经济绩效动态实证分析——基于DEA和Malmquist生产率指数法

在全球化和新型城镇化大背景下,城市群是辐射面最广、潜力最大、活力最强的核心增长极,但其高速成长背后是各类要素的大量投入,客观评估城市群经济绩效对于推动中国城镇化持续健康发展意义深远。在总结既有研究的基础上,选取中国13个典型城市群为样本,以2000-2013年为研究时段,采用资本、土地、劳动、科技和经济五大要素长时间序列数据,在全要素生产率(TFP)分析框架下,通过数据包络分析方法(DEA)静态评价时间截面的城市群投入产出效率,进而运用Malmquist生产率指数法动态分析城市群TFP年际变化,探讨其时空格局和内在演化机制。研究发现：城市群经济绩效进步明显,但空间分布仍不均衡;科技进步贡献的滞后在一定程度上抵消了通过规模扩张和资源配置优化带来的正效应,只有长三角、珠三角和京津冀三大城市群初步实现依靠科技进步促进发展,表明各城市群所处发展阶段和动力机制差异显著。据此,提出针对不同地区、不同发展阶段城市群的发展策略。     

全球植被与大气之间碳通量的模式估计

用大气植被相互作用模式(AⅥM)模拟了全球陆地植被的净初级生产力(NPP)。AⅥM由相互耦合的两部分组成：物理过程，包括陆地表面水分和能量在土壤、植被与大气之间的传输；以及生理生态过程，如：光合、呼吸、干物质分配、凋落和物候等。全球的植被分为13类，土壤按质地分为6类。用EMDI提供的全球1637个包括不同植被类型的NPP观测点数据对模型进行了检验。NPP模拟的结果表明：全球陆地植被的平均NPP为405.13 g C m-2yr-1，不同植被类型的平均NPP变化范围在99.58 g C m-2yr-l(苔原)到996.2 g C m-2yr-l(热带雨林)之间。全球年总NPP为60.72 Gt C yr-l，其中最大的部分为热带雨林，15.84 Gt C yr-1，占全球的26.09％。最大的碳汇是在北半球的温带。模式模拟的NPP在全球的空间和季节分布是合理的。     

1999/2000年夏季南极普里兹湾及湾口区叶绿素a和初级生产力

20 0 0年 1月 1 9日至 2 7日在 70°3 0′E- 75°3 0′E,6 2°S以南的南极普里兹湾近岸陆架区的陆隆向深海区设三条纵断面进行浮游生物现存量、真光层深度和光合作用速率的现场观测。并在冰间湖站 - 1 2进行连续昼夜观测。结果表明 ,观测海区叶绿素 a浓度高值位于近岸海湾、冰间湖和测区中部的陆坡区 ;陆坡中部站 - 6和 - 8,0 - 5 0 m的浅水层为叶绿素 a高值区 (2 .1 6- 5 .0 8μg/dm3 )。各测站平均叶绿素 a浓度 2 5 m次表层 (1 .49± 1 .6 1 μg/dm3 )高于表层 (1 .1 4±1 .1 9μg/dm3 ) ,5 0 m以下更深层的浓度随深度的增加而降低 ,2 0 0 m层叶绿素 a浓度仅 0 .0 3±0 .0 2μg/dm3 。昼夜观测结果表明表层叶绿素 a浓度在南极夏季的午后出现最大值 ,晨间出现最小值 ;2 5 m以浅水层的叶绿素 a浓度明显高于深层水 ,与封冰消融冰藻的释放有关。测区真光层潜在初级生产力为 0 .76 - 1 2 .5 9mg C/(m3· h) ,平均值为 4.0 1± 4.0 7mg C/(m3· h) ;海湾和陆架区现场生产力均超过 1 .5 g C/(m2 · d) ,陆坡、深海区约 0 .5 g C/(m2 · d)。高生产力位于高生物量的近岸海湾、陆架冰间湖区。光合作用同化数在 0 .88- 3 .1 0 mg C/(mg Chla· h)。表层叶绿素a浓度与海水中溶解氧浓度呈紧密相关 (Y=0 .0 5 9X     

Mid-chain ketocarboxylic acids in the remote marine atmosphere: Distribution patterns and possible formation mechanisms

In remote marine aerosol samples collected from the North Pacific ocean, Enewetak Atoll, American Samoa, and New Zealand, series of mid-chain ketocarboxylic acids in the range of C₆-C₁₈ were detected. All the positional isomers, except for the 2-oxo and 3-oxo species, were detected for major ketoacid families (e.g. C₉, C₁₁ and C₁₃). Higher ketoacid concentrations (up to 19 ng/m³) were obtained in the northern North Pacific aerosol samples, which generally showed an odd carbon-numbered predominance with 5-oxoundecanoic acid being the major species. By contrast, lower concentrations were obtained in the lower-latitude or subtropical aerosol samples, where even carbon-numbered ketoacids were relatively abundant.The distribution patterns of the odd carbon-numbered ketoacids could not be explained by the primary emissions from source materials including terrestrial higher plants, soil particles, and ocean surfaces. We consider that the isomeric ketocarboxylic acids are produced in the atmosphere by the photochemical oxidation of semi-volatile monocarboxylic acids, which are counterparts of the oxidative degradation of unsaturated fatty acids emitted from seawater surfaces. Atmospheric production of the ketoacids is seemingly enhanced in the northern North Pacific, probably due to an enhanced primary productivity.