陆地生态系统氮饱和对植物影响的生理生态机制

由于化石燃料的燃烧、含氮化肥的使用以及畜牧业等人类活动的影响,向大气中排放的含氮化合物数量不断上升,从而引起大气氮沉降的增加,使得某些陆地生态系统出现氮饱和现象。丈章综述了全球氮沉降与陆地生态系统氮饱和现状,探讨了氮饱和对植物光合作用、养分平衡和抗逆性的影响机制。     

Light Use Efficiency over Two Temperate Steppes in Inner Mongolia, China

Vegetation light use efficiency (LUE) is a key parameter of Production Efficiency Models (PEMs) for simulating gross primary production (GPP) of vegetation, from regional to global scales. Previous studies suggest that grasslands have the largest inter-site variation of LUE and controlling factors of grassland LUE differ from those of other biomes, since grasslands are usually water-limited ecosystems. Combining eddy covariance flux data with the fraction of photosynthetically active radiation absorbed by the plant canopy from MODIS, we report LUE on a typical steppe and a desert steppe in Inner Mongolia, northern China. Results show that both annual average LUE and maximum LUE were higher on the desert steppe (0.51 and 1.13 g C MJ(-1)) than on the typical steppe (0.34 and 0.88 g C MJ(-1)), despite the higher GPP of the latter. Water availability was the primary limiting factor of LUE at both sites. Evaporative fraction (EF) or the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET) can explain 50-70% of seasonal LUE variations at both sites. However, the slope of linear regression between LUE and EF (or AET/PET) differed significantly between the two sites. LUE increased with the diffuse radiation ratio on the typical steppe; however, such a trend was not found for the desert steppe. Our results suggest that a biome-dependent LUE(max) is inappropriate, because of the large inter-site difference of LUE(max) within the biome. EF could be a promising down-regulator on grassland LUE for PEMs, but there may be a site-specific relationship between LUE and EF.     

气候变化对我国自然生态系统影响的研究综述

现代工业的迅速发展 ,伐林、垦荒、过牧、矿石燃料燃烧及化工合成产品的使用等人类活动 ,导致大气中温室气体含量剧增 ,全球气候变暖 ,荒漠化扩展 ,海平面上升等一系列环境变化 ,对人类及生物赖以生存的环境及生态系统将产生重大影响。因此 ,研究气候变化及其对自然生态系统的影响已引起各国政府、科学界及公众的极大关注。我国在“八五”科技攻关中 ,曾开展了气候变化对我国自然地带、冰雪圈及冻土带、山区生态系统的研究。在美国支持的气候变化国家研究中曾对我国森林、草地生态系统的影响进行了模拟实验研究。在国家自然科学基金和有关部…     

European Experience on Application of Site-Specific Ecological Risk Assessment in Terrestrial Ecosystems

This article describes the current state of the development toward a common European framework for site-specific ecological risk assessment (SS-ERA) Although common progression has been slow in the past two years, earlier activities were very promising. Results are presented of a 2001 workshop to discuss the scientific development and policy needs in preparation of such a common framework. The framework was recommended to follow a tiered approach. Other important elements for a common European framework for SS-ERA were identified to be the use of generic values in the first tier and bioassays in later tiers, to address bioavailability in the assessment, to differentiate for land use. Also, the framework should allow for negotiation between stakeholders specific to the site. These aspects are present in the Dutch approach to SS-ERA, and this article further presents some experience with the application of this framework in a large case of SS-ERA in The Netherlands. The derivation of suitable ecological parameters and assessment criteria in view of land use in a tiered approach risk assessment is focused on, and the interactive process between stakeholders and ongoing discussions concerning references and criteria for assessment are illustrated.     

Effects of Enhanced UV-B Radiation on Nitrogen Fixation in Arctic Ecosystems

Recent global climate models predict a further significant loss of ozone in the next decades, with up to 50% depletion of the ozone layer over large parts of the Arctic resulting in an increase in ultraviolet-B radiation (UV-B) (280–315 nm) reaching the surface of the Earth. The percentage of total annual ecosystem N input due to biological nitrogen fixation by cyanobacteria might be as high as 80% and the contribution to total annual N uptake by plants up to 20%. A possible reduction of nitrogen fixation raises serious concerns about already nutrient impoverished plant communities. This review shows that nitrogen fixation by moss-associated cyanobacteria in arctic vegetation was dramatically reduced after six years of exposure to enhanced UV-B radiation. In subarctic vegetation, nitrogen fixation activity of moss-associated cyanobacteria was not affected by 6 years of enhanced UV-B radiation. However, a 50% increase of summer precipitation resulted in a 5- to 6-fold increase in activity. Long-term effects of UV-B radiation on nitrogen fixation activity have been examined only in two lichens, giving contrasting results. Peltigera aphthosa (L.) Willd., having external cephalodia, experienced a significant reduction, whereas Peltigera didactyla (With.) J.R. Laudon, having cyanobacteria in the photobiont layer below the upper cortex, did not experience any changes due to radiation regimes. The difference is probably related to the location of the cyanobacteria. While the Nostoc cells are protected by the fungal, melanized upper cortex in P. didactyla, they are exposed and unprotected in P. aphthosa, and their own synthesis of UV-B absorbing compounds appears to be low. Under certain environmental conditions, an increasing UV-B radiation will dramatically affect nitrogen fixation in arctic tundra vegetation, which in turn may have severe influence on the nitrogen budget in these environments. Further long-term studies are necessary to conclude if these effects are temporal and how concurrent climatic changes will influence the nitrogen balance of the ecosystem.     

Growth of Lettuce, Onion, and Red Beet. 1. Growth Analysis, Light Interception, and Radiation Use Efficiency

A field experiment was carried out to analyse the growth oflettuce, onion and red beet in terms of: (a) canopy architecture,radiation interception and absorption; (b) efficiency of conversionof absorbed radiation into biomass; and (c) dry matter partitioning.Growth analysis, total solar radiation interception, PAR interceptionand absorption by the crop canopy, ground cover, maintenancerespiration of onion bulbs and red beet storage roots were measured.Models for different leaf angle distribution and ground coverwere used to simulate light transmission by the crop canopy. The three crops are shown to have contrasting growth patternsfrom both a morphological and a physiological point of view.Lettuce showed very high light interception and growth afterthe early growth stages but, throughout the growth cycle, thisleafy crop showed the lowest radiation use efficiency due tothe respirational cost of the high leaf area. Onion showed alower early relative growth rate than lettuce and red beet.This was due partly to the low light interception per unit leafarea in the later stages of growth and partly to the low initialradiation use efficiency compared with the other two crops.On the other hand, thanks to more uniform distribution of theradiation inside the canopy, to the earlier termination of leafdevelopment and to the very low level of bulb respiration, onionshowed high radiation use efficiency and was able to producea large amount of dry matter. Red beet leaf posture and canopystructure resulted in high light interception and absorption.Its radiation use efficiency was lower than that of onion, partlyperhaps because of the more adverse distribution of the interceptedradiation fluxes within the canopy and partly because of thehigh respiration cost of a continuous dry-matter allocationto the leaves. However, this crop can accumulate a very largeamount of dry matter as leaf blade development and storage rootgrowth can both continue almost indefinitely, providing continuouslyavailable sinks. Ground cover gave a good estimate of the PAR interception onlyat low values of light interception but, in general, it underestimatedPAR interception in all three crops. Ratios between attenuationcoefficients established by considering PAR or total solar radiationand LAI or ground cover were calculated. Lettuce,Lactuca sativa L. var.crispa ; onion,Allium cepa L.; red beet; Beta vulgaris L. var.conditiva ; growth analysis; light interception and absorption; canopy architecture; ground cover; radiation use efficiency; maintenance respiration rate; dry matter distribution     

南亚热带酸雨地区陆地生态系统植被、土壤与地表水现状的研究

工业化程度的不断提高给环境带来的压力是全球性的普遍问题。矿物燃料的大量使用 ,使大气中ＳＯ2 、ＮＯＸ 和其它酸性颗粒物等污染物浓度增加 ,导致大气环境质量恶化 ,影响全球植被生态系统的生产力。排放到大气中的ＳＯ2 、ＮＯＸ 是形成酸雨的重要来源 ,大范围的迁移是它的一个重要特征。国内外已取得的研究结果证明 ,ＳＯ2 、ＮＯＸ等污染气体及其沉降化合物直接导致植物生长量生物量的下降、叶伤害、光合作用减弱、呼吸作用增强。另一方面 ,酸雨的形成导致土壤酸化、土壤缓冲能力下降、Ａ1离子的释放、盐基离子的淋洗、营养亏损 ,使树…     

涡动相关法与波文比-能量平衡法测算森林蒸散的比较研究--以长白山阔叶红松林为例

分别采用涡动相关法与波文比-能量平衡法(BREB法)测算了长白山阔叶红松林2002年9、10月的森林蒸散量.结果表明,9月,涡动相关法与BREB法测算的森林蒸散量分别为83.1和87.9 mm,后者相对于前者的误差不到6%,且两者日蒸散量有较好的相关性(0.78),表明涡动相关法与BREB法在森林蒸散研究中有很好的一致性.10月,随着秋季落叶,林内水汽压梯度减小.涡动相关法测算的森林蒸散量为42.5 mm,BREB法测算的结果为49.1 mm,后者相对于前者的误差达到了16%,两者日蒸散量相关系数为0.53.在水汽压梯度较小时,BREB法会产生较大误差.9月中上旬,森林主要热量消耗是用于蒸散,约占辐射平衡量的71%;落叶后,森林主要热量消耗变为森林-大气间的感热交换,蒸散耗热只占辐射平衡量的40%.     

黄土高原半湿润区气候变化对冬小麦生育及水分利用效率的影响

利用黄土高原半湿润区1981～2010冬小麦生长发育定位观测资料和对应平行气象观测资料,分析气候变化对冬小麦生长发育的影响,以及冬小麦水分利用效率与气象条件的关系。结果表明:(1)研究区域降水量年际变化呈波动变化,20世纪90年代降水量最少,并存在3年、8年的年际周期变化;气温年际变化呈上升趋势,气温变化曲线线性拟合倾向率为0.325℃/10年;作物生长季干燥指数呈显著上升趋势,干燥指数变化曲线线性拟合倾向率为0.069/10年,20世纪90年代至2010年明显趋于暖干化;研究区域冬小麦播种至成熟期间≥0℃积温为2 000℃～2 200℃,降水量为300～350mm,日照时数为1 900～2 100h。(2)受气候变暖的影响,研究区域冬小麦播种期每10年推后2～3d,返青期每10年提前4～5d,开花期和成熟期每10年提前5～6d;冬小麦越冬期每10年缩短5～6d、全生育期每10年缩短7～8d。(3)由于研究区冬春季气温显著升高,越冬死亡率下降,冬小麦水分利用率呈上升趋势;冬小麦播种～出苗期和起身～拔节期气温对冬小麦水分利用效率的影响为负效应,其余时段气温对水分利用效率的影响为正效应,其中的乳熟期～成熟期水分利用效率对气温变化十分敏感;播种～出苗期、分蘖～冬前停止生长期和乳熟～成熟期降水量对冬小麦水分利用效率影响为负效应,且乳熟期～成熟期水分利用效率对降水量变化十分敏感;越冬期和返青～拔节期降水量对冬小麦水分利用效率影响为正效应,并在冬小麦越冬后期和返青期前后水分利用效率对降水量变化十分敏感。     

基于Malmquist指数的我国省际医院生产效率分析

目的 分析我国医院效率的动态变化及来源。方法 利用马奎斯特指数及分解。结果 2010—2014年间我国医院的马奎斯特指数呈上升趋势。结论 目前我国医院的全要素生产率改善主要来自纯技术效率的变化,说明我国医院逐步从以前粗放式发展阶段迈向精耕细作的新阶段,规模效率大于1,表明组建医药集团经营的可行性。     

基于DEA的全国中医医院卫生资源配置效率评价

目的 对2003—2014年全国中医医院卫生资源配置效率进行比较研究,探讨其投入、产出是否适当及存在问题,寻找有效的措施和途径以进一步优化其卫生资源配置。方法 利用数据包络分析的理论和方法,对全国中医医院的卫生资源配置进行横向分析和纵向分析评价。结果 数据包络分析横向评估中,卫生资源配置效率存在地区差异;数据包络分析纵向评估中,2003－2014年全国中医医院卫生资源配置综合效率总体稳定,规模效益递减。结论 统筹规划,重点加强弱势地区中医医院的医疗卫生服务体系建设。     

中国玉米遗传单一性的经济影响

广泛采用少数优良种质资源,可能会引起作物遗传多样性下降,降低品种的抗病和抗逆能力,影响作物的产量。本研究采用系谱分析方法,研究了我国20个主产省玉米遗传单一性的变化及其对我国玉米生产的影响。结果表明,遗传单一性与玉米单产之间呈显著的负相关关系：遗传单一性每增加1%,玉米平均单产将降低13%;研究同时也表明遗传单一性和品种单一性是两个相互独立的变量,品种单一性不一定导致遗传基础的单一性。政府应从调节育种人员行为上制定相应的政策,防止遗传基础单一化,在增加作物遗传多样性的同时,选育优质高产的品种。     

基于DEA的Malmquist指数的我国大型综合医院跨期效率研究

目的 评价大型综合医院效率。方法 采用DEA的CCR模型、BCC模型进行年度分析,再采用Malmquist指数进行跨期分析。结果 在所研究的22所大型综合医院中,2006—2007年有68.2%的医院处于规模报酬固定阶段;2006—2007年,63.6%的医院生产率变化主要是受到技术变化的影响,13.6%生产率变化是受到效率变化的影响,其他变化则是技术变化和效率变化共同作用。结论 研究期间,22所大型综合医院纯技术效率基本稳定,多数医院处于规模报酬固定阶段,生产率主要受技术变化的影响。     

A Modeling Study on Responses of Alkaline Grassland Ecosystems to Climate Change in Light of Diversity and Spatial Patterns

Temporal variations of spatial coverage patterns of major plant species in the alkaline grasslands in northeast China subject to climate change were studied using a spatial simulation model. The model stressed the coupling between soil alkali and vegetation coverage. The modeled species coverage patterns were shown in close agreement with observations on a fenced one-hectare alkaline grassland from 1989 to 1993. The impacts of climate change on the species coverage were studied by subtracting the output patterns of the model under contemporary climate from those under altered climate. To relate the difference patterns to various landscape indices, the one-hectare region was divided into 25 subregions. The differencein species coverage between the present and altered climate and spatial pattern and diversity indices were computed for each subregion. A statistical analysis showed that for plants with wide ranges of tolerance to soil alkali and strong spatial migration capability, the impact of climate change was significantly related to spatial patterns, but not to diversity. However, for plants with narrow ranges of tolerance to soil alkali and less capability to migrate spatially, the impact of climate change was related to both diversity and spatial patterns.     

Study on Equity and Efficiency of Health Resources and Services Based on Key Indicators in China

Background

This study aims to evaluate the dialectical relationship between equity and efficiency of health resource allocation and health service utilization in China.

Methods

We analyzed the inequity of health resource allocation and health service utilization based on concentration index (CI) and Gini coefficient. Data envelopment analysis (DEA) was used to evaluate the inefficiency of resource allocation and service utilization. Factor Analysis (FA) was used to determine input/output indicators.

Results

The CI of Health Institutions, Beds in Health Institutions, Health Professionals and Outpatient Visits were -0.116, -0.012, 0.038, and 0.111, respectively. Gini coefficient for the 31 provinces varied between 0.05 and 0.43; out of these 23 (742%) were observed to be technically efficient constituting the “best practice frontier”. The other 8 (25.8%) provinces were technically inefficient.

Conclusions

Health professionals and outpatient services are focused on higher income levels, while the Health Institutions and Beds in Health Institutions were concentrated on lower income levels. In China, a few provinces attained a basic balance in both equity and efficiency in terms of current health resource and service utilization, thus serving as a reference standard for other provinces.     

基于DEA模型的中国生物产业上市企业绩效评估

目的 随着生物产业的快速发展,越来越多的生物企业涌现,其中以生物医药企业为主.如何促进生物企业产出效率是政府和企业自身最关心的问题.方法 论文构建了生物产业上市企业绩效评估DEA模型,对全国370家生物产业上市企业的投入产出效率情况进行评估.结果 全国生物产业上市企业平均综合技术效率为0.596,还有很大进步空间.结论...     

区域气候背景对城市热岛效应的影响规律

城市热岛效应受到区域气候背景的影响而具有显著的时空差异性,尚缺少大尺度对比研究。利用1991-2019年的月均气象数据,量化了我国69个典型城市的大气城市热岛效应强度,从热带、干带、暖温带、冷温带和极地带五个气候带,分析城市热岛效应的时空特征规律。结果表明：（1）区域差异：干带热岛效应明显高于其他气候带,极地带最弱,且表现为较强的冷岛效应,热带、暖温带、冷温带热岛效应较弱,而冷温带的京津冀地区由于城市化程度较高,表现出较强的热岛效应,温暖带中西南地区较为明显;（2）季节性差异：不同季节城市热岛效应的强弱关系在不同气候带有所不同,秋季热岛效应较为稳定,热岛和冷岛效应均主要处于弱强度范围,春、冬热岛效应较为波动,易出现强热岛、强冷岛效应的极端现象,夏季热岛效应发生率最高;（3）时间演变规律：城市热岛效应的多年演变规律在相同气候带较为一致,2010年前后是各气候带各季节城市热岛效应的变化拐点,2010年后,干带、冷温带、暖温带热岛效应均有所下降,热带、极地带有所上升。     

模拟大气氮沉降对中国森林生态系统影响的研究进展

人类活动加剧了活性氮的生产和排放,并导致氮沉降日益增加并全球化。目前,人类活动对全球氮循环的干扰已经超出了地球系统安全运行的界限。中国已成为全球氮沉降的高发区域,高氮沉降已经威胁到生态系统的健康和安全,并成为生态文明建设过程中亟待理清和解决的热点问题。对国际上和中国森林生态系统模拟氮沉降研究的概况进行了综述,并从生物学和非生物学两大过程重点阐述模拟氮沉降增加对中国主要森林生态系统影响的研究进展。中国自2000年以后才开始重视大气氮沉降产生的生态环境问题,中国科学院华南植物园在国内森林生态系统模拟氮沉降试验研究上做出了开创性的贡献。模拟氮沉降研究表明,持续高氮输入将会显著改变森林生态系统的结构和功能,并威胁生态系统的健康发展,特别是处于氮沉降热点区域的中国中南部。森林生态系统的氮沉降效应依赖于系统的氮状态、土地利用历史、气候特征、林型和林龄等。最后,对未来的研究提出了一些建议,包括加强长期跟踪研究和不同气候带站点之间的联网研究,特别是在森林生态系统对长期氮沉降响应与适应的过程机制、地下碳氮吸存潜力研究、以及与其他全球变化因子的耦合研究等方面,以期为森林生态系统的可持续发展提供理论基础和管理依据。