Limnology of Lake Waikaremoana with special reference to littoral and pelagic primary producers

Lake Waikaremoana, the North Island's deepest lake (248 m), lies in a natural forested catchment, but the lake itself has been modified for hydro‐electric power generation and by the introduction of trout, smelt, and adventive aquatic plants. The lake is a warm monomictic water body of low conductivity (82 μS cm^‐1) and a high seasonal water column stability. The waters are oligotrophic, with epilimnetic dissolved reactive phosphorus concentrations typically < 1 mg m^‐3. The concentration of NO₃‐N is seasonally variable but generally high in winter and spring with maximum epilimnetic values approaching 70 mg m ³. This contrasts with other central North Island lakes. Horizontal variability in surface chlorophyll a is low as are the absolute values (< 1–2 mg m^‐3). A notable feature is the formation of a deep chlorophyll maximum within the metalim‐nion comprised largely of Sphaewcystis schweteri as opposed to diatoms and flagellates which normally dominate the epilimnion. Vascular macro‐phytes (maximum biomass 659 g m² dry weight) extended to 9 m and characeans (maximum biomass 447 g m²dry weight) to 16 m. Total phyto‐plankton primary production was calculated as 4524 tCy^‐1 and macrophyte production as 578 t C y^‐1. The proportion of macrophyte to phy‐toplankton production (0.14) is higher than in the other deep lakes of the central North Island.     

1998～2007年中国农业用水分析

中国农业用水在未来将面临巨大的挑战。根据国际农业用水研究和政策领域近10年出现的范式变迁的核心内容,建立了基于"绿水"、"蓝水"的中国农业用水的新综合分析框架。并利用广义农业水资源量和广义农业水土资源匹配的概念和评估方法,分析了全国1998～2007年10年间4种主要粮食作物(水稻、小麦、玉米和大豆)的农业用水、耗水以及水分生产力变化趋势和现状。结果表明:中国广义农业水资源量中57%来源于耕地有效降水的"绿水",43%来源于耕地灌溉"蓝水"。主要粮食作物水分生产力水平已经接近或达到世界较高水平。未来继续提升水分生产力的任务将会更加艰巨。因此,为保证中国粮食安全,建议国家设立"粮食安全水资源红线"。同时,根据广义农业水资源量的分析计算,主要粮食作物用水安全红线应该划定在大约7800亿m3左右。     

生物标志物重建浮游植物生产力及群落结构研究进展

海洋浮游植物生产力和群落结构在地质年代中的变化对深入理解碳循环的演变规律和机理有着重要的意义.生物标志物方法作为一种较新的研究手段,其含量与比值的变化被广泛用于浮游植物生产力与群落结构变化的重建.讨论了生物标志物方法在各大洋及我国边缘海的应用现状,提出了生物标志物的细胞产生量及其在环境中的保存效率的2种主要不确定因素,使目前多参数生物标志物方法只能够半定量地重建古生产力与群落结构的变化.针对我国边缘海,提出有必要通过现场调查和实验室培养建立生物标志物含量(比值)与浮游植物生产力(群落结构)的定量关系式,以达到能够定量重建生产力和群落结构变化的目的.     

页岩气藏压裂水平井产能模型及影响因素

由于页岩气在储层中存在解吸、扩散和渗流相互作用,使页岩气藏压裂水平井与常规气藏压裂水平井在渗流特征及产能递减规律方面有较大差异.综合考虑页岩气解吸、扩散和渗流特征,建立页岩气藏压裂水平井产能模型,应用Laplace变换和Duhamel原理,结合Stehfest数值反演求解产能模型,绘制页岩气藏压裂水平井产能递减曲线,分析解吸系数、无因次储容系数、无因次解吸时间、无因次人工裂缝间距、人工裂缝条数和裂缝表皮系数对产能递减曲线的影响.该结果对认识页岩气藏压裂水平井产能递减规律、评价预测产能及优化压裂裂缝提供参考.     

The effect of land use changes on soil conditions in arid region

Biography:CHEN Fu(1974－ ), male,a native of Sheyang County, Jiangsu Province, doctoral candidate.His research interests include land use management.1 INTRODUCTION Land use change may influence a variety of natural and ecological processes, including soil nutrient, soil moisture, soil erosion, land productivity (FU et al., 1999), biodiversity, cycle of biographical geochemistry, and so on (VITOUSEK, 1994). So, it is very important that the studies of land use changes understand re…     

The Relationship between Normalized Difference Vegetation Index （NDVI） and Climate Factors in the Semiarid Region： A Case Study in Yalu Tsangpo River Basin of Qinghai-Tibet Plateau

The Yalu Tsangpo River basin is a typical semi-arid and cold region in the Qinghai-Tibet Plateau, where significant climate change has been detected in the past decades. The objective of this paper is to demonstrate how the regional vegetation, especially the typical plant types, responds to the climate changes. In this study, the model of gravity center has been firstly introduced to analyze the spatial-temporal relationship between NDVI and climate factors considering the time-lag effect. The results show that the vegetation grown has been positively influenced by the rainfall and precipitation both in moving tracks of gravity center and time-lag effect especially for the growing season during the past thirteen years. The herbs and shrubs are inclined to be influenced by the change of rainfall and temperature, which is indicated by larger positive correlation coefficients at the 0.05 confidence level and shorter lagging time. For the soil moisture, the significantly negative relationship of NDV-PDI indicates that the growth and productivity of the vegetation are closely related to the short-term soil water, with the correlation coefficients reaching the maximum value of o.81 at Lag 0-1. Among the typicalvegetation types of plateau, the shrubs of low mountain, steppe and meadow are more sensitive to the change of soil moisture with coefficients of -0.95, -0.93, -0.92, respectively. These findings reveal that the spatial and temporal heterogeneity between NDVI and climatic factors are of great ecological significance and practical value for the protection of eco-environment in Qinghai-Tibet Plateau.     

广西来宾铁桥二叠系剖面生物地球化学信号的解读

二叠纪被认为是全球生物繁盛的重要时期,其大气含氧量、温度等条件和现代地球极为相似,因 此,二叠纪古海洋生物和环境的研究对当代环境和气候变化研究具有重要的启示作用。通过分析广西来宾铁桥 二叠系剖面的275个海相碳酸盐岩样品的地球化学组成,考察Ca,Mg,Al,Ti 及其比值的变化特征,研究它们 的生物和环境意义。结果发现,从栖霞组沉积时期到吴家坪组沉积时期,海水中Mg/Ca值总体上呈单调下降趋 势,表明海底洋中脊扩张,洋中脊热液循环加快,全球海平面上升;Al/Ti值在栖霞组沉积时期到吴家坪组沉积 时期呈现一种起伏式的变化,其中栖霞组沉积中期和茅口组沉积后期表现出与其他时段有显著差异的高值,表 明这两个时期海洋生产力繁盛;在瓜德卢普统-乐平统界线,Al/Ti值低,与玄武岩(Al/Ti 值约为6)相近, 指示火山活动强烈,为火山活动导致生物绝灭说提供了地球化学新证据。     

全球变化压力下中国东部样带植被与农业生态系统格局的可能性变化

在中国东部南北样带NSTEC大量实验数据的基础上 ,对热量梯度驱动下自然植被生态系统连续带的生产力变化进行模拟 ,对反映植被组成结构特征的生活型谱的变化 ,以及在全球变化平均温度可能增加的情况下 ,农业生态系统的生产格局的变化进行分析。在这一样带中 ,从南到北地带性植被有北热带季节雨林、南亚热带季风常绿阔叶林、中亚热带常绿阔叶林、北亚热带常绿落叶混交林、暖温带落叶阔叶林、温带针阔叶混交林和寒温带针叶林。模拟在温度增加 1℃的情况下生产力的变化 ;由南部的北热带季节雨林和南亚热带季风常绿阔叶林增加约 1%到温带针阔叶混交林和寒温带针叶林增加约 5 %～ 6 %,显示出生产力增加强度随纬度增大具一定相关关系。植被的物种结构变化比生产力变化缓慢得多。对样带的森林植被的生活型谱进行分析 ,表明其存在着 8种主要的生活谱结构类型。在平均温度增加的情况下 ,不同生活型谱结构的生态系统分布呈现向北扩展位移的趋势。在农业生态系统的格局中 ,在平均温度增加的情况下 ,南亚热带水稻三熟将不会季节太紧而有可能进行大面积三造生产。中亚热带双季稻连作一年三熟受低温影响减少。北亚热带一年二熟季节上有保证。暖温带许多地方能有二造收成。温带和寒温带的生产面积将有较大幅度的增加。总     

云南元谋干热河谷造林区植被生长与土壤渗透性的关系

通过云南元谋干热河谷造林区林分生物量及生产力指标与双环入渗试验的土壤入渗性能指标的相关分析，发现乔木生长与土壤渗透性具有显著正相关关系(P＜0.01)，地表枯枝落叶量与土壤渗透性的相关关系也较密切(P＜0.05)，而灌草生长与土壤渗透性无显著相关。研究指出，改善土壤入渗性能的措施，如沿等高线开深沟种植、禁止放牧践踏、保护地表枯枝落叶等均对林木生长有积极的影响。     

湖泊沼泽化与水生植物初级生产力研究进展

湖泊水生植物初级生产力较大,其残体淤积于湖底,使得湖泊逐渐变浅而发生沼泽化,所以水位下降是导致湖泊沼泽化的重要原因.光照、温度和水文条件是影响水生植物初级生产力的主要因素,植物收割和生态清淤的方法是治理湖泊沼泽化的有效措施.针对浅水湖泊沼泽化日益严重的现象,主要从触发沼泽化的原因、湖泊沼泽化的治理以及水生植物初级生产力的估算方法和初级生产力的主要影响因子等方面,综述了湖泊沼泽化和水生植物初级生产力的相关研究及二者的关系;指出定量调控水生植物初级生产力以及加强对水生植物初级生产力影响要素的综合调控作用,将是今后湖泊沼泽化治理的重点.