PIXGRO: A model for simulating the ecosystem CO2 exchange and growth of spring barley

A model, PIXGRO, developed by coupling a canopy flux sub-model (PROXEL_NEE; PROcess-based piXEL Net Ecosystem CO₂ Exchange) to a vegetation structure submodel (CGRO), for simulating both net ecosystem CO₂ exchange (NEE) and growth of spring barley is described. PIXGRO is an extension of the stand-level CO₂ and H₂O-flux model PROXEL_NEE, that simulates the NEE on a process basis, but goes further to include the dry matter production, partitioning, and crop development for spring barley. Dry matter partitioned to the leaf was converted to leaf area index (LAI) using relationships for the specific leaf area (SLA). The canopy flux component, PROXEL_NEE was calibrated using information from the literature on C3 plants and was tested using CO₂ flux data from an eddy-covariance (EC) method in Finland with long-term observations. The growth component (CGRO) was calibrated using data from the literature on spring barley as well as data from the Finland site. It was then validated against field data from two sites in Germany and partly via the use of MODIS remotely sensed LAI from the Finland site.Both the diurnal and the seasonal patterns of gross CO₂ uptake were very well simulated (R² = 0.92). A slight seasonal bias may be attributed to leaf ageing. Crop growth was also well simulated; simulated dry matter agreed with field observed data from Germany (R² = 0.90). For LAI, the agreement between the simulated and observed was good (R² = 0.80), giving an indication that functions describing the conversion of fixed CO₂ to dry matter and the subsequent partitioning leaf dry matter and LAI simulation were robust and provided reliable estimates.The MODIS LAI at a resolution of 1000 m agreed poorly (R² = 0.45) with the PIXGRO simulated LAI and the observed LAI at the Finland site in 2001. We attributed this to the coarse resolution of the image and/or the small size of the barley field (about 17 ha or 0.25 km²) at the Finland site. By deriving a regression relation between the observed LAI and NDVI from a higher resolution MODIS (500 m resolution), the MODIS-recalculated LAI agreed better with the PIXGRO-simulated LAI (R² = 0.86).PIXGRO provides a prototype model bridging the disciplines of plant physiology, crop modeling and remote sensing, for use in a spatial context in evaluating carbon balances and plant growth at stand level, landscape, regional, and with some care, continental scales. Since almost 50% of the European land surface is covered by crops, such a model is needed for the dynamic estimation of LAI and NEE of croplands.     

The Blue Green Algal Bloom in the Nearshore Waters of Cukai Bay Facing the South China Sea

Since the early 1990's, large areas of mangrove forest along the nearshore waters of Cukai bay had been cleared to give way for the development of aquaculture activities, human settlement and setting up of new small scale fish processing industries. The Cukai bay, facing the South China Sea, has inflows from the Cukai river estuaries and other numerous small river tributaries. The water quality examined (April 1993 to March 1994) in the bay indicated that the ammonium, nitrate and phosphorus contents were high during the pre-wet monsoon (October 1993) with values of 28.2, 30.1 and 29.6 g L^-1, respectively. The source of nutrients in the estuary were from the newly established fish processing cottage industries, nearby fish culture activities, agro-based effluents (mainly fertilisers from surrounding paddy plantations), untreated human (from nearby villages) and animal wastes (from domestic cattle and goat farms) and siltation due to erosion from land development. The main bulk of the microplankton were comprised of diatoms, dinoflagellates, ciliophora and blue green algae. The blue green algae encountered were species of Lyngbya, Oscillatoria, Phormodium and Trichodesmium while those of diatom were species of Asterionella, Chaetoceros, Coscinodiscus, Navicula and Nitzschia. Peak microplankton production in the water column occurred in October 1993, reaching a maximum value of 173 g C L^-1 d^-1. This comprised primarily of the blue green alga, Trichodesmium thiebautii.     

汉江水华的影响因素分析及控制方法初探

从分析汉江水华的状况、影响因素及其水华发生的参数阈值着手，初步探讨了汉江水华的控制方法。     

不同光照强度下香溪河浮游植物演替过程研究

为丰富三峡水库浮游植物演替机制,为三峡水库“潮汐式”调度提供理论依据和基础数据,基于前期香溪河水华易发区现场监测结果,其水下光照强度变化范围为1 800~17 000 lx,据此开展不同梯度恒定光照条件下香溪河源水混合浮游植物群落演替过程的室内控制试验.结果表明:①按照R*法则和关键光强假说,在其他环境条件适宜的情况下,光照为4 500 lx时,香溪河源水中混合浮游植物的生物量和多样性最高.②CSR理论（Competitor-Stress Tolerator-Ruderals Theory）中的浮游植物环境适应机制及生长策略不能准确解释不同梯度恒定光照控制条件下浮游植物的演替规律.光照条件是影响浮游植物群落演替方向的关键要素,而演替方向由群落发生演替时的光照条件与该群落中藻种关键光强的匹配程度决定.③香溪河源水中混合藻种的不同梯度恒定光照控制试验结果显示,小球藻（Chlorella sp.）、衣藻（Chlamydomonas sp.）、栅藻（Scenedesmus sp.）、肾形藻（Nephrocytium sp.）、微囊藻（Microcystis sp.）、色球藻（Chroococcus sp.）、隐藻（Cryptomonas sp.）和小环藻（Cyclotella sp.）的最适光强分别为3 000、8 000、13 000、6 000、6 000、13 000、13 000和6 000 lx.研究显示,将光照控制在合适的阈值范围,有助于维持浮游植物的多样性,对水华防治具有重要意义.      

利用络氨铜控制景观水体藻华

研究了络氨铜对不同生长期的典型蓝藻（铜绿微囊藻,Microcystis aeruginosa）15d生长抑制影响的基础上,开展了络氨铜对不同时期景观池水中叶绿素a含量的影响,并跟踪测定了其中的有效铜离子浓度变化.结果表明,络氨铜在0.10mg·L-1（络氨铜的有效浓度,下同）时,可完全抑制适应期铜绿微囊藻的生长;在4d...     

凤眼莲化感物质对铜绿微囊藻、斜生栅藻生长及细胞数相对比例的影响

为探索化感物质在蓝藻水华治理方面的应用潜力,选取在凤眼莲根系分泌物中发现的5种化感物质（亚油酸、亚油酸甘油酯、丙酰胺、N-苯基—2-萘胺和壬酸）,研究了3种剂量下（0.1、1.0、10.0mg.L-1）其对单一、混合培养铜绿微囊藻和斜生栅藻生长的影响.结果发现,化感物质成分、剂量和藻类培养方式对铜绿微囊藻和斜生栅藻生长...     

应用生态系统模型研究淀山湖富营养化控制方案

由于淀山湖上游污染负荷以及周边污水的排放,淀山湖已经严重富营养化。通过建立淀山湖生态系统模型,基于大量现场实测数据,对生态系统模型进行率定和验证,并利用生态系统模型对淀山湖N,P营养盐时间变化规律和藻类生长演替进行了系统研究,对各污染负荷削减的富营养化控制方案的效果进行模拟。模拟结果显示:该生态模型较好地模拟了常规水质和藻类的动态变化;淀山湖污染负荷主要来自于上游负荷,削减上游负荷对水质改善效果明显好于其他污染源削减方案;削减上游负荷95%以上,才能有效抑制蓝藻水华;P对蓝藻生长的控制效果好于控制氮。     

赤潮对近岸水体生物光学特性的影响

研究了赤潮对近岸水体生物光学特性的影响.从大连湾采集11个站位的水体生物光学数据,分析了赤潮发生时生物要素、反射光谱以及吸收光谱的变化特征.结果表明,大连湾本次赤潮由微微型藻类引起;赤潮对水体遥感反射率的光谱形状影响明显,与正常水体相比,由于高浓度叶绿素a的强吸收作用,导致440、632 nm波段附近出现反射谷,红光波...     

加拿大一枝黄花提取物对铜绿微囊藻的抑制作用

研究加拿大一枝黄花提取物对铜绿微囊藻的抑制效果,采用两种不同的有机溶剂(水、乙酸乙酯)及水蒸气蒸馏法(挥发油成分)提取加拿大一枝黄花中的抑藻活性物质并进行抑藻试验研究。结果表明三种提取物对铜绿微囊藻均具有较强的抑制作用,在试验设定浓度下,水浸提物在30 g/L时具有最高抑藻率89.89%,乙酸乙酯提取物在浓度为8 g/L时即达到60.88%的抑藻率,而挥发油成分在浓度为10 g/L时有最高抑藻率45.11%。研究表明,加拿大一枝黄花具有抑藻效果,其中乙酸乙酯提取物抑制效果最好,具有应用于水体富营养化的治理和开发新型抑藻剂的潜力。     

Distribution and sources of solvent extractable organic compounds in PM2:5 during 2007 Chinese Spring Festival in Beijing

The solvent extractable organic compounds (SEOC), including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, anddicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing, were measured via gas chromatography-massspectrometry for determining the characteristics and sources of these organic pollutants. The concentrations of total n-alkanes, PAHs,and organic acids before Chinese Spring Festival Eve (1025.5, 95.9, and 543.3 ng/m3, respectively) were higher than those after (536.6,58...