不同氮浓度下盐胁迫对坛紫菜(Pyropia haitanensis)生长和光合作用的影响

为了探讨在不同氮浓度条件下盐度胁迫对坛紫菜(Pyropia haitanensis)生长和光合生理的影响,设置高(500μmol/L)、低(50μmol/L)2个氮浓度和15、30和45三个盐度水平,将坛紫菜叶状体在不同的氮和盐度条件下适应培养7d后,测定藻体的生长、色素含量、光合放氧和快速光反应曲线等生理指标。结果显示:在低氮条件下,坛紫菜的生长速率随盐度增加而递减;在高氮下,30盐度水平培养的藻体具有最大生长速率。低氮条件下,叶绿素a(Chl a)、类胡萝卜素(Car)、藻红蛋白(PE)和藻蓝蛋白(PC)的含量在盐度15中较高,而在盐度30和45之间没有显著差异;高氮条件下,盐度对藻体Chl a和Car的含量没有显著影响,但相对于盐度30的处理,盐度15和45都显著降低了PE和PC的含量,虽然这两种色素含量在两个盐度处理间没有显著差异。不同的氮和盐度处理对藻体的光合放氧速率几乎没有影响,除了高氮条件下,单位湿重的放氧速率在盐度30中较低而单位Chl a的放氧速率在盐度45中稍高。从快速光反应曲线的结果看出,盐度虽然对光饱和点(Ik)、电子传递效率(α)和最大相对电子传递速率(r ETRmax)没有显著影响,但高盐胁迫显著提高了光抑制项的值(a)。综上所述,高盐度胁迫能够抑制坛紫菜的生长和光合作用,氮的浓度对这种抑制作用没有显著影响;低盐度胁迫对藻体的生长和光合没有抑制,甚至在低氮条件下表现出对生长的促进。这些结果为坛紫菜的栽培和对富营养化海水的修复提供了一定的理论参考。     

Cyanobacteria in New Zealand inland waters: Experimental studies

A small volume of experimental work with cyanobacteria in New Zealand has been produced through the last two decades. Except for some studies with geothermal organisms biased to New Zealand conditions, most work has followed the world‐wide trends in cyanobacterial research. There has been some emphasis on N₂‐fixing species, but symbiotic relationships, metabolic kinetics, nutrient and other environmental factors promoting ecological dominance, and toxicity have been investigated.     

CO2升高和阳光紫外辐射对坛紫菜生长和光合特性的耦合效应

大气CO₂持续升高,导致溶入海水中的CO₂增多,海水表层的H+浓度增加,从而引起海洋酸化。为了探讨近岸定生大型海藻对这种环境变化的响应,本文选择经济海藻坛紫菜为实验材料,研究海洋酸化与紫外辐射对藻体生长以及光合特性的影响。实验分两个CO₂处理,分别为正常空气水平(390 ppmv)和高CO₂水平(800 ppmv); 三种辐射处理,分别为全波长辐射(PAB)、滤除紫外线B(PA)和仅接受可见光处理(PAR)。研究结果表明,CO₂培养下的坛紫菜,在仅有可见光(P)或者同时有紫外线A(PA)存在的情况下,显著促进藻体的生长;但在全波长辐射处理下(PAB),这种作用不明显。高CO₂降低了藻体在P和PA处理下的光合作用速率,但对PAB处理作用不显著。高CO₂处理下的藻体,UV-B显著降低了全波长辐射下藻体紫外吸收物质的含量,但在正常CO₂水平下,紫外辐射的作用不显著。这表明高CO₂导致的生长优势被紫外辐射的负面效应所抵消,在全球变化的过程中,紫外辐射的进一步加强在海洋酸化的背景下甚至有可能降低坛紫菜的产量。     

多环芳烃在赤潮微藻光合作用中所起作用的研究

采用实验生态学的方法,研究了3种多环芳烃-菲、芘和蒽对3种赤潮微藻-赤潮异弯藻、亚历山大藻和中肋骨条藻光合速率的影响。结果表明:较低浓度的菲、芘和蒽处理使3种赤潮微藻的光合速率有所提高,而较高浓度处理则降低了藻细胞的光合速率。3种多环芳烃-菲、芘和蒽胁迫对赤潮异弯藻光合速率的96h·EC50分别为0.089、0.110和0.124mg·L-1,对中肋骨条藻的96h半抑制剂量分别为0.103、0.127和0.138mg·L-1,对亚历山大藻的96h半抑制剂量分别为0.116、0.131和0.141mg·L-1,说明3种多环芳烃对赤潮微藻均表现出一定的毒性效应,其中菲的毒性作用最强。UV-B辐射(0.3J·m-2的辐射剂量)和多环芳烃的联合作用一方面增强了菲、芘和蒽对3种赤潮微藻光合效率的抑制作用,导致光合速率明显降低,另一方面在一定程度上改变了3种多环芳烃毒性作用的强弱,使芘的毒性作用变得最强。     

Impacts of reduced wind speed on physiology and ecosystem carbon flux of a semi-arid steppe ecosystem

Decreasing wind speed is one aspect of global climate change as well as global warming, and has become a new research orientation in recent decades. The decrease is especially evident in places with frequent perennially high wind speeds. We simulated decreased wind speed by using a steel-sheet wind shield in a temperate grassland in Inner Mongolia to examine the changes in physical environmental variables, as well as their impacts on the photosynthesis of grass leaves and net ecosystem exchange （NEE）. We then used models to calculate the variation of boundary layer conductance （BLC） and its impact on leaf photosynthesis, and this allowed us to separate the direct effects of wind speed reduction on leaf photo- synthesis （BLC） from the indirect ones （via soil moisture balance）. The results showed that reduced wind speed primarily resulted in higher moisture and temperature in soil, and indirectly affected net assimilation and water use efficiency of the prevalent bunch grass Stipa krylovii. Moreover, the wind-sheltered plant community had a stronger ability to sequester carbon than did the wind-exposed community during the growing season.     

环境污染对成都市古树名木的危害及防治对策研究

对成都市的主要古树名木被环境污染物质危害的现状进行实地调查，从受害症状入手，对受害机理作分析。并提出保护古树名木的具体措施。此工作对本市治理污染及合理绿化将有意义。     

SIMPLE SIMULATION OF THE ANNUAL VARIATION OF THE SPECIFIC PHOTOSYNTHESIS RATE IN JIAOZHOU BAY

A simple diagnostic simulation of the annual cycling of the surface specific photosynthesis rate (SPR) in Jiaazhou Bay is described in this paper. Light intensity, temperature and nutrients(nitrate ammonia, phosphate) were considered as main factors controlling photosynthesis of phytoplankton and were introduced into the model by different function equations. The simulated variation ofspecific photosynthesis rate coincided with the measured data. Analysis of the effect of every factor onphotosynthesis indicated that the variation of photosynthesis rate was controlled by all these three factors,while temperature showed good correlation with SPR as measurement showed. This diagnostic simulationyielded the values of some parameter relating with the photosynthesis in Jiaozhou Bay.     

Seasonal variation of carbon exchange of typical forest ecosystems along the eastern forest transect in China

The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0℃and 10℃were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (NEE) of CBS occurred in early summer because maximum ecosystem photosynthesis (GPP) occurred earlier than maximum ecosystem respiration (Rθ). During summer, QYZ experienced severe drought and NEE decreased significantly mainly as a result of the depression of GPP. At DHS and XSBN, NEE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem GPP was dispressed. The Q10 and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual NEE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and -320.0 g·C·m-2·a-1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of WEE/Rθincreased with latitude, while Rθ/Gpp, ecosystem light use efficiency (LUE), precipitation use efficiency and average daily GPP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems.     

Simulation of CO2 and latent heat fluxes in the North China Plain

We constructed a coupled model for simulating plant photosynthesis and evapotranspiration (CPCEM). In the model, non-rectangular hyperbola is used to simulate leaf photosynthesis rate that is scaled up to estimate canopy gross photosynthesis rate by an integral method. Whole canopy in the model is separated into multi-layers, each of which is divided into sunlit leaves and shade leaves. Canopy net photosynthesis rate is expressed as a function of canopy conductance which is coupled with evapotranspiration. Included the coupled function,evapotranspiration is estimated with a two-layer submodel. The main features of CPCEM are: (1)easy suitability, (2) good physiological base, and (3) simple calculation procedure. Simulated results of CPCEM were compared with those by an eddy covariance system that was installed in a winter wheat farmland of the North China Plain. CPCEM gave a quite well diurnal and seasonal dynamics of net ecosystem exchange, compared with the measurements. The root mean square error between simulation and measurements was only about 2.94 μ mol m-2 s-1. Diurnal and seasonal patterns of latent heat flux with the CPCEM were similar to those of measurements.Whereas, simulated latent heat flux was evidently higher than the measured.     

小兴安岭湿地植物的光合作用日变化研究

对同一区域内两种不同类型森林沼泽的生态环境及生长在其中的植物进行调查和观测,分析讨论两种不同小气候形成的原因及对植物的影响,比较分析两种沼泽中主要植物的气孔导度、Ci/C、蒸腾、光合作用的日进程变化特性。高位沼泽中优势植物小灌木的气孔导度较高,蒸腾及光合速率高;光合曲线表现为双峰型,有明显的“午休”现象,引起“午休”现象的原因是非气孔限制因子;测试条件下高位沼泽植物的饱和光强范围是1 044.24-1 205.43μmoL/(m2·s);低位沼泽优势植物光合日变化曲线表现为单峰型和平展型,无“午休”现象。其中阴生植物蓝靛果忍冬和修氏苔草的光补偿点<18μmoL/(m2·s),低位沼泽林下落叶松和油桦的光合作用限制因子为光照强度不足,而土壤矿质营养贫乏和水的强酸性是高位沼泽中油桦和落叶松光合能力的重要限制因子。