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51.
IntroductionTheclimatechangeissignificantlyaffectinghumanlivingenvironmentsinglobal,regional,andlocalscales.Intermsoftheregionalscale ,oneofthemostpromisingapproachesforsimulationofregionalclimatechangeisthedevelopmentofregionalclimatemodel (RCM) .Itiswel… 相似文献
52.
林国元 《防灾科技学院学报》2005,7(1):46-50
乌鸦咀泉电导率具有明显的夏高冬低年动态变化,如果受到构造应力变化的影响,一般会产生畸变,其异常特征:振荡的短临异常,在年变正常中局部出现转折或加速下降和上升,破年变异常。初步探讨水化异常机理,乌鸦咀泉电导率异常幅度和异常持续时间基本上能反映与震级大小成正比,与震中距成反比。 相似文献
53.
利用2013~2015年水稻生长季期间气象因子、O3浓度和气孔导度的实测数据,分析了O3浓度与AOT40的变化,引入并修订了水稻气孔导度模型,模拟了水稻气孔O3吸收通量的动态变化,评估了当前和未来气候变化情景下O3污染所造成的水稻产量损失.结果表明:2013~2015年水稻生长季期间的白天时段,平均O3浓度分别为35.8,42.0,47.9nL/L,AOT40值分别为5.33,9.03,11.25μL/(L·h).修订后的模型可用于本地区水稻气孔导度的模拟,2013~2015年水稻气孔O3通量AFst02分别为2.02,6.42,7.79mmol/m2.2013~2015年地表O3造成水稻平均相对产量损失分别为4.9%、11.7%和14.3%.在未来气候变化情景下若不考虑O3浓度的变化,O3对水稻的胁迫效应将会降低,若考虑未来O3浓度的变化,O3造成水稻产量的损失将增加4.7~5.7%. 相似文献
54.
在铜胁迫下,以水培的方法,对污染区、非污染区海州香薷的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、气孔限制值(Ls)、叶绿素(Chl)等进行比较研究。结果表明,15μmol/L和45μmol/L铜处理下,污染区、非污染区海州香薷Pn均显著下降,但是污染区Pn下降了16%~27%,非污染区Pn下降了56%~62%。此外,非污染区海州香薷Gs、Ci均明显下降,Ls明显上升,Chla、Chlb含量没有明显变化(15μmol/L铜的Chla含量除外),表明其净光合速率下降的主要原因是气孔限制;但是,污染区海州香薷Gs、Ci、Ls上升或轻微变化,Chla、Chlb含量均明显下降,表明其光合作用可能不存在气孔限制,同时Chl含量明显下降可能是其净光合速率下降的原因之一。此研究揭示了金属型植物光合作用差异及其气孔和非气孔限制,可为进一步查明其生长限制因子提供科学依据。 相似文献
55.
Stomatal conductance (g) is a key parameter in controlling energy and water exchanges between canopy and the atmosphere. Stomatal conductance models proposed by Ball, Woodrow and Berry (BWB) and Leuning have been increasingly used in land surface schemes. In a recent study, a new diagnostic index was developed by Wang et al. to examine the response of g to humidity and new models were proposed to resolve problems identified in the BWB and Leuning models. This approach is theoretically sound, but relies on canopy latent heat and CO2 fluxes and environmental variables at the leaf surface which are not available at most eddy correlation (EC) observation sites. In this study, we tested the diagnostic index by empirically correcting EC measurements to canopy-level fluxes and by replacing leaf surface variables by their corresponding ambient air variables, and re-examined the stomatal conductance models of BWB, Leuning, and Wang et al. We found that the impact of the above modifications on the evaluation of g–humidity relationships is very small. This study provides a practical approach to investigate the stomatal response to humidity using routine EC measurements. 相似文献
56.
Katre Kets Joseph N.T. Darbah Johanna Riikonen David F. Karnosky 《Environmental pollution (Barking, Essex : 1987)》2010,158(4):1000-1007
The diurnal changes in light-saturated photosynthesis (Pn) under elevated CO2 and/or O3 in relation to stomatal conductance (gs), water potential, intercellular [CO2], leaf temperature and vapour-pressure difference between leaf and air (VPDL) were studied at the Aspen FACE site. Two aspen (Populus tremuloides Michx.) clones differing in their sensitivity to ozone were measured. The depression in Pn was found after 10:00 h. The midday decline in Pn corresponded with both decreased gs and decreased Rubisco carboxylation efficiency, Vcmax. As a result of increasing VPDL, gs decreased. Elevated [CO2] resulted in more pronounced midday decline in Pn compared to ambient concentrations. Moreover, this decline was more pronounced under combined treatment compared to elevated CO2 treatment.The positive impact of CO2 on Pn was relatively more pronounced in days with environmental stress but relatively less pronounced during midday depression. The negative impact of ozone tended to decrease in both cases. 相似文献
57.
Joseph N.T. Darbah Thomas D. Sharkey David F. Karnosky 《Environmental pollution (Barking, Essex : 1987)》2010,158(4):1008-1014
The effect of high temperature on photosynthesis of isoprene-emitting (aspen) and non-isoprene-emitting (birch) trees were measured under elevated CO2 and ambient conditions. Aspen trees tolerated heat better than birch trees and elevated CO2 protected photosynthesis of both species against moderate heat stress. Elevated CO2 increased carboxylation capacity, photosynthetic electron transport capacity, and triose phosphate use in both birch and aspen trees. High temperature (36-39 °C) decreased all of these parameters in birch regardless of CO2 treatment, but only photosynthetic electron transport and triose phosphate use at ambient CO2 were reduced in aspen. Among the two aspen clones tested, 271 showed higher thermotolerance than 42E possibly because of the higher isoprene-emission, especially under elevated CO2. Our results indicate that isoprene-emitting trees may have a competitive advantage over non-isoprene emitting ones as temperatures rise, indicating that biological diversity may be affected in some ecosystems because of heat tolerance mechanisms. 相似文献
58.
目前电导率测定在实验室是一个十分普遍而重要的项目,标定电极常数的方法有直接测定法和比较测定法。在直接测定法的基础上,针对现代数显电导仪的特点,设计了标准溶液直读法标定电极常数,绕过了标定过程中需要测定电导G(电阻)的步骤。该方法直观易懂,操作简单,不需要计算,省时省力,适用于所有需要调节并能读出该电极常数的电导率仪。 相似文献
59.
Zapletal M Cudlín P Chroust P Urban O Pokorný R Edwards-Jonášová M Czerný R Janouš D Taufarová K Večeřa Z Mikuška P Paoletti E 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1024-1034
Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s−1 and 0.36 cm s−1 by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s−1. In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O3 concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation. 相似文献
60.
Gerosa G Marzuoli R Rossini M Panigada C Meroni M Colombo R Faoro F Iriti M 《Environmental pollution (Barking, Essex : 1987)》2009,157(5):1727-1736
Stomatal ozone uptake, determined with the Jarvis' approach, was related to photosynthetic efficiency assessed by chlorophyll fluorescence and reflectance measurements in open-top chamber experiments on Phaseolus vulgaris. The effects of O3 exposure were also evaluated in terms of visible and microscopical leaf injury and plant productivity. Results showed that microscopical leaf symptoms, assessed as cell death and H2O2 accumulation, preceded by 3-4 days the appearance of visible symptoms. An effective dose of ozone stomatal flux for visible leaf damages was found around 1.33 mmol O3 m−2. Significant linear dose-response relationships were obtained between accumulated fluxes and optical indices (PRI, NDI, ΔF/Fm′). The negative effects on photosynthesis reduced plant productivity, affecting the number of pods and seeds, but not seed weight. These results, besides contributing to the development of a flux-based ozone risk assessment for crops in Europe, highlight the potentiality of reflectance measurements for the early detection of ozone stress. 相似文献