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171.
We measured CO2 efflux from stems of seven subtropical tree species situated along an elevational gradient in the Luquillo Mountains, Puerto Rico and scaled these measurements up to the landscape level based on modeled and empirical relations. The most important determinants of ecosystem stem respiration were species composition and stem temperature. At a species scale, measured CO2 efflux per unit bole surface area at a given temperature was highest in the early successional species Cecropia schreberiana and lowest in species that inhabit high elevations such as Micropholis garciniifolia and Tabebuia rigida. Carbon dioxide efflux rates followed a diel pattern that lagged approximately 6 h behind changes in sapwood temperatures. At an ecosystem scale, our simulation model indicates a decreasing trend of stem respiration rates with increasing elevation due to shifts in species composition, lower temperatures and reductions in branch surface area. The highest estimated stem respiration rates were present in the lowland tabonuco forest type and the lowest rates were present in the elfin forest type (mean 7.4 and 2.1 Mg C ha−1 yr−1, respectively). There was slight temperature-induced seasonal variation in simulated stem respiration rates at low elevations, with a maximum difference of 19% between the months of February and July. Our results coincide well with those of Odum and Jordan [Odum, H.T., Jordan, C.F., 1970. Metabolism and evapotranspiration of the lower forest in a giant plastic cylinder. In: Odum, H.T., Pigeon, R.F. (Eds.), A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. U.S. Atomic Energy Commission, Oak Ridge, TN, pp. I165–I189] for the tabonuco forest type and extend their work by presenting estimates and spatial patterns of woody tissue respiration for the entire mountain rather than for a single forested plot. 相似文献
172.
Modeling carbon sequestration under zero tillage at the regional scale. I. The effect of soil erosion 总被引:3,自引:0,他引:3
Thomas Gaiser Karl Stahr Norbert Billen Mohammad Abdel-Razek Mohammad 《Ecological modelling》2008,218(1-2):110-120
Zero tillage is recognized as a potential measure to sequester carbon dioxide in soils and to reduce CO2 emissions from arable lands. An up-scaling approach of the output of the Environmental Policy Integrated Climate (EPIC) model with the information system SLISYS-BW has been used to estimate the CO2-mitigation potential in the state of Baden-Württemberg (SW-Germany). The state territory of 35,742 km2 is subdivided into eight agro-ecological zones (AEZ), which have been further subdivided into a total of 3976 spatial response units. Annual CO2-mitigation rates where estimated from the changes in soil organic carbon content comparing 30 years simulations under conventional and zero tillage. Special attention was given to the influence of tillage practices on the losses of organic carbon through soil erosion, and consequently on the calculation of CO2-mitigation rates. Under conventional tillage, mean carbon losses through erosion in the AEZ were estimated to be up to 0.45 Mg C ha−1 a−1. The apparent CO2-mitigation rate for the conversion from conventional to zero tillage ranges from 0.08 to 1.82 Mg C ha−1 a−1 in the eight AEZ, if the carbon losses through soil erosion are included in the calculations. However, the higher carbon losses under conventional tillage compared to zero tillage are composed of both, losses through enhanced CO2 emissions, and losses through intensified soil erosion. The adjusted net CO2-mitigation rates of zero tillage, subtracting the reduced carbon losses through soil erosion, are between 0.07 and 1.27 Mg C ha−1 a−1 and the estimated net mitigation rate for the entire state amounts to 285 Gg C a−1. This equals to 1045 Gg CO2-equivalents per year with the cropping patterns in the reference year 2000. The results call attention to the necessity to revise those estimation methods for CO2-mitigation which are exclusively or predominantly based on the measurements of differential changes in total soil organic carbon without taking into account the tillage effects on carbon losses through soil erosion. 相似文献
173.
Modeling the carbon cycle of urban systems 总被引:2,自引:0,他引:2
Although more than 80% of carbon dioxide emissions originate in urban areas, the role of human settlements in the biosphere evolution and in global carbon cycling remains largely neglected. Understanding the relationships between the form and pattern of urban development and the carbon cycle is however crucial for estimating future trajectories of greenhouse gas concentrations in the atmosphere and can facilitate mitigation of climate change. In this paper I review state-of-the-art in modeling of urban carbon cycle. I start with the properties of urban ecosystems from the ecosystem theory point of view. Then I discuss key elements of an urban system and to which degree they are represented in the existing models. In conclusions I highlight necessity of including biophysical as well as human related carbon fluxes in an urban carbon cycle model and necessity of collecting relevant data. 相似文献
174.
生物活性炭纤维处理微污染源水 总被引:1,自引:0,他引:1
在生物活性炭的基础上,以活性炭纤维替代颗粒活性炭,研制了生物活性炭纤维(BACF)新型吸附材料,用于处理水中有机污染物。用扫描电镜观察了微生物在ACF上的固定情况,以水处理常用指标CODMn、UV254及,GC-MS图谱分析考察BACF对于微污染源水的处理效果。研究结果显示BACF技术作为一种新颖的水的深度处理工艺,结合了吸附与生物降解的双重效能,可以有效提高对源水的净化效果,提高出水水质,同时也可以扩大水源水的取水范围,是一项先进的水处理技术。 相似文献
175.
针对目前碳排放初始权区域分配模型中分配原则、指标体系不一致的问题,提出了碳排放初始权区域分配协调度概念,并确定了公平性原则、效率性原则、可持续发展原则、保障工业生产原则、保护环境原则作为碳排放初始权区域分配的具体原则,构造了基于各个分配原则下的碳排放初始权区域分配协调度子函数,建立了以碳排放初始权分配系统协调度最大为目标的协调度分配模型。将此模型应用到华东电网区域的碳排放初始权分配中,结果表明该模型合理、有效、可行性高,能较好的兼顾各个分配原则。该区域分配模型不依赖分配指标体系,能有效避免分配指标体系混乱问题,所建立的模型可以为碳排放初始权区域分配的研究提供借鉴。 相似文献
176.
177.
178.
李维安 《中国安全科学学报》2005,15(5):109-112
提出了一个利用碳纤维混凝土与普通混凝土进行复合,实现结构安全监测的技术方法。根据普通混凝土与碳纤维混凝土之间良好的亲和能力,将碳纤维混凝土浇铸在结构承载的薄弱部分,利用碳纤维混凝土的压敏特性,可以对该部分的服役状态进行监测,获得结构的变形情况;另一方面,利用碳纤维混凝土的基本特性,还可以适当改善结构的承载强度。笔者所提出的复合结构既具有普通混凝土结构的基本特征,又赋予了结构的自我监测功能,比较有效地克服了全碳纤维混凝土结构建造所面临的电阻率波动、骨料石子影响和建设成本等几个方面的技术问题。 相似文献
179.
于2013年7月对东海和南黄海海水中CO的浓度分布、时空变化、海-气通量和表层海水中CO微生物消耗进行了研究.夏季东海和南黄海大气中CO的体积分数范围为68×10-9~448×10-9,平均值为117×10-9(SD=68×10-9,n=36),呈现出近岸高、远海低的特点.夏季东海和南黄海表层海水中CO的浓度范围为0.23~7.10 nmol·L-1,平均值为2.49 nmol·L-1(SD=2.11,n=36),CO的浓度受太阳辐射影响明显;不同站位CO浓度的垂直分布特征基本相同,CO浓度最大值一般出现在表层,随深度增加CO浓度迅速减小.夏季东海和南黄海海水中CO浓度具有明显的周日变化,最大值是最小值的6~40倍.各层最大值基本出现在中午,最小值基本上出现在凌晨前后.CO明显的周日变化特征进一步证明海水中CO主要由光化学产生.调查期间东海和南黄海表层海水中CO相比大气处于过饱和状态,过饱和系数变化范围为1.99~99.18,平均值为29.36(SD=24.42,n=29),表明调查海域是大气中CO的源.调查期间CO的海-气通量变化范围为0.37~44.84μmol·(m2·d)-1,平均值为12.73μmol·(m2·d)-1(SD=11.40,n=29).调查海域CO的微生物消耗培养实验中,CO的浓度随时间增长呈指数降低,消耗过程符合一级反应的特点,微生物消耗速率常数KCO范围为0.12~1.45 h-1,平均值为0.47 h-1(SD=0.55,n=5),微生物消耗速率与盐度之间有一定的相关性. 相似文献
180.
孔径分布和溶液浓度对碳气凝胶电极电吸附除盐性能的影响分析 总被引:1,自引:0,他引:1
在不同进水浓度下,采用两种比表面积相似但是孔径分布不同的碳气凝胶作为电极进行了一系列电吸附除盐平衡试验.结果表明,随着溶液浓度的变化,不同的孔径分布对碳气凝胶除盐效果影响不一样.其机理为双电层的存在,使得碳气凝胶空隙内的双电层扩散层相互叠加;同时,根据德拜定律,碳气凝胶空隙内的双电层扩散层在不同浓度溶液中厚度不同,从而使得双电层扩散层相互叠加的情况也随浓度变化而变化.这两种作用共同导致了实验结果.当溶液浓度为 0.01 mol·L-1时,选择主要孔径不小于20hm的碳气凝胶电极;当溶液浓度为 0.1 mol·L-1时,应选用主要孔径不小于 10nm 的材料;当溶液浓度为几 mol·L-1时.则分散层几乎消失,孔径大小对电吸附性能影响几乎不考虑. 相似文献