CO_2浓度升高对水体硝化、反硝化作用的影响研究进展

大气CO_2浓度升高潜移默化地影响着水体生态系统的碳循环过程.然而,该过程如何影响与其耦合的氮循环过程仍不明确.水体硝化、反硝化过程作为水体氮循环的重要环节,必然会对大气CO_2浓度升高产生一系列的响应.本文总结了国内外关于大气CO_2浓度升高对水体理化性质、硝化作用、反硝化作用及N形态转化影响方面的研究工作,发现大气CO_2浓度升高会降低水体的p H,增加水中CO_2和HCO_3^-含量,但对富营养化与寡营养化水体中硝化、反硝化作用的影响具有明显差异.大气CO_2浓度升高抑制寡营养化水体的硝化作用和反硝化作用,降低N2_O的释放通量,抑制富营养化水体的硝化作用,但当水体pH在7～9时,可能促进反硝化作用,增加N2_O的释放通量,最终可能导致水体中NH_4^+的积累及NO_3^-浓度的降低,影响水体中微生物的多样性.在此基础上提出目前相关研究存在的瓶颈问题及值得深入探讨的科学问题,为进一步深入理解温室效应背景下全球CO_2浓度升高对水体生态系统N循环的影响提供参考.     

大气CO2浓度升高对农产品品质影响的研究进展

大气中不断升高的CO₂浓度以及人类饮食的营养质量是目前我们面临的两个重大问题.目前,大气中CO₂浓度已达到380 μmol·mol^-1,预测到2050年大气CO₂浓度将达到550 μmol·mol^-1.农产品的品质不仅取决于遗传基因,而且受生长环境条件的影响.大量研究表明,农作物的生长发育和产量形成都对CO₂浓度升高做出了响应,而且这种变化对农产品的品质也产生了重要影响.本文对目前国内外模拟CO₂浓度升高对农产品品质影响研究中采用的常见方法进行了比较,并综述了近年来在CO₂浓度升高对水稻、小麦、大豆和其他一些蔬菜类农产品品质影响方面的研究进展.大量试验结果表明,CO₂浓度升高条件下,大宗作物籽粒中蛋白质含量下降,微量元素总体上有下降趋势,而蔬菜类农产品的品质有一定程度改善.最后,本文根据目前研究现状对一些问题进行了讨论并提出了今后的研究方向.     

CO2浓度升高对凤梨叶片生长和光合特性的影响

研究了CO2浓度升高对开顶式气室中凤梨叶片的生长与光合生理的影响。结果表明:高CO2浓度(1000±100μmolmol-1)下生长的凤梨植株的株高、叶面积、鲜重和干重均高于对照(360±30μmolmol-1),处理90d时分别为对照的120.19%、119.22%、177.91%和161.04%;凤梨叶片的净光合速率也增加了136%-259%,且促进了叶片中可溶性糖和淀粉的积累,但叶绿素含量则下降了33.91%。高CO2浓度处理的凤梨叶片中RuBP羧化酶活性没有明显变化,乙醇酸氧化酶活性则明显下降。     

CO2浓度升高对木荷幼苗光合特征的影响

IPCC(Intergovernmental Panel on Climate Change)报告预测,到2100年CO₂浓度会出现430～480、580～720、720～1000和>1000μmol·mol^-1 4种不同情景,而目前同时探究所有CO₂情景下植物响应情况的研究很少。本试验利用开顶式气室分别探究自然大气浓度(约400μmol·mol^-1)、550、750和1000μmol·mol^-1 4个CO₂水平在生长季内对一年生木荷(Schima superba)幼苗气体交换参数、光合色素含量及生物量的影响。结果表明：熏气期间,550、750和1000μmol·mol^-1浓度下木荷幼苗净光合速率分别平均提升32.7%、66.7%、82.7%,胞间CO₂浓度分别平均增加60.3%、126.2%、223.9%,而高浓度CO₂对净光合速率的提升作用随着熏气时间延长,可能受叶片氮含量减少等非...     

大气CO2浓度升高对稻田土壤氮素的影响

利用中国稻/麦轮作FACE(Free-Air Carbon=Dioxide Enrichment)试验平台,研究大气CO₂浓度升高200 μmol·mol^-1(周围大气中CO₂浓度约370 μmol·mol^-1)对稻季各生育期不同深度土壤溶液NH₄⁺-N和NO₃^--N浓度的影响.结果表明：高CO2浓度条件下耕层土壤溶液NH₄⁺-N浓度在水稻生育前期有所增加,但在生育后期明显下降;大气CO₂浓度升高增加了稻季5、15、30、60和90 cm处土壤溶液NO₃^--N浓度,分别比对照平均提高了46.5%、36.8%、23.3%、103.7%和42.7%,在60和90 cm处差异分别达到统计上的极显著和显著水平.     

CO2浓度升高与氮添加对三江平原湿地小叶章生长的影响

利用开顶箱薰气室,设置正常大气CO₂浓度(350 μmol·mol^-1)、高CO₂浓度(700 μmol·mol^-1)2个CO₂水平和不施氮(0 g N·m^-2)、中氮(5 g N·m^-2)和高氮(15 g N·m^-2)3个氮素水平,研究CO₂浓度升高和氮肥施用对三江平原草甸小叶章生长的影响.结果表明：随着CO₂浓度升高,小叶章物候期提前,其中抽穗期提前1～2 d,成熟期提前3 d;不施氮、中氮和高氮水平下, CO₂浓度升高使小叶章的分蘖分别增加8.2%(P<0.05)、8.4%(P<0.05)和5.5%(P>0.05);在小叶章生长初期,CO₂浓度升高对其生物量的增加有促进作用,拔节期和抽穗期小叶章地上生物量分别增加12.4%和20.9%(P<0.05);生长后期则对小叶章地下生物量的促进作用增大,腊熟期和成熟期的地下生物量分别增加20.5%和20.9% (P<0.05).小叶章生物量对高浓度CO₂的响应与供氮水平有关,供氮充足条件下, 高浓度CO₂对生物量的促进效应更大.     

大气CO2浓度升高与森林群落结构的可能性变化

大气ＣＯ２浓度升高的所引起的森林生态系统稳定性的变化会导致森林在结构和功能上的变动,概述了大气ＣＯ２浓度升高和陆地森林生态系统可能性变化之间的相互关系的研究情况。由于大气ＣＯ２浓度升高出现了额外多的Ｃ,供应,讨论了以这些额外多的Ｃ经大气－植物－土壤途径的流动走向,来研究大气ＣＯ２浓度的升高,与森林结构的相互作用,探讨了大气ＣＯ２浓度升高对森林植物生长、冠层结构、引发的生物量增量的分配、凋落物质量和     

冬小麦幼苗生长和化感物质对CO2和O3浓度升高的响应

利用开顶式气室(OTC), 采用盆栽试验研究了CO₂浓度为550 μL·L^-1、O₃浓度为60 μL·L^-1及CO₂浓度为550 μL·L^-1+O₃浓度为60 μL·L^-1对7个冬小麦品种幼苗生物量和化感物质丁布(DIMBOA)的影响.结果表明：在高CO₂浓度下,冬小麦幼苗地上生物量与丁布含量在品种间存在显著差异,品种碧蚂1号幼苗和根干质量比对照（CO₂浓度为370 μL·L^-1,O₃浓度为40 μL·L^-1）增加了36.8%和24.7%;丁布含量增幅为5.7%~184.6%.除碧蚂1号和陕139外,高浓度O₃导致冬小麦生物量降低,但使所有品种丁布含量显著增加,变幅为0.5~3倍.交互作用下所有品种根干质量降低,长武134地上部质量、根质量和丁布含量降幅最大,分别为82%、27.9%和35.5%;与长武134、远丰175和兰考217丁布含量降低相反,陕139丁布含量增加84.6%.聚类分析显示,不同处理和不同品种均显著影响丁布含量,陕139、兰考217和长武134在高CO₂和O₃浓度处理下聚为一类,而陕139在所有处理中丁布含量均表现为增加.表明化感物质丁布可以作为气候变化条件下,尤其是CO₂和O₃变化下抗性育种的特定指标.     

温度和CO2浓度升高对甜椒光合生理和虫害发生的影响

全球温度和CO₂浓度持续性升高对农业活动产生了显著影响。研究甜椒光合生理对气候变化的响应,可为甜椒等茄科蔬菜在应对未来气候变化的栽培管理措施及果实加工提供科学依据。本研究利用控制气室,采用盆栽试验研究模拟温度升高(常温+2℃)和CO₂浓度升高(600μmol·mol^-1)下甜椒品种‘甜椒115’光合生理及虫害发生的响应。结果表明:温度和CO₂浓度升高均可使甜椒净光合速率(P_n)、气孔导度(G_s)、叶片蒸腾速率(T_r)和水分利用率(WUE)极显著增加,温度升高后胞间二氧化碳浓度(Ci)降低;升温可显著增加叶绿素a、叶绿素b的含量,而CO₂浓度升高导致甜椒光合色素含量降低,温度和CO₂浓度对甜椒果实Vc含量交互作用显著;温度与CO₂浓度升高对甜椒产量(鲜重)无显著影响,但会影响其产量构成因素;温度和CO₂浓度升高后甜椒蚜虫及其他虫害加重;温度和CO     

气温、CO2浓度和降水交互作用对作物生长和产量的影响

气温、大气CO₂浓度和降水等气候因子是影响作物生长发育的关键因子,而不同的气候因子对作物的影响并非独立的,多气候因子交互作用对作物的影响目前已成为研究的焦点问题.研究不同气候因子交互作用的影响,其结果更接近作物生长的实际情况,有助于了解作物甚至作物生态系统对气候变化的真实响应.国内外关于不同气候因子对作物影响的报道较多,要全面总结不同气候因子交互作用对作物的影响是非常困难的.因此,本文只对近年来有关气温升高、大气CO₂浓度增加和降水变化交互作用对作物生长发育、光合生理及产量影响的研究进展做一简要评述,并提出目前研究的不足和需要解决的关键问题,以期为气候变化对作物生长发育及产量影响的研究提供参考.     

Elevated atmospheric CO2 in open top chambers increases net nitrification and potential denitrification

The control of soil nitrogen (N) availability under elevated atmospheric CO₂ is central to predicting changes in ecosystem carbon (C) storage and primary productivity. The effects of elevated CO₂ on belowground processes have so far attracted limited research and they are assumed to be controlled by indirect effects through changes in plant physiology and chemistry. In this study, we investigated the effects of a 4‐year exposure to elevated CO₂ (ambient + 400 µmol mol^?1) in open top chambers under Scots pine (Pinus sylvestris L) seedlings on soil microbial processes of nitrification and denitrification. Potential denitrification (DP) and potential N₂O emissions were significantly higher in soils from the elevated CO₂ treatment, probably regulated indirectly by the changes in soil conditions (increased pH, C availability and NO₃^– production). Net N mineralization was mainly accounted for by nitrate production. Nitrate production was significantly larger for soil from the elevated CO₂ treatment in the field when incubated in the laboratory under elevated CO₂ (increase of 100%), but there was no effect when incubated under ambient CO₂. Net nitrate production of the soil originating from the ambient CO₂ treatment in the field was not influenced by laboratory incubation conditions. These results indicate that a direct effect of elevated atmospheric CO₂ on soil microbial processes might take place. We hypothesize that physiological adaptation or selection of nitrifiers could occur under elevated CO₂ through higher soil CO₂ concentrations. Alternatively, lower microbial NH₄ assimilation under elevated CO₂ might explain the higher net nitrification. We conclude that elevated atmospheric CO₂ has a major direct effect on the soil microbial processes of nitrification and denitrification despite generally higher soil CO₂ concentrations compared to atmospheric concentrations.     

氮素对高大气CO2浓度下小麦叶片光合作用的影响

通过测定小麦拔节期叶片的光合气体交换参数和光强-光合速率（P_n）响应曲线,研究了氮素对长期高大气CO₂浓度（760 μmol·mol^-1）下小麦叶片光合作用的影响.结果表明：在长期高大气CO₂浓度下,增施氮肥能提高小麦叶片P_n、蒸腾速率（T_r）和瞬时水分利用效率（WUE_i）;与正常大气CO₂浓度相比,高大气CO₂浓度下小麦叶片的P_n和WUE_i增加,气孔导度（G_s）和胞间CO₂浓度(C_i）降低.随光合有效辐射的增强,高大气CO₂浓度下小麦叶片的P_n和WUE_i均高于正常大气CO₂浓度处理,G_s则较低,而C_i和T_r无显著变化.高氮水平下小麦叶片G_s与P_n、T_r、WUE_i呈线性正相关,G_s与C_i在正常大气CO₂浓度下呈线性负相关,但高大气CO₂浓度下二者无相关性;低氮水平下小麦叶片的G_s与P_n、WUE_i无相关性,而与C_i和T_r呈线性正相关,表明高大气CO₂浓度下低氮水平的小麦叶片P_n由非气孔因素限制.     

N2 fixation by Acacia species increases under elevated atmospheric CO2

In the present study the effect of elevated CO₂ on growth and nitrogen fixation of seven Australian Acacia species was investigated. Two species from semi‐arid environments in central Australia (Acacia aneura and A. tetragonophylla) and five species from temperate south‐eastern Australia (Acacia irrorata, A. mearnsii, A. dealbata, A. implexa and A. melanoxylon) were grown for up to 148 d in controlled greenhouse conditions at either ambient (350 µmol mol^?1) or elevated (700 µmol mol^?1) CO₂ concentrations. After establishment of nodules, the plants were completely dependent on symbiotic nitrogen fixation. Six out of seven species had greater relative growth rates and lower whole plant nitrogen concentrations under elevated versus normal CO₂. Enhanced growth resulted in an increase in the amount of nitrogen fixed symbiotically for five of the species. In general, this was the consequence of lower whole‐plant nitrogen concentrations, which equate to a larger plant and greater nodule mass for a given amount of nitrogen. Since the average amount of nitrogen fixed per unit nodule mass was unaltered by atmospheric CO₂, more nitrogen could be fixed for a given amount of plant nitrogen. For three of the species, elevated CO₂ increased the rate of nitrogen fixation per unit nodule mass and time, but this was completely offset by a reduction in nodule mass per unit plant mass.     

Interactions between elevated CO2 concentration, nitrogen and water: effects on growth and water use of six perennial plant species

Two experiments are described in which plants of six species were grown for one full season in greenhouse compartments with 350 or 560 μ mol mol^–1 CO₂. In the first experiment two levels of nitrogen supply were applied to study the interaction between CO₂ and nitrogen. In the second experiment two levels of water supply were added to the experimental set-up to investigate the three-way interaction between CO₂, nitrogen and water. Biomass and biomass distribution were determined at harvests, while water use and soil moisture were monitored throughout the experiments. In both experiments a positive effect of CO₂ on growth was found at high nitrogen concentrations but not at low nitrogen concentrations. However, plants used much less water in the presence of low nitrogen concentrations. Drought stress increased the relative effect of elevated CO₂ on growth. Available soil moisture was used more slowly at high CO₂ during drought or at high nitrogen concentrations, while at low nitrogen concentrations decreased water use resulted in an increase in soil moisture. The response to the treatments was similar in all the species used. Although potentially faster growing species appeared to respond better to high CO₂ when supplied with a high level of nitrogen, inherently slow-growing species were more successful at low nitrogen concentrations.     

The effect of elevated CO2 concentration and soil pH on the relationship between plant growth and rhizosphere denitrification potential

The effect of CO₂ concentration on plant growth and the size of the rhizosphere denitrifier population was investigated for ryegrass grown at 3 different soil pH values (pH 4.3, 5.9 and 7.0). Soil microcosms were planted with ryegrass and maintained under constant growth conditions at either ambient (450ppm) or elevated (720ppm) CO₂ concentration. At harvest, the rhizosphere soil was collected and subjected to a potential denitrification assay to provide an estimate of the size of the denitrifier population present. Ryegrass dry matter production varied across the pH range studied and contrary to other studies, elevated CO₂ concentration did not consistently increase growth. Plant growth was reduced by ≈ 35% and 23% at pH 4.3 and pH 5.9, respectively, under elevated CO₂ concentration. At pH 7.0, however, plant growth was increased by ≈ 45% under elevated CO₂. Potential denitrification rates within the rhizosphere followed a similar pattern to plant growth in the different treatments, suggesting that plant growth and the size of denitrifier population within the rhizosphere are coupled. This study investigates the relationship between plant growth and rhizosphere denitrification potential, thereby providing an estimate of the size of the denitrifier population under increased CO₂ concentration and soil pH.     

Widespread foliage δ15N depletion under elevated CO2: inferences for the nitrogen cycle

Leaf ¹⁵N signature is a powerful tool that can provide an integrated assessment of the nitrogen (N) cycle and whether it is influenced by rising atmospheric CO₂ concentration. We tested the hypothesis that elevated CO₂ significantly changes foliage δ¹⁵N in a wide range of plant species and ecosystem types. This objective was achieved by determining the δ¹⁵N of foliage of 27 field‐grown plant species from six free‐air CO₂ enrichment (FACE) experiments representing desert, temperate forest, Mediterranean‐type, grassland prairie, and agricultural ecosystems. We found that within species, the δ¹⁵N of foliage produced under elevated CO₂ was significantly lower (P<0.038) compared with that of foliage grown under ambient conditions. Further analysis of foliage δ¹⁵N by life form and growth habit revealed that the CO₂ effect was consistent across all functional groups tested. The examination of two chaparral shrubs grown for 6 years under a wide range of CO₂ concentrations (25–75 Pa) also showed a significant and negative correlation between growth CO₂ and leaf δ¹⁵N. In a select number of species, we measured bulk soil δ¹⁵N at a depth of 10 cm, and found that the observed depletion of foliage δ¹⁵N in response to elevated CO₂ was unrelated to changes in the soil δ¹⁵N. While the data suggest a strong influence of elevated CO₂ on the N cycle in diverse ecosystems, the exact site(s) at which elevated CO₂ alters fractionating processes of the N cycle remains unclear. We cannot rule out the fact that the pattern of foliage δ¹⁵N responses to elevated CO₂ reported here resulted from a general drop in δ¹⁵N of the source N, caused by soil‐driven processes. There is a stronger possibility, however, that the general depletion of foliage δ¹⁵N under high CO₂ may have resulted from changes in the fractionating processes within the plant/mycorrhizal system.     

The interaction of rising CO2 and temperatures with water use efficiency

Abstract. Recent data concerning the impact of elevated atmospheric CO₂ upon water use efficiency (WUE) and the related measure, instantaneous transpiration efficiency (ITE), are reviewed. It is concluded from both short and long-term studies that, at the scale of the individual leaf or plant, an increase in WUE or ITE is generally observed in response to increased atmospheric CO₂ levels. However, the magnitude of this increase may decline with time. The opinion that elevated CO₂ may substantially decrease transpiration at the regional scale is discussed. The mechanisms by which elevated CO₂ may cause a change in these measures are discussed in terms of stomatal conductance, assimilation and respiration responses to elevated CO₂. Finally, recent experimental data and model outputs concerning the impact of the interaction of increased temperature with elevated CO₂ on WUE, ITE and yield are reviewed. It is concluded that substantially more data is required before reliable predictions about the regional scale response of WUE and catchment hydrology can be made.