大气 CO2 浓度升高对水稻氮代谢影响的研究进展

自工业革命以来,大气中浓度不断升高的CO2对C3植物生长发育的影响十分显著。CO2浓度升高条件下,植物光合作用增强,C同化产物增多,C、N代谢的平衡受到影响,植株N代谢发生变化。水稻(Oryza sativa L.)作为世界上最主要的食物来源之一,其N素营养状况的变化必然引起人类食物品质的改变,近年来已成为人们关注的焦点。本文结合气室条件的研究结果,从水稻N吸收和N积累量、N浓度、N代谢相关酶、不同形态的N(主要是蛋白氮)、C/N比、根系含N分泌物以及N与光合适应的关系等方面,重点收集和整理开放式空气中CO2浓度升高(FACE,Free Air Carbon-dioxide Enrichment)条件下水稻对N素的吸收、分配和利用等方面的研究进展,并对有待进一步深入的问题进行了探讨。     

土壤微生物对大气CO_2浓度升高的响应研究

土壤微生物对大气CO2浓度升高的响应是全面评价大气CO2浓度变化对陆地生态系统影响的关键。文章简要回顾了人工控制微域生态环境CO2浓度增高的研究技术及其发展,并着重介绍了新兴的FACE(Free-air CO2enrichm ent,开放式空气CO2浓度增高)研究手段,进而从土壤微生物区系和生物量、微生物呼吸和酶活性、菌根菌侵染和根瘤共生、土壤硝化和反硝化四个方面综述了大气CO2浓度升高影响土壤微生物的试验报道结果,最后结合新兴的土壤微生物分子生态学研究手段论述了该领域今后应关注开展的主要方向。     

稻田CO2排放对大气CO2浓度升高的响应

利用FACE (free-air carbon dioxide enrichment)平台,采用静态暗箱-气相色谱法,研究了大气CO2浓度升高对稻田土壤CO2通过土壤-大气(土气)和植被-大气(植气)界面排放的影响.在整个水稻生长季中,土气界面CO2排放通量与土壤表面水层深度指数负相关,且在中期烤田和收获前排水阶段出现较大值;而植气界面CO2排放通量与根系生物量的变化趋势基本一致.在低氮(N 125 kg/hm2)和常氮(N 250 kg/hm2)水平上,高浓度CO2(对照大气CO2浓度+200 μmol/mol)有提高水稻生物量、降低土气和植气界面CO2累积排放量的趋势.在水稻的拔节、抽穗和成熟期,较高的施氮量显著增加水稻地上部分生物量,促进植气界面CO2的排放.研究结果表明,未来大气CO2浓度升高的环境下,稻田生态系统有增加CO2的固定(增加水稻生物量),减少CO2的排放(土气和植气界面CO2的排放)的趋势,可能发挥着碳汇的作用.     

大气CO2浓度升高对稻麦轮作下土壤中AM真菌多样性的影响

本试验研究了大气CO2浓度升高对稻麦系统中AM真菌多样性的影响。结果表明,大气CO2浓度升高对土壤中AM真菌侵染能力没有显著影响;在常N施肥处理中,大气CO2浓度升高减少了土壤中AM真菌种类总数,但对AM真菌平均种类数没有显著影响,而在高N施肥处理中大气CO2浓度升高的影响不显著;N肥施用量增加降低了土壤中AM真菌的多样性。     

大气CO2浓度升高对土壤碳库的影响

土壤碳库是输入、输出土壤碳量的平衡:大气CO2浓度升高有可能通过生态系统中的各种生理过程来增加输入土壤的碳量,输入土壤碳量的增加使土壤成为一个潜在的碳汇,有可能缓解大气CO2浓度的升高;但另一方面输入土壤碳量的增加,为微生物的生长提供了能量,从而提高了微生物的活性,因此土壤呼吸增强,土壤碳输出增加.本文综述了大气CO2浓度升高对土壤碳输入、输出的影响以及目前研究中存在的争论,并提出有待进一步研究的领域和方向.     

大气CO_2浓度升高对陆地生态系统土壤固碳的可能影响

陆地生态系统碳循环是全球碳循环的重要组成部分,在全球碳收支中占主导地位。大气CO2浓度升高直接或间接地影响土壤碳的固定,碳在土壤的不同固定机理反映了碳的稳定性和周转过程,本文综述了影响碳固定的物理、化学和生物学机理,土壤碳固定的不同状态发生的主要机理不同;受大气CO2浓度升高影响时间长短不一,主要过程有所侧重,但三种机理相互影响。     

开放式空气CO2浓度升高对水稻/小麦轮作土壤速效钾的影响

采用FACE（Free air carbon dioxide enrichment）技术,研究了不同施N水平下,大气CO2浓度升高对水稻/小麦轮作土壤速效钾的影响。结果表明,相对于对照处理,在不同氮水平下CO2浓度升高使作物生物量增加,导致作物生长季对土壤钾的吸收增加,但并没有降低作物主要生长期土壤（0―5、5―15 cm土层）速效钾的含量;CO2浓度升高使土壤速效钾增加的幅度在作物根际达6.3%~22.3%,在行间达3.7%~11.2%,且土壤速效钾增加的幅度在小麦季大于水稻季。表明根系对土壤速效钾的影响很大,因此,短期内土壤钾含量不会成为限制因素而影响作物对高CO2浓度的响应,反而会增加土壤钾的有效性。但在土壤肥力较低的土壤上可能会产生消极影响。     

大气CO2浓度升高对绿豆生长发育与产量的影响

研究大气CO2浓度升高对绿豆影响,有助于人们了解未来气候变化后绿豆生产的变化,以提前采取必要的应对措施趋利避害.本研究利用FACE(Free Air CO2 Enrichment)系统在大田条件进行了绿豆生长发育及产量受CO2浓度升高影响的试验.结果表明:大气CO,浓度升高后,绿豆叶面积、株高、节数、茎粗增加;倒数第一...     

铜镉污染土壤上CO2升高对水稻光合特性的影响

采用盆栽试验,在开顶式气室(Open Top Chamber,OTC)中种植水稻,研究了南北方10个水稻品种(5种籼稻、5种粳稻)在CO2浓度升高下不同污染土壤上不同生育期的光合特性影响.研究结果表明:高CO2浓度和正常CO2浓度条件下,大部分的水稻品种最大光合速率在分蘖期,在成熟期最小;CO2浓度升高使水稻在不同生育期光合速率都增加,且在不同污染土壤上的水稻品种光合速率变化一致,5种粳稻光合速率增加幅度均在抽穗期最大,其增加幅度在高污染土壤和低污染土壤上分别为:64.14％～ 143.19％、73.58％ ～132.3％,5种籼稻光合速率增加幅度均在成熟期最大,其增加幅度在高污染土壤和低污染土壤上分别为:104.33％ ～ 256.00％、100.99％～254.81％.CO2浓度的升高对光合速率、胞间CO2浓度的影响表现出趋势一致性变化,且都达到了显著水平,气孔导度与蒸腾速率在CO2浓度升高的情况下在各个生育期的变化趋势不一致,且都没有达到显著水平.     

土壤酶活性对温度和CO2浓度升高的响应研究

作为土壤生态系统中的重要组成部分及生物元素循环的积极参与者,土壤酶在陆地生态系统地下生态过程中扮演着十分重要的角色。升高温度和(或)大气CO2浓度可能直接或者间接影响其活性。但目前对温度和(或)大气CO2浓度升高对土壤酶的影响机理、过程及土壤酶对其的响应机制研究相对薄弱。本文初步总结了国内外关于温度和(或)大气CO2浓度升高对土壤酶活性影响研究的现状,并指出了目前研究中存在的不足。     

Long-term (42 years) effect of thinning on soil CO2 emission in a mixed broadleaved-Korean pine (Pinus koraiensis) forest in Northeast China

Thinning is an important forest management practice that has great potential to influence regional soil carbon storage and dynamics.The present study measured soil respiration(RS,the efflux of CO2 emitted)and its two components(heterotrophic(RH)and autotrophic(RA)respiration)from soil 42 years after thinning in comparison to un-thinning(control).Autotrophic respiration was significantly greater in the thinning plot,approximately 44%higher compared to the control,while both RSand RHwere slightly,but not significantly,higher in the thinning plot.Higher fine root biomass might have contributed to the higher RAin the thinning plot.Both RSand RHshowed clear soil temperature-dependent seasonal patterns,whereas RAwas less responsive to changes in temperature,especially within one specific season.The annual and season-specific temperature sensitivities of RSand RHwere lower in the thinning plot,specifically during the mid-growing season.Furthermore,variations in the season-specific temperature sensitivity of RSand RHwere less intense in the thinning plot.We conclude that forest thinning can reduce the temperature sensitivity of RSand RHduring the mid-growing season and increase soil CO2 emission in the long term.     

长期施肥下红壤旱地土壤CO2排放及碳平衡特征

在国家肥力网红壤旱地长期定位试验地上,采用静态箱/气相色谱法测定土壤CO2排放速率,同时利用根去除法区分根系对土壤呼吸的贡献,通过计算净生态系统生产力（NEP）,判断长期不同施肥下红壤旱地农田碳汇强度。结果表明,小麦、玉米生长季各处理的土壤和土体呼吸速率随着作物生长、温度升高均呈现明显的季节变化规律;玉米生长季土壤和土体累积呼吸量大于小麦生长季,小麦、玉米生长季均以NPKM处理土壤和土体呼吸累积呼吸量最大,且显著高于其它处理（P0.05）,NP和NPK处理次之,CK和NK处理最小（P0.05）;小麦、玉米生长季各处理根际呼吸占土壤呼吸的比例分别为7.6 %～17.4 %、4.7%～16.6 %,均以NPKM处理根际呼吸贡献率最大;小麦季NPKM处理、玉米季CK和NPKM处理的NEP值为负,是大气CO2的汇,且NPKM处理的净初级生产力与土壤呼吸的比值（NPP/Rs）最大,其它处理NEP值均为正,是大气CO2的源。有机无机肥配施（NPKM）相比其它处理具有较强的碳汇功能,是红壤旱地比较合理的施肥措施。     

土壤肥力与大气CO2浓度的升高对颤杨Populus tremuloides叶片、茎杆和根的暗呼吸的影响

An open-top chamber experiment was conducted at the University of Michigan Biological Station near Pellston,Michigan,USA,to study the effects of soil fertility and CO2 on leaf,sdtem and root dark respiration (Rd) of Populus tremuloides.Overall,area-based daytime leaf Rd(Rda) was significantly greater at elevated than at ambient CO2 in high-fertility soil,but not in low-fertility soil.Mass-based leaf Rd(Rdm) was overall greater for high-than for low-fertility soil grown trees at elevated,but not at ambient CO2 .Nighttime leaf Rda and Rdm were unaffected by soil fertility or CO2,nor was stem Rda ,which ranged from 1.0 to 1.4μmol m^-2s^-1 in the spring and 3.5 to 4.5μmol m^-2s^-1 in the summer.Root Rda was significantly higher in high-than in low-fertiliy soil,but was unaffected by CO2.Since biomass production of P.tremuloides will be significantly greater at elevated CO2 while specific Rd will either increase or remain unchanged,we predict that carbon loss to the atmosphere through respiration from this ecologically important species would increase at higher CO2.Soil fertility would also interact with elevated CO2 in affecting the carbon flow in the plant-soil-air system.     

间伐对杉木林土壤CO2通量的影响

Forest management is expected to influence soil CO₂ efflux (FCO₂) as a result of changes in microenvironmental conditions, soil microclimate, and root dynamics. Soil FCO₂ rate was measured during the growing season of 2006 in both thinning and non-thinning locations within stands ranging from 0 to 8 years after the most recent thinning in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in Huitong Ecosystem Research Station, Hunan, China. Soil temperature and moisture were also measured to examine relationships between FCO₂ and soil properties. Forest thinning resulted in huge changes in FCO₂ that varied with time since cutting. Immediately following harvest (year 0) FCO₂ in thinning area increased by about 30%, declined to 20%-27% below pre-cutting levels during years 4-6, and recovered to pre-cutting levels at 8 years post-cutting. A similar temporal pattern, but with smaller changes, was found in non-thinning locations. The initial increase in FCO₂ could be attributed to a combination of root decay, soil disturbance, and increased soil temperature in gaps, while the subsequent decrease and recovery to the death and gradual regrowth of active roots. Strong effects of soil temperature and soil water content on FCO₂ were found. Forest thinning mainly influenced FCO₂ through changes in tree root respiration, and the net result was a decrease in integrated FCO₂ flux through the entire felling cycle.     

Seasonality of soil biological properties in a poplar plantation growing under elevated atmospheric CO2

Microorganisms are the regulators of decomposition processes occurring in soil, they also constitute a labile fraction of potentially available N. Microbial mineralization and nutrient cycling could be affected through altered plant inputs at elevated CO_2. An understanding of microbial biomass and microbial activity in response to belowground processes induced by elevated CO₂ is thus crucial in order to predict the long-term response of ecosystems to climatic changes. Microbial biomass, microbial respiration, inorganic N, extractable P and six enzymatic activities related to C, N, P and S cycling (β-glucosidase, cellulase, chitinase, protease, acid phosphatase and arylsulphatase) were investigated in soils of a poplar plantation exposed to elevated CO_2. Clones of Populus alba, Populus nigra and Populus x euramericana were grown in six 314 m² plots treated either with atmospheric (control) or enriched (550 μmol mol⁻¹ CO₂) CO₂ concentration with FACE technology (free-air CO₂ enrichment). Chemical and biochemical parameters were monitored throughout a year in soil samples collected at five sampling dates starting from Autumn 2000 to Autumn 2001.

The aim of the present work was: (1) to determine if CO₂ enrichment induces modifications to soil microbial pool size and metabolism, (2) to test how the seasonal fluctuations of soil biochemical properties and CO₂ level interact, (3) to evaluate if microbial nutrient acquisition activity is changed under elevated CO₂.

CO₂ enrichment significantly affected soil nutrient content and three enzyme activities: acid phosphatase, chitinase and arylsulphatase, indicators of nutrient acquisition activity. Microbial biomass increased by a 16% under elevated CO₂. All soil biochemical properties were significantly affected by the temporal variability and the interaction between time and CO₂ level significantly influenced β-glucosidase activity and microbial respiration. Data on arylsulphatase and chitinase activity suggest a possible shift of microbial population in favour of fungi induced by the FACE treatment.     

大气CO2浓度的升高、施氮及土壤水分对春小麦干物质积累和氮吸收的影响

Spring wheat (Thiticum aestivum L.cv.Dingxi No.8654) was treated with two concentrations of atmospheric CO2 (350 and 700 μmol mol^-1),two levels of soil moisture (well-watered and drought) and five rates of nitrogen fertilizer(0,50,100,150,and 200 mg kg^-1 soil) to study the atmospheric CO2 concentration effect on dry matter accumulation and N uptake of spring wheat.The effects of CO2 enrichment of the shoot and total mass depended largely on soil nitrogen level,and the shoot and total mass increased significantly in the moderate to high N treatments but did not increase significantly in the low N treatment.Enriched CO2 concentration did not increase more shoot and total mass in the drought treatment than in the well-watered treatment.Thus,elevated CO2 did not ameliorate the depressive effects of drought and nitrogen stress.In addition,root mass decreased slightly and root/shoot ratio decreased significantly due to CO2 enrichment in no N treatment under well-watered condition.Enriched CO2 decreased shoot N content and shoot and total N uptake;but it reduced root N content and uptake slightly.Shoot critical N concentration was lower for spring wheat grown at 700 μmol mol^-1 CO2 than at 350μmol mol^-1 CO2 in both well-watered and drought treatments. The critical N concentrations were 16 and 19 g kg^-1 for the well-watered treatment and drought treatment at elevated CO2 and 21 and 26 g kg^-1 at ambient CO2,respectively. The reductions in the movement of nutrients to the plant roots through mass flow due to the enhancement in WUE (water use efficiency) and the increase in N use efficiency at elevated CO2 could elucidate the reduction of shoot and root N concentrations.     

长期施肥对冬小麦/夏玉米轮作下土壤呼吸及其组分的影响

为阐明施肥对农田土壤呼吸的影响,于2002年6月至2003年6月在河南封丘潮土上进行的长期试验地上测定了玉米/冬小麦轮作系统下的土壤呼吸,分析了土壤呼吸与土壤水分和温度的关系,并利用统计分析方法研究了土壤呼吸各组分的贡献。土壤呼吸变化与作物生长发育规律一致,施肥通过影响作物的生长发育而对土壤呼吸产生影响。不同作物生长期,根际呼吸、土壤原有机质以及前作根茬和有机肥中碳对土壤呼吸的贡献不同。玉米期土壤有机质、根际呼吸、前作根茬和有机肥中的碳对土壤呼吸的平均贡献率分别为70.19%、19.43%和10.37%;而小麦生长期则分别为23.75%、62.26%和14.11%。由于不同施肥处理的作物生长量、土壤有机质含量以及前作根茬和有机肥施入而进入的有机碳量不同,造成土壤呼吸个体上存在着较大差异。土壤有机质的消耗主要发生在玉米生长阶段。     

在FACE条件下作物轮作过程中碳的流通

Mostly based on assumptions derived from controlled-environment studies, predicted future atmospheric CO2 concentrations [CO2] are expected to have considerable impacts on carbon （C） turnover in agro-ecosystems. In order to allow the in situ examination of C-transformations in the plant-soil system of arable crop rotations under future [002], a free air carbon dioxide enrichment （FACE） experiment （550 μmol mol^-1 CO2） was started at Braunschweig, Germany in 1999. The crop rotation under investigation comprised winter barley, a cover crop （ryegrass）, sugar beets and winter wheat. Assessments of CO2 effects included the determination of above- and belowground biomass production, measurements of canopy CO2- and H2O- fluxes, soil microbial biomass and in situ soil respiration. The results obtained during the 1st crop rotation cycle （3 years） showed that for the selected crops elevated [CO2] entailed significant positive effects （P 〈 0.05） on aboveground （6%-14% stimulation） and belowground biomass production （up to 90% stimulation）, while canopy evapotranspiration was reduced. This resulted in increased soil water content. Also, depending on crop type and season, high CO2 stimulated in situ soil respiration （up to 30%）, while soil microbial biomass did not show significant respouses to elevated [CO2] during the first rotation cycle.     

大气CO2浓度升高对温带森林土壤微生物活性的影响

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide (CO2) as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 (2006) and 9 (2007) of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon (C), nitrogen (N) and phosphorus (P) cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly (P < 0.01) increased in the August 2006 samples that received the elevated CO2 treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly (P < 0.04) decreased by elevated CO2 treatments in the August 2006 and June 2007 (P < 0.09) samples. β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.