内蒙古锡林河流域羊草草原净初级生产力及其对全球气候变化的响应

利用CENTURY模型对内蒙古锡林河流域羊草草原在未来气候变化以及大气CO₂浓度增高条件下的年地上净初级生产力(annual aboveground net primary productivity,ANPP)动态进行了模拟研究.结果表明：CENTURY模型可以较好地预测ANPP的变化.进一步的情景模拟发现,虽然全球气候变化所引起的温度和降水改变、以及大气CO₂浓度升高都会影响ANPP,但降水是关键的影响因子.多个全球气候模型(GCM) 预测该地区未来降水量会减少,故可能导致其ANPP降低,但在以下气候变化情景下研究区ANPP可能会升高：1)CO₂浓度倍增,温度升高2 ℃,降水保持不变或增加10%～20%;2)CO₂浓度保持不变,温度升高2 ℃,降水增加20%.气候变化将对内蒙古锡林河流域羊草草原产生显著影响.     

基于Biome-BGC模型的北方杨树人工林碳水通量对气候变化的响应研究

研究中国北方杨树人工林碳水通量对气候变化的响应,对于制定合理的经营管理措施以应对区域的气候变化具有重要意义。基于对杨树人工林碳水通量的连续监测数据和对Biome-BGC模型参数的校准,模拟分析杨树人工林碳水通量及水分利用效率(WUE)对气候变化(气温上升、降水变化和大气CO_2浓度上升)的响应规律。结果表明,Biome-BGC模型校准后显著提升了其对杨树人工林碳水通量的模拟精度,对GPP、ET模拟结果的Nash-Sutcliffe效率系数(NS)分别为0.69和0.63,各自提高了64.3%和80%,均方根误差(RMSE)则分别降低至1.94 g C m~(-2) d~(-1)和0.88 mm/d,分别下降了26.5%和25.4%。在未来气候变化情景中,单独的气温上升、降水增加和大气CO_2浓度上升分别造成GPP的降低、升高和升高,其中GPP对大气CO_2浓度上升的响应程度(28%—44%)远高于对气温上升(1%—5%)和降水变化(3%—10%)的,ET则主要受降水的影响,响应程度在5%—14%之间。GPP和ET对气候变化的响应则受不同水平的气温上升、降水变化和大气CO_2浓度上升三者综合作用的影响。基于GPP和ET对气候变化的响应,WUE随气温上升、降水增加表现为降低趋势,随降水减少和大气CO_2浓度升高则呈升高趋势;其对未来气候中大气CO_2浓度升高的响应程度为27.7%—43.6%,远高于对气温上升(1.2%—5.8%)和降水变化(1.2%—3.5%)的,说明未来气候变化中大气CO_2浓度上升是促进杨树生长的主要因素;其中相对于当前WUE(2.8 g C/kg H_2O),C2T2P1和C0T3P0情景下WUE的升高和降低幅度最大,分别为45.4%和5.8%。     

二氧化碳和臭氧浓度升高对春小麦生长及次生代谢的影响

通过开顶式气室(OTCs)研究了OTC对照（自然CO₂浓度约342 μmol·mol^-1,O₃浓度约30 nmol·mol^-1）、高浓度CO₂（550 μmol·mol^-1）、高浓度O₃（浓度为80 nmol·mol^-1）及其交互作用（CO₂ 550 μmol ·mol^-1,O₃ 80 nmol·mol^-1）对春小麦不同发育时期生物量、总酚量、黄酮含量及成熟期产量性状的影响.结果表明：CO₂浓度增加条件下,春小麦生物量和产量性状都显著高于OTC对照（P<0.05）;而O₃浓度升高条件下,小麦生物量降低,株高、穗长、穗粒质量及千粒重也显著低于对照;CO₂和O₃交互作用下各项指标处于二者之间.说明CO₂可以缓解O₃对小麦的负效应,而O₃对CO₂的正效应具有削弱作用,但二者的作用并非简单的叠加.CO₂、O₃浓度增加及其交互作用显著增加了春小麦叶片中的总酚含量,其中两者交互作用的效应更大,但在小麦生长后期,总酚含量增加量比对照有所降低.在小麦生长前期,各处理总黄酮含量均低于对照;而在成熟期,各处理都显著高于对照.     

供氮和增温对倍增二氧化碳浓度下荫香叶片光合作用的影响

供给0～0.6 mg N的盆栽荫香(Cinnamomum burmannii)幼树分别生长在倍增CO ₂(+CO₂,731 μmol·mol^-1)和正常空气CO ₂浓度(CO ₂,365 μmol·mol^-1)的生长箱内,昼夜温度分别为25/23 ℃和32/25 ℃,自然光照下生长30 d.以生长在CO₂和25/23 ℃下的植株为对照研究增温和氮对+CO₂叶片光合作用的影响.结果表明,在+CO₂和25/23 ℃下无氮和氮处理植株的平均光合速率(Pnsat)较+CO₂和32/25 ℃下的叶片高5.1%,温度增高降低叶片Pnsat;而Pnsat随供氮而增高.在+CO₂条件下,生长在32/25 ℃下的叶片Rubisco最大羧化速率(Vcmax)和最大电子传递速率(Jmax)较25/23 ℃下的低(P＜0.05),温度增高降低+CO₂下叶片的Vcmax和Jmax在+CO2下叶片光合呼吸速率(Rp)较低,生长温度增高提升Rp.在CO₂下生长温度从25/23 ℃增至32/25 ℃,叶片的Rubisco含量(NR)和Rubisco活化中心浓度(M)降低,而供氮能增高NR和M.供氮能减缓温度增高对倍增CO₂下荫香叶片光合作用的限制.     

大气二氧化碳浓度变化对禾谷缢管蚜种群动态的影响

利用开顶式熏气室研究了大气CO₂浓度和土壤水分对禾谷缢管蚜Rhopalosiphum padi (L.)种群动态的影响,并分析了禾谷缢管蚜密度与被处理小麦叶片化学成分的关系。结果表明：（1）禾谷缢管蚜种群密度随CO₂浓度升高而持续增大并与土壤水分密切相关,各CO₂浓度下均以60%田间持水量时的密度最大;（2）CO₂和土壤水分对小麦叶片化学成分有明显的影响,麦叶水分、可溶性蛋白质、可溶性糖、淀粉含量随CO₂浓度和土壤水分含量上升而增加,纤维素含量随CO₂浓度上升而增加、随土壤水分含量上升而降低,单宁、丁布（DIMBOA）含量在CO₂浓度为550 μl/L时最高,但单宁含量随土壤水分上升而增加,丁布含量在60%田间持水量时最低;（3）禾谷缢管蚜密度与叶片水分、可溶性蛋白质、可溶性糖、淀粉含量呈正相关,与丁布、单宁含量呈负相关。结论：在未来的气候条件下,随着CO₂浓度升高禾谷缢管蚜种群可能会持续增长,这种增长在半干旱区更加突出。禾谷缢管蚜种群增长的原因之一是大气CO₂和土壤水分条件改变了植物的化学成分构成。     

大气二氧化碳浓度变化对禾谷缢管蚜种群动态的影响

利用开顶式熏气室研究了大气CO₂浓度和土壤水分对禾谷缢管蚜Rhopalosiphum padi (L.)种群动态的影响,并分析了禾谷缢管蚜密度与被处理小麦叶片化学成分的关系。结果表明：（1）禾谷缢管蚜种群密度随CO₂浓度升高而持续增大并与土壤水分密切相关,各CO₂浓度下均以60%田间持水量时的密度最大;（2）CO₂和土壤水分对小麦叶片化学成分有明显的影响,麦叶水分、可溶性蛋白质、可溶性糖、淀粉含量随CO₂浓度和土壤水分含量上升而增加,纤维素含量随CO₂浓度上升而增加、随土壤水分含量上升而降低,单宁、丁布（DIMBOA）含量在CO₂浓度为550 μl/L时最高,但单宁含量随土壤水分上升而增加,丁布含量在60%田间持水量时最低;（3）禾谷缢管蚜密度与叶片水分、可溶性蛋白质、可溶性糖、淀粉含量呈正相关,与丁布、单宁含量呈负相关。结论：在未来的气候条件下,随着CO₂浓度升高禾谷缢管蚜种群可能会持续增长,这种增长在半干旱区更加突出。禾谷缢管蚜种群增长的原因之一是大气CO₂和土壤水分条件改变了植物的化学成分构成。     

在高CO2浓度下生长的小麦对棉铃虫生长发育和繁殖的影响

通过室内饲养实验研究了在高CO₂浓度（738.8±25.7μL/L）中生长的小麦对棉铃虫 Helicoverpa armigera (Hübner)生长发育,繁殖以及营养效应的影响。结果表明： （1）取食高CO₂浓度大气中生长的麦粒的棉铃虫对食料的取食量和粪便排泄量增加,与对照相比,取食量和粪便排泄量分别增加46.3%（P<0.05）和37.8%;（2）大气CO₂浓度增加影响了麦粒中的营养成分的含量,其中,可溶性蛋白、游离氨基酸、葡萄糖和总糖的含量及碳氮比(C∶N)都显著增加,果糖和粗蛋白的含量都显著降低;（3）大气 CO₂浓度升高所导致的麦粒营养成分的变化影响了棉铃虫幼虫的食物利用效率,与对照组相比,棉铃虫幼虫对食物的毛转化率和净转化率分别降低27.2%和25.4%,对食物的相对取食率则显著提高58.8%（P < 00.1）。据此推测,未来高CO₂浓度的大气环境会降低春小麦的营养价值,从而影响棉铃虫的生长发育,加重其对小麦的危害。     

脱落酸对UV-C胁迫下小麦幼苗光合特性及抗氧化酶活性的影响

研究了UV-C辐射下短期和长期脱落酸（ABA）处理对小麦幼苗CO₂同化作用、羧化效率、光合CO₂响应以及抗氧化酶活性等的影响.结果表明,在无UV-C辐射情况下,短期和长期ABA处理能提高光合速率,比对照增加14.69%和20.46%,降低气孔导度,比对照降低14.74%和17.31%,但对胞间CO₂浓度和羧化效率影响不大.当受到UV-C辐射时,光合速率、羧化效率、气孔导度和胞间CO₂浓度逐渐降低.长期ABA处理变化最小,其次为ABA短期处理,对照降低最大.ABA处理能够提高小麦光合对CO₂的响应,UV-C辐射抑制光合对CO₂的响应.ABA处理能够提高小麦抗氧化酶（CAT、SOD、POD）活性而降低MDA含量.在UV-C辐射下,CAT活性先升高随后降低,在辐射处理1 h时活性达最大值,ABA处理的SOD和POD活性先升高后降低,且ABA长期处理比短期处理增加明显,对照则逐渐降低.ABA处理可能通过提高小麦CO₂同化作用和抗氧化酶活性增强对UV-C胁迫的抗性,且ABA长期处理比短期处理效果更明显.     

增强UV-C辐射作用下小麦和豌豆幼苗光合响应及其相对抗性

以小麦和豌豆为材料,研究了UV-C辐射(波长<280 nm)对叶片光合特性及抗氧化酶活性的影响.结果表明: UV-C辐射增强,可使豌豆叶片光合速率减弱,气孔导度、胞间CO₂浓度、蒸腾速率和羧化效率明显降低,而对小麦叶片上述各项指标的影响则是先增加、后降低;在UV-C辐射下,豌豆的CO₂补偿点逐渐升高,而小麦的CO₂补偿点先降低、后升高.UV-C辐射除了使豌豆的POD活性和小麦的SOD活性逐渐降低外,其他抗氧化酶活性则呈先升高、后降低的变化趋势.小麦对短时间UV-C辐射的抗性比豌豆强,但随着UV-C辐射时间的延长,小麦和豌豆的抗氧化酶活性均降低,光合作用减弱.     

热带季节雨林冠层树种绒毛番龙眼的光合生理生态特性

采用Li-6400便携式光合作用测定仪,对西双版纳热带季节雨林冠层树种绒毛番龙眼成树树冠上、中、下3层叶片进行了测定,分析西双版纳热带季节雨林冠层树木的光合作用.结果表明,绒毛番龙眼成树具有喜光的光合特性,光饱和点较高(1 000～1 500 μmol·m^-2·s^-1),而光补偿点较低(7.7～15.3 μmol·m^-2·s^-1),对光环境有较强的适应和调节能力,光合有效辐射是影响绒毛番龙眼光合日进程的关键因子;12月,叶片处于成熟期,生长良好,光合能力较强,树冠上层净光合速率（P_n）日变化为单峰型,最大净光合速率（A_max）约为8.9 μmol CO₂·m^-2·s^-1;4月处于新老树叶更替期,光合能力下降,树冠上层P_n日变化为双峰型,中午出现“午休”现象,树冠上层A_max约为4.3 μmol CO₂·m^-2·s^-1;7月上、中层叶片P_n为单峰型,下层出现“午休”.如人为使CO₂浓度在短期内迅速升高,则绒毛番龙眼的P_n会增加,而气孔导度和蒸腾速率降低;CO₂浓度从400 μmol·mol^-1升高到800 μmol·mol^-1时,干季水分利用效率（WUE）提高约50%～100％,雨季WUE较低.     

Temperate Grassland Responses to Climate Change: an Analysis using the Hurley Pasture Model

The Hurley Pasture Model is process-based and couples the carbon,nitrogen and water cycles in the soil-grass-animal system. Itwas used to examine the responses of grasslands in southern,lowland and northern, upland climates in Britain. Short-termresponse to step-wise increases in CO₂concentration (350 to700 µmol mol^-1) and temperature (5 °C) were contrastedwith long-term equilibrium (the term ‘equilibrium’is equivalent to ‘steady state’ throughout thispaper) responses and with responses to gradually increasing[CO₂] and temperature. Equilibrium responses to a range of climatevariables were also examined. Three conclusions were drawn regarding the interpretation ofexperiments: (1) initial ecosystem responses to step-wise changescan be different in both magnitude and sign to equilibrium responses,and this can continue for many years; (2) grazing can drasticallyalter the magnitude and sign of the response of grasslands toclimate change, especially rising temperatures; and (3) effectsof changes in climate, especially temperature and rainfall,are likely to be highly site-specific. It was concluded thatexperiments should try to lessen uncertainty about processeswithin models rather than try to predict ecosystem responsesdirectly. Three conclusions were also drawn about the operation of grasslandsas carbon sinks: (1) increasing [CO₂] alone will produce a carbonsink, as long as it continues to accelerate photosynthesis andincrease net primary productivity; (2) by contrast, increasingtemperatures alone are likely to produce a carbon source, becausesoil respiration is accelerated more than net primary productivity,even when assuming the same temperature function for most soiland plant biochemical processes; and (3) the net effect of projectedincreases in [CO₂] and temperature is likely to be a carbonsink of 5–15 g C m^-2yr^-1in humid, temperate grasslandsfor several decades, which is consistent with the magnitudeof the hypothesized current global terrestrial carbon sink. Grassland; climate change; carbon dioxide; temperature; ecosystem; model; carbon sink     

Initial effects of experimental warming on above- and belowground components of net ecosystem CO2 exchange in arctic tundra

The Arctic contains extensive soil carbon reserves that could provide a substantial positive feedback to atmospheric CO₂ concentrations and global warming. Evaluation of this hypothesis requires a mechanistic understanding of the in situ responses of individual components of tundra net ecosystem CO₂ exchange (NEE) to warming. In this study, we measured NEE, total ecosystem respiration and respiration from below ground in experimentally warmed plots within Alaskan acidic tussock tundra. Soil warming of 2-4°C during a single growing season caused strong increases in total ecosystem respiration and belowground respiration from moss-dominated inter-tussock areas, and similar trends from sedge-dominated tussocks. Consequently, the overall effect of the manipulation was to substantially enhance net ecosystem carbon loss during mid-summer. Components of vascular plant biomass were closely correlated with total ecosystem respiration and belowground respiration in control plots of both microsites, but not in warmed plots. By contrast, in the warmed inter-tussock areas, belowground respiration was most closely correlated with organic-layer depth. Warming in tussock areas was associated with increased leaf nutrient pools, indicating enhanced rates of soil nutrient mineralisation. Together, these results suggest that warming enhanced net ecosystem CO₂ efflux primarily by stimulating decomposition of soil organic matter, rather than by increasing plant-associated respiration. Our short-term experiment provides field evidence to support previous growth chamber and modelling studies indicating that arctic soil C reserves are relatively sensitive to warming and could supply an initial positive feedback to rising atmospheric CO₂ concentrations/changing climate.     

Elevated CO2 does not stimulate carbon sink in a semi‐arid grassland

Elevated CO₂ is widely accepted to enhance terrestrial carbon sink, especially in arid and semi‐arid regions. However, great uncertainties exist for the CO₂ fertilisation effects, particularly when its interactions with other global change factors are considered. A four‐factor (CO₂, temperature, precipitation and nitrogen) experiment revealed that elevated CO₂ did not affect either gross ecosystem productivity or ecosystem respiration, and consequently resulted in no changes of net ecosystem productivity in a semi‐arid grassland despite whether temperature, precipitation and nitrogen were elevated or not. The observations could be primarily attributable to the offset of ecosystem carbon uptake by enhanced soil carbon release under CO₂ enrichment. Our findings indicate that arid and semi‐arid ecosystems may not be sensitive to CO₂ enrichment as previously expected and highlight the urgent need to incorporate this mechanism into most IPCC carbon‐cycle models for convincing projection of terrestrial carbon sink and its feedback to climate change.     

CO2浓度增加和不同氮肥水平对冬小麦根系呼吸及生物量的影响

 依托FACE(Free-air CO₂ enrichment)研究平台, 利用特制分根集气生长箱, 采用静态箱-GC(Gas chromatography)法, 连续两年研究 了大气CO₂浓度升高和不同氮肥水平对冬小麦拔节期、孕穗抽穗期和灌浆末期的根系呼吸及生物量的影响。两季结果表明, CO₂浓度升高和高氮 肥量均不同程度地增加了3个阶段的地上部和地下部的生物量, 这有利于增加根茬的还田量; CO₂浓度升高对冬小麦不同生长阶段的根系呼吸影 响不同, 在拔节期影响较小;孕穗抽穗期显著增加了根系呼吸, 2004~2005季分别增加33.8%(148.1 mg N&;#8226;kg^-1 干土, HN)和43.9%(88.9 mg N&;#8226;kg^-1 干土, LN), 2005~2006季分别为23.8%(HN)和28.9%(LN); 而灌浆末期显著降低了根系呼吸, 2004~2005季分别降低31.4%(HN)和23.3% (LN), 2005~2006季分别为25.1%(HN)和18.5%(LN); 高施氮量比低施氮量促进了根系呼吸; 随着作物生长根系呼吸与地下生物量呈显著线性负相 关, 高CO₂环境中的R²变小,表明随着作物生长发育高CO₂浓度降低了作物根系呼吸与地下部生物量积累间的相关性.     

Sensitivity analysis of ecosystem CO<Subscript>2</Subscript> exchange to climate change in High Arctic tundra using an ecological process-based model

Arctic terrestrial ecosystems are extremely vulnerable to climate change. A major concern is how the carbon balance of these ecosystems will respond to climate change. In this study, we constructed a simple ecological process-based model to assess how the carbon balance will be altered by ongoing climate change in High Arctic tundra ecosystems using in situ observations of carbon cycle processes. In particular, we simulated stand-level photosynthesis, root respiration, heterotrophic respiration, and hence net ecosystem production (NEP) of a plant community dominated by vascular plants and mosses. Analyses were carried out for current and future temperature and precipitation conditions. Our results showed that the tundra ecosystem was a CO₂ sink (NEP of 2.3–18.9 gC m^?2 growing season^?1) under present temperature conditions. Under rising temperature (2–6 °C), carbon gain is significantly reduced, but a few days’ extension of the foliage period caused by their higher temperatures compensated for the negative effect of temperature on NEP. Precipitation is the major environmental factor driving photosynthetic productivity of mosses, but it had a minor influence on community-level NEP. However, NEP decreased by a maximum 15.3 gC m^?2 growing season^?1 under a 30-day prolongation of the moss-growing season, suggesting that growing season extension had a negative effect on ecosystem carbon gain, because of poorer light conditions in autumn. Because the growing season creates a weak CO₂ sink at present, lengthening of the snow-free season coupled with rising temperature could seriously affect the future carbon balance of this Arctic tundra ecosystem.     

Fine-root biomass and fluxes of soil carbon in young stands of paper birch and trembling aspen as affected by elevated atmospheric CO2 and tropospheric O3

Rising atmospheric CO₂ may stimulate future forest productivity, possibly increasing carbon storage in terrestrial ecosystems, but how tropospheric ozone will modify this response is unknown. Because of the importance of fine roots to the belowground C cycle, we monitored fine-root biomass and associated C fluxes in regenerating stands of trembling aspen, and mixed stands of trembling aspen and paper birch at FACTS-II, the Aspen FACE project in Rhinelander, Wisconsin. Free-air CO₂ enrichment (FACE) was used to elevate concentrations of CO₂ (average enrichment concentration 535 µl l^-1) and O₃ (53 nl l^-1) in developing forest stands in 1998 and 1999. Soil respiration, soil pCO₂, and dissolved organic carbon in soil solution (DOC) were monitored biweekly. Soil respiration was measured with a portable infrared gas analyzer. Soil pCO₂ and DOC samples were collected from soil gas wells and tension lysimeters, respectively, at depths of 15, 30, and 125 cm. Fine-root biomass averaged 263 g m^-2 in control plots and increased 96% under elevated CO₂. The increased root biomass was accompanied by a 39% increase in soil respiration and a 27% increase in soil pCO₂. Both soil respiration and pCO₂ exhibited a strong seasonal signal, which was positively correlated with soil temperature. DOC concentrations in soil solution averaged ~12 mg l^-1 in surface horizons, declined with depth, and were little affected by the treatments. A simplified belowground C budget for the site indicated that native soil organic matter still dominated the system, and that soil respiration was by far the largest flux. Ozone decreased the above responses to elevated CO₂, but effects were rarely statistically significant. We conclude that regenerating stands of northern hardwoods have the potential for substantially greater C input to soil due to greater fine-root production under elevated CO₂. Greater fine-root biomass will be accompanied by greater soil C efflux as soil respiration, but leaching losses of C will probably be unaffected.     

全球变化下植物的碳氮关系及其环境调节研究进展——从分子到生态系统

在全球变化条件下,温度的升高和降水格局的变化,导致淡水资源更加匮乏。环境因子胁迫,如干旱和高温等,它们单独或联合的作用将导致作物大幅度减产,引发自然生态系统退化。植物的碳氮代谢及其分配相互联系、不可分割,其生物过程及外界环境调节共同决定着植物的净生产力和营养水平。该文试图从分子、组织、器官、个体和生态系统等层面上,就植物的碳氮关系及其环境调节(温度、水分和CO₂浓度等)进行综述,并提出了进一步展开相关研究应重点关注的几个方面。     

Warming prevents the elevated CO2-induced reduction in available soil nitrogen in a temperate, perennial grassland

Rising atmospheric carbon dioxide concentration ([CO₂]) has the potential to stimulate ecosystem productivity and sink strength, reducing the effects of carbon (C) emissions on climate. In terrestrial ecosystems, increasing [CO₂] can reduce soil nitrogen (N) availability to plants, preventing the stimulation of ecosystem C assimilation; a process known as progressive N limitation. Using ion exchange membranes to assess the availability of dissolved organic N, ammonium and nitrate, we found that CO₂ enrichment in an Australian, temperate, perennial grassland did not increase plant productivity, but did reduce soil N availability, mostly by reducing nitrate availability. Importantly, the addition of 2 °C warming prevented this effect while warming without CO₂ enrichment did not significantly affect N availability. These findings indicate that warming could play an important role in the impact of [CO₂] on ecosystem N cycling, potentially overturning CO₂‐induced effects in some ecosystems.     

Effects of Elevated CO2 and Nitrogen Deposition on Ecosystem Carbon Fluxes on the Sanjiang Plain Wetland in Northeast China

Background

Increasing atmospheric CO₂ and nitrogen (N) deposition across the globe may affect ecosystem CO₂ exchanges and ecosystem carbon cycles. Additionally, it remains unknown how increased N deposition and N addition will alter the effects of elevated CO₂ on wetland ecosystem carbon fluxes.

Methodology/Principal Findings

Beginning in 2010, a paired, nested manipulative experimental design was used in a temperate wetland of northeastern China. The primary factor was elevated CO₂, accomplished using Open Top Chambers, and N supplied as NH₄NO₃ was the secondary factor. Gross primary productivity (GPP) was higher than ecosystem respiration (ER), leading to net carbon uptake (measured by net ecosystem CO₂ exchange, or NEE) in all four treatments over the growing season. However, their magnitude had interannual variations, which coincided with air temperature in the early growing season, with the soil temperature and with the vegetation cover. Elevated CO₂ significantly enhanced GPP and ER but overall reduced NEE because the stimulation caused by the elevated CO₂ had a greater impact on ER than on GPP. The addition of N stimulated ecosystem C fluxes in both years and ameliorated the negative impact of elevated CO₂ on NEE.

Conclusion/Significance

In this ecosystem, future elevated CO₂ may favor carbon sequestration when coupled with increasing nitrogen deposition.     

二氧化碳储存通量对森林生态系统碳收支的影响

涡度相关系统观测高度以下的CO₂储存通量对准确评价森林生态系统与大气间净CO₂交换量（NEE）有着重要的影响.本研究以长白山阔叶红松林为研究对象,利用2003年的涡度相关观测数据以及CO₂浓度廓线数据,分析了CO₂储存通量的变化规律及其对碳收支过程的影响.结果表明：涡度相关观测高度以下的CO₂储存通量具有典型的日变化特征,其最大变化量出现在大气稳定与不稳定层结转换期.利用涡度相关系统观测的单点CO₂浓度变化方法与利用CO₂浓度廓线方法计算的CO₂储存通量差异不显著.忽略CO₂储存通量,在半小时尺度上会造成对夜间和白天的NEE分别低估25%和19%,在日和年尺度上,会对NEE低估10%和25%;忽略CO₂储存通量,会低估Michaelis-Menten光响应方程及Lloyd-Taylor呼吸方程的参数,并且对表观初始量子效率α和参考呼吸R_ref的低估最大;忽略CO₂储存通量,在半小时、日及年尺度上,均会对总光合作用（GPP）和生态系统呼吸（R_e）低估约20%.