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1.
子午岭辽东栎林林窗主要树种更新生态位   总被引:5,自引:0,他引:5  
李永兵  王辉  付菁 《生态学杂志》2008,27(12):2062-2066
在对子午岭林区辽东栎林中54个不同大小林窗调查的基础上,分析不同树种的更新生态位,结果表明:辽东栎林中不同树种的优势度随着林窗大小级的变化差异较大;根据各主要树种在不同大小级林窗内生态位宽度的变化,可分为生态幅度宽、中等、较小和狭小4类,其中大多数树种属于狭小生态幅宽度;辽东栎林中各主要树种在不同大小级林窗中的生态位重叠度较小,其中在100~200 m2林窗中的重叠度最小;在100~200 m2大小级林窗中,实生和萌生辽东栎的重要值和生态位宽度均大于0~100和200~300 m2 2个大小级林窗中的辽东栎,说明100~200 m2大小级林窗可为辽东栎的天然更新提供场所。  相似文献   

2.
王卓  范秀华 《应用生态学报》2009,20(5):1044-1050
利用Li-6400光合测定系统,研究了长白山阔叶红松林4个不同尺度林窗内光照强度的异质性,分析红松幼树在林窗内9个方位的光合作用日变化特征.结果表明:林窗内9个方位出现光合有效辐射(PAR)峰值顺序为:西实际林窗、北扩展林窗、林窗中心>南实际林窗、南扩展林窗、东扩展林窗、东实际林窗>西扩展林窗、北实际林窗,光照呈东-西、南-北不对称分布,光照梯度在西、北方向变化较大,但各方向距中心不同距离的日均PAR无显著差异.林窗Ⅰ~Ⅳ日均PAR分别为21.85、45.57、66.02和23.48 μmol·m-2·s-1,相互之间均达显著差异水平(P<0.05).PAR与净光合速率(Pn)呈显著正相关,且相关系数随PAR增大而增大.随林窗面积的增大,PAR和Pn均先增大后减小; 当林窗面积为267 m2时,二者同时达到最大值.  相似文献   

3.
嫁接对低温弱光下甜椒幼苗光合作用的影响   总被引:2,自引:0,他引:2  
以‘卫士’和‘部野丁’为砧木,以‘赤峰特选’为接穂进行嫁接,在光照培养箱内对甜椒自根苗和嫁接苗进行低温(8 ℃/ 5℃)弱光(100 μmol·m-2·s-1)处理,处理7 d后在正常条件(25 ℃/18 ℃,PFD 550~600 μmol·m-2·s-1)下恢复3 d,研究低温弱光下甜椒嫁接苗和自根苗气体交换参数、羧化效率和荧光参数等的变化.结果表明:低温弱光胁迫3 d时,甜椒幼苗叶片的光合速率(Pn)、气孔导度(Gs)和羧化效率(CE)均下降50%以上,之后Pn、Gs趋于平稳,CE持续下降;胞间CO2浓度(Ci)呈先下降后上升趋势.低温弱光下,甜椒幼苗的暗下最大光化学效率(Fv/Fm)、光下实际光化学效率(ФPSⅡ)及电子传递速率(ETR)显著降低,初始荧光(Fo)有所升高,表明其光合机构受到一定伤害,但处理结束3 d后基本恢复.与自根苗相比,嫁接苗在各处理阶段的Pn、Gs、CE、ФPSⅡ、Fv/Fm和ETR都有不同程度的提高,Fo明显降低.可见,嫁接可显著提高甜椒幼苗的光合功能,减轻低温弱光对其光合作用的影响.  相似文献   

4.
对镇江北固山湿地优势植物——〓草的光合作用进行了试验研究。结果表明,春夏季晴天〓草净光合速率(Pn)的日变化为双峰曲线,有明显的光合“午休”现象;多云天〓草的Pn主要受光强制约,随光合有效辐射(PAR)变化而变化。经统计学验证,〓草的Pn与PAR、气孔导度(Gs)有显著正相关关系,而与细胞间隙CO2浓度(Ci)呈显著负相关。用一元二次方程拟合了〓草的光响应曲线,得到光补偿点为38.572 μmol·m-2·s-1,光饱和点为2 087.5 μmol·m-2·s-1。  相似文献   

5.
模拟酸雨胁迫下硅对髯毛箬竹光合特性的影响   总被引:1,自引:0,他引:1  
以髯毛箬竹为试验材料,研究了模拟酸雨胁迫(pH 3.0)下硅对髯毛箬竹叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响.结果表明:20和100 mg·L-1 Na2SiO3预处理可以不同程度地抑制酸雨胁迫下髯毛箬竹叶片叶绿素含量的显著下降,且以100 mg·L-1浓度处理效果最佳,叶绿素含量可提高22.7%,而高浓度(500 mg·L-1)预处理则无缓解作用-酸雨胁迫下,髯毛箬竹光合“午休”现象加重,日平均净光合速率(Pn)、气孔导度(Gs)和气孔限制值(Ls)明显降低,而胞间CO2浓度(Ci)增大,经过20~100 mg·L-1硅预处理后,Pn、Gs、Ls不同程度增加,而Ci有所降低,且以100 mg·L-1硅预处理效果最佳,日平均Pn增加39.2%.酸雨胁迫下,箬竹PSⅡ最大荧光(Fm)、最大光化学效率(Fv/Fm)、潜在活性(Fv/Fo)、有效光化学效率(Fv′/Fm′)、最大荧光产额(Fm′)、光化学淬灭系数(qP)、非光化学淬灭系数(qN)、PSII实际光化学效率(ΦPSⅡ)降低,暗适应和光适应下的最小荧光产额Fo、Fo′ 则升高;而100 mg·L-1硅预处理明显抑制了胁迫下各荧光参数的变化,Fv/Fm、Fv/Fo、Fv′/Fm′和ΦPSⅡ分别增加35.2%、146.2%、55.0%和24.3%.说明外源适宜浓度硅预处理能有效地缓解酸雨胁迫导致的髯毛箬竹光合活性下降和光合系统损伤,从而提高胁迫下植物的光合能力.  相似文献   

6.
东北地区森林生态系统因其面积大,碳贮量高而在本地区和我国碳平衡中占有重要的地位。土壤表面CO2通量(RS)作为陆地生态系统向大气圈释放的主要CO2源,其时空变化直接影响到区域碳循环。该研究采用红外气体分析法比较测定我国东北东部次生林区6个典型的森林生态系统的RS及其相关的土壤水热因子,并深入分析土壤水热因子对RS的影响。研究结果表明:影响RS的主要环境因子是土壤温度、土壤含水量及其交互作用,但其影响程度因生态系统类型和土壤深度而异。包括这些环境因子的综合RS模型解释了 67.5%~90.6%的RS变异。在整个生长季中,不同生态系统类型的土壤温度差异不显著 ,而土壤湿度的差异显著(α= 0.05)。蒙古栎(Quercus mongolica)林、红松(Pinus koraiensis)林、 落叶松(Larix gmelinii)林、硬阔叶林、杂木林和杨桦(Populus davidiana_Betula platyphylla)林的RS变化范围依次为:1.89~5.23 µmol CO2•m-2•s-1,1.09~4.66µmol CO2•m-2•s-1,0.95~3.52µmol CO2•m-2•s-1,1. 13~5.97µmol CO2•m-2•s-1,1.05~6.58µmol CO2•m-2•s-1和1.11~5.76µmol CO2•m-2•s-1。RS的季节动态主要受土壤水热条件的驱动而呈现单峰曲线,其变化趋势大致与土壤温度的变化相吻合。Q10从小到大依次为:蒙古栎林2.32,落叶松林2 .57,红松 林2.76,硬阔叶林2.94,杨桦林3.54和杂木林3.55。Q10随土壤湿度的升高而增大;但超过 一定的阈值后,土壤湿度对Q10起抑制作用。该研究结果强调对该地区生态系统 土壤表面CO2通量的估测应同时考虑土壤水热条件的综合效应。  相似文献   

7.
 以砂培菊芋(Helianthus tuberosus)幼苗作为试验材料,分别进行不同浓度NaCl (50、 100、150、200、250 mmol&;#8226;L-1)和Na2CO3 (25、50、 75、100、125 mmol&;#8226;L-1)胁迫处理,以1/2全营养液作为对照,处理7 d后研究NaCl和Na2CO3胁迫处理对菊芋幼苗叶片光合作用及叶绿素动力学 参数的影响。结果表明:1)在NaCl处理下,当浓度小于150 mmol&;#8226;L-1时,增加了菊芋的叶绿素含量、净光合速率(Net photosynthetic rate, Pn)和气孔导度(Stomatal conductivity, Gs),对荧光参数PSⅡ的电子传递情况( Fm/Fo)、PSⅡ原初光能转换效率(Fv/Fm)、PSⅡ量子效率 (Actual quantum yield of PSⅡ under actinic irradiation,φPSⅡ)和光化学猝灭系数(Photochemical quenching coefficient, qP)和非 光化学猝灭系 数(Non-photochemical quenching coefficient, NPQ)没有显著影响,随着浓度的增加,各项生理指标与对照相比除了NPQ显著 增加,其余均显著降低;2)在Na2CO3胁迫处理下,随着Na2CO3浓度的增加,与对照相比菊芋幼苗叶绿素含量、Pn、Gs以及叶绿素a荧光诱导动力 学参数Fm/Fo、Fv/Fm、φPSⅡ和qP均显著降低,NPQ显著增加;3)就NaCl和Na2CO3相比而言,在相同Na+浓度情况下,处于Na2CO3胁迫下的菊芋 幼苗的叶绿素含量、Pn、Gs以及叶绿素a荧光诱导动力学参数Fm/Fo、Fv/Fm、φPSⅡ和qP下降幅度和NPQ的增加幅度均显著大于NaCl,这说明 NaCl和Na2CO3胁迫均对菊芋幼苗造成不同程度的伤害,但在相同Na+浓度情况下,Na2CO3的伤害程度大于NaCl。由此说明菊芋对盐的忍耐程度高 于碱。  相似文献   

8.
四种温带森林土壤氧化亚氮通量及其影响因子   总被引:9,自引:0,他引:9  
以中国东北东部4种典型森林生态系统(人工红松林、落叶松林、天然次生蒙古栎林和硬阔叶林)为研究对象,采用静态暗箱-气相色谱法,比较其土壤N2O通量的季节动态及其影响因子.结果表明:在生长季, 4种森林生态系统土壤总体上表现为大气N2O的排放源, 其N2O通量大小顺序为:硬阔叶林(21.0±4.9 μg·m-2·h-1)> 红松林(17.6±4.6 μg·m-2·h-1)>落叶松林(9.8±5.9 μg·m-2·h-1)>蒙古栎林(1.6±12.6 μg·m-2·h-1).各生态系统的N2O通量没有明显的季节动态,只在夏初出现排放峰值(蒙古栎林为吸收峰).4种生态系统N2O通量均与10 cm深土壤含水量呈极显著正相关,与NO3--N呈显著负相关;N2O通量对土壤温度和NH4+-N的响应出现分异:针叶林N2O 通量与NH4+-N呈显著正相关,而与5 cm深土壤温度呈不相关;阔叶林与针叶林正相反.在较为干旱的2007年,土壤水分是影响4种林型土壤N2O通量的关键因子.植被类型与环境因子及氮素有效性对N2O通量的相互作用将是未来研究的重点.  相似文献   

9.
采用开顶式人工熏气装置,对1年生樟树幼苗进行了为期2个月不同体积分数NO2(0.1、0.5和4.0 μl·L-1)熏气试验,研究其对幼苗生长及光合作用的影响.结果表明:0.5和0.1 μl·L-1 NO2处理促进了樟树幼苗生长,而4.0 μl·L-1 NO2处理则抑制其生长.各处理樟树幼苗叶片净光合速率(Pn)日变化呈不对称的双峰型曲线,存在光合“午休”现象;在光合日进程中,0.5 μl·L-1 NO2处理使叶片Pn提高,最大值达8.542 μmol CO2·m-2s-1,4.0 μl·L-1NO2处理的大多数时段使Pn降低,而0.1 μl·L-1 NO2处理对Pn的影响则依时段而不同;0.5和4.0 μl·L-1 NO2处理提高了叶片气孔导度(Gs)和胞间CO2浓度(Ci)的最大值和最小值,0.1 μl·L-1 NO2处理提高了Ci的最大值和最小值,降低了Gs的最大值和最小值.熏气处理中、后期,0.5μl·L-1 NO2处理叶片的日均净光合速率显著高于其他处理.在熏气处理前期,0.5和4.0 μl·L-1 NO2处理使叶片最大PSⅡ的光能转换效率(Fv/Fm)显著下降;在熏气处理后期,4.0 μl·L-1 NO2处理的叶片Fv/Fm仍显著低于对照.  相似文献   

10.
不同氮素水平下二氧化碳加富对草莓叶片光抑制的影响   总被引:7,自引:1,他引:6  
用便携式调制叶绿素荧光仪和光合仪研究了强光下不同供氮水平(12、4和0.4 mmol·L-1)和不同CO2浓度下(700和390 μl·L-1)丰香草莓叶片的荧光参数及净光合速率的变化.结果表明,CO2和氮素对草莓叶片光抑制有明显的互作效应.在富CO2下,12 mmol·L-1供氮水平的草莓叶片净光合速率升高了62.7%,4和0.4 mmol·L-1供氮水平则分别降低了7.4%和21.3%;12 mmol·L-1供氮水平的Fm和Fv/Fm在强光胁迫时降辐减小,暗恢复时Fm和Fv/Fm恢复程度提高,而4和0.4 mmol·L-1供氮水平却相反.表明氮素供应不足时草莓叶片在富CO2环境下光合作用出现适应性下调,光抑制增强.  相似文献   

11.
Two methods were used to estimate construction costs for leaves,stems, branches and woody roots of yellow-poplar (LiriodendrontulipiferaL.) trees grown at ambient (35 Pa) and elevated (65Pa) CO2for 2.7 years and trees of white oak (Quercus albaL.)grown at these same CO2partial pressures for 4 years. Samplecombustion in a bomb calorimeter combined with measurementsof ash and nitrogen content provided the primary method of estimatingtissue construction costs (WG; g glucose g-1dry mass). Thesevalues were compared with a second, simpler method in whichcost estimates were derived from tissue ash, carbon and nitrogencontent (VG). Estimates of WGwere lower for leaves, branchesand roots of yellow-poplar and for leaves of white oak grownat elevated compared with ambient CO2partial pressures. TheseCO2-induced differences in WGranged from 3.7% in yellow-poplarroots to 2.1% in white oak leaves. Only in the case of yellow-poplarleaves, however, were differences in VGobserved between CO2treatments.Leaf VGwas 1.46 g glucose g-1dry mass in ambient-grown treescompared with 1.41 g glucose g-1dry mass for CO2-enriched trees.Although paired-estimates of WGand VGclustered about a 1:1 linefor leaves and branches, estimates of VGwere consistently lowerthan WGfor stems and roots. Construction costs per unit leafarea were 95 g glucose m-2for yellow-poplar trees grown at ambientCO2and 106 g glucose m-2for trees grown at elevated CO2partialpressures. No differences in area-based construction costs wereobserved for white oak. Whole-plant energy content was 1220g glucose per tree in ambient-grown white oak compared with2840 g glucose per tree for those grown at elevated CO2partialpressures. These differences were driven largely by CO2-inducedchanges in total biomass. We conclude that while constructioncosts were lower at elevated CO2partial pressures, the magnitudeof this response argues against an increased efficiency of carbonuse in the growth processes of trees exposed to CO2enrichment. Bomb calorimeter; construction costs; elevated CO2; energy allocation; global change; growth respiration; heat of combustion; respiration; Liriodendron tulipifera; Quercus alba  相似文献   

12.
The mixing behaviour of the liquid phase in concentric-tube airlift bioreactors of different scale (RIMP: VL=0.070 m3; RIS-1: VL=2.50 m3; RIS-2: VL=5.20 m3) in terms of mixing time was investigated. This mixing parameter was determined from the output curves to an initial Dirac pulse, using the classical tracer response technique, and analyzed in relation to process and geometrical parameters, such as: gas superficial velocity, xSGR; top clearance, hS; bottom clearance, hB, and ratio of the resistances at downcomer entrance, Ad/AR. A correlation between the mixing time and the specified operating and geometrical parameters was developed, which was particularized for two flow regimes: bubbly and transition (xSGRА.08 m/s) and churn turbulent flow (xSGR> 0.08 m/s) respectively. The correlation was applied in bioreactors of different scale with a maximum error of ᆲ%.  相似文献   

13.
Cell cycle-dependent calcium oscillations in mouse embryonic stem cells   总被引:2,自引:0,他引:2  
During cell cycle progression, somatic cells exhibit different patterns of intracellular Ca2+ signals during the G0 phase, the transition from G1 to S, and from G2 to M. Because pluripotent embryonic stem (ES) cells progress through cell cycle without the gap phases G1 and G2, we aimed to determine whether mouse ES (mES) cells still exhibit characteristic changes of intracellular Ca2+ concentration during cell cycle progression. With confocal imaging of the Ca2+-sensitive dye fluo-4 AM, we identified that undifferentiated mES cells exhibit spontaneous Ca2+ oscillations. In control cultures where 50.4% of the cells reside in the S phase of the cell cycle, oscillations appeared in 36% of the cells within a colony. Oscillations were not initiated by Ca2+ influx but depended on inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release and the refilling of intracellular stores by a store-operated Ca2+ influx (SOC) mechanism. Using cell cycle synchronization, we determined that Ca2+ oscillations were confined to the G1/S phase (70% oscillating cells vs. G2/M with 15% oscillating cells) of the cell cycle. ATP induced Ca2+ oscillations, and activation of SOC could be induced in G1/S and G2/M synchronized cells. Intracellular Ca2+ stores were not depleted, and all three IP3 receptor isoforms were present throughout the cell cycle. Cell cycle analysis after EGTA, BAPTA-AM, 2-aminoethoxydiphenyl borate, thapsigargin, or U-73122 treatment emphasized that IP3-mediated Ca2+ release is necessary for cell cycle progression through G1/S. Because the IP3 receptor sensitizer thimerosal induced Ca2+ oscillations only in G1/S, we propose that changes in IP3 receptor sensitivity or basal levels of IP3 could be the basis for the G1/S-confined Ca2+ oscillations. pluripotent; IP3; store operated Ca entry; IP3 receptor  相似文献   

14.
CO2-exchange rates (CER) of the sixth and the flag leaves oftwo spring-wheat varieties, Kolibri and Famos, were comparedusing an open-circuit infrared gas analysing system. Measurementswere repeated every two weeks starting when leaf blades werefully expanded. Single plants were grown in a controlled environmenthaving a photopuiod of 15 h and a day/night temperature of 24/19°C(H), 18/13 °C (M), and 12/7 °C (L) respectively untilapprox. 2 weeks after anthesis and at 18/13 °C until maturity.The photosynthetic photon-flux density (PPFD) at the top ofthe plants was 500 µE m–2 sec–1. During themeasurements PPFD was gradually reduced from 2000 to 0 µEm–2 sec–1 whereas the temperature was maintainedat the respctive growth-temperatures during the light period.The CER of the sixth leaf declined fairly similarly for bothvarieties, except for Kolibri where a faster decline was observedduring the first two weeks after full leaf expansion. The CERof the flag leaf declined more slowly than that of the sixthleaf. With the flag leaf of Famos, the decline was nearly linear,whereas with Kolibri it was very slow during the first few weeksbut rapid as the leaves further senesced. This pattern becamemore pronounced as the growth temperature decreased. The declinein relation to leaf age was much smaller at low PPFD than athigh PPFD during the same period. At full leaf expansion Kolibrireached higher maximum CER than Famos except at H. As the PPFDwas reduced the difference became smaller and at very low PPFDsuch as 50 µE m–2 sec–1 was reversed for thesixth leaf. Under optimum growth conditions maximum values ofCER were greater than 50mg CO2 dm–2h–1 and PPFDfor light saturation was close to 2000 µE m–2 sec–1.A comparison between the actual CER and a fitted curve widelyused, PN=(a+b/l)–1–DR, showed that the goodnessof fit strongly depends on cultivar, treatment and leaf ageas well as on the number and the level of PPFD from which datafor calculations are taken. Triticum aestivum, L., wheat, photosynthesis, photon-flux density, light response, carbon, dioxide exchange  相似文献   

15.
The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1 and 11.93 106 total cells I–1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]–1 h–1 [µmol m s–1]–1the maximum photosynthetic rate, pBm, between 0.66 and 1.85µg C [µghla]–1 h–1; lk (the photoadaptationindex) from 14 to 69 µ,mol m–2 s–1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm–2 s–1) ranged from 16 to 25 pg C cell–1h and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with PBmof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom.  相似文献   

16.
 为探讨西双版纳独特地方气候背景下,热带季节雨林CO2浓度的时空变化特征和不同时间尺度上环境因素对森林CO2浓度时间分布的作用,以及 为研究热带季节雨林的碳通量、净生态系统交换量(Net ecosystem exchange, NEE)等提供支持,我们利用热带季节雨林林冠上方和林内近地层 CO2浓度连续监测资料,结合同步气象资料进行了统计分析。研究结果表明:在植被生理活动、土壤呼吸以及林内湍流的共同作用下,西双版纳 热带季节雨林CO2浓度表现出明显的日变化、季节变化和林冠上下差异。在日尺度上,林冠上方的CO2浓度时间变化曲线为“单峰型”,林内近 地层CO2浓度时间变化曲线为“双峰型”,造成林内近地层傍晚第二个峰值的主要因子是地形因子作用下形成的局地环流。在季节尺度上,林冠 上方CO2浓度主要受林冠代谢作用的影响,呈现雨季低、干季高的特点,而林内近地层的CO2浓度则主要受地表呼吸过程所控制,季节变化趋势 与林冠上方相反。林冠上方CO2浓度低于林内近地层CO2浓度,且差异较大;在日尺度上,各月(除12月外)CO2浓度的最大差值皆大于80 mg·m -3,且出现在傍晚;在季节尺度上,最大值为-62.9 mg·m-3,出现在10月,最小值为-8.4 mg·m-3,出现在12月。  相似文献   

17.
华西雨屏区苦竹林土壤呼吸对模拟氮沉降的响应   总被引:15,自引:2,他引:13       下载免费PDF全文
 2007年11月至2008年11月, 对华西雨屏区苦竹(Pleioblastus amarus)人工林进行了模拟氮沉降试验, 氮沉降水平分别为对照(CK, 0 g N·m–2·a–1)、低氮(5 g N·m–2·a–1)、中氮(15 g N·m–2·a–1)和高氮(30 g N·m–2·a–1)。每月下旬, 采用红外CO2分析法测定土壤呼吸速率, 并定量地对各处理施氮(NH4NO3)。结果表明: 2008年试验地氮湿沉降量为8.241 g·m–2, 超出该地区氮沉降临界负荷。在生长季节, 苦竹林根呼吸占总土壤呼吸的60%左右。模拟氮沉降促进了苦竹林土壤呼吸速率, 使苦竹林土壤每年向大气释放的CO2增加了9.4%~28.6%。在大时间尺度上(如1 a), 土壤呼吸主要受温度的影响。2008年6~10月, 土壤呼吸速率24 h平均值均表现为: 对照<低氮<中氮<高氮。氮沉降处理1 a后, 土壤微生物呼吸速率和土壤微生物生物量碳、氮增加, 并且均与氮沉降量具有相同趋势。各处理土壤呼吸速率与10 cm土壤温度、月平均气温呈极显著指数正相关关系, 利用温度单因素模型可以解释土壤呼吸速率的大部分。模拟氮沉降使得土壤呼吸Q10值增大, 表明氮沉降可能增强了土壤呼吸的温度敏感性。在氮沉降持续增加和全球气候变暖的背景下, 氮沉降和温度的共同作用可能使得苦竹林向大气中排放的CO2增加。  相似文献   

18.
Ten-year-old trees from four Italian populations of Pinus leucodermis (populations A, B, C and D), which were collected from different sites at different altitudes, were grown near Florence, Italy. Needle CO2 gas exchange and chlorophyll fluorescence response to increasing light intensities were evaluated; gas exchange and chlorophyll fluorescence variation between April and July were also monitored. Populations A, B and C showed a similar photosynthetic response to increasing photosynthetic photon flux density (PPFD) intensities, while at various light intensities population D, which originated from the highest altitude, showed the highest photosynthetic rates. In this population photosynthesis was saturated at PPFDs higher than 900 µmol m-2s-1 and a slow decrease of effective photosystem II quantum yield and F'V/F'M in response to increasing PPFDs were found. The same trees also showed a faster recovery in photosynthesis from limitations induced by winter temperatures than the other three populations. This work showed that photosynthetic response to light in population D was different from the other populations; trees from this population were probably naturally selected to prevent photoinhibition due to excess light.  相似文献   

19.
In-situ estimates of fast-ice algal productivity at Cape Evans, McMurdo Sound, in 1999 were lower than at the same site in previous years. Under-ice irradiance was between 0 and 8 µmol photons m-2 s-1; the ice was between 1.9 and 2.0 m thick and the algal biomass averaged 150 mg chl a m-2, although values as high as 378 mg chl a m-2 were recorded. Production on 11 and 12 November was between 0.053 and 1.474 mg C m-2 h-1. When the data from 11 November were fitted to a hyperbolic tangent function, a multilinear regression gave estimates for Pmax of 0.571 nmol O2 cm-2 s-1, an ! of 0.167 nmol O2 cm-2 s-1 µmol-1 photons m-2 s-1 and an Ek of 3.419 µmol photons m-2 s-1. A Pmax of 2.674 nmol O2 cm-2 s-1, an ! of 0.275 nmol O2 cm-2 s-1 µmol-1 photons m-2 s-1, r of 0.305 nmol O2 cm-2 s-1 and an Ek of 9.724 µmol-1 photons m-2 s-1 were estimated from the 12 November data. The sea-ice algal community was principally comprised of Nitzschia stellata, Entomoneis kjellmanii and Berkeleya adeliensis. Other taxa present included N. lecointei, Fragilariopsis spp., Navicula glaciei, Pleurosigma spp. and Amphora spp. Variations in the method for estimating the thickness of the diffusive boundary layer were not found to significantly affect the measurements of oxygen flux. However, the inability to accurately measure fine-scale variations in biomass is thought to contribute to the scatter of the P versus E data.  相似文献   

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