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1.
为了探究台风风暴潮导致的盐度脉冲、潮汐涨落以及两者的耦合作用对河口湿地土壤二氧化碳(CO2)与甲烷(CH4)排放产生的影响,选取闽江河口道庆洲短叶茳芏湿地土壤为研究对象,通过室内模拟实验,研究不同潮汐过程情景下由于盐度和潮水涨落变化,河口湿地CO2与CH4排放特征并分析其主要影响因子。研究结果表明:(1)潮汐淹水显著抑制CO2排放,但促进CH4排放(P<0.05)。盐度增加(0-8‰)促进了土壤CO2排放(P>0.05);0-2‰盐度促进土壤CH4排放(P>0.05),2‰-8‰盐度抑制土壤CH4排放(P<0.05)。(2)盐度脉冲耦合潮汐过程显著抑制了CH4排放(P<0.05),且一定程度上抑制了CO2排放(P>0.05)。(3) CO2排放与孔隙水中的氨态氮(NH4+-N)呈极显著正相关(P<0.01),与硝态氮(NO3--N)、可溶性有机碳(DOC)和土壤pH呈显著负相关(P<0.05)。盐度脉冲耦合潮汐过程对CO2与CH4排放的影响是一个正负消长的博弈过程,在0-8‰的盐度内,潮汐淹水对CO2排放的影响更大,而盐度在CH4排放中起主导作用。相较于盐度,潮汐淹水是影响闽江河口湿地含碳温室气体全球增温潜势的主导因素。 相似文献
2.
为研究枯落物输入变化对云南松(Pinus yunnanensis)林地CO2释放的影响。本研究于2018年3月至2020年2月,应用枯落物添加和去除实验(DIRT),设置对照(CK)、双倍枯落物(DL)、去除枯落物(NL)、去除有机层和A层(O/A-Less)、去除根系(NR)和无输入(NI)6个处理水平,采用Li-6400便携式光合作用测量仪及TRIME-PICO 64/32土壤温度水分测定仪对不同处理样地每月的CO2通量(Rs)、土壤温度和土壤水分(15cm)进行了测定。结果表明:(1)不同处理样地CO2通量均呈现出明显的月变化,7至8月最高,1至4月最低,平均值表现为Rs (DL)=8.10 μmol m-2 s-1 > Rs (CK)=6.27 μmol m-2 s-1 > Rs (NL)=5.44 μmol m-2 s-1 > Rs (NR)=4.46 μmol m-2 s-1 > Rs (O/A-Less)=3.86 μmol m-2 s-1 > Rs (NI)=2.94 μmol m-2 s-1。(2)与CK相比,DL样地CO2通量升高了29.12%,而去除地上枯落物和地下根系样地CO2通量显著降低,CO2通量平均变幅分别为α(NR)=-28.85%,α(NI)=-53.14%,α(O/A-Less)=-38.46%,α(NL)=-13.29%。(3)不同处理土壤水分和土壤温度均存在显著的月变化(P<0.01),NL和O/A-Less的土壤水分显著低于CK,而其余处理与CK间无显著差异(P>0.05);不同处理间土壤温度表现为NR和NI均显著高于CK,其余处理与CK间无显著差异(P>0.05)。(4)不同处理样地CO2通量与土壤温度呈显著指数相关(P<0.01),与土壤水分在NI和O/A-Less处理中无显著相关(P>0.05);与CK相比,NI、O/A-Less和NL处理的Q10增加,而NR和DL处理的Q10则降低;不同处理林地CO2通量与土壤水热因子双因素模型能更好的解释林地CO2通量的变化。本研究表明枯落物不同处理通过改变土壤碳输入和土壤环境因子从而影响生态系统碳排放,研究结果可为未来气候变化和人为干扰下云南松林的碳循环提供基础数据。 相似文献
3.
生态系统水分利用效率(WUE)是表征碳水耦合过程的关键指标,然而,有关气候变化和退耕还林还草工程背景下黄土高原WUE的时空变化特征及其主导因子仍未明晰。研究利用遥感驱动的生态系统过程模型BEPS模拟2001-2020年黄土高原总初级生产力(GPP)和蒸散(ET),并结合基于敏感性试验的多控制因子联立求解方法定量分析气候和植被因子对黄土高原WUE变化(WUE=GPP/ET)的贡献。结果表明:(1)2001-2020年黄土高原GPP和ET分别以12.9 gC m-2 a-1和3.7 mm/a速率显著升高,并使得WUE增长显著(0.021 gC mm-1 m-2 a-1)。(2)2001-2020年间黄土高原80.12%的区域叶面积指数(LAI)显著升高(全区增速为0.014 m2 m-2 a-1)而气候因子变化均不显著。(3)植被因子和气候因子对WUE变化分别呈正贡献和负贡献,植被因子作为主要影响因子主导了黄土高原86.74%地区的WUE变化。研究结果有望为干旱区生态水文管理和相关政策制定提供一定科学参考。 相似文献
4.
不同恢复方式下大兴安岭重度火烧迹地林地土壤温室气体通量 总被引:3,自引:3,他引:0
为研究大兴安岭重度火烧迹地在不同恢复方式下林地土壤CO2、CH4和N2O排放特征及其影响因素,采用静态箱/气相色谱法,在2017年生长季(6月-9月)对3种恢复方式(人工更新、天然更新和人工促进天然更新)林地土壤温室气体CO2、CH4、N2O通量进行了原位观测。研究结果表明:(1)3种恢复方式林地土壤在生长季均为大气CO2、N2O的源,CH4的汇;生长季林地土壤CO2排放通量大小关系为人工促进天然更新((634.40±246.52)mg m-2 h-1) > 人工更新((603.63±213.22)mg m-2 h-1) > 天然更新((575.81±244.12)mg m-2 h-1),3种恢复方式间无显著差异;人工更新林地土壤CH4吸收通量显著高于人工促进天然更新;天然更新林地土壤N2O排放通量显著高于其他两种恢复方式。(2)土壤温度是影响3种恢复方式林地土壤温室气体通量的关键因素;土壤水分仅对人工更新林地土壤N2O通量有极显著影响(P < 0.01);3种恢复方式林地土壤CO2通量与大气湿度具有极显著的响应(P < 0.01);土壤pH仅与天然更新林地土壤CO2通量显著相关(P < 0.05);土壤全氮含量仅与人工促进天然更新林地土壤CH4通量显著相关(P < 0.05)。(3)基于100年尺度,由3种温室气体计算全球增温潜势得出,人工促进天然更新(1.83×104 kg CO2/hm2) > 人工更新(1.74×104 kg CO2/hm2) > 天然更新(1.67×104 kg CO2/hm2)。(4)阿木尔地区林地土壤年生长季CO2和N2O排放量为8.85×106 t和1.88×102 t,CH4吸收量为1.05×103 t。 相似文献
5.
由于全球气候变化,预计未来我国亚热带地区干旱频率和持续时间将会增加。森林土壤CO2的释放是陆地生态系统碳循环的重要组成部分,然而,有关不同深度土壤CO2通量对干旱响应的理解仍相当有限。选择武夷山针叶林(Coniferous Forest,CF)和常绿阔叶林(Evergreen Broadleaved Forest,EBF)为研究对象,于2014年6月至2015年12月,采用梯度法计算10、30 cm和50 cm深度各层土壤CO2通量,探讨模拟干旱对其影响。结果表明:CF和EBF样地土壤CO2浓度均随土壤深度的增加而升高。CF和EBF样地对照(CK)处理10 cm深度土壤CO2生产量分别占总CO2生产量的53.5%和55.7%,表明土壤CO2生产量主要来源于浅层土壤,这可能与浅层土壤有高的有机碳含量及细根生物量主要分布区有关。干旱处理使CF和EBF样地不同深度土壤CO2通量均显著减少。在两个样地土壤CO2通量的温度敏感性(Q10)值均随着土壤深度的增加而减少。干旱处理显著减少了CF样地浅层土壤的Q10值(P=0.02),对深层土壤影响不显著(30 cm:P=0.30;50 cm:P=0.23);而在EBF样地干旱处理显著减少了深层土壤的Q10值(30 cm:P=0.02;50 cm:P=0.01),对浅层土壤影响不显著(P=0.32)。 相似文献
6.
为研究不同CO2浓度升高和氮肥水平对水稻叶绿素荧光特性的影响,利用由开顶式气室(OTC)组成的CO2浓度自动调控平台开展田间试验。以粳稻9108为试验材料,CO2浓度设置CK(对照,环境大气CO2浓度)、C1(CO2浓度比CK增加160 μmol/mol)和C2(CO2浓度比CK增加200 μmol/mol)3个水平;氮肥设置低氮(N1:10 g/m2)、中氮(N2:20 g/m2)和高氮(N3:30 g/m2)3个水平。结果表明,在低氮条件下,与CK相比,C1处理使拔节期的Fo上升4.8%(P=0.031);C2处理使拔节期的Fo上升6.3%(P=0.015),Fv/Fm下降4.8%(P=0.003),使孕穗期的Fo上升12.7%(P=0.039),Fv/Fo下降18.2%(P=0.039)。在高氮条件下,与CK相比,C2处理使灌浆期的Fm、Fv和Fv/Fm分别下降3.6%(P=0.039)、4.9%(P=0.013)和1.3%(P=0.039)。在中氮条件下,与CK相比,C1和C2处理的影响不明显。在整个生育期内,CO2浓度升高与施氮处理交互作用对水稻叶绿素荧光特性的影响未到达显著水平。研究表明,大气CO2浓度升高使水稻叶片光系统Ⅱ受损,抑制其电子传递能力、电子受体QA氧化还原情况、最大光化学效率和潜在活性,通过适量施氮可以有效地缓解其负面效应。 相似文献
7.
陆地生态系统是全球第二大碳库,其碳收支一直是气候变化研究的热点领域,而研究二氧化碳(CO2)施肥效应又是全球变化碳循环领域较为关注的前沿部分。CO2与生态系统关系复杂,当前仍无法厘清CO2对陆地生态系统碳循环的影响作用。基于太阳辐射数据、气温数据及归一化植被指数数据等,利用光能利用率遥感模型,模拟2019年甘南地区的碳循环,选取三个指标,即GPP (陆地生态系统总初级生产力)、NPP (净初级生产力)和NEP (净生态系统生产力)来分析甘南地区植被固碳的时空变化特征及CO2施肥效应。结果表明:(1)甘南地区2019年植被固碳总量约为2611 tC。甘南地区生态系统GPP、NPP和NEP季节性特征明显,其值均在夏季达到最高;而在空间上,GPP、NPP表现为东高西低的特征,NEP呈现出北高南低的分布特征。(2) CO2对GPP、NPP存在正向的施肥效应,分别增加了14.4%和14.3%;而对NEP具有负向反馈效应,使其减少了0.3%,并且CO2对NEP的影响整体也表现为北高南低的特征。研究揭示出:虽然CO2在提升GPP和NPP时,正向的施肥效应明显,但是对甘南地区的NEP,即固碳量来说,CO2的影响却很有限。因此在研究CO2施肥效应时不应一概而论,生态地理环境对其的影响不可忽视。研究可以为揭示陆地生态系统碳循环的动态机制提供一定的理论依据。 相似文献
8.
为了更好理解若尔盖高原不同微生境下沼泽湿地生态系统CO2排放通量的变化特征,以若尔盖高原湿地自然保护区为研究对象,2013和2014年生长季期间,采用了静态箱和快速温室气体法原位观测了3种湿地5种微生境下沼泽湿地CO2排放通量时空变化规律。结果表明:长期淹水微地貌草丘区湿地(PHK)和洼地区湿地(PHW) CO2排放通量变化范围分别为38.99-1731.74 mg m-2 h-1和46.69-335.22 mg m-2 h-1,季节性淹水区微地貌草丘区湿地(SHK)和洼地区湿地(SHW) CO2排放通量变化范围分别为193.90-2575.60 mg m-2 h-1和49.93-1467.45 mg m-2 h-1,而两者过渡区的无淹水区沼泽湿地(Lawn) CO2排放通量变化范围194.20-898.75 mg m-2 h-1。相关性分析表明5种微地貌区沼泽湿地CO2排放通量季节性变化与不同深度土壤温度均存在显著正相关,与水位存在显著负相关(PHW、SHW、SHK、Lawn)或不相关(PHK),并且水位和温度(5 cm)共同解释了CO2排放通量季节性变化的87%。3种湿地5种微生境下沼泽湿地CO2排放通量存在空间变化规律,主要受水位影响,但植物也影响沼泽湿地CO2排放通量空间变化规律,并且表明沼泽湿地CO2排放通量与水位平均值存在显著负相关。 相似文献
9.
武夷山国家公园不同林地土壤呼吸动态变化及其影响因素 总被引:2,自引:0,他引:2
探明亚热带山岳型国家公园不同林地利用方式下土壤呼吸(Rs)的动态变化规律以及影响因素,对准确评价和预测该区域以国家公园为主体的自然保护地体系的碳收支具有重要的现实意义。以武夷山国家公园为研究对象,利用Li-8100开路式土壤碳通量测定系统对茶园、锥栗(Castanea henryi(Skam) Rehd.et Wils.)林、马尾松(Pinus massoniana Lamb.)林和裸地的土壤呼吸及近地面气温、土壤温度、土壤湿度、土壤养分和土壤微生物碳(MBC)、氮(MBN)进行测定。结果显示:(1)与近地面气温、土壤温度和土壤湿度相同,不同林地的Rs均呈现夏 > 春 > 秋 > 冬的季节动态,Rs的季节均值按大小排序为茶园(3.10 μmol m-2 s-1) > 马尾松(2.96 μmol m-2 s-1) > 锥栗(2.32 μmol m-2 s-1) > 裸地(1.43 μmol m-2 s-1),锥栗和裸地之间、锥栗与马尾松之间均差异显著(P<0.01)。除马尾松林外,其他林地水热因子(近地面气温、土壤温度和土壤湿度)的单因子二次多项式模型对Rs的拟合度最高。水热因子共同建立的复合模型中,土壤温度、湿度的幂-指数模型对茶园Rs的拟合度较高,土壤温度和土壤湿度能够解释Rs变化的80%,马尾松林的Rs较适用于土壤温度、湿度建立的对数函数模型,而三因子线性模型(进入回归法)对锥栗林和裸地的Rs的拟合度最优,R2分别为0.565和0.281。(2)茶园和锥栗林的碳、氮、磷含量均高于马尾松林和裸地,MBN含量茶园 > 马尾松 > 锥栗 > 裸地。茶园的Rs与全磷(TP)、有效磷(AP)、全钾(TK)、速效钾(AK)含量呈极显著(P<0.01)正相关,马尾松林的Rs受TP、TK、AK含量的影响极显著(P<0.01),锥栗林的Rs与TK、AK、MBN含量呈现显著(P<0.05)正相关,裸地的Rs受MBN含量影响较为显著(P<0.05),4种林地土壤呼吸与养分的多元逐步回归方程R2均接近1。综上,茶园和马尾松林土壤呼吸速率较高,且所有林地的土壤呼吸均呈现夏 > 春 > 秋 > 冬的季节动态。温度和湿度与土壤呼吸的相关性强,是水热条件丰富的亚热带山岳地区土壤呼吸季节变化的主导因素,其中武夷山茶园土壤呼吸对水热因子的响应在4种林地中最为敏感。除温度和湿度外,各林地土壤呼吸受P、K元素的影响较大,其中茶园主要受P元素影响,马尾松林地受K元素影响较多。 相似文献
10.
利用叶片荧光参数估算油蒿灌丛群落生态系统生产力 总被引:1,自引:1,他引:0
生态系统生产力(GEP)在全球碳循环中具有重要意义,但其准确估算仍然是一个挑战。近年来,叶绿素荧光和冠层GEP的关联成为生态学的研究热点,关系尚不清楚且存在广泛争议。于2015年对宁夏盐池毛乌素沙地荒漠灌木油蒿(Artemisia ordosica)灌丛生态系统碳交换(NEE)特征进行连续观测,使用多通道荧光监测仪对通量贡献区内油蒿叶片的实时荧光(Fs)和光下荧光(Fm'')进行原位连续监测,叶面积指数(LAI)、归一化植被指数(NDVI)以及环境因子同步观测。利用光合有效辐射(PAR)、LAI和实际光化学效率(ΦPSII)等参数构建基于叶绿素荧光的生态系统生产力(GEPChlF)模型,探究叶片和冠层尺度不同参数对环境因子波动的响应,比较分析GEPChlF和基于涡度相关法监测生态系统生产力(GEPEC)相关性及GEPChlF的适用性。研究发现,ΦPSII和NEE日变化规律一致,ΦPSII、GEPChlF和GEPEC由PAR控制,受空气温度(Ta)和饱和水汽压差(VPD)调控,土壤含水量(SWC)和ΦPSII呈显著正相关(P<0.01)。PAR处于400-800 μmol m-2 s-1时,GEPChlF与GEPEC线性关系最优,斜率为0.627(R2=0.67,P<0.01);弱光下GEPChlF的低估可能是由于冠层实际光能拦截率高造成;强光下GEPChlF显著高于GEPEC,呈非线性关系,可能是GEPEC基于夜间温度敏感性所拟合的生态系统呼吸(Re)无法预测光呼吸部分所导致。GEPChlF具有荧光参数的特性,对环境波动更加敏感,和环境因子相关性优于GEPEC。结果表明,高辐射、极端温度、高蒸腾和干旱是限制叶片和冠层尺度下油蒿光合过程的主要胁迫因素。本研究构建的荒漠生态系统光合过程模型GEPChlF能够替代GEPEC作为一个良好的冠层尺度生态参数,所提出的空间尺度上推方法可为促进区域可持续发展提供数据支撑和决策参考。 相似文献
11.
Masaki Uchida Ayaka Kishimoto Hiroyuki Muraoka Takayuki Nakatsubo Hiroshi Kanda Hiroshi Koizumi 《Journal of plant research》2010,123(1):79-85
We examined factors controlling temporal changes in net ecosystem production (NEP) in a high Arctic polar semi-desert ecosystem
in the snow-free season. We examined the relationships between NEP and biotic and abiotic factors in a dominant plant community
(Salix polaris–moss) in the Norwegian high Arctic. Just after snowmelt in early July, the ecosystem released CO2 into the atmosphere. A few days after snowmelt, however, the ecosystem became a CO2 sink as the leaves of S. polaris developed. Diurnal changes in NEP mirrored changes in light incidence (photosynthetic photon flux density, PPFD) in summer.
NEP was significantly correlated with PPFD when S. polaris had fully developed leaves, i.e., high photosynthetic activity. In autumn, NEP values decreased as S. polaris underwent senescence. During this time, CO2 was sometimes released into the atmosphere. In wet conditions, moss made a larger contribution to NEP. In fact, the water
content of the moss regulated NEP during autumn. Our results indicate that the main factors controlling NEP in summer are
coverage and growth of S. polaris, PPFD, and precipitation. In autumn, the main factor controlling NEP is moss water content. 相似文献
12.
JIAHONG LI THOMAS L. POWELL TROY J. SEILER DAVID P. JOHNSON HANS P. ANDERSON ROSVEL BRACHO† BRUCE A. HUNGATE‡ CHARLES R. HINKLE§ BERT G. DRAKE 《Global Change Biology》2007,13(6):1101-1113
Hurricane disturbances have profound impacts on ecosystem structure and function, yet their effects on ecosystem CO2 exchange have not been reported. In September 2004, our research site on a fire‐regenerated scrub‐oak ecosystem in central Florida was struck by Hurricane Frances with sustained winds of 113 km h−1 and wind gusts as high as 152 km h−1. We quantified the hurricane damage on this ecosystem resulting from defoliation: we measured net ecosystem CO2 exchange, the damage and recovery of leaf area, and determined whether growth in elevated carbon dioxide concentration in the atmosphere (Ca) altered this disturbance. The hurricane decreased leaf area index (LAI) by 21%, which was equal to 60% of seasonal variation in canopy growth during the previous 3 years, but stem damage was negligible. The reduction in LAI led to a 22% decline in gross primary production (GPP) and a 25% decline in ecosystem respiration (Re). The compensatory declines in GPP and Re resulted in no significant change in net ecosystem production (NEP). Refoliation began within a month after the hurricane, although this period was out of phase with the regular foliation period, and recovered 20% of the defoliation loss within 2.5 months. Full recovery of LAI, ecosystem CO2 assimilation, and ecosystem respiration did not occur until the next growing season. Plants exposed to elevated Ca did not sustain greater damage, nor did they recover faster than plants grown under ambient Ca. Thus, our results indicate that hurricanes capable of causing significant defoliation with negligible damage to stems have negligible effects on NEP under current or future CO2‐enriched environment. 相似文献
13.
Strong links between teleconnections and ecosystem exchange found at a Pacific Northwest old-growth forest from flux tower and MODIS EVI data 总被引:1,自引:0,他引:1
SONIA WHARTON LAURA CHASMER† MATTHIAS FALK‡ KYAW THA PAW U 《Global Change Biology》2009,15(9):2187-2205
Variability in three Pacific teleconnection patterns are examined to see if net carbon exchange at a low‐elevation, old‐growth forest is affected by climatic changes associated with these periodicities. Examined are the Pacific Decadal Oscillation (PDO), Pacific/North American Oscillation (PNA) and El Niño‐Southern Oscillation (ENSO). We use 9 years of eddy covariance CO2, H2O and energy fluxes measured at the Wind River AmeriFlux site, Washington, USA and 8 years of tower‐pixel remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to address this question. We compute a new Composite Climate Index (CCI) based on the three Pacific Oscillations to divide the measurement period into positive‐ (2003 and 2005), negative‐ (1999 and 2000) and neutral‐phase climate years (2001, 2002, 2004, 2006 and 2007). The forest transitioned from an annual net carbon sink (NEP=+217 g C m?2 yr?1, 1999) to a source (NEP=?100 g C m?2 yr?1, 2003) during two dominant teleconnection patterns. Net ecosystem productivity (NEP), water use efficiency (WUE) and light use efficiency (LUE) were significantly different (P<0.01) during positive (NEP=?0.27 g C m?2 day?1, WUE=4.1 mg C g?1 H2O, LUE=0.94 g C MJ?1) and negative (NEP=+0.37 g C m?2 day?1, WUE=3.4 mg C g?1 H2O, LUE=0.83 g C MJ?1) climate phases. The CCI was linked to variability in the MODIS Enhanced Vegetation Index (EVI) but not to MODIS Fraction of absorbed Photosynthetically Active Radiation (FPAR). EVI was highest during negative climate phases (1999 and 2000) and was positively correlated with NEP and showed potential for using MODIS to estimate teleconnection‐driven anomalies in ecosystem CO2 exchange in old‐growth forests. This work suggests that any increase in the strength or frequency of ENSO coinciding with in‐phase, low frequency Pacific oscillations (PDO and PNA) will likely increase CO2 uptake variability in Pacific Northwest conifer forests. 相似文献
14.
Akihiko Ito Hiroyuki Muraoka Hiroshi Koizumi Nobuko Saigusa Shohei Murayama Susumu Yamamoto 《Ecological Research》2006,21(1):137-149
Seasonal changes in gross primary production (GPP) and net ecosystem production (NEP) in temperate deciduous forests are mostly driven by environmental conditions and the phenology of leaf demography. This study addresses another factor, temporal changes in leaf properties, i.e., leaf aging from emergence to senescence. A process-based model was used to link the ecosystem-scale carbon budget with leaf-level properties on the basis of field observation and scaling procedures; temporal variations in leaf thickness (leaf mass per area, LMA), photosynthetic rubisco (Vcmax) and electron-transport (Jmax) capacity, and dark respiration (Rd) were empirically parameterized. The model was applied to a cool-temperate deciduous broad-leaved forest at Takayama, in central Japan, and validated with data of net ecosystem CO2 exchange (NEE=–NEP) measured using the eddy-covariance method. NEP of the Takayama site varied seasonally from 3 g C m–2 day–1 net source in late winter to 5 g C m–2 day–1 net sink in early to mid-summer. A sensitivity experiment showed that removing the leaf-aging effect changed the seasonal CO2 exchange pattern, and led to overestimation of annual GPP by 6% and annual NEP by 38%. We found that seasonal variation in Vcmax affected the seasonal pattern and annual budget of CO2 exchange most strongly; LMA and Rd had moderate influences. The rapid change in Vcmax and Rd during leaf emergence and senescence was important in evaluating GPP and NEP of the temperate deciduous forest. 相似文献
15.
R. F. GRANT A. G. BARR† T. A. BLACK‡ D. GAUMONT-GUAY‡ H. IWASHITA§ J. KIDSON† H. McCAUGHEY ¶ K. MORGENSTERN‡ S. MURAYAMA§ Z. NESIC‡ N. SAIGUSA§ A. SHASHKOV T. ZHA† 《Global Change Biology》2007,13(7):1423-1440
Life cycle analysis of climate and disturbance effects on forest net ecosystem productivity (NEP) is necessary to assess changes in forest carbon (C) stocks under current or future climates. Ecosystem models used in such assessments need to undergo well-constrained tests of their hypotheses for climate and disturbance effects on the processes that determine CO2 exchange between forests and the atmosphere. We tested the ability of the model ecosys to simulate diurnal changes in CO2 fluxes under changing air temperatures (Ta) and soil water contents during forest regeneration with eddy covariance measurements over boreal jack pine (Pinus banksiana) stands along a postclearcut chronosequence. Model hypotheses for hydraulic and nutrient constraints on CO2 fixation allowed ecosys to simulate the recovery of C cycling during the transition of boreal jack pine stands from C sources following clearcutting (NEP from −150 to −200 g C m−2 yr−1) to C sinks at maturity (NEP from 20 to 80 g C m−2 yr−1) with large interannual variability. Over a 126-year logging cycle, annualized NEP, C harvest, and net biome productivity (NBP=NEP–harvest removals) of boreal jack pine averaged 47, 33 and 14 g C m−2 yr−1. Under an IPCC SRES climate change scenario, rising Ta exacerbated hydraulic constraints that adversely affected NEP of boreal jack pine after 75 years. These adverse effects were avoided in the model by replacing the boreal jack pine ecotype with one adapted to warmer Ta. This replacement raised annualized NEP, C harvest, and NBP to 81, 56 and 25 g C m−2 yr−1 during a 126-year logging cycle under the same climate change scenario. 相似文献
16.
Contrasting ecosystem CO2 fluxes of inland and coastal wetlands: a meta‐analysis of eddy covariance data
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Weizhi Lu Jingfeng Xiao Fang Liu Yue Zhang Chang'an Liu Guanghui Lin 《Global Change Biology》2017,23(3):1180-1198
Wetlands play an important role in regulating the atmospheric carbon dioxide (CO2) concentrations and thus affecting the climate. However, there is still lack of quantitative evaluation of such a role across different wetland types, especially at the global scale. Here, we conducted a meta‐analysis to compare ecosystem CO2 fluxes among various types of wetlands using a global database compiled from the literature. This database consists of 143 site‐years of eddy covariance data from 22 inland wetland and 21 coastal wetland sites across the globe. Coastal wetlands had higher annual gross primary productivity (GPP), ecosystem respiration (Re), and net ecosystem productivity (NEP) than inland wetlands. On a per unit area basis, coastal wetlands provided large CO2 sinks, while inland wetlands provided small CO2 sinks or were nearly CO2 neutral. The annual CO2 sink strength was 93.15 and 208.37 g C m?2 for inland and coastal wetlands, respectively. Annual CO2 fluxes were mainly regulated by mean annual temperature (MAT) and mean annual precipitation (MAP). For coastal and inland wetlands combined, MAT and MAP explained 71%, 54%, and 57% of the variations in GPP, Re, and NEP, respectively. The CO2 fluxes of wetlands were also related to leaf area index (LAI). The CO2 fluxes also varied with water table depth (WTD), although the effects of WTD were not statistically significant. NEP was jointly determined by GPP and Re for both inland and coastal wetlands. However, the NEP/Re and NEP/GPP ratios exhibited little variability for inland wetlands and decreased for coastal wetlands with increasing latitude. The contrasting of CO2 fluxes between inland and coastal wetlands globally can improve our understanding of the roles of wetlands in the global C cycle. Our results also have implications for informing wetland management and climate change policymaking, for example, the efforts being made by international organizations and enterprises to restore coastal wetlands for enhancing blue carbon sinks. 相似文献
17.
Measurement of net ecosystem production and ecosystem respiration in a Zoysia japonica grassland,central Japan,by the chamber method 总被引:1,自引:0,他引:1
Dhital Deepa Muraoka Hiroyuki Yashiro Yuichiro Shizu Yoko Koizumi Hiroshi 《Ecological Research》2010,25(2):483-493
Measuring light, temperature, soil moisture, and growth provides a better understanding of net ecosystem production (NEP),
ecosystem respiration (R
eco), and their response functions. Here, we studied the variations in NEP and R
eco in a grassland dominated by a perennial warm-season C4 grass, Zoysia japonica. We used the chamber method to measure NEP and R
eco from August to September 2007. Biomass and leaf area index (LAI) were also measured to observe their effects on NEP and R
eco. Diurnal variations in NEP and R
eco were predicted well by light intensity (PPFD) and by soil temperature, respectively. Maximum NEP (NEPmax) values on days of year 221, 233, 247, and 262, were 2.44, 2.55, 3.90, and 4.17 μmol m−2 s−1, respectively. Throughout the growing period, the apparent quantum yield (α) increased with increasing NEPmax that ranged from 0.0154 to 0.0515, and NEP responded to the soil temperature changes by 44% and R
eco changes by 48%, and R
eco responded from 88 to 94% with the soil temperature diurnally. NEP’s light response and R
eco’s temperature response were affected by soil water content; more than 27% of the variation in NEP and 67% of the variation
in R
eco could be explained by this parameter. NEP was strongly correlated with biomass and LAI, but R
eco was not, because environmental variables affected R
eco more strongly than growth parameters. Using the light response of NEP, the temperature response of R
eco, and meteorological data, daily NEP and R
eco were estimated at 0.67, 0.81, 1.17, and 1.56 g C m−2, and at 2.88, 2.50, 3.51, and 3.04 g C m−2, respectively, on days of year 221, 233, 247, and 262. The corresponding daily gross primary production (NEP + R
eco) was 3.5, 3.3, 4.6, and 4.6 g C m−2. 相似文献
18.
TAKASHI HIRANO HENDRIK SEGAH† TSUYOSHI HARADA SUWIDO LIMIN† TANIA JUNE‡§ RYUICHI HIRATA¶ MITSURU OSAKI 《Global Change Biology》2007,13(2):412-425
Tropical peatlands, which coexist with swamp forests, have accumulated vast amounts of carbon as soil organic matter. Since the 1970s, however, deforestation and drainage have progressed on an enormous scale. In addition, El Niño and Southern Oscillation (ENSO) drought and large‐scale fires, which grow larger under the drought condition, are accelerating peatland devastation. That devastation enhances decomposition of soil organic matter and increases the carbon release to the atmosphere as CO2. This phenomenon suggests that tropical peatlands have already become a large CO2 source, but related quantitative information is limited. Therefore, we evaluated the CO2 balance of a tropical peat swamp forest in Central Kalimantan, Indonesia, using 3 years of CO2 fluxes measured using the eddy covariance technique from 2002 through 2004. The forest was disturbed by drainage; consequently, groundwater level (GL) was reduced. The net ecosystem CO2 production (NEP) measurements showed seasonal variation, which was slightly positive or almost zero in the early dry season, and most‐negative late in the dry season or early the rainy season. This seasonality is attributable to the seasonal pattern of climate, tree phenology and fires. Slightly positive NEP resulted from smaller ecosystem respiration (RE) and larger gross primary production (GPP) under conditions of high photosynthetic photon flux density (PPFD) and large leaf area index (LAI). The most‐negative NEP resulted from smaller GPP and larger RE. The smaller GPP was related to high vapor pressure deficit (VPD), small LAI and low PPFD because of smoke from fires. The larger RE was related to low GL. Annual NEP values were estimated respectively as −602, −382 and −313 g C m−2 yr−1 for 2002, 2003 and 2004. These negative NEP values show that the tropical peat swamp forest, disturbed by drainage, functioned as a CO2 source. That source intensity was highest in 2002, an ENSO year, mainly because of low PPFD caused by dense smoke emitted from large fires. 相似文献
19.
Current Carbon Balance of the Forested Area in Sweden and its Sensitivity to Global Change as Simulated by Biome-BGC 总被引:3,自引:0,他引:3
Fredrik Lagergren Achim Grelle Harry Lankreijer Meelis Mölder Anders Lindroth 《Ecosystems》2006,9(6):894-908
Detailed information from the Swedish National Forest Inventory was used to simulate the carbon balance for Sweden by the
process-based model Biome-BGC. A few shortcomings of the model were identified and solutions to those are proposed and also
used in the simulations. The model was calibrated against CO2 flux data from 3 forests in central Sweden and then applied to the whole country divided into 30 districts and 4 age classes.
Gross primary production (GPP) ranged over districts and age classes from 0.20 to 1.71 kg C m−2 y−1 and net ecosystem production (NEP) ranged from −0.01 to 0.44. The 10- to 30-year age class was the strongest carbon sink
because of its relatively low respiration rates. When the simulation results were scaled up to the whole country, GPP and
NEP were 175 and 29 Mton C y−1, respectively, for the 22.7 Mha of forests in Sweden. A climate change scenario was simulated by assuming a 4°C increase
in temperature and a doubling of the CO2 concentration; GPP and NEP then increased to 253 and 48 Mton C y−1, respectively. A sensitivity analysis showed that at present CO2 concentrations NEP would peak at an increase of 5°C for the mean annual temperature. At higher CO2 levels NEP showed a logarithmic increase. 相似文献
20.
川中丘陵区冬水田种植模式转旱作土壤呼吸组分特征及碳平衡 总被引:1,自引:0,他引:1
冬水田-水稻是川中丘陵区传统的稻田种植模式,冬水田种植模式转变是实现多熟种植及机械化的重要途径。为探究冬水田-水稻种植模式转旱作过程中作物季及休闲期土壤呼吸速率及其组分构成,试验设置冬水田-水稻转旱作(FTD)、冬水田-水稻(FR)和冬闲田-玉米(FM)3种不同种植模式,采用根排除法和静态明箱-气相色谱法原位取样测定作物季及季后休闲期土壤呼吸及其组分,并通过测算净生态系统生产力(NEP)进而判断冬水田-水稻转旱作过程的农田系统碳汇强度。结果表明:(1)FTD显著提高了土壤总呼吸速率及其自养和异养呼吸速率,从而提高了其累积排放量(P<0.05)。与FR相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了13.14倍、11.32倍和15.56倍(P<0.05);与FM相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了70.56%、40.83%和115.47%(P<0.05)。(2)与FR和FM相比,FTD均降低了土壤呼吸及其组分的温度敏感性(Q10),且土壤总呼吸的温度敏感性介于异养呼吸和自养呼吸之间。(3)FR,FM和FTD的净生态系统生产力(NEP)均为正值,其数值分别为7911.66 kg/hm2,5667.89 kg/hm2和1583.46 kg/hm2,均表现为大气CO2的碳汇,但与FR与FM相比,FTD显著降低了其净生态系统生产力,呈现出较弱的碳汇。 相似文献