黄河三角洲芦苇湿地生态系统碳、水热通量特征

利用涡度相关法对黄河三角洲芦苇湿地生态系统进行了连续两年的通量观测,对2009—2010年生长季芦苇湿地的净生态系统碳交换量(NEE),感热通量(Hs)和潜热通量(LE)数据进行了分析。结果表明,在日尺度上,芦苇湿地NEE日变化特征表现为两个CO2吸收高峰,分别出现在11:00和16:00左右,其特点是在午间出现了碳交换通量的降低。CO2吸收的日最大值在两个生长季出现的时间有所不同,分别出现在2009年7月(-0.30 mg CO2m-2s-1)和2010年6月(-0.37 mg CO2m-2s-1)。CO2排放的日最大值两个生长季均出现在9月,分别为0.19和0.25 mg CO2m-2s-1。Hs和LE的日动态均为单峰型,极值都出现在中午前后,生长季生态系统的能量消耗主要以潜热为主,且在日尺度上,热通量和NEE有显著的负相关关系。在季节尺度上,芦苇湿地生长季具有明显的碳汇功能,2009年生长季生态系统白天固定354.63 g CO2/m2,同时期夜间释放159.24 g CO2/m2,净CO2吸收量为-195.39 g CO2/m2。2009年整个生长季生态系统总初级生产力(GPP)为-651.13 g CO2/m2,生态系统呼吸(Re)为455.74 g CO2/m2,系统表现为碳汇。路径分析表明:光合有效辐射(PAR)显著影响NEE的日动态(R2=0.46—0.84),而NEE的季节动态主要受土壤温度的影响,降水和PAR的影响次之。     

北京海淀公园绿地二氧化碳通量

作为城市生态系统的重要组成部分,城市绿地有着释氧固碳、降温增湿、吸收有毒有害气体、降尘、减噪等多种生态功能。在对北京海淀公园2006年5月到2007年3月的CO2通量观测数据进行质量评价、数据剔除和插补的基础上,通过与温度、太阳辐射等气象数据的相关性分析,定量研究了海淀公园绿地CO2通量的日变化、年变化以及影响因子。结果表明,海淀公园绿地日CO2通量在一年内具有明显的季节变化,植物生长季3—10月份以吸收CO2为主,11月至翌年2月份以释放CO2为主;年净生态系统生产力(NEP)为8.7554 tCO2/hm2a,反映了海淀公园绿地具有较强的固碳能力。     

科尔沁沙丘-草甸梯级生态系统土壤温室气体通量特征及其影响因素

采用静态箱-气相色谱法,对科尔沁半干旱地区典型的沙丘-草甸梯级生态系统中半流动沙丘和草甸湿地的温室气体(CO₂、CH₄、N₂O)通量进行了观测,分析了生长季温室气体的动态变化及其与环境影响因子的关系.结果表明: 生长季半流动沙丘和草甸湿地CH₄通量均整体表现为吸收,平均值分别为-52.7和-34.7 μg·m^-2·h^-1,介于-176.1～49.8 μg·m^-2·h^-1之间变化,8月22日半流动沙丘CH₄吸收值达到生长季最大值;8、9月降雨集中时段内草甸湿地CH₄通量表现为持续排放,与半流动沙丘呈明显差异.N₂O通量在7月21日达到生长季最大值,半流动沙丘N₂O通量的月均值表现为7月>8月>9月>6月>5月.土壤温湿度是影响CO₂和CH₄通量的关键因子,N₂O通量主要受土壤温度的影响.样地土壤温度敏感性(Q₁₀)表现为半流动沙丘(1.009)<草甸湿地(1.474),半流动沙丘土壤受到水分胁迫,导致其温室气体通量对土壤温度变化的敏感性明显低于草甸湿地.     

扎龙芦苇湿地生长季的甲烷排放通量

为研究高寒地区天然淡水芦苇湿地的甲烷排放特征,采用静态箱-气相色谱法,测定了扎龙不同水位芦苇湿地生长季的甲烷排放通量.结果表明:观测期内,扎龙芦苇湿地甲烷排放通量平均为7.67 mg·m^-2·h^-1（-21.18～46.15 mg·m^-2·h^-1）,其中深水区(平均水深100 cm)和浅水区(平均水深25 cm)的平均甲烷排放通量分别为5.81和9.52 mg·m^-2·h^-1,排放峰值分别出现在8月和7月,最低值均出现在10月.深水区夏季(6-7月)的甲烷排放通量显著低于浅水区,而春(5月)、秋(8-10月)季节显著高于浅水区.生长季甲烷排放通量的变化为夏季>秋季>春季;昼夜排放量为12:00和14:00最高,0:00最低.温度和水位是高寒地区淡水芦苇湿地甲烷排放通量变化的主要影响因子.     

内蒙古克氏针茅草原生态系统碳通量数据质量评价及日和季节变化特征

利用内蒙古锡林浩特国家气候观象台2010年3月至2011年2月全年的大气湍流观测资料,在数据质量控制的基础上,对内蒙古克氏针茅草原生态系统碳通量数据进行质量评价,并分析了日变化和季节变化特征。结果表明:在惯性副区,湍流通量的功率谱和协谱基本呈-2/3和-4/3的斜率变化。经过质量控制后的通量数据中,可用于基础研究的高质量数据约为74%,约有8%的低质量数据需要剔除。克氏针茅草原生长季中碳通量的日变化分为单峰和双峰两种类型,均有明显的不对称性,上午碳吸收强于下午。克氏针茅草原在冬季由于低温碳通量值很小,春季气温缓慢回升,草原处于早期发展阶段,表现为弱的碳汇,夏季的6月碳吸收达全年最强,7月和8月受干旱胁迫影响,碳通量逐渐减小,秋季草原开始枯黄,表现为弱的碳汇。内蒙古克氏针茅草原CO2年总量达-348 g CO2·m-2·a-1。克氏针茅草原7月夜间碳排放达最大值,6月白天碳吸收全年最强。本研究加深了对草原生态系统生长季和非生长季碳通量交换特征的理解,为陆面过程模型及相关碳模型参数修正提供了参考。     

涡度相关观测的太湖CH4通量数据插补方法评价

涡度相关法是在湖泊开展CH₄通量长期连续观测的重要方法。受到多种因素的影响,CH₄通量观测数据存在大量缺失。为重构完整的CH₄通量时间序列,就需要适宜的数据插补方法。本研究利用太湖涡度通量观测网络东部的避风港站点2014—2017年的常规气象数据及涡度相关观测的CH₄通量数据,在分析半小时尺度以及日尺度CH₄通量影响要素的基础上,测试了非线性回归法以及随机森林算法和误差反向传播算法在半小时尺度及日尺度上插补CH₄通量缺失数据的可行性。结果表明: 在半小时尺度上,避风港站生长季CH₄通量主要受到底泥温度、摩擦风速、气温、相对湿度、潜热通量和20 cm处水温的影响,非生长季主要受到相对湿度、潜热通量、风速、感热通量和底泥温度的影响,而在日尺度上CH₄通量主要受潜热通量和相对湿度的影响。在对CH₄通量缺失数据的插补中,随机森林模型在所有时间尺度上都表现为最佳的插补性能,其中,将日序、太阳高度角、底泥温度、摩擦风速、气温、20 cm处水温、相对湿度、气压和风速作为输入变量的随机森林模型更适用于半小时尺度缺失数据的插补;将日序、底泥温度、摩擦风速、气温、20 cm处水温、相对湿度、气压、风速和向下短波辐射作为输入变量的随机森林模型更适用于日尺度缺失数据的插补;整体上,插补模型对日尺度缺失数据的插补优于半小时尺度。     

荒漠杜加依林冠层水热变化及CO2交换特征

选取新疆艾比湖湿地国家级自然保护区荒漠杜加依林为研究对象,利用通量塔连续观测数据分析新疆艾比湖流域内杜加依林冠层界面水热垂直变化和CO_2交换特征,进一步比较了冠层界面湍流碳通量、植物冠层储存碳通量及净碳交换量,探讨了不同时间和垂直空间序列下杜加依林冠层界面温湿廓线与CO_2交换过程的相互关系。结果表明,新疆艾比湖流域内杜加依林冠层上方大气稳定度生长季的6—9月为中性(z/L=0.009),非生长季为不稳定(z/L=-0.449),全年总体呈不稳定水平(z/L=-0.194);冠层界面上气温垂直变幅小于5℃,随高度呈递增趋势,湿度垂直变幅超过40%;地-气碳通量呈秋冬小春夏大规律,年碳收支高于干旱区平均水平,为-0.026 mg CO_2m~(-2)s~(-1),表现为碳汇;垂直空间尺度上垂直温湿度差与生态系统净碳交换量(NEE,Net Ecosystem Exchange)拟合较好,温度拟合结果为R~2=0.7350(P﹤0.01),湿度拟合结果为R~2=0.3627(P﹤0.01),水热变点分别为5%和1℃,而季节尺度上温度拟合结果较好,温度拟合结果为R~2=0. 5221(P﹤0. 01),湿度拟合结果为R~2=0.1716(P﹤0.01),变点为55%和18℃。生长季较小的冠层垂直温差有利于杜加依林对大气CO_2的吸收,而冠层高湿环境则会抑制杜加依林对CO_2的吸收。     

锡林浩特草原净生态系统碳交换量特征及源区分布

为探究草原生态系统固碳能力,利用锡林浩特国家气候观象台2018—2021年的涡动相关资料分析了锡林浩特草原生态系统CO₂通量的变化特征以及环境因子对CO₂通量的影响,并对通量源区分布进行了探讨。结果表明：研究区全年盛行西南风,生长季的源区面积大于非生长季,大气稳定条件下的源区面积大于不稳定条件;90%贡献率的源区最大长度接近400 m,与经典法则估算的长度一致。锡林浩特草原净生态系统碳交换量(NEE)具有明显的日变化和季节变化,生长季白天为碳汇,夜间为碳源,非生长季白天和夜间均为弱碳源。2018—2021年,年总NEE分别为-15.59、-46.28、-41.94和-78.14 g C·m^-2·a^-1,平均值为-45.49 g C·m^-2·a^-1,表明锡林浩特草原有较强的固碳能力。饱和水汽压差和光合有效辐射有助于草原生态系统吸收大气中CO₂;夜间,当温度高于0℃时,气温和土壤温度升高会促进植被呼吸作用释放CO₂。     

亚热带-暖温带过渡区天然栎林的能量平衡特征

利用开路涡度相关系统和常规气象观测仪器观测了我国北亚热带-暖温带气候过渡带(河南南阳)的一片锐齿栎天然林的能量通量及常规气象。以一个完整年(2016年10月—2017年9月)的观测数据为依据,定量分析了此锐齿栎林的能量通量的日变化、季节变化以及各能量分量的分配特征,并计算了能量闭合度以及波文比。结果表明:锐齿栎林观测期间一整年净辐射为2626.17 MJ/m~2,感热通量为867.1 MJ/m~2,潜热通量为1417.25 MJ/m~2,土壤热通量为-2.60 MJ/m~2,土壤为热源;各能量分量日变化基本呈单峰型曲线,季节变化特征明显。非生长季,锐齿栎林的能量主要分配给感热通量,占净辐射的54.18%;生长季,能量主要分配给潜热通量,占净辐射的67.48%。观测期间研究区年降雨量较平均值稍大(1231.8 mm),森林蒸散量为579 mm,仅为降雨量的47%。波文比受森林物候变化影响较大,在非生长季平均值约为2.1,生长季约为0.2。土壤热通量在生长季2017年4—9月份为正值,土壤表现为热汇,其余月份皆为热源。土壤热通量的变化过程主要受净辐射调控,森林物候也起了一定的作用。河南宝天曼锐齿栎森林通量观测站全年能量闭合度为67%,在国际同类观测站的范围之内(55%—99%)。不能完全闭合的原因可能与通量源区面积不匹配、计算能量平衡时忽略冠层热存储等有关。     

呼伦贝尔地区贝加尔针茅草甸草原土壤CO_2排放特征

采用Li-8150多通道土壤碳通量自动观测系统,于2009年6月—2010年6月对呼伦贝尔地区贝加尔针茅草甸草原土壤呼吸进行连续野外观测,分析该地区土壤CO2通量排放特征.结果表明:生长季内贝加尔针茅草甸草原土壤呼吸日动态呈单峰曲线,最高值出现在13:00—15:00,最低值出现在5:00—6:00,土壤呼吸呈明显的季节变化,与土壤温度和土壤含水量季节动态相吻合.土壤呼吸与各层土壤温度和土壤含水量关系可以用线性模型和指数-乘幂模型来表示;土壤呼吸与各层土壤温度呈显著的指数回归关系,Q10变化范围分别为1.68~2.14和3.03~3.60,非生长季土壤温度对土壤呼吸的影响更为显著;生长季内土壤呼吸与10 cm土壤含水量呈显著正相关.2009和2010年土壤CO2年排放量分别为488.47和507.20 g C·m-2·a-1,生长季排放量约占年排放量的90%.     

CO2 flux in alpine wetland ecosystem on the Qinghai-Tibetan Plateau, China

Using the CO₂ flux data measured by the eddy covariance method in the northeast of Qinghai-Tibetan Plateau in 2005, we analyzed the carbon flux dynamics in relation to meteorological and biotic factors. The results showed that the alpine wetland ecosystem was the carbon source, and it emitted 316.02 gCO₂ · m⁻² to atmosphere in 2005 with 230.16 gCO₂ · m⁻² absorbed in the growing season from May to September and 546.18 gCO₂ · m⁻² released in the non-growing season from January to April and from October to December. The maximum of the averaged daily CO₂ uptake rates and release rates was (0.45 ± 0.0012) mgCO₂ · m⁻² · s⁻¹ (Mean ± SE) in July and (0.22 ± 0.0090) mgCO₂ · m⁻² · s⁻¹ in August, respectively. The averaged diurnal variation showed a single-peaked pattern in the growing season, but exhibited very small fluctuation in the non-growing season. Net ecosystem exchange (NEE) and gross primary production (GPP) were all correlated with some meteorological factors, and they showed a negatively linear correlation with aboveground biomass, while a positive correlation existed between the ecosystem respiration (R_es) and those factors.     

青藏高原高寒湿地生态系统CO2通量

依据涡度相关系统连续观测的2005年CO2通量数据,对青藏高原东北隅的高寒湿地生态系统源/汇功能及其部分环境影响因素进行了分析.结果表明,高寒湿地生态系统为明显的碳源,在植物生长季(5～9月份)吸收230.16 gCO2·m-2,非生长季(1～4月份及10～12月份)释放546.18 gCO2·m-2,其中净排放最高在5月份,为181.49 gCO2·m-2,净吸收最高在8月份,为189.69 gCO2·m-2,年释放量为316.02 gCO2·m-2.在平均日变化中,最大吸收值出现在7月份12:00,为(0.45±0.0012) mgCO2·m-2·s-1,最大排放速率出现在8月份0:00,为(0.22±0.0090) mgCO2·m-2·s-1.生长季中6～9月份表现为明显的单峰型日变化,非生长季的变化幅度较小.净生态系统交换量(NEE)和生态系统总初级生产力(GPP)与气温、空气水气饱和亏和地表反射率等环境因素呈现相似的相关性,与地上生物量和群落叶面积指数则为线性负相关,生态系统呼吸(Res)则与上述因子的相关性呈现相反的趋势.     

Seasonal patterns in soil surface CO<Subscript>2</Subscript> flux under snow cover in 50 and 300 year old subalpine forests

Soil CO₂ flux can contribute as much as 60–80% of total ecosystem respiration in forests. Although considerable research has focused on quantifying this flux during the growing season, comparatively little effort has focused on non-growing season fluxes. We measured soil CO₂ efflux through snow in 50 and ~300 year old subalpine forest stands near Fraser CO. Our objectives were to quantify seasonal patterns in wintertime soil CO₂ flux; determine if differences in soil CO₂ flux between the two forest ages during the growing season persist during winter; and to quantify the sample size necessary to discern treatment differences. Soil CO₂ flux during the 2002–2003 and 2003–2004 snow season averaged 0.31 and 0.35 μmols m⁻² s⁻¹ for the young and old forests respectively; similar to the relative difference observed during summer. There was a significant seasonal pattern of soil CO₂ flux during the winter with fluxes averaging 0.22 μmols m⁻² s⁻¹ in December and January and increasing to an average of 0.61 μmols m⁻² s⁻¹ in May. Within-plot variability for measurements used in calculating flux was low. The coefficients of variation (CV) for CO₂ concentration, snowpack density, and snow depth were 17, 8 and 14%, respectively, yielding a CV for flux measurements within-plot of 29%. A within plot CV of 29% requires 8 sub-samples per plot to estimate the mean flux with a standard error of ±10% of the mean. Variability in CO₂ flux estimates among plots (size = 400 m²) was similar to that within plot and was also low (CV = ~28%). With a CV of 28% among plots, ten plots per treatment would have a 50% probability of detecting a 25% difference in treatment means for α = 0.05.     

华南地区5种人工幼林的土壤呼吸及其季节性变化

为了解华南人工林的碳固存机制,对广东鹤山的尾叶桉(Eucalyptus urophylla)纯林、30种树种混交林、10种树种混交林、红椎(Castanopsis hystrix)纯林、厚荚相思(Acacia crassicarpa)纯林5种人工林(林龄2–5 a)的土壤总呼吸(Rs)和自养呼吸(Ra)的季节变化进行了研究。结果表明,从2007年到2012年,5种人工林的Rs为81.3~103.9 mg C m–2h–1,Ra为11.2~22.3 mg C m–2h–1,自养呼吸贡献率(RC)为12.4%~26.9%,且5种人工林间的Rs、Ra及RC差异不显著。5种人工林湿季的Rs均显著大于干季的,平均高出311.4%;Ra、RC的季节性差异不显著。湿季土壤温度与Rs具有显著相关性,土壤温度解释了90.2%的变异,而两者关系在干季不显著。人工林间的微环境和土壤条件差异不明显,可能是由于造林时间短,土壤还处于干扰的恢复过程中,导致人工林间土壤呼吸差异不显著。     

太湖流域典型稻麦轮作农田生态系统碳交换及影响因素

利用涡度相关技术观测太湖流域典型稻麦轮作农田生态系统2a净生态系统碳交换(NEE)变化过程,分析其碳交换特征及影响机理,结果表明:太湖流域典型稻麦轮作农田年NEE为-749.49—-785.38 g C m-2a-1,考虑作物籽粒碳和秸秆还田后净吸收88.12 g C m-2a-1,为弱碳汇;稻/麦季日均NEE和白天NEE季节变化直接受作物植被生长影响;麦季夜间NEE与10 cm土壤温度呈显著指数关系,2012/2013年温度敏感系数(Q10)分别为3.03和2.67;当土壤水分低于田间持水量时,麦季夜间NEE主要受土壤温度影响,反之,夜间NEE受土壤温度和水分双重影响;降水对麦季夜间NEE有短时的激发效应;稻季淹水对土壤呼吸产生较明显的阻滞效应,降低了夜间NEE对土壤温度的敏感性,2012和2013年分别为1.88和1.39,稻季淹水与烤田交替变化对土壤呼吸产生明显的抑制或激发的短时效应。     

CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos,Venezuela

CO₂ exchange between the atmosphere and soil algal crusts of the Trachypogon savannas of the Orinoco Llanos has been analyzed using an open gas exchange system. These savannas encompass a wide range of physiognomic types, from herbaceous communities to savanna woodlands. A maximum CO₂ flux of 0.207 mg m^-2 s^-1 was measured in the crusts of the Guanipa savannas, while in the other examined crusts (0.035–0.105 mg m^-2 s^-1) the flux was similar to values reported for terrestrial algae. The CO₂ flux data were statistically fitted to the photosynthetically active radiation by a logarithmic relationship, and the photosynthetic efficiencies of the crusts were compared. The activation energy calculated for the CO₂ fixation indicates that limitations by diffusion and photochemical processes were excluded in the Guanipa crusts (above 12 kcal mole^-1), whereas they were evident in the other crust studied. An optimum CO₂ incorporation as a function of the crust water potential was established and carbon gain strategies were proposed on the basis of the results and characteristics of the habitats.     

西南喀斯特地区轮作旱地土壤CO2通量

中国已承诺大幅降低单位GDP碳排放,农业正面临固碳减排的重任.西南喀斯特地区环境独特,旱地面积占据优势比例,土壤碳循环认识亟待加强.以贵州省开阳县玉米-油菜轮作旱地为研究对象,采用密闭箱-气相色谱法对整个轮作期土壤CO2释放通量进行了观测研究,结果表明:(1)整个轮作期旱地均表现为CO2的释放源.其中油菜生长季土壤CO2通量为(178.8±104.8)mg CO2·m-2·h-1,玉米生长季为(403.0±178.8) mg CO2·m-2·h-1,全年平均通量为(271.1±176.4) mg CO2·m-2·h-1,高于纬度较高地区的农田以及同纬度的次生林和松林;(2)CO2通量日变化同温度呈现显著正相关关系,季节变化与温度呈现显著指数正相关关系,并受土壤湿度的影响,基于大气温度计算得出的Q10为2.02,高于同纬度松林以及低纬度的常绿阔叶林;(3)CO2通量与土壤pH存在显著线性正相关关系,显示出土壤pH是研究区旱地土壤呼吸影响因子之一.     

High rates of net ecosystem carbon assimilation by Brachiara pasture in the Brazilian Cerrado

To investigate the consequences of land use on carbon and energy exchanges between the ecosystem and atmosphere, we measured CO₂ and water vapour fluxes over an introduced Brachiara brizantha pasture located in the Cerrado region of Central Brazil. Measurements using eddy covariance technique were carried out in field campaigns during the wet and dry seasons. Midday CO₂ net ecosystem exchange rates during the wet season were ?40 μmol m^?2 s^?1, which is more than twice the rate found in the dry season (?15 μmol m^?2 s^?1). This was observed despite similar magnitudes of irradiance, air and soil temperatures. During the wet season, inferred rates of canopy photosynthesis did not show any tendency to saturate at high solar radiation levels, with rates of around 50 μmol m^?2 s^?1 being observed at the maximum incoming photon flux densities of 2200 μmol m^?2 s^?1. This contrasted strongly to the dry period when light saturation occurred with 1500 μmol m^?2 s^?1 and with maximum canopy photosynthetic rates of only 20 μmol m^?2 s^?1. Both canopy photosynthetic rates and night‐time ecosystem CO₂ efflux rates were much greater than has been observed for cerrado native vegetation in both the wet and dry seasons. Indeed, observed CO₂ exchange rates were also much greater than has previously been reported for C₄ pastures in the tropics. The high rates in the wet season may have been attributable, at least in part, to the pasture not being grazed. Higher than expected net rates of carbon acquisition during the dry season may also have been attributable to some early rain events. Nevertheless, the present study demonstrates that well‐managed, productive tropical pastures can attain ecosystem gas exchange rates equivalent to fertilized C₄ crops growing in the temperate zone.     

Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covariance

Eddy covariance measurements of methane (CH₄) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May–September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH₄ net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH₄ emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH₄ emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181–215, nighttime average CH₄ efflux was only 47% of the average midday values. The peak value for daily average CH₄ emission rate was approximately 80 nmol m^?2 s^?1 (4.6 mg CH₄ m^?2 h^?1), and seasonal variation in CH₄ flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144–269 (late May–late September)], the total CH₄ emission was 3.2 g CH₄ m^?2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO₂ sequestration that was measured (18.1 mol CO₂ m^?2 or 217 g C m^?2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH₄ emission over the last 50 years.     

青海湖北岸草甸草原CO2通量年际动态及其驱动机制

青藏高原草甸草原是生态系统中重要的植被类型,准确评估高寒草甸草原生态系统碳源汇状况及碳储量变化尤为重要。基于涡度相关系统观测,分析了2009年至2016年8年期间青海湖北岸草甸草原环境因子以及碳通量的变化特征,运用结构方程模型(SEM)分析环境因子对总初级生产力(GPP)、净生态系统CO₂交换量(NEE)、生态系统呼吸(Re)的调控机制。结果表明：2009—2016年8年NEE日均值在-2.02—0.88 gC m^-2 d^-1之间,5—9月NEE为负值,表现为碳吸收,雨热同期的6、7、8月是CO₂净吸收最强的时期,平均每月吸收CO₂ 39.85 gC m^-2 month^-1,NEE负值日数约占全年的48%,10月—翌年4月为正值,表现为碳释放,初春3月和秋末11月是CO₂净释放最强的时期;Re日均值为1.69 gC m^-2 d^-1,受季节温度的影响,呈夏季强,冬季弱的态...