Gap Filling of Net Ecosystem CO₂Exchange (NEE) above Rain-Fed Maize Using Artificial Neural Networks (ANNs)

The eddy covariance technique is an accurate and direct tool to measure the Net Ecosystem Exchange (NEE) of carbon dioxide. However, sometimes conditions are not amenable to measurements using this technique. Thus, different methods have been developed to allow gap-filling and quality assessment of eddy covariance data sets. In this study first, two different Artificial Neural Networks (ANNs) approaches, the Multi-layer Perceptron (MLP) trained by the Back-Propagation (BP) algorithm, and the Radial Basis Function (RBF), were used to fill missing NEE data measured above rain-fed maize at the University of Nebraska-Lincoln Agricultural Research and Development Center near Mead, Nebraska. The gap-filled data were then compared by different statistical indices to gap-filled data obtained with the technique suggested by Suyker and Verma in 2005 [S&V method], and the ANN approach presented by Papale in 2003. The results showed that the RBF network was able to find better fits for missing values compared to the MLP (BP) network and S&V method. In addition, unlike the S&V method, which depends on different gap-filling procedures over the year;the structure of RBF and MLP (BP) networks was constant. However, data analysis indicated Papale’s approach gave better fits than the RBF and MLP (BP) methods. Thus, based on this work, Papale’s approach is the best method to estimate the missing data;though the applied statistical indices, which were used for model evaluation, show little difference between Papale’s approach and the RBF and MLP (BP).

Estimated Net Ecosystem Exchange （NEE） of Turfgrass at Different Management Intensities in a Golf Course in the Province of Verona

The carbon （C） sequestration potential of turfgrass systems has been investigated and demonstrated from several studies. The role of these ecosystems in continental and Mediterranean climates though, is not yet clearly understood because environmental limiting factors and management intensities can strongly influence the overall C budget. The aim of the present study is to improve the understanding of the mechanisms underlying C fluxes in a turfgrass ecosystem and to assess its C sequestration potential by estimating the annual C budget. NEE （Net Ecosystem Exchange） of turfgrass was calculated in its seasonal variation over one year, and compared between areas characterized by different degrees of maintenance. The C sequestration potential of the turfgrass was investigated in a golf course near Verona （Italy）, adopting a small-chamber enclosure approach. The measurements of gas exchanges between biosphere and atmosphere, permitted to estimate the NEE, as a function of different management intensities. The intensity of management seems to have influence on its C balance. This study needs further research to understand which maintenance variables are determinant on turfgrass C sequestration.

Direct Radiative Effect of Aerosols on Net Ecosystem Carbon Exchange in the Pearl River Delta Region

The environmental impact of aerosols is currently a hot issue that has received worldwide attention. Lacking simultaneous observations of aerosols and carbon flux, the understanding of the aerosol radiative effect of urban agglomeration on the net ecosystem carbon exchange(NEE) is restricted. In 2009-2010, an observation of the aerosol optical property and CO_(2) flux was carried out at the Dongguan Meteorological Bureau Station(DMBS) using a sun photometer and eddy covariance systems. The different components of photosynthetically active radiation(PAR),including global PAR(GPAR), direct PAR(DPAR), and scattered PAR(FPAR), were calculated using the Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART) model. The effects of PAR on the NEE between land-atmosphere systems were investigated. The results demonstrated that during the study period the aerosol optical depth(AOD)reduced the DPAR by 519.28±232.89 μmol photons · m^(-2)s^(-1), but increased the FPAR by 324.93±169.85μmol photons ·m^(-2)s^(-1),ultimately leading to 194.34±92.62 μmol photons · m^(-2)s^(-1);decrease in the GPAR. All the PARs(including GPAR,DPAR, and FPAR) resulted in increases in the NEE(improved carbon absorption), but the FPAR has the strongest effect with the light use efficiency(LUE) being 1.12 times the values for the DPAR. The absorption of DPAR by the vegetation exhibited photo-inhibition in the radiation intensity > 600 photons · m^(-2)s^(-1);in contrast, the absorptions of FPAR did not exhibit apparent photo-inhibition. Compared with the FPAR caused by aerosols, the DPAR was not the primary factor affecting the NEE. On the contrary, the increase in AOD significantly increased the FPAR, enhancing the LUE of vegetation ecosystems and finally promoting the photosynthetic CO_(2) absorption.

Impact of Cloud on Net Ecosystem CO_(2) Exchange of Alpine Meadow in Tibetan Plateau

Meteorological elements and CO_(2) fluxes over alpine meadow ecosystem were observed continuously from 2004 to 2005 in Damxung Alpine Meadow Flux Station,China Flux Network.Based on the eddy covariance CO_(2) fluxes and meteorological data obtained,the relationships among the CO_(2) fluxes,the cloud amount,and the meteorological factors in alpine meadow ecosystem were explored and analyzed.Some conclusions can be drawn from the discussion with previous researches as following:(1)the cloud amount can affect the net ecosystem CO_(2) exchange(NEE)of alpine meadow on Tibetan Plateau;(2)the soil temperature sensitive to the cloud amount,is a major environmental controlling factor for NEE,and closely relates to the maximum of NEE.In the moming period with large cloud amount,the NEE reaches its maximum when the clearness index ranges from 0.5 to 0.7;yet in the afternoon it comes to the maximum with the index from 0.2 to 0.35.The span of soil temperature covers from 12 to 15℃as the NEE at its highest;(3)the scatterplots between NEE and photosynthetic available radiation(PAR)was a significant inverse triangle in the clear day,two different kinds of concave curves in the cloudy day,and strongly convergent rectangular hyperbola in the overcast day.These differences were controlled by the changes of light radiation and soil temperature.

Seasonal and Interannual Variations of Carbon Exchange over a Rice–Wheat Rotation System on the North China Plain

Rice-wheat （R-W） rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding the seasonal and interannual variation of the carbon budget over R-W rotation systems. In this study, measurements of CO2 fluxes and meteorological variables over an R-W rotation system on the North China Plain from 2007 to 2010 were analyzed. To analyze the abiotic factors regulating Net Ecosystem Exchange （NEE）, NEE was partitioned into gross primary production （GPP） and ecosystem respiration. Nighttime NEE or ecosystem respiration was controlled primarily by soil temperature, while daytime NEE was mainly determined by photosythetically active radiation （PAR）. The responses of nighttime NEE to soil temperature and daytime NEE to light were closely associated with crop development and photosynthetic activity, respectively. Moreover, the interannual variation in GPP and NEE mainly depended on precipitation and PAR. Overall, NEE was negative on the annual scale and the rotation system behaved as a carbon sink of 982 g C m 2 per year over the three years. The winter wheat field took up more CO2 than the rice paddy during the longer growing season, while the daily NEE for wheat and rice were -2.35 and -3.96 g C m-2, respectively. After the grain harvest was subtracted from the NEE, the winter wheat field became a moderately strong carbon sink of 251-334 g C m-2 per season, whereas the rice paddy switched to a weak carbon sink of 107-132 per season.

我国东部山地针阔混交林碳通量特征分析

以浙江省金华市武义县大毛尖山为研究区域,开展复杂山地森林生态系统碳汇能力的观测研究,并利用涡动相关法在2022年6月~2023年5月进行观测,经过数据质量控制和质量评价分析,得到42%的优质CO_(2)通量数据.结果表明,大毛尖山周边以针阔混交林为主,能量闭合度为0.89,能够很好的代表站点通量情况.CO_(2)通量在日尺度上均表现为U型变化,范围为-1.20~0.89mgCO_(2)/(m^(2)·s).四季碳汇能力强弱依次为,夏季、春季、秋季、冬季;各月份净生态系统碳交换量(NEE)均为负值,整体表现为碳汇.CO_(2)通量与气象因子中的空气温度呈负相关,相对湿度和平均风速正相关,夜间因呼吸作用产生的CO_(2)通量与土壤温度正相关.本研究初步解释了大毛尖山森林生态系统的碳汇特征.

知识交流生态视角下的用户跨平台知识交流行为偏好研究

[目的/意义]从知识交流生态视角出发,探究基于视频资源的用户跨平台知识交流行为偏好规律,为用户利用多平台开展交互、实现高价值知识交流提供有效指导。[方法/过程]通过对齐在B站和微博上进行跨平台知识交流的用户,并获取他们在两个平台发布的全量视频内容7215条和同质化视频的330367条评论文本,基于知识生态系统框架,分别针对知识生产者和知识分解者进行内容发布和评论互动等跨平台知识交流偏好的探究。[结果/结论]知识生产者会在不同平台规律性地发布同质化视频以获得知识消费者更好的互动反馈,且根据平台定位和平台功能差异进行标题差异化展示;跨平台知识交流中,知识分解者的评论互动偏好与平台特性相关。[局限]仅选择B站和微博中高影响力知识生产者群体进行研究,后续研究中可对更为多元的知识交流平台以及更丰富的大众知识生产者行为规律进行拓展分析。

青藏高原东南缘不同类型生态系统碳、水交换特征

青藏高原东南缘横断山脉地区是南亚和东亚季风的交汇处,也是大气变化的敏感区和热源区。开展该地区地气相互作用对区域水热过程影响机制及其参数化研究,对于研究青藏高原大气水汽传输的关键过程问题有重大意义。本文介绍了基于涡动观测法开展的青藏高原东南缘地区的地气相互作用观测试验,并总结了洱海湖面、丽江高山草甸及腾冲北海湿地的地气交换特征,以及利用数值模式开展复杂山地局地环流特征的研究工作。目前已初步明确和揭示青藏高原东南缘横断山脉不同类型下垫面的地气交换特征及其影响因素,主要结论如下:青藏高原东南缘高山草甸的碳、水交换过程受降水分布影响显著,“浮毯型”湿地(水面常年覆盖有“浮毯”状苔草草排)的碳、水交换除了受气象因素影响外,也受到下垫面植被和水体比例变化的影响。不同类型生态系统的碳、水交换过程在不同时间尺度的影响因子存在差别。风速始终是湖泊潜热和CO_(2)交换的关键影响因子,而降水在较长时间尺度对湖泊CO_(2)通量也有显著影响。此外,青藏高原东南缘的复杂地形对于生态系统的碳、水交换过程也有显著影响。复杂地形产生的不同类型的局地环流对于生态系统的碳、水交换过程有不同的影响。

NEE观测误差分布类型对陆地生态系统机理模型参数估计的影响--以长白山温带阔叶红松林为例

基于观测数据的陆地生态系统模型参数估计有助于提高模型的模拟和预测能力,降低模拟不确定性。在已有参数估计研究中,涡度相关技术测定的净生态系统碳交换量(NEE)数据的随机误差通常被假设为服从零均值的正态分布。然而近年来已有研究表明NEE数据的随机误差更服从双指数分布。为探讨NEE观测误差分布类型的不同选择对陆地生态系统机理模型参数估计以及碳通量模拟结果造成的差异,以长白山温带阔叶红松林为研究区域,采用马尔可夫链-蒙特卡罗方法,利用2003～2005年测定的NEE数据对陆地生态系统机理模型CEVSA2的敏感参数进行估计,对比分析了两种误差分布类型(正态分布和双指数分布)的参数估计结果以及碳通量模拟的差异。结果表明,基于正态观测误差模拟的总初级生产力和生态系统呼吸的年总量分别比基于双指数观测误差的模拟结果高61～86gCm-2a-1和107～116gCm-2a-1,导致前者模拟的NEE年总量较后者低29～47gCm-2a-1,特别在生长旺季期间有明显低估。在参数估计研究中,不能忽略观测误差的分布类型以及相应的目标函数的选择,它们的不合理设置可能对参数估计以及模拟结果产生较大影响。

不同刈割强度对晋北赖草草地生态系统CO_(2)交换的影响

刈割是草地的主要利用方式,合理的刈割强度对维持草地生态系统碳平衡具有重要意义。本研究以山西省右玉县赖草(Leymus secalinus)草地生态系统为研究对象,动态监测2021年生长季不刈割、轻度刈割、中度刈割和重度刈割对草地生态系统净碳交换(Net ecosystem carbon exchange,NEE)、生态系统呼吸(Ecosystem respiration,ER)和生态系统总初级生产力(Gross ecosystem productivity,GEP)的影响,探究草地生态系统CO_(2)交换对不同刈割强度的响应。实验结果显示,刈割显著影响GEP,主要是由于GEP在中度刈割处理下较不刈割和重度刈割分别提高了21.4%和21.5%,NEE在中度刈割处理下较轻度刈割和重度刈割分别显著降低了54.4%和53.6%,但刈割对ER影响不显著。在不同刈割强度下,土壤温度和土壤无机氮含量是影响生态系统CO_(2)交换的重要因子。本研究结果表明中度刈割可以促进碳吸收而重度刈割会导致生态系统由碳汇转变为碳源,因此中度刈割为晋北赖草草地最适刈割强度。

中国北方针叶林碳通量动态变化及其影响因素分析

基于北方针叶林典型站点——呼中定位观测站2014~2018年不同时间尺度碳通量观测数据,探究了该生态系统长时间序列碳通量动态变化及其影响因素。结果表明:受总初级生产力(Gross Primary Productivity,GPP)和生态系统呼吸(Ecosystem Respiration,RE)的综合作用影响,北方针叶林生态系统净碳交换量(Net Ecosystem Exchange,NEE)年际变化差异较大,在2.64~17.63 g(C)m^(-2) a^(-1)之间波动;从季节上看,在生长季(6~8月)GPP值大于RE,北方针叶林以净碳吸收为主,在非生长季,NEE与RE相等,北方针叶林为弱碳源;逐日尺度上,NEE呈倒“U”形变化特征,RE和GPP则呈“U”形特征。日尺度NEE主要受净辐射、相对湿度、气温、土壤温度等因素影响,这些环境因素构建的回归方程可以解释45.19%的NEE日变化;月尺度上NEE主要受净辐射、相对湿度、气温3个因素影响,回归方程可以解释78.42%的NEE月变化。

冬季放牧对高寒草甸生长季NEE的影响

本研究于2011年冬季对青藏高原高寒矮嵩草草甸进行不同放牧强度处理,并于2012年5月到10月之间采用Li-6400便携式光合仪和密闭式箱法,对其生长季NEE、Reco和GPP进行分析测定。结果表明,1NEE、Reco和GPP均表现明显的月际变化,NEE在整个生长季的变化趋势呈"U"型,Reco和GPP为单峰型变化趋势;2放牧活动对NEE、Reco和GPP均产生影响,放牧能够促进NEE提早达到最大值;3在中度放牧强度下,高寒草甸的NEE和GPP具有最大值,有利于维持高寒草甸生态系统较高的碳汇水平。

我国净生态系统碳交换量(NEE)的时空变化特征研究

利用LPJ（Lund-Potsdam-Jena）全球动态植被模型,对1971~1998年我国陆地净生态系统碳交换量（NEE）的年总量变化、空间分布格局及变化特征进行了分析。结果表明,近30年来我国的碳汇强度在波动中呈增强趋势,多年平均总碳汇强度为-0.25 Gt.C/a。全国不同区域年均净碳交换量差别显著,整体表现为东部碳汇强而西部弱,除西北部分荒漠草原地区外,全国大部分地区为碳汇区。1985~1998年平均相对于1971~1984年平均,我国不同地区NEE的变化存在较大的空间差异,其中内蒙的中部地区则由原来的弱碳汇区转为弱碳源区,大部分地区碳汇增强。

降水调节荒漠草原生态系统碳交换对增温和氮添加的响应

气候变暖和大气氮沉降对草地生态系统功能有重要影响。然而,降水变化如何调节荒漠草原生态系统生产功能对气候变暖和氮沉降的响应还不清楚。本研究基于内蒙古短花针茅(Stipa breviflora Griseb.)荒漠草原长期增温和氮添加试验平台,分析两个连续降水差异较大年份中植物生产力和生态系统碳交换对增温和氮添加响应的不同。结果表明:(1)植物群落地上生物量在干旱和湿润年份有显著差异。在干旱年份,氮添加使得C_(3)植物地上生物量显著降低了10.50%;在湿润年份,氮添加使得植物群落地上生物量和C_(3)植物地上生物量分别显著增加了11.69%和8.06%。(2)在干旱年份,氮添加显著促进了净生态系统碳固定,而增温显著降低了总生态系统生产力;在湿润年份,增温和氮添加对生态系统碳交换均没有显著影响。因此,野外长期监测结合年际间降水波动对分析全球变化影响草原生态系统功能十分必要。

全球典型流域地表覆盖变化与净生态系统碳交换量时空相关性分析

随着社会经济的发展,流域管理目标已从早期的防洪、供水、航运等转变为注重资源利用和生态保护的综合管理,并在全球生态系统碳平衡中扮演着重要角色。作为量化生态系统固碳能力的重要指标,净生态系统碳交换量(NEE)在不同地表覆盖类型中的碳源/汇能力存在显著差异。探究全球典型流域地表覆盖类型与NEE的时空相关性对流域生态管理等具有重要意义。本文以全球30 m地表覆盖数据(GlobeLand30)和全球陆地净生态系统碳交换量数据为基础,分析2000—2020年全球8个典型流域的地表覆盖及NEE时空变化特征,研究地表覆盖类型变化与NEE的时空相关性。结果表明:①2000—2020年,流域内耕地、裸地、人造地表、湿地、水体及苔原面积增加,草地面积先增加后减少,整体为增加状态;②2000—2020年,流域整体NEE先减小后增加,整体为减小趋势,碳汇能力增强;③2000—2020年,草地与NEE呈显著负相关,耕地、裸地、人造地表、湿地及水体面积与NEE在2010—2020年呈正相关,地表覆盖类型变化对NEE有显著影响。本文可为流域碳中和管制和土地利用空间优化调控提供理论参考,推动流域协同减排和高质量发展。

Water-use efficiency in response to simulated increasing precipitation in a temperate desert ecosystem of Xinjiang, China

Water-use efficiency（WUE） is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes： increasing by 33.9% in the wet year（i.e., the normal precipitation years）and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.

Impacts of reduced wind speed on physiology and ecosystem carbon flux of a semi-arid steppe ecosystem

Decreasing wind speed is one aspect of global climate change as well as global warming, and has become a new research orientation in recent decades. The decrease is especially evident in places with frequent perennially high wind speeds. We simulated decreased wind speed by using a steel-sheet wind shield in a temperate grassland in Inner Mongolia to examine the changes in physical environmental variables, as well as their impacts on the photosynthesis of grass leaves and net ecosystem exchange （NEE）. We then used models to calculate the variation of boundary layer conductance （BLC） and its impact on leaf photosynthesis, and this allowed us to separate the direct effects of wind speed reduction on leaf photo- synthesis （BLC） from the indirect ones （via soil moisture balance）. The results showed that reduced wind speed primarily resulted in higher moisture and temperature in soil, and indirectly affected net assimilation and water use efficiency of the prevalent bunch grass Stipa krylovii. Moreover, the wind-sheltered plant community had a stronger ability to sequester carbon than did the wind-exposed community during the growing season.

Net Ecosystem CO2 Flux and Effect Factors in Peatland Ecosystem of Central China

Peatland ecosystems play an important role in the global carbon cycle because they act as a pool or sink for the carbon cycle. However, the relationship between seasonality effect factors and net ecosystem CO2 exchange (NEE) remains to be clarified, particularly for the non-growing season. Here, based on the eddy covariance technique, NEE in the peatland ecosystem of Central China was examined to measure two years’ (2016 and 2017) accumulation of carbon dioxide emissions with contrasting seasonal distribution of environmental factors. Our results demonstrate the cumulative net ecosystem CO2 emissions during the study period was in the first non-growing season 2.94 ± 4.83 μmolCO2 m-2.s-1 with the lowest values in the same year in first growing season was -2.79 ± 4.92 μmolCO2 m-2.s-1. The results indicate the effect of seasonal variations of NEE can be directly reflected in daily and seasonal variations in growth and respiration of peatland ecosystem by environmental parameters over different growing stages.

青藏高原高寒草甸和荒漠碳交换特征及其气象影响机制

以青藏高原玛沁地区高寒草甸和沱沱河地区高寒荒漠草原为观测研究站,利用涡动协方差技术获取高寒生态系统水平上的CO_(2)通量以及水和能量通量,通过REddyProc、随机森林(Random Forest,RF)进行了数据后处理,探究了不同下垫面典型环境因子对净生态系统CO_(2)交换量(Net Ecosystem Exchange,NEE)的影响机制。结果表明:1)玛沁高寒草甸在6—7月以吸收为主,表现为碳汇,吸收峰值出现在11:00—12:00(北京时,下同)之间,而在3、4、5、8月以排放为主,表现为碳源,排放峰值出现在21:00—23:00之间;沱沱河高寒荒漠在3—8月以吸收为主,表现为净碳汇,吸收峰值出现在13:00—14:00之间;整个生长季前后(3—8月),玛沁和沱沱河的累计NEE分别为79.50 g C/m^(2)和79.24 g C/m^(2),都表现为碳汇。2)不同尺度不同下垫面,气象因子对NEE的重要程度不同,小时尺度上,高寒草甸辐射对NEE的重要性最大,高寒荒漠草原蒸散发对NEE的重要性最大;日尺度上,高寒草甸土壤含水率对NEE的重要性最大,高寒荒漠草原风速对NEE的重要性最大;3)生态系统呼吸(Ecosystem Respiration,Reco)和NEE都受到总初级生产力(Gross Primary Productivity,GPP)的显著限制,高寒荒漠草原GPP对NEE的影响远大于高寒草甸GPP对NEE的影响;4)NEE与蒸散发呈显著相关性,表明水分条件是控制高寒草甸和高寒荒漠草原碳和水收支变化的最重要因素。

Impact of Drought Stress on Net CO_2 Exchange above an Alpine Grassland Ecosystem in the Central Tibetan Plateau

Drought may impact the net ecosystem exchange of CO2 （NEE） between grassland ecosystems and the atmosphere during growth seasons. Here, carbon dioxide exchange and controlling factors in alpine grassland under drought stress in the hinterland of Tibetan Plateau （Damxung, Tibet, China） were investigated. Data were obtained using the covariance eddy technique in 2009. Severe drought stress appeared in the early growing season （May to early July） and September. Drought conditions during the early growing season limited grass production and the green leaf area index （GLAD increased slowly, with an obvious decline in June. When encountering severe water stress, diurnal patterns of NEE in the growth season altered with a peak carbon release around 16：00 h or a second carbon uptake period before sunset. NEE variations in daytime related most closely with O other than PAR when daily averaged @〈0.1 m3 m 3. Seasonal patterns of gross primary production （GPP） and NEE were also influenced by drought： the maximum and minimum of daily-integrated NEE were 0.9 g C m-2 d-1 on 3 July 2009, and -1.3 g C m-2 d-1 on 12 August 2009 with a GPP peak （-2.3 g C m-2 d-1） on the same day, respectively. Monthly NEE from May to July remained as carbon release and increased gradually; peak values of monthly NEE and GPP both appeared in August, but that of ecosystem respiration （R^co） was reached in July. Annual NEE, GPP and Reco of the alpine grassland ecosystem were 52.4, -158.1 and 210.5 g C m-2, respectively. Therefore, the grassland was a moderate source of COs to the atmosphere in this dry year. Interannual variation in NEE was likely related to different water conditions in the growing season. The three greatest contributors to seasonal variation in NEE, GPP and R^co respectively were GLAI〉Ta〉O, GLAI〉O〉PPT, and Ta〉GLAI〉PAR. Seasonality of GLAI explained 60.7% and 76.1% of seasonal variation in NEE and GPP, respectively. GPP or NEE was more sensitive than Reco to variation in GLAI, and ecosystem water conditions.