植物生态学报 ›› 2022, Vol. 46 ›› Issue (12): 1448-1460.DOI: 10.17521/cjpe.2021.0428

所属专题: 碳水能量通量

• 中国典型生态脆弱区碳水通量过程研究专题论文 • 上一篇    下一篇

中国北方干旱半干旱区草原生态系统能量平衡闭合的季节和年际变异

王彦兵, 游翠海, 谭星儒, 陈波宇, 许梦真, 陈世苹()   

  1. 中国科学院植物研究所植被与环境变化国家重点实验室, 北京 100093
    中国科学院大学, 北京 100049
  • 收稿日期:2021-11-22 接受日期:2022-04-22 出版日期:2022-12-20 发布日期:2023-01-13
  • 通讯作者: *陈世苹(spchen@ibcas.ac.cn)
  • 基金资助:
    国家重点研发计划(2017YFA0604801);国家自然科学基金(32071565);国家自然科学基金(41773084)

Seasonal and interannual variations in energy balance closure over arid and semi-arid grasslands in northern China

WANG Yan-Bing, YOU Cui-Hai, TAN Xing-Ru, CHEN Bo-Yu, XU Meng-Zhen, CHEN Shi-Ping()   

  1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-11-22 Accepted:2022-04-22 Online:2022-12-20 Published:2023-01-13
  • Contact: *CHEN Shi-Ping(spchen@ibcas.ac.cn)
  • Supported by:
    National Key R&D Program of China(2017YFA0604801);National Natural Science Foundation of China(32071565);National Natural Science Foundation of China(41773084)

摘要:

能量平衡闭合状况是评估通量观测数据质量的重要参考指标, 为客观评价中国北方干旱半干旱涡度观测数据的质量, 确定数据分析方法和改进策略, 加深对能量闭合度与环境因子之间关系的理解, 该研究基于内蒙古3种不同草原类型(荒漠草原、典型草原和草甸草原) 6个涡度相关通量观测站点(四子王旗站、锡林浩特割草站、锡林浩特围封站、西乌珠穆沁旗站、多伦站和额尔古纳站)的56个站年的能量通量和气象因子测定数据集, 利用能量平衡比率(EBR)和最小二乘法线性回归(OLS)这两种常用的方法, 分析了北方干旱半干旱区不同站点和草原类型能量闭合的状况、季节和年际变异及主要影响因素。主要结果表明: 1) 6个站点多年EBR均值为0.89 ± 0.11, OLS斜率均值为0.96 ± 0.04, 能量闭合程度明显高于国际通量网和中国通量网站点的能量闭合状况。2)不同站点和草原类型间EBR存在明显差异, 表现为荒漠草原(1.01 ± 0.09)和典型草原(0.90 ± 0.11)都高于草甸草原(0.83 ± 0.05), 各站点EBR均存在明显的季节变异, 生长季基本都在1附近并且相对稳定, 非生长季低于1并且变化较大, 主要受气温(Ta)、饱和水汽压差(VPD)、土壤含水量(SWC)和反照率(Albedo)的影响, 其中较低的Ta和较高的Albedo是导致非生长季EBR较低的主要原因。3)不同站点和草原类型EBR存在显著年际变异, 主要受潜热分配(潜热通量/净辐射比值, LE/Rn)、年平均气温(MAT)和生长季Albedo显著影响, 其中LE/Rn的年际波动对EBR年际变异起主要的调控作用, 可解释EBR年际变异的44%。此外, 各站点EBR均表现出随年份逐渐降低的趋势, 植被盖度显著增大后引起Albedo降低可能是造成EBR下降的主要原因。综上所述, 为更加全面地评估能量闭合状况, EBR和OLS斜率两种方法建议结合起来使用。

关键词: 能量平衡闭合, 涡度相关, 季节变异, 年际变异, 草原

Abstract:

Aims Eddy covariance (EC) systems are widely used for measuring the fluxes of carbon, water, and energy, as well as meteorological factors. As one important reference of independently evaluating scalar flux by EC technique, energy balance closure is widely used for evaluating data quality of carbon, water, and energy fluxes.

Methods Using the data of energy fluxes and meteorological variables retrieved from 56 site-year, the energy balance closure of six sites across three ecosystems (i.e. desert steppe, typical steppe, and meadow steppe) was analyzed by two widely used methods: linear regression from the ordinary least squares (OLS) and the energy balance ratio (EBR). The overall evaluation of energy balance closure, the seasonal and interannual variations and the related influencing factors were investigated.

Important findings The results show that: 1) the multiple-year EBR and OLS slope over the six sites had a mean value of 0.89 ± 0.11 and 0.96 ± 0.04, respectively, which are better than the results of the FLUXNET and ChinaFLUX. 2) There were significant differences over different sites and grassland types, with EBR of desert steppe (1.01 ± 0.09) and typical steppe (0.90 ± 0.11) both higher than meadow steppe (0.83 ± 0.05). There were seasonal variations of EBR over the six studied sites, and with better and stable results in growing season than non-growing season. The air temperature (Ta), vapor pressure deficit (VPD), soil moisture (SWC), and Albedo regulated the seasonal variation of EBR, with the low Ta and high Albedo remarkably reducing EBR during the non-growing season. 3) There were significant interannual variations of EBR across different sites and grassland types. The latent heat fraction (the ratio of latent heat flux to net radiation, LE/Rn), mean annual air temperature (MAT) and growing season Albedo significantly influenced interannual variation of EBR. The LE/Rn showed the strongest impact and explained 44% of the interannual variation of EBR. The significantly increasing in leaf area index (LAI) strongly regulated the upward of the available energy (net radiation minus ground heat flux, Rn- G0), which contributes to the significant downward of EBR during observed years. It should be noted that EBR and OLS slope should be combined to better evaluate the energy balance closure. In conclusion, this study help improve our understanding of the potential linkage between energy balance closure and environmental factors, evaluate the quality of scalar flux estimates from EC technique, as well as improve the data processing protocol of flux data in the semi-arid and arid grassland region.

Key words: energy balance closure, eddy covariance, seasonal variation, interannual variation, grassland