植物生态学报 ›› 2018, Vol. 42 ›› Issue (1): 6-19.DOI: 10.17521/cjpe.2017.0266

所属专题: 青藏高原植物生态学:生态系统生态学 碳水能量通量

• 研究论文 • 上一篇    下一篇

青藏高原高寒灌丛草甸和草原化草甸CO2通量动态及其限制因子

柴曦1,3,李英年2,段呈1,3,张涛4,宗宁1,石培礼1,3,*(),何永涛1,3,张宪洲1,3   

  1. 1 中国科学院地理科学与资源研究所生态系统网络观测与模拟重点实验室, 北京 100101
    2 中国科学西北高原生物研究所, 西宁 810001
    3 中国科学院大学资源与环境学院, 北京 100190
    4 沈阳农业大学农学院, 沈阳 110866
  • 出版日期:2018-01-20 发布日期:2018-03-08
  • 通讯作者: 石培礼 ORCID: 0000-0002-1120-0003
  • 基金资助:
    国家自然科学基金(41703079);国家自然科学基金(41271067);国家重点研发计划(2016YFC0502001);国家重点研发计划(2017YFA0604801)

CO2 flux dynamics and its limiting factors in the alpine shrub-meadow and steppe-meadow on the Qinghai-Xizang Plateau

CHAI Xi1,3,LI Ying-Nian2,DUAN Cheng1,3,ZHANG Tao4,ZONG Ning1,SHI Pei-Li1,3,*(),HE Yong-Tao1,3,ZHANG Xian-Zhou1,3   

  1. 1 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

    2 Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810001, China

    3 College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China

    4 College of Agronomy, Shenyang Agricultural University, Shenyang 110866, China
  • Online:2018-01-20 Published:2018-03-08
  • Contact: SHI Pei-Li, ORCID: 0000-0002-1120-0003
  • Supported by:
    Supported by the National Natural Science Foundation of China(41703079);Supported by the National Natural Science Foundation of China(41271067);the National Key Research and Development Project of China(2016YFC0502001);the National Key Research and Development Project of China(2017YFA0604801)

摘要:

高寒灌丛草甸和草甸均是青藏高原广泛分布的植被类型, 在生态系统碳通量和区域碳循环中具有极其重要的作用。然而迄今为止, 对其碳通量动态的时空变异还缺乏比较分析, 对碳通量的季节和年际变异的主导影响因子认识还不够清晰, 不利于深入理解生态系统碳通量格局及其形成机制。该研究选取位于青藏高原东部海北站高寒灌丛草甸和高原腹地当雄站高寒草原化草甸年降水量相近的5年(2004-2008年)的涡度相关CO2通量连续观测数据, 对生态系统净初级生产力(NEP)及其组分, 包括总初级生产力(GPP)和生态系统呼吸的季节、年际动态及其影响因子进行了对比分析。结果表明: 灌丛草甸的CO2通量无论是季节还是年际累积量均高于草原化草甸, 并且连续5年表现为“碳汇”, 平均每年NEP为70 g C·m -2·a -1, 高寒草原化草甸平均每年NEP为-5 g C·m -2·a -1, 几乎处于碳平衡状态, 但其源/汇动态极不稳定, 在2006年-88 g C·m -2·a -1的“碳源”至2008年54 g C·m -2·a -1的“碳汇”之间转换, 具有较大的变异性。这两种高寒生态系统源/汇动态的差异主要源于归一化植被指数(NDVI)的差异, 因为NDVI无论在年际水平还是季节水平都是NEP最直接的影响因子; 其次, 灌丛草甸还具有较高的碳利用效率(CUE, CUE = NEP/GPP), 而年降水量和NDVI是决定两生态系统CUE大小的关键因子。两地区除了CO2通量大小的差异外, 其环境影响因子也有所不同。采用结构方程模型进行的通径分析表明, 灌丛草甸生长季节CO2通量的主要限制因子是温度, NEPGPP主要受气温控制, 随着气温升高而增加; 而草原化草甸的CO2通量多以季节性干旱导致的水分限制为主, 其次才是气温的影响, 受二者的共同限制。此外, 两生态系统生长季节生态系统呼吸主要受GPP和5 cm土壤温度的直接影响, 其中GPP起主导作用, 非生长季节生态系统呼吸主要受5 cm土壤温度影响。该研究还表明, 水热因子的协调度是决定青藏高原高寒草地GPPNEP的关键要素。

关键词: 青藏高原, 高寒草地生态系统, CO2通量, 温度, 土壤含水量, 涡度相关

Abstract:

Aims Alpine shrub-meadows and steppe-meadows are the two dominant vegetation types on the Qinghai-Xizang Plateau, and plays an important role in regional carbon cycling. However, little is known about the temporal-spatial patterns and drivers of CO2 fluxes in these two ecosystem types.

Methods Based on five years of consecutive eddy covariance measurements (2004-2008) in an eastern alpine shrub-meadow at Haibei and a hinterland alpine steppe-meadow at Damxung, we investigated the seasonal and annual variation of net ecosystem productivity (NEP) and its components, i.e. gross primary productivity (GPP) and ecosystem respiration (Re).

Important findings The CO2 fluxes (NEP, GPP and Re) were larger in the shrub-meadow than in the steppe-meadow during the study period. The shrub-meadow functioned as a carbon sink through the five years, with the mean annual NEP of 70 g C·m -2·a -1. However, the steppe-meadow acted as a carbon neutral, with mean annual NEP of -5 g C·m -2·a -1. The CO2 fluxes of steppe-meadow exhibited large variability due to the inter-annual and seasonal variations in precipitation, ranging from a carbon sink (54 g C·m -2·a -1) in 2008 to a carbon source (-88 g C·m -2·a -1) in 2006. The differences in carbon budget between the two alpine ecosystems were firstly attributed to the discrepancy of normalized difference vegetation index (NDVI) because NDVI was the direct factor regulating the seasonal and inter-annual NEP. Secondly, the shrub-meadow had higher carbon use efficiency (CUE), which was substantially determined by annual precipitation (PPT) and NDVI. Our results also indicated that the environmental drivers of CO2 fluxes were also different between these two alpine ecosystems. The structure equation model analyses showed that air temperature (Ta) determined the seasonal variations of CO2 fluxes in the shrub-meadow, with NEP and GPP being positively correlated with Ta. By contrast, the seasonal CO2 fluxes in the steppe-meadow were primarily co-regulated by soil water content (SWC) and Ta, and increased with the increase of SWC and Ta. In addition, the changes of Re during the growing season in two ecosystems were directly affected by GPP and soil temperature at 5 cm depth (Ts), while Re during non-growing season were determined by Ts. These results demonstrate that the synergy of soil water and temperature played crucial roles in determining NEP and GPP of the two alpine meadows on the Qinghai-Xizang Plateau.

Key words: Qinghai-Xizang Plateau, alpine meadow ecosystems, CO2 fluxes, temperature, soil water content, eddy covariance