亚洲中部干旱区3个典型生态系统生长季水碳通量特征

doi:10.3724/SP.J.1258.2014.00075

摘要/Abstract

摘要：

亚洲中部干旱区地处欧亚大陆腹地, 干旱少雨, 生态环境十分脆弱, 研究该地区大气与地表之间的能量和物质交换对干旱区水资源利用和生态环境保护具有重要意义。该文分析了亚洲中部干旱区荒漠与草地生态系统能量、水汽和CO₂通量的日变化及季节变化特征, 探究了水汽和CO₂通量对主要环境因子的响应。通过分析亚洲中部干旱区3个站点的涡度相关资料发现: 亚洲中部干旱区荒漠和草地生态系统在生长季(4-10月)能量、水汽通量、净CO₂通量和总初级生产力的日变化呈“单峰型”, 而荒漠生态系统呼吸日变化相对稳定; 草地生态系统白天的潜热通量占净辐射通量的比例明显高于荒漠生态系统; 草地生态系统在5-8月呈现较强的碳汇, 而荒漠生态系统表现为弱碳汇。亚洲中部干旱区草地和荒漠生态系统水汽通量和总初级生产力对降水、净辐射通量或光合有效辐射、饱和水汽压差、气温均表现出明显的敏感性。

关键词: 亚洲中部干旱区, CO₂通量, 涡度相关, 能量通量, 水汽通量

Abstract:

Aims The arid region in central Asia, in the hinterland of Eurasia, is characterized by low precipitation and extremely fragile ecological environment. Study of energy and matter exchange between atmosphere and the land surface is essential to understanding the balance of water resources and ecosystem functioning in arid region. The objective of this study was to investigate the characteristics of water and carbon fluxes and responses to environmental factors in a typical ecosystem of central Asia.
Methods Eddy covariance measurements were made at three sites representing desert and grassland ecosystems in the central Asia. We analyzed the responses of evaporation and gross primary productivity to selective environmental factors using the enveloped curve fitting method, which determines the response of a dependent variable to a given independent factor while fixing other factors at their best values.
Important findings During growing season from April to October, the diurnal variations of energy, water vapor, net ecosystem CO₂ exchange and gross primary productivity showed patterns of “single peak curve” at the three sites; whereas ecosystem respiration in the desert ecosystem kept relatively stable. The ratio of latent heat flux to net solar radiation in the grassland ecosystem (76.3%) was greater than in the desert ecosystem (32.7%). The grassland ecosystem occurred as a strong carbon sink, whilst the desert ecosystem showed weak carbon fixation. Evapotranspiration and gross primary productivity in the two types of ecosystems were susceptible to changes in precipitation, net solar radiation or photosynthetically active radiation, vapor pressure deficit and air temperature.

Key words: central areas of Asia, CO₂ flux, eddy covariance, energy flux, vapor flux

王玉辉, 井长青, 白洁, 李龙辉, 陈曦, 罗格平. 亚洲中部干旱区3个典型生态系统生长季水碳通量特征. 植物生态学报, 2014, 38(8): 795-808. DOI: 10.3724/SP.J.1258.2014.00075

WANG Yu-Hui, JING Chang-Qing, BAI Jie, LI Long-Hui, CHEN Xi, LUO Ge-Ping. Characteristics of water and carbon fluxes during growing season in three typical arid ecosystems in central Asia. Chinese Journal of Plant Ecology, 2014, 38(8): 795-808. DOI: 10.3724/SP.J.1258.2014.00075

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2014.00075

https://www.plant-ecology.com/CN/Y2014/V38/I8/795

图/表 10

图1 哈萨克斯坦咸海站(KZ-Ara)、哈萨克斯坦巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)能量闭合状况。实线为拟合线, 其斜率代表能量闭合率, 虚线为1:1参考线。G, 土壤热通量; R2,决定系数; RMSE, 均方根误差; Rnet, 净辐射通量; Qle, 潜热通量; Qh, 感热通量。

Fig. 1 Energy balance closure at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China). The slope of the solid line (fitted line) represents energy closure ratio, and the dash line is the 1:1 reference. G, soil heat flux; R2, coefficient of determination; RMSE, root mean square error; Rnet, net radiation flux; Qle, latent heat flux; Qh, sensible heat flux.

图2 哈萨克斯坦咸海站(KZ-Ara)、巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)能量各分量的日变化(平均值±标准偏差)。G, 土壤热通量; Rnet, 净辐射通量; Qle, 潜热通量; Qh, 感热通量。正值表示地表吸收能量, 能量由大气流向地表; 负值则表示地表向大气释放能量。实线为研究时段的平均值, 阴影表示标准偏差, 虚线表示零参考线。KZ-Ara、KZ-Bal和CN-Fuk的研究时段分别为2012年5-8月、2012年5-9月和2009年4-10月。

Fig. 2 The diurnal variations of energy fluxes at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China) (mean ± SD). G, soil heat flux; Rnet, net radiation flux; Qle, latent heat flux; Qh, sensible heat flux. Positive values indicate the ecosystem absorbs energy from the atmosphere; negative values indicate ecosystem releases energy to the atmosphere. The solid line represents average values of energy fluxes during observational periods, the shading illustrates the standard deviations, and the dash line is the zero reference line. The data period used is May to August 2012 for KZ-Ara, May to September 2012 for KZ-Bal, and April to October 2009 for CN-Fuk.

图3 哈萨克斯坦咸海站(KZ-Ara)、巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)的水汽通量(ET)的日变化(平均值±标准偏差)。实线为研究时段的平均值, 阴影表示标准偏差, 虚线表示零参考线。KZ-Ara、KZ-Bal和CN-Fuk的研究时段分别为2012年5-8月、2012年5-9月和2009年4-10月。

Fig. 3 The diurnal variations of water fluxes (ET) at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China) (mean ± SD). The solid line represents average values, the shading illustrates the standard deviations, and the dash line is the zero reference. The data period used is May to August 2012 for KZ-Ara, May to September 2012 for KZ-Bal, and April to October 2009 for CN-Fuk.

图4 哈萨克斯坦咸海站(KZ-Ara)、巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)的水汽通量(ET)与降水量的季节变化。实线为ET, 柱状表示降水。KZ-Ara、KZ-Bal和CN-Fuk的研究时段分别为2012年5-8月、2012年5-9月和2009年4-10月。

Fig. 4 Seasonal variations of water fluxes (ET) and precipitation at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China). The line represents ET and bars indicate precipitations. The data period used is May to August 2012 for KZ-Ara, May to September 2012 for KZ-Bal, and April to October 2009 for CN-Fuk.

图5 哈萨克斯坦咸海站(KZ-Ara)、巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)半小时尺度的水汽通量(ET)与净辐射通量(Rnet)(A, D, G)、饱和水汽压差(VPD) (B, E, H)和气温(C, F, I)的响应曲线。虚线表示95%的置信区间的外廓线。

Fig. 5 Responses of half hourly water flux (ET) to net radiation flux (Rnet) (A, D, G), vapor pressure deficit (VPD) (B, E, H) and air temperature (C, F, I) at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China). Dash line indicates the 95% confidence boundary.

表1 图5中哈萨克斯坦咸海站(KZ-Ara)、哈萨克斯坦巴尔喀什湖站(KZ-Bal)和中国新疆中国科学院阜康荒漠生态系统观测试验站(CN-Fuk)的ET(水汽通量)与净辐射通量(Rnet)、饱和水汽压差(VPD)以及气温的响应方程的拟合参数

Table 1 Estimated values of the fitted model parameters in Fig. 5 in responses of ET (evaporation) to net solar radiation (Rnet), vapor pressure deficit (VPD) and air temperature at KZ-Ara (site located in Aral Lake, Kazakhstan), KZ-Bal (site located in Balkhash Lake, Kazakhstan) and CN-Fuk (Fukang Desert Ecosystem Observation and Experiment Station, Chinese Academy of Sciences in Xinjiang, China)

站点 Site	ET对R_net的响应 Response of ET to R_net		ET对VPD的响应 Response of ET to VPD				ET对气温的响应 Response of ET to air temperature
站点 Site	ET_max	b	ET_max	k₁	k₂	k₃	ET_max	k₁	k₂	k₃
KZ-Ara	0.27	98.58	0.22	0.06	0.02	0.43	0.22	59.98	17 531.00	35.76
KZ-Bal	1.19	500.64	0.70	-1.27	-23.66	3.37	0.74	0.13	15.24	37.48
CN-Fuk	0.61	371.36	0.37	91 000.00	615 000.00	2.75	0.35	-12 481.00	-1 971 624.00	29.34

图6 哈萨克斯坦咸海站(KZ-Ara)和巴尔喀什湖站(KZ-Bal)生长季总初级生产力(GPP)、生态系统呼吸(Res)和净CO2通量(NEE)的日变化。NEE正值表示生态系统向大气释放CO2, 负值表示生态系统从大气吸收CO2。实线为研究时段的平均值, 阴影表示标准偏差, 虚线表示零参考线。KZ-Ara和KZ-Bal 的研究时段分别为2012年5-8月、2012年5-9月。

Fig. 6 Diurnal variations of gross primary productivity (GPP), ecosystem respiration (Res) and net ecosystem CO2 exchange (NEE) at KZ-Ara (site located in Aral Lake, Kazakhstan) and KZ-Bal (site located in Balkhash Lake, Kazakhstan) during growing season. The positive NEE indicates ecosystem releases CO2 into the atmosphere, while negative NEE indicates ecosystem absorbs CO2 from the atmosphere. The solid line represents average values of CO2 flux during observational periods, the shading illustrates the standard deviations, and the dash line is the zero reference. The data period used is May to August 2012 for KZ-Ara and May to September 2012 for KZ-Bal.

图7 哈萨克斯坦咸海站(KZ-Ara)和巴尔喀什湖站(KZ-Bal)生长季总初级生产力(GPP)、生态系统呼吸(Res)、净CO2通量(NEE)和降水(Precipitation)的季节变化。柱状表示降水, 虚线表示0参考线。KZ-Ara、KZ-Bal的研究时段分别为2012年5-8月、2012年5-9月。

Fig. 7 Seasonal variations of gross primary productivity (GPP), ecosystem respiration (Res), net ecosystem CO2 exchange (NEE), and precipitation at KZ-Ara (site located in Aral Lake, Kazakhstan) and KZ-Bal (site located in Balkhash Lake, Kazakhstan) during growing season. Black bars represent precipitation and the dash line is the zero reference. The data period used is May to August 2012 for KZ-Ara and May to September 2012 for KZ-Bal.

图8 哈萨克斯坦咸海站(KZ-Ara)和巴尔喀什湖站(KZ-Bal)半小时尺度的总初级生产力(GPP)与光合有效辐射 (PAR)(A, D)、饱和水汽压差(VPD) (B, E)和气温(C, F)的响应曲线。虚线表示95%的置信区间的外廓线。

Fig. 8 Responses of half hourly gross primary productivity (GPP) to photosynthetically active radiation (PAR) (A, D), vapor pressure deficit (VPD) (B, E) and air temperature (C, F) at KZ-Ara (site located in Aral Lake, Kazakhstan) and KZ-Bal (site located in Balkhash Lake, Kazakhstan). Dash line indicates the 95% confidence boundary.

表2 图8中哈萨克斯坦咸海站(KZ-Ara)和巴尔喀什湖站(KZ-Bal)的总初级生产力(GPP)与光合有效辐射 (PAR)、饱和水汽压差(VPD)和气温的响应方程的拟合参数

Table 2 Estimated values of the fitted model parameters in Fig. 8 in responses of gross primary productivity (GPP) to photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and air temperature at KZ-Ara (site located in Aral Lake, Kazakhstan) and KZ-Bal (site located in Balkhash Lake, Kazakhstan)

站点 Site	GPP对PAR的响应 Response of GPP to PAR		GPP对VPD的响应 Response of GPP to VPD				GPP对气温的响应 Response of GPP to air temperature
站点 Site	GPP_max	b	GPP_max	k₁	k₂	k₃	GPP_max	k₁	k₂	k₃
KZ-Ara	10.29	359.42	7.86	0.08	0.32	1.06	7.72	0.32	62.94	33.04
KZ-Bal	36.24	464.86	29.12	0.06	0.94	4.65	29.58	8 685.86	2 291 884.00	35.37

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