干旱胁迫降低了内蒙古羊草草原的碳累积

doi:10.3773/j.issn.1005-264x.2010.08.002

摘要/Abstract

摘要：

采用涡度相关法, 分析了2004年(平水年)和2005-2006年(干旱年)生长季内蒙古锡林河流域羊草(Leymus chinensis)草原的净生态系统碳交换(net ecosystem exchange, NEE)、总初级生产力(gross primary productivity, GPP)和生态系统呼吸(ecosystem respiration, R_e)的季节和年度变化。结果表明: 平水年羊草草原的日最大GPP和R_e分别为4.89和1.99 g C·m^-2·d^-1, 而干旱年GPP和R_e分别为1.53-3.01和1.38-1.77 g C·m^-2·d^-1。与平水年相比, 干旱年日最大GPP、R_e分别下降了38%-68%和11%-12%。平水年羊草草原累积的GPP、R_e分别为294和180 g C·m^-2, 而在干旱年分别为102-123 g C·m^-2和132-158 g C·m^-2。和平水年相比, 干旱年的GPP、R_e分别下降了58%-65%和12%-27%。用Van’t Hoff模型模拟的8个窄土壤含水量(θ)跨度生态系统呼吸(R_e)对土壤温度(T_s)的敏感程度表明: 曲线斜率在θ = 0.16-0.17 m³·m^-3范围内达到最大, 高于或者低于这个阈值, R_e对T_s的敏感度降低。干旱胁迫降低了生态系统生产力和生态系统呼吸量。与平水年相比, 干旱年的GPP比R_e下降的幅度更大, 干旱胁迫降低了内蒙古羊草草原的碳累积, 使生态系统由碳汇变为碳源。

关键词: 碳累积, 干旱, 生态系统呼吸, 总初级生产力, 羊草草原, 净生态系统交换

Abstract:

Aims Droughts are common in arid and semiarid regions and affect the capacity of carbon sequestration of grassland ecosystems by influencing the process of ecosystem carbon cycling. We analyzed the continuous measurements of ecosystem CO₂ fluxes during three growing seasons (May-September) over a Leymus chinensis steppe in Inner Mongolia in order to examine the effect of drought stress on carbon accumulation of this grassland ecosystem.

Methods We used the eddy covariance technique to measure CO₂ fluxes during the 2004-2006 growing seasons. Only 126 and 215 mm precipitation fell during the 2005 and 2006 growing seasons, respectively, far less than normal (in 2004, 364 mm); therefore, the steppe was in an extreme drought condition.

Important findings Maxima for gross primary productivity (GPP) and ecosystem respiration (R_e) were 4.89 and 1.99 g C·m^-2·d^-1, respectively, in the 2004 growing season (normal year). However, in drought years, GPP and R_e were 1.53-3.01 and 1.38-1.77 g C·m^-2·d^-1, respectively. GPP and R_e in the drought years decreased by 68% and 11%, respectively, compared with the normal year. Accumulated GPP and R_e were 294 and 180 g C·m^-2, respectively, during the growing season in 2004 and 102-123 and 132-158 g C·m^-2, respectively, in drought years. Accumulated GPP and R_edecreased 58%-65% and 12%-27%, respectively, in drought years compared with those of the normal year. The slope of the curve in the sensitivity for R_e to T_s (Vant’Hoff type) reached its maximum at θ = 0.16-0.17 m³·m^-3; below or above this value of θ, the sensitivity of R_e to T_s decreases. GPP and R_e decline under drought stress conditions, with GPP having a larger decline. Long-term and continuous drought reduced C-accumulation and resulted in the steppe ecosystem switching from a carbon sink in typical years to a carbon source in drought years.

Key words: carbon accumulation, drought, ecosystem respiration, gross primary productivity, Leymus chinensis steppe, net ecosystem exchange

郝彦宾, 王艳芬, 崔骁勇. 干旱胁迫降低了内蒙古羊草草原的碳累积. 植物生态学报, 2010, 34(8): 898-906. DOI: 10.3773/j.issn.1005-264x.2010.08.002

HAO Yan-Bin, WANG Yan-Fen, CUI Xiao-Yong. Drought stress reduces the carbon accumulation of the Leymus chinensis steppe in Inner Mongolia, China. Chinese Journal of Plant Ecology, 2010, 34(8): 898-906. DOI: 10.3773/j.issn.1005-264x.2010.08.002

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链接本文: https://www.plant-ecology.com/CN/10.3773/j.issn.1005-264x.2010.08.002

https://www.plant-ecology.com/CN/Y2010/V34/I8/898

图/表 9

图1 内蒙古羊草草原2004-2006年生长季降雨量、土壤含水量(土壤0-20 cm深处) (A)、空气温度和土壤温度(0-5 cm深处) (B)的变化。

Fig. 1 Variations of precipitation, soil water content (0-20 cm depth) (A), air temperature and soil temperature (0-5 cm depth) (B) during 2004-2006 growth seasons over Leymus chinensis steppe of Inner Mongolia.

表1 内蒙古羊草草原2004-2006年生长季(5-9月)的月降水量、平均空气温度和5 cm深度土壤温度(平均值±标准偏差)

Table 1 Monthly total precipitation, average air temperature and 0-5 cm depth soil temperature during 2004-2006 growth seasons over the Leymus chinensis steppe of Inner Mongolia (mean ± SD)

年份 Year		5月 May	6月 Jun.	7月 Jul.	8月 Aug.	9月 Sept.	5-9月 May-Sept.
2004	降雨量 Precipitation (mm)	20.0	75.0	60.5	120.8	58.5	334.8
	空气温度 Air temperature (℃)	11.0 ± 4.6	17.5 ± 3.0	18.0 ± 3.3	15.5 ± 3.3	11.2 ± 4.2	14.7 ± 4.8
	土壤温度 Soil temperature (℃)	13.5 ± 3.1	20.3 ± 3.3	21.2 ± 3.1	18.1 ± 2.6	13.0 ± 3.0	17.2 ± 4.5
2005	降雨量 Precipitation (mm)	14.6	38.3	46.1	24.6	2.4	126.0
	空气温度 Air temperature (℃)	10.2 ± 4.7	17.3 ± 3.2	19.5 ± 3.2	18.3 ± 3.3	12.4 ± 4.0	15.5 ± 5.2
	土壤温度 Soil temperature (℃)	12.6 ± 3.4	19.3 ± 3.0	21.1 ± 2.9	20.1 ± 2.6	15.8 ± 2.7	17.8 ± 4.3
2006	降雨量 Precipitation (mm)	15.0	76.0	122.9	21.9	39.0	274.8
	空气温度 Air temperature (℃)	11.9 ± 4.0	16.1 ± 3.4	18.6 ± 2.2	19.3 ± 2.1	11.3 ± 4.8	15.5 ± 4.8
	土壤温度 Soil temperature (℃)	14.1 ± 3.0	18.9 ± 3.5	22.2 ± 1.4	21.8 ± 1.9	12.4 ± 3.7	18.0 ± 4.8

图2 内蒙古羊草草原2004-2006年生长季总初级生产力(GPP)和生态系统呼吸(Re)的季节变化。

Fig. 2 Seasonal variations of gross primary productivity (GPP) and ecosystem respiration (Re) during 2004-2006 growth seasons over the Leymus chinensis steppe of Inner Mongolia.

图3 内蒙古羊草草原2004-2006年生长季白天(光合有效辐射(PAR) > 0)和夜间(PAR = 0)以及积分的日净生态系统交换的季节变化。

Fig. 3 Seasonal variations of daytime (photosynthetic active radiation (PAR) > 0), nighttime (PAR = 0) and diurnal integrated net ecosystem during 2004-2006 growth seasons over the Leymus chinensis steppe of Inner Mongolia.

图4 不同土壤含水量时土壤温度(5 cm深度)对生态系统呼吸的影响。

Fig. 4 Effects of soil temperature at a 5-cm depth on ecosystem respiration (Re ) as influenced by different soil water content at a 20 cm-depth.

图5 土壤含水量(20 cm深度)和总初级生产力对Van’t Hoff模型参数Q10和R10的影响。

Fig. 5 Effects of soil water content and gross primary productivity (GPP) at a 20 cm-soil depth (θ) on the Q10 and R10 parameters in Van’t Hoff model.

图6 2004-2006年叶面积指数的季节变化。

Fig. 6 Seasonal variations of leaf area index during 2004-2006 growth seasons.

表2 内蒙古羊草草原土壤含水量(0.2 m深度)对Van’t Hoff模型参数R10和Q10的影响

Table 2 Effects of soil water content at the 0.2 m depth (θ) on the parameters in the Van’t Hoff model over the Leymus chinensis steppe of Inner Mongolia

土壤含水量 Soil water content (m³·m^-3)	R₁₀	Q₁₀	R²	平均土壤温度 Average soil temperature T_s(℃)	p
> 0.2	1.09 ± 0.19	1.57 ± 0.36	0.25	17.14	0.08
0.19-0.18	0.66 ± 0.11	2.19 ± 0.46	0.41	16.60	0.04
0.17-0.16	0.54 ± 0.04	2.48 ± 0.22	0.72	14.02	0.04
0.15-0.14	0.68 ± 0.06	1.67 ± 0.21	0.10	15.64	0.07
0.13-0.12	0.68 ± 0.04	1.65 ± 0.09	0.40	18.82	0.04
0.11-0.10	0.40 ± 0.04	2.45 ± 0.23	0.63	18.57	0.04
0.09-0.08	0.37 ± 0.03	1.87 ± 0.14	0.57	16.53	0.10
< 0.07	0.30 ± 0.04	1.56 ± 0.21	0.32	18.24	0.10

表3 内蒙古羊草草原日平均总初级生产力(GPP, g C·m-2·d-1), 日最大总初级生产力(g C·m-2·d-1)和生态系统呼吸(Re, g C·m-2·d-1), 累积的年净生态系统碳交换(NEE, g C·m-2·a-1)、GPP和Re的变化(平均值±标准偏差)

Table 3 Variations of daily average gross primary productivity (GPP, g C·m-2·d-1), daily maximal GPP (g C·m-2·d-1), ecosystem respiration (Re, g C·m-2·d-1), accumulated NEE (g C·m-2·a-1), GPP and Re (mean ± SD)

年份 Year	日平均GPP Daily average GPP	日最大GPP Daily maximal GPP	日平均R_e Daily average R_e	日最大R_e Daily maximal R_e	日平均NEE Daily average NEE	累积的NEE Accumulated NEE	累积的GPP Accumulated GPP	累积的R_e Accumulated R_e
2004	1.91 ± 0.40	4.89	1.17 ± 0.36	1.99	-0.04 ± 0.86	-114	294	180
2005	0.65 ± 0.26	1.53	0.85 ± 0.31	1.38	0.51 ± 0.26	30	102	132
2006	0.81 ± 0.23	3.01	1.04 ± 0.37	1.77	0.70 ± 0.28	35	123	158

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