杨桂山. Characteristics of net ecosystem exchange and environmental factors of rice-wheat rotation system in the Yangtze River Delta of China

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1 Chinese Journal of Eco-Agriculture, Jul. 2015, 23(7): DOI: /j.cnki.cjea * 1,2,3 孙小祥 1** 常志州 3 杨桂山 3 徐昔保 ( ; ; ) 采用涡度相关技术对我国长三角地区典型稻麦轮作农田生态系统 (2011 年 11 月 2012 年 10 月 ) 的 CO 2 通量进行连续观测, 分析了农田生态系统净碳交换 (NEE) 的变化特征及其环境影响因子 结果表明 : 长三角地区稻麦轮作生态系统 NEE 具有明显的日变化和季节变化特征, 具有很强的固碳能力 NEE 月平均日变化总体呈 U 型曲线, 不同月份 U 型高度不同 ; NEE 季节变化则呈显著的 W 型双峰特征, 分别对应两季作物 ( 小麦 水稻 ) 的生长季节 小麦 / 水稻月平均最大碳吸收峰出现在 4 月 /8 月, 分别达到 1.12 mg m 2 s mg m 2 s 1 ; 日最大累积碳吸收量分别为 g(c) m 2 d g(c) m 2 d 1, 长三角地区稻麦轮作生态系统年固碳量达到 g(c) m 2 a 1 光合有效辐射是影响白天 NEE 的主要环境影响因子, Michaelis-Menten 方程可以很好地表示作物生长季节两者之间的关系 (R 2 =0.37~0.83); 在同一光合有效辐射条件下, 长三角地区稻麦轮作生态系统白天 NEE 随着气温的升高而增加, 而当光合有效辐射大于 µmol m 2 s 1 时存在着一定程度的光抑制 温度是影响夜间农田生态系统呼吸特征的主要环境影响因子, 长三角地区稻麦轮作生态系统夜间 NEE 与不同层次温度之间均存在显著的指数相关关系, 但是不同作物夜间 NEE 的最适温度略有差异, 小麦夜间 NEE 与土壤温度 (10 cm) 相关性最好 (0.60), 而水稻夜间 NEE 与气温相关系数最高 (0.49) 涡度相关碳通量净碳交换农田生态系统稻麦轮作 : S314 : A : (2015) Characteristics of net ecosystem exchange and environmental factors of rice-wheat rotation system in the Yangtze River Delta of China SUN Xiaoxiang 1,2,3, CHANG Zhizhou 1, YANG Guishan 3, XU Xibao 3 (1. Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing , China; 2. College of Urban and Resource Environment, Yancheng Teachers University, Yancheng , China; 3. Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing , China) Abstract Agro-ecosystem is one of the terrestrial ecosystems under intensive control and human disturbance. The estimation of carbon (C) source or sink in agro-ecosystems is a focal research in global C-cycle studies. As carbon dioxide (CO 2 ) is generally the main greenhouse gas with significant effect on climate change, there has been a growing interest in analyzing and understanding C-flux from agro-ecosystems as affected by regional environmental conditions. To determine diurnal and seasonal variations in net ecosystem exchange (NEE) and to explore the effects of environmental factors, CO 2 flux was continuously measured in using the eddy covariance technique in rice-wheat rotation system in the Yangtze River Delta. During the study, eddy covariance measurement together with measurements of various soil and meteorological conditions were taken for two full growing seasons per year. To derive complete time series of NEE, flux partitioning and * [CX(12)1002] ( ) ( , ) ** :, czhizhou@hotmail.com, jssun2004@163.com : :

2 gap-filling methods were devised. The results showed significant trends of monthly average diurnal and seasonal variations in NEE in rice-wheat rotation system with a large C-sequestration capacity. Monthly average diurnal variations in NEE for different months depicted a U-shaped curve with varying peak values, the maximum peaks appearing at about 12:00 at noon. Seasonal variation in NEE tracked a W-shaped curve in the year for the two crops (winter wheat and summer rice). Maximum daily net CO 2 uptake reached 1.12 mg m 2 s 1 in April for wheat and 1.45 mg m 2 s 1 in August for rice. At the same time, daily cumulative C-uptake of wheat and rice reached the maximum values of g(c) m 2 d 1 and g(c) m 2 d 1, respectively. The rice-wheat rotation system in the Yangtze River Delta was a strong C-sink, with annual carbon fixation of g(c) m 2 a 1 for the period On the whole, the characteristics of NEE were closely related with crop growth and meteorological conditions. The environmental factors influencing NEE at daytime were different from those at nighttime for both winter wheat and summer rice. The main environmental factor impacting NEE was photosynthetically active radiation (PAR) during the daytime and the relationship between PAR and daytime NEE during the two crop growing seasons was well represented by Michaelis-Menten Equation (R 2 = ). NEE increased with rising temperature and PAR, and decreased when PAR exceeded µmol m 2 s 1. Temperature was identified as the main environmental factor influencing NEE at nighttime. There was significant exponential correlation between nighttime NEE and temperature at different levels (air temperature, soil temperatures at 10 cm, 20 cm, and 40 cm depths) in rice-wheat rotation system in the Yangtze River Delta. However, the most related temperature level for nighttime NEE was driven by climatic conditions and crop growth. Correlation analysis of nighttime NEE and temperature suggested that 10 cm depth soil temperature was the most related for winter wheat and air temperature most related for summer rice. To further explore the relationship between temperature and nighttime NEE, there was need for monitoring nighttime fluxes with the combined use of eddy covariance and chamber-based method. Keywords Eddy covariance; Carbon flux; Net ecosystem exchange; Agro-ecosystem; Rice-wheat rotation system (Received Jan. 4, 2015; accepted May 9, 2015), [1] (net ecosystem exchange, NEE) [2 3],, CO 2, [4 6], CO 2,, [6 12] CO 2 /,,, %, 22.1% [13], [14],, [15] [16],,,, (eddy covariance) [7,17 18],,,,,,, 1 材料与方法 1.1 ( N, E, 5 m),,, 15~16, ~5 200, 225~250 d, l 000~l 400 mm, 150 m,, /

3 7 : , , 6 15, 11 2 ( N) (P 2 O 5 ) (K 2 O) 517 kg hm kg hm kg hm 2 ;,.. = , , ( ) ( ) ( d), 1.2 CO 2 / H 2 O (EC150, Campbell) (CR1000, Campbell), CO 2, 10 Hz, PC (2G) (LP02-L, Hukseflux) (HMP155A, Vaisala) (TE525MM, Texas Electronics), (TDT, Campbell) 0.10 m 0.20 m 0.40 m 30 min (CR1000, Campbell) 1.3, (TK2 Alteddy ECPack Eddysoft Edire ethflux TUDD), CO 2 [19], Edire,, WPL, 30 min [20 21] Level-0, ; Level-1, ; Level-2,,,, 17%~50% [22 25] , 67%, 75%,, 58% : [26],, : 1) 2 h ; 2) 2 h, 14 d 7 d [7,25 27] 2 结果与分析 NEE ( ) ( ) CO 2, (NEE) U ( 1) 11 12,, NEE 0.16~ 0.13 mg m 2 s 1, NEE, 0; 1 2, CO 2,, 0.42 mg m 2 s 1, NEE, (11 2 ), NEE 0.04~ 0.48 mg m 2 s 1,, NEE 3 5, NEE 0.63~ 1.12 mg m 2 s 1,, : CO 2 ( ) ( ),, NEE, 12:00,, NEE, 18:00, NEE : 6,,,, NEE 0.00~ 0.15 mg m 2 s 1,, ; 7 9,,, NEE 0.80~ 1.44 mg m 2 s 1,, NEE 12,, ,

4 Fig. 1 图 1 稻麦轮作系统净碳交换 (NEE) 的月平均日变化 Monthly average diurnal variation of net ecosystem exchange (NEE) in each month of rice-wheat rotation system 35.76, NEE ; 10,, NEE 0.77 mg m 2 s NEE W, NEE (NEE ),, (NEE ) 3, 5 ; 7, 10 ( 2) 236 d, NEE 4.67~ g(c) m 2 d 1, 2.16 g(c) m 2 d 1, 4 26, g(c) m 2 d 1 ; 8 12, g(c) m 2 d 1 NEE,,,, ;,, ( 2) 5 24, 4.67 g(c) m 2 d 1,,,, g(c) m 2 a 1, g(c) m 2 a g(c) m 2 a 1, 2.2 NEE NEE (PAR) Michaelis-Menten [23,28 29] : 图 2 稻麦轮作系统净碳交换 (NEE) 的季节变化 Fig. 2 Seasonal variation of net ecosystem exchange (NEE) in rice-wheat rotation system NEE=R e P max PAR/(K m +PAR) (1) : P max, R e, K m Michaelis-Menten Level-0, CO 2, [30] NEE, Michaelis-Menten (3 5 ) (7 10 ) Michaelis-Menten,, NEE ( 1) 4 8 NEE 0.83;, NEE 0.68~0.83, 0.37~0.83

5 7 : 807 Table 1 Crop Wheat Rice 表 1 稻麦轮作生态系统作物生长季净碳交换 (NEE) 与光合有效辐射回归模型参数 Coefficients of Michaelis-Menten model [NEE=R e P max PAR/(K m +PAR)] between net ecosystem exchange (NEE) and photosynthetically active radiation (PAR) in crop growing season of rice-wheat rotation system Month (P max ) Max photosynthetic rate (mg m 2 s 1 ) (R e ) Respiration rate (mg m 2 s 1 ) Constant (K m ) R n,, (P max ), (R e ), (P max ) (R e ),, NEE NEE, NEE [31], NEE, NEE 1, 100 µmol m 2 s,, NEE [32] ( 3) 5, 20, NEE ; 5, 20, NEE, CO 2 ; 15, 25, NEE, µmol m 2 s 1, CO 2,,,, CO 2, NEE, NEE 15 >5~15 > 5, NEE 25 >20~25 > 20 Fig. 3 图 3 不同气温等级 (Ta) 稻麦轮作系统白天净碳交换 (NEE) 与光合有效辐射 (PAR) 的关系 Relationship between daytime net ecosystem exchange (NEE) and photosynthetically active radiation (PAR) at different temperature grades (Ta) of rice-wheat rotation system 2.3 NEE NEE Level-0, CO 2 ( 4 5) : NEE (10 cm) (10 cm); NEE (10 cm) (10 cm) NEE (10 cm) 0.09~ ~0.49,,,,,, (10 cm) NEE (10 cm), 49%~59%, NEE

6 图 4 稻麦轮作系统小麦夜间净碳交换 (NEE) 与环境因子关系 Fig. 4 Relationship between net ecosystem exchange (NEE) and environmental factors at night in wheat of rice-wheat rotation system Fig. 5 图 5 稻麦轮作系统水稻夜间净碳交换 (NEE) 与环境因子关系 Relationship between net ecosystem exchange (NEE) and environmental factors at night in rice of rice-wheat rotation system NEE,,,, NEE 0~0.5 mg m 2 s 1, 5.3~31.7, 10 cm

7 7 : ~30.3,, NEE, NEE ( 4 5),, Lloyd & Taylor NEE ( 2), : NEE,, (10 cm) NEE, 0.57; NEE, NEE, (10 cm), 0.60; NEE, 0.49, Table 2 表 2 稻麦轮作系统夜间净碳交换 (NEE) 与不同层次温度的相关系数 Correlation coefficients of nighttime net ecosystem exchange (NEE) and temperature at different levels of rice-wheat rotation system Temperature at different level Wheat Rice Annual Air temperature (10 cm) Soil temperature at 10 cm depth (20 cm) Soil temperature at 20 cm depth (40 cm) Soil temperature at 40 cm depth 结论与讨论 NEE, NEE U, U ; NEE W, ( ) NEE : / NEE 4 /8, 1.12 mg m 2 s mg m 2 s 1, ( / ) ( 0.81~ 1.07 mg m 2 s ~ 1.42 mg m 2 s 1 ) [7] ; / NEE g(c) m 2 d g(c) m 2 d 1, ( / ) [ g(c) m 2 d g(c) m 2 d 1 ] [33], g(c) m 2 a 1, [ ~ g(c) m 2 a 1 ] [ g(c) m 2 a 1 ], [7,33], NEE Michaelis-Menten (R 2 =0.37~0.83), 4 8 (R 2 =0.83) [34] (R 2 =0.12~0.77), 0.77; [10] (R 2 =0.33~0.90), 0.90, [8] 0.88~0.97,, 3 PAR NEE,, NEE ; µmol m 2 s 1, NEE, [35] Anthoni [36] (2 cm 4 cm 8 cm 16 cm), ; [35] (5 cm),,, NEE, NEE, NEE (10 cm) (0.60), NEE (0.49),,, (R 2 =0.88) (R 2 =0.74) [37], NEE, 参考文献 [1],,,.

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