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	Carbon dioxide exchange and the mechanism of environmental control in a farmland ecosystem in North China Plain
	Yu Q.; Li J.; Wang J.; Wang J.; Li J.
	2006
关键词	net ecosystem exchange gross primary productivity ecosystem respiration carbon budget eddy covariance winter wheat summer maize water-vapor exchange gap filling strategies terrestrial ecosystems european forests co2 exchange respiration variability atmosphere fluxnet balance
英文摘要	CO2 flux was measured continuously in a wheat and maize rotation system of North China Plain using the eddy covariance technique to study the characteristic of CO2 exchange and its response to key environmental factors. The results show that nighttime net ecosystem exchange (NEE) varied exponentially with soil temperature. The temperature sensitivities of the ecosystem (Q(10)) were 2.94 and 2.49 in years 2002-2003 and 2003-2004, respectively. The response of gross primary productivity (GPP) to photosynthetically active radiation (PAR) in the crop field can be expressed by a rectangular hyperbolic function. Average A(max) and a for maize were more than those for wheat. The values of a increased positively with leaf area index (LAI) of wheat. Diurnal variations of NEE were significant from March to May and from July to September, but not remarkable in other months. NEE, GPP and ecosystem respiration (Rep) showed significantly seasonal variations in the crop field. The highest mean daily CO2 uptake rate was -10.20 and -12.50 gC (.) m(-2 .) d(-1) in 2003 and 2004, for the maize field, respectively, and -8.19 and -9.50 gC (.) m(-2) (.) d(-1) in 2003 and 2004 for the wheat field, respectively. The maximal CO2 uptake appeared in April or May for wheat and mid-August for maize. During the main growing seasons of winter wheat and summer maize, NEE was controlled by GPP which was chiefly influenced by PAR and LAI. Rep reached its annual maximum in July when Rep and GPP contributed to NEE equally. NEE was dominated by Rep in other months and temperature became a key factor controlling NEE. Total NEE for the wheat field was -77.6 and -152.2 gC (.) m(-2 .) a(-1) in years 2002-2003 and 2003-2004, respectively, and -120.1 and -165.6 gC (.) m(-2) (.) a(-1) in 2003 and 2004 for the maize field, respectively. The cropland of North China Plain was a carbon sink, with annual -197.6 and -317.9 gC (.) m(-2) (.) a(-1) in years 2002-2003 and 2003-2004, respectively. After considering the carbon in grains, the cropland became a carbon source, which was 340.5 and 107.5 gC (.) m(2) (.) a(-1) in years 2002-2003 and 2003-2004, respectively. Affected by climate and filed managements, inter-annual carbon exchange varied largely in the wheat and maize rotation system of North China Plain.
出处	Science in China Series D-Earth Sciences
卷	49
页	226-240
收录类别	SCI
语种	英语
ISSN号	1006-9313
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/23657]
专题	地理科学与资源研究所_历年回溯文献
推荐引用方式 GB/T 7714	Yu Q.,Li J.,Wang J.,et al. Carbon dioxide exchange and the mechanism of environmental control in a farmland ecosystem in North China Plain. 2006.

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