Abstract
Interannual variation in plant phenology can lead to major modifications in the interannual variation of net ecosystem production (NEP) and net biome production (NBP) as a result of recent climate change in croplands. Continuous measurements of carbon flux using the eddy covariance technique were conducted in two winter wheat and summer maize double-cropped croplands during 2003–2012 in Yucheng and during 2007–2012 in Luancheng on the North China Plain. Our results showed that the difference between the NEP and the NBP, i.e., the crop economic yield, was conservative even though the NEP and the NBP for both sites exhibited marked fluctuations during the years of observation. A significant and positive relationship was found between the annual carbon uptake period (CUP) and the NEP as well as the NBP. The NEP and the NBP would increase by 14.8±5.2 and 14.7±6.6 g C m−2 yr−1, respectively, if one CUP-day was extended. A positive relationship also existed between the CUP and the NEP as well as the NBP for winter wheat and summer maize, respectively. The annual air temperature, through its negative effect on the start date of the CUP, determined the length of the CUP. The spring temperature was the main indirect factor controlling the annual carbon sequestration when a one-season crop (winter wheat) was considered. Thus, global warming can be expected to extend the length of the CUP and thus increase carbon sequestration in croplands.
Highlights
The potential of cropland to mitigate the greenhouse effect has received much attention in recent years [1]
Because the straw residue of the summer maize remained in the field after harvesting, the rate of the decrease in the air temperature was more dramatic than the soil temperature when extreme cold weather occurred during the years of 2008–2009 and 2011–2012 in Luancheng
Annual carbon budget and comparison with other terrestrial ecosystem Our study showed that the annual net ecosystem production (NEP) was 475.66159.4 g C
Summary
The potential of cropland to mitigate the greenhouse effect has received much attention in recent years [1]. The North China Plain, which is the largest agricultural production center in China, has an area of 36105 km and supports the production of food for over 300 million people [3]. This plain is a large area planted in winter wheat and summer maize double-cropping systems and supplies more than 50% of China’s wheat and 33% of its maize [4]. Owing to its large area, this agricultural center has great potential to store carbon and reduce the emissions of greenhouse gases. Long-term continuous measurements of carbon flux using eddy covariance technology is a practical method to assess the carbon balance and can sufficiently reflect the interannual variations in carbon exchange, which would provide scientists with valuable information for understanding the response of ecosystem processes to climate change [6]
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