Abstract
BackgroundUnder the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of farmlands have been determined in many countries. However, studies are very limited for drip irrigation maize the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced.ResultsTo study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014–2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between − 407 ~ − 729 g C m−2, 485.46 ~ 975.46 g C m−2, and 1068.23 ~ 1705.30 g C m−2. In four of the 5 study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was − 234 g C m−2, and the drip-irrigated maize field was a carbon source.ConclusionsThis study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux.
Highlights
Under the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention
The carbon fluxes in farmland ecosystems are directly affected by human activities, such as irrigation methods, planting patterns and agronomic measures, and these activities in turn influence global carbon fluxes due to the relatively high percentage of land areas devoted to farming [20, 30, 38]
Reducing carbon emissions from farmland ecosystems can have a significant impact on mitigating climate change
Summary
Under the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Based on eddy covariance system, studying how to maintain the balance in the carbon budget of terrestrial ecosystem, in particular farmland, has important scientific significance. The carbon fluxes in farmland ecosystems are directly affected by human activities, such as irrigation methods, planting patterns and agronomic measures, and these activities in turn influence global carbon fluxes due to the relatively high percentage of land areas devoted to farming [20, 30, 38]. Study have shown that drip irrigation with plastic mulching significantly increased soil C O2 emissions [46]. The results of a long-term situ experiment showed that the net ecosystem exchange of maize was negative, but its net biome productipn was positive (NBP remained positive indicating a carbon net loss) [13]
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