Abstract
This study investigated the dynamics of CO2 flux in a rain-fed wheat field ecosystem using an eddy covariance technique during the 2011 to 2012 wheat-growing season at the Loess Plateau, China. Results showed that the daily CO2 flux was closely related to photosynthetically active radiation (PAR), growth stage, soil temperature and rainfall. The average CO2 flux at different growth stages followed the order jointing and booting > erecting > reviving > heading > wintering > seeding and tillering > grain filling > ripening. The first four stages were carbon sinks, whereas the last four stages were carbon sources. The relationship between nighttime CO2 flux and air temperature was significant and fitted the index model (y=aebt). The relationship between daytime CO2 flux and PAR was also significant and fitted the quadratic model (y=ax2+bx+c). Moreover, daytime CO2 flux was significantly correlated with air temperature and PAR at the erecting, jointing and booting, and heading stages. Nighttime CO2 flux was also significantly correlated with soil temperature at 5 cm depth at the heading as well as jointing and booting stages. The carbon budget in the rain-fed wheat ecosystem was -401 g C m-2 yr-1, which was higher than those in other wheat ecosystems. This study implies that the ability of carbon-sequestration in different wheat field ecosystems may respond differently to climate and environment change.
Highlights
Global warming is an environmental problem primarily caused by increasing greenhouse gas concentrations (Shvaleva et al, 2011)
Variations in the daily mean of environmental conditions at the experimental site from September 2011 to June 2012 are plotted in Fig. 1, including air relative humidity, soil temperature at 5 cm depth, air temperature, photosynthetically active radiation (PAR), and precipitation
The low temperature inhibited the activity of soil microbes and reduced soil CO2 emissions
Summary
Global warming is an environmental problem primarily caused by increasing greenhouse gas concentrations (Shvaleva et al, 2011). The atmospheric CO2 concentration before the industrial revolution was 280 μmol mol–1 but is currently 370 μmol mol–1 and increases at a rate of 1 to 2 μmol mol–1 every year (Genthon et al, 1987). Changes in the carbon cycle in terrestrial ecosystems are receiving increased attention from scientists and policymakers (IPCC, 2001). Many studies have focused on the net ecosystem CO2 exchange in forest ecosystems possibly because forests can sequester high carbon levels (Pacala et al, 2001). Less attention is paid to the net ecosystem CO2 exchange in wheat (Triticum aestivum L.) field ecosystems even though these ecosystems comprise approximately 33% of the grain crops worldwide (Gu & Zha, 2013)
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