Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices

作者：Wagle Pradeep^*; Gowda Prasanna H; Northup Brian K; Turner Kenneth E; Neel James P S; Manjunatha Priyanka; Zhou Yuting

来源：Atmospheric Environment, 2018, 185: 100-108.

DOI：10.1016/j.atmosenv.2018.05.003

• Ecosystem light use efficiency
• Eddy covariance
• Net ecosystem CO2 exchange
• No-till
• Spatial variability

Carbon dioxide (CO2) fluxes from six winter wheat (Triticum aestivum L.) paddocks (grain only, graze-grain, and graze-out) managed under conventional till (CT) and no-till (NT) systems were synthesized for the 2016-2017 growing season to compare the magnitudes and seasonal dynamics of CO2 fluxes and to investigate among-site variability of CO2 fluxes. Large variations in CO2 fluxes were observed among paddocks. Maximum daily (7-day averages) net ecosystem CO2 exchange (NEE) ranged from - 3.39 to - 8.68 g C m(-2), gross primary production (GPP) ranged from 7.33 to 16.92 g C m(-2), and ecosystem respiration (ER) ranged from 5.85 to 9.98 g C m(-2). Seasonal sums of NEE ranged from -137 to -542 g C m(-2). Optimum photosynthetically active radiation (PAR), air temperature (T-a), and vapor pressure deficit (VPD) for NEE were approximately 1700 mu mol m(-2) s(-1), 22 degrees C, and 1.25 kPa, respectively. Across-site analysis showed percent of canopy cover (Canopy%) was strongly correlated with NEE (R-2 = 0.76) and ecosystem light use efficiency (ELUE, R-2 = 0.76). Integration of PAR with leaf area index (LAI) and integration of T-a with dry biomass weight (DW) explained 81% and 74% of variations in GPP and ER, respectively. Remotely-sensed enhanced vegetation index (EVI) explained 66% and normalized difference vegetation index (NDVI) explained 69% of the variations in NEE. Integration of PAR with NDVI or EVI explained similar to 80% of variations in GPP, while NDVI x T-a explained 58% of variations in ER. Results illustrated that differences in wheat canopies related to paddock management, as indicated by differences in DW, LAI, Canopy%, NDVI, and EVI, must be accounted for explaining among-site variability of CO2 fluxes. Long-term measurements from our clustered and paired eddy covariance towers will provide insights into the effects of tillage and different grazing practices on CO2 dynamics in winter wheat.

• 出版日期2018-7