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Dynamics of CO2 and H2O fluxes in Johnson grass in the U.S. Southern Great Plains.
- Source :
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Science of the Total Environment . Oct2020, Vol. 739, pN.PAG-N.PAG. 1p. - Publication Year :
- 2020
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Abstract
- Johnson grass (Sorghum halepense (L.) Pers.) is rapidly spreading throughout the continental United States (U.S.). Thus, determining magnitudes and seasonal dynamics of carbon dioxide (CO 2) and water vapor (H 2 O) fluxes in Johnson grass is crucial to understand regional changes in hydrology and carbon balance. Using eddy covariance (EC), CO 2 and H 2 O fluxes were measured from June 2017 to October 2019 over a rainfed Johnson grass field in central Oklahoma. Hay was harvested from late May to early July each year, with biomass yield ~7.5 t ha−1. Weekly averaged daily integrated net ecosystem CO 2 exchange (NEE), gross primary production (GPP), and evapotranspiration (ET) reached −8.28 ± 0.76 g C m−2, 20.02 ± 1.62 g C m−2, and 5.42 ± 0.26 mm, respectively. Ecosystem water use efficiency (EWUE) and ecosystem light use efficiency (ELUE) ranged from 3.22 to 3.93 g C mm−1 ET and 0.34 to 0.41 g C mol−1 PAR (photosynthetically active radiation), respectively, during peak growths. Based on aggregated fluxes for each month over the three years (2017–2019), cumulative annual NEE was −434 ± 112 g C m−2, indicating a carbon gain by the Johnson grass field. Cumulative annual ET (858 ± 72 mm) was ~86% of the average annual rainfall (996 ± 100 mm). Results showed Johnson grass could be a carbon sink from May to September in the U.S. Southern Great Plains. Both NEE and ET did not decline up to air temperature (T a) of ~33 °C and vapor pressure deficit (VPD) of ~2 kPa, suggesting optimum T a of ≥33 °C and VPD of ≥2 kPa for the fluxes. Results indicated that Johnson grass might be well suited for dryland production in the region. Additionally, these findings provide initial baseline information on CO 2 fluxes and ET for Johnson grass relative to other forage species in the region. Unlabelled Image • First work to thoroughly study dynamics of CO 2 and H 2 O fluxes in Johnson grass. • Johnson grass harvested for hay showed large carbon uptake potential at annual scales. • Johnson grass could be a carbon sink in the southern plains during May–Sept period. • CO 2 uptake did not decrease up to air temperature of ~33 °C. • Cumulative annual ET (858 ± 72 mm) was ~86% of the average annual rainfall. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00489697
- Volume :
- 739
- Database :
- Academic Search Index
- Journal :
- Science of the Total Environment
- Publication Type :
- Academic Journal
- Accession number :
- 145210681
- Full Text :
- https://doi.org/10.1016/j.scitotenv.2020.140077