Abstract

Accurate representation of photosynthetic capacity and its seasonal variations is critical for modeling carbon sequestration of cropland ecosystems through photosynthesis. Previous studies indicated that the maximum carboxylation rate at 25 °C (Vcmax25) is the key determinant of photosynthetic capacity and can be mapped according to leaf nitrogen (N) and chlorophyll (Chl) contents. However, whether relationships of Vcmax25 with leaf nitrogen and chlorophyll contents in cropland ecosystems change over the whole growing season remain unclear. To address this question, we conducted intensive field campaigns in winter wheat and paddy rice farmlands of Eastern China, with leaf Vcmax25, the maximum electron transport rate at 25 °C (Jmax25), N, and Chl measured every 7 to 10 days from the tillering stage to maturity. Results showed that Vcmax25 and Jmax25 varied significantly during the growing seasons and maximized at flowering stages. For both winter wheat and paddy rice, Chla (Chl content at the area unit) showed significantly different relationships with Vcmax25 pre- and post- flowering while Na (N content at the area unit) did not. When different empirical models were used for pre- flowering and post- flowering stages, Vcmax25 estimated from Chla was closer to observations (R2 = 0.875, RMSE = 9.479 µmol m−2 s−1) than that estimated from Na (R2 = 0.565, RMSE = 17.718 µmol m−2 s−1). The findings in this study imply that the combination of remotely sensed leaf Chla content and phenology would improve the mapping of Vcmax25 for crops at regional and even global scales.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.