Abstract
Abstract. Carbon fluxes from agroecosystems contribute to the
variability of the carbon cycle and atmospheric [CO2]. This study is a
follow-up to Gahlot et al. (2020), which used the Integrated Science
Assessment Model (ISAM) to examine spring wheat production and its drivers.
In this study, we look at the carbon fluxes and their drivers. ISAM
was calibrated and validated against the crop phenology at the IARI wheat
experimental site in Gahlot et al. (2020). We extended the validation of
the
model on a regional scale by comparing modeled leaf area index (LAI) and yield against site-scale observations and regional datasets. Later, ISAM-simulated carbon
fluxes were validated against an experimental spring wheat site at IARI for
the growing season of 2013–2014. Additionally, we compared with the published
carbon flux data and found that ISAM captures the seasonality well.
Following that, regional-scale runs were performed. The results revealed
that fluxes vary significantly across regions, primarily owing to
differences in planting dates. During the study period, all fluxes showed
statistically significant increasing trends (p<0.1). Gross primary production (GPP), net primary production (NPP), autotrophic
respiration (Ra), and heterotrophic respiration
(Rh) increased at 1.272,
0.945, 0.579, 0.328, and 0.366 TgC yr−2, respectively. Numerical experiments
were conducted to investigate how natural forcings such as changing
temperature and [CO2] levels as well as agricultural management practices such
as
nitrogen fertilization and water availability could contribute to the
rising
trends. The experiments revealed that increasing [CO2], nitrogen
fertilization, and irrigation water contributed to increased carbon fluxes,
with nitrogen fertilization having the most significant effect.
Funder
Indian Space Research Organisation
Subject
General Earth and Planetary Sciences