Monsoon rainfall trends and change point detection affecting kharif paddy ecosystems and gross primary productivity in Odisha

This study uses data from 1901 to 2023 to investigate the long-term spatiotemporal variations and trends in monsoon rainfall. It also looks at how these changes may affect Kharif Paddy production in the state's agro-climatic zones from 2000 to 2022. The Pettitt test was used to identify sudden alterations in rainfall patterns, and the Mann-Kendall (MK) test was used to assess rainfall trends. The findings show that most districts in Odisha have no significant change in monsoon rainfall, indicating a generally consistent pattern over the past 123 years. Only Sundergarh in the North-Western Plateau Zone showed a significant negative trend (-2.51), highlighting potential localized vulnerabilities. Change detection analysis shows the probable change years vary by districts (under agro-climatic zones) ranging from 1919 to 2009, whereas inter-seasonal rainfall variability was recorded to increase after 1980. The relationship between GPP and rainfall revealed non-linear characterises. Meanwhile, the seasonal trend from 2000 to 2022 showed a favourable increase in Gross Primary Productivity (GPP), averaging 10.88 gC/m² per year. Sensitivity analysis revealed that the GPP of forested areas in a region or district is more responsive to rainfall fluctuations than cropped areas within Odisha's agro-climatic zones. Additionally, threshold analysis was conducted to identify the optimal range of monsoon rainfall that maximizes GPP for the studied districts across different agro-climatic zones. Understanding long-term rainfall variability is crucial for ensuring sustainable agricultural productivity, particularly in monsoon-dependent regions like Odisha, where shifting precipitation patterns can significantly affect Kharif paddy production.