Abstract: In recent years, eco-environment in the main urban area of Chongqing has undergone great changes due to the impacts of climate change and rapid urbanization. Based on MOD17A3 dataset of net primary productivity (NPP) from 2000 to 2020, combined with regional climate and land use data, we analyzed the variations of NPP in the main urban area of Chongqing and explored the impacts of climate and land use change by using the methods of trend analysis, correlation analysis, and quantitative attribution. Over the past 21 years, NPP showed a fluctuating upward trend, with total NPP increasing from 2.15 Tg C to 2.87 Tg C. The contribution of cropland to total NPP was the largest, reaching 65.30%, followed by forest (30.28%). Precipitation and temperature were positively correlated with NPP, and the relationship between precipitation and NPP was the most prominent, while solar radiation had no significant effect. In general, climatic factors were the dominant driving factors for the increase of total NPP. During the periods of 2000-2005, 2005-2010 and 2010-2015, climate change positively contributed to the increase of total NPP, with a contribution rate of 88.65%, 80.53%, and 90.93%, respectively. However, it showed an inhibitory effect on total NPP during 2015-2020, with a contribution rate of 35.95%. Land use change caused by urban expansion had a significant negative effect on total NPP change. The contribution rate of land use change to total NPP during 2000-2005, 2005-2010, 2010-2015, and 2015-2020 were 10.92%, 16.77%, 8.56%, and 56.51%, respectively. Moreover, the increases of landscape patch density and Shannon diversity index and the decrease of landscape aggregation had a promoting effect on increasing total NPP. Our findings are of great significance for understanding carbon sequestration capacity under the background of urbanization, and can provide theoretical basis for promoting regional ecological monitoring and protection and spatial planning.

Key words: land use change, net primary productivity, MOD17A3 NPP, landscape pattern index