Assessment of Forest Carbon Sink Function under the Influence of Compound Dry and Heat Events

With global warming, compound dry and heat events have attracted extensive attention due to their synergistic effects on ecosystems. The forest ecosystem is one of the largest carbon pools in terrestrial ecosystems, which means its carbon sink function is of great significance to maintain the global carbon cycle balance. Taking the unchanged forest in Enshi City of Hubei Province from 2000 to 2022 as the research object, it comprehensively used multi-source remote sensing data and identified compound dry and heat events by calculating SPI and STI, which means the standardized precipitation index and standardized temperature index. Next, the paper chose the improved Carnegie-Ames-Stanford Approach model (which is also called the CASA model) to estimate forest net primary productivity (NPP) to analyze the driving mechanism and lag response characteristics of compound dry and heat events on forest carbon sink changes with the help of the geographical detector (GD). The results showed that three compound dry and heat events in Enshi occurred in July 2011, October 2013, and August 2022, and the response time of forest carbon sequestration was about one month. The drought factor has a stronger effect on forest carbon sink change than the high temperature factor, and the interaction between them shows a significant nonlinear enhancement effect. The results will help to deeply understand how climate change makes impacts on mountain forest ecosystems, and provide a scientific basis for regional forest resource management.