Spatiotemporal variations of productivity and carbon use efficiency of forests in Eastern Inner Mongolia and their responses to drought from 2001 to 2021

The present study selected MODIS data and meteorological observation data from Inner Mongolia Autonomous Region between 2001 and 2021, and analyzed the seasonal variations of the Wetness Index in this region, as well as the response characteristics of the net primary productivity (NPP), gross primary productivity (GPP), and carbon use efficiency (NPP/GPP) of the forest ecosystem in eastern Inner Mongolia to drought.The results showed that the average NPP and GPP of the forests in eastern Inner Mongolia were 418.79 g C·m^-2·a^-1 and 703.12 g C·m^-2·a^-1, respectively, and the NPP/GPP ratio was 0.59.The spatial distributions of NPP and GPP were higher in the north and lower in the south, while the NPP/GPP ratio decreased from northwest to southeast.From 2001 to 2021, the NPP and GPP of the forests in eastern Inner Mongolia shifted from a stable pattern to a fluctuating growth pattern, with the NPP/GPP ratio showing a weak increasing trend, indicating an enhanced carbon sequestration capacity.In the eastern part of the Greater Khingan Range, the NPP and GPP showed an increasing trend, while the northern region showed a decreasing trend, and the overall change in NPP/GPP was relatively small.Summer drought had a stronger inhibitory effect on the increase of NPP and GPP, while autumn drought had a certain degree of influence on the NPP/GPP.