Temporal and spatial variation of gross primary productivity and its response to extreme climate in Mongolia

Mongolia has extremely fragile ecosystems and rich vegetation resources in arid and semi-arid zones. It is highly affected by extreme climatic events and is important in the global carbon cycle. In global warming, it is important to study its vegetation changes for ecological security. In this paper, based on the gross primary productivity (GPP) data with daily maximum temperature, daily minimum temperature and daily precipitation data of Mongolia from 2000 to 2023, the characteristics of spatial and temporal changes in GPP and its response to climate extremes were analyzed by using Sen Slope + Mann-Kendall trend analysis, MK mutation test, Pearson’s correlation analysis method, and structural equation modeling (SEM). The main findings of the studyare as follows: (1) The overall trend of GPP in Mongolia from 2000 to 2023 is upward. Most areas with high GPP values are located in the northern Sayanleng and Khangai Mountains, and the areas with significant increases account for 61 % of the total area of the study area; (2) Extreme temperature indices (SU, TNx, TNn) and extreme precipitation index R20 show an increasing trend at most weather stations in Mongolia, while other extreme precipitation indices (R95P, SDII) show a decreasing trend;(3) Extreme precipitation indices contributed to the effect of GPP in the study area, but they all inhibited GPP in Zabkhan province. R20 is the main factor influencing vegetation growth. Extreme temperature indices TNx and SU inhibited GPP and promoted GPP excepting the cold all year round Khuvsgul province, where GPP was promoted due to summers became warmer; (4) R20 and R95P significantly affect GPP positively and negatively, respectively. This opposed relationship reflects the dual role of precipitation pattern and intensity in regulating vegetation productivity. Other indices may influence ecosystem dynamics through indirect pathways under extreme climate change scenarios. The study’s results can provide scientific references for Mongolia’s ecological environment protection and green sustainable development.