Relationship between nitrogen deposition and LUCC and its impact on terrestrial ecosystem carbon budgets in China

Increased nitrogen(N) deposition and land-use and land-cover change(LUCC) have influenced the terrestrial ecosystem carbon budget in China over the past few decades.However,the coupling effects of N deposition and LUCC on the carbon cycle remain unclear.This study first evaluated the effects of LUCC on N deposition based on estimated N deposition data from NOcolumn remote sensing data and the GlobeLand30 LUCC dataset,and then assessed the coupling effects of N deposition and LUCC on carbon budgets in China based on a terrestrial ecosystem process-based model.The results showed that the average rate of increase in N deposition in China was 0.35 Tg N yr(Tg = 10g),which caused net primary production(NPP) and net ecosystem production(NEP) to rise by 92.2 Tg C yrand 46.9 Tg C yr,respectively.The effects of LUCC reduced N deposition by 0.21 GgNyr(Gg= 10~9g).The land changed from forest to cropland had the greatest rate of increase in N deposition among all types of land-cover change.Changes from cropland to forest slowed the rate of N deposition increase the most.Generally,the change in N deposition resulting from LUCC reduced NPP and NEP by 0.7 and 0.4 Gg C yr,respectively.Compared with the total effects of N deposition on NPP and NEP,N deposition changes caused by LUCC had a limited aggregate effect on the C budget.