How do land use changes affect carbon and nitrogen stocks in Amazon soils under different climatic types?

The conversion of forests to pastures and croplands has affected soil carbon (C) and nitrogen (N) stocks, particularly in the Amazon. This study aimed to evaluate how different land uses influence soil C and N stocks in two edaphoclimatic contexts in the Amazon Deforestation Arc, Pará, Brazil: São Miguel do Guamá (Af) and Paragominas (Aw). Soil samples were collected from deep soil profiles (0–100 cm) at eight depth intervals across four land use systems (forest, agriculture, intensive pasture, and nominal pasture). In the Af site, intensive pasture presented the highest C (42.36 and 80.21 mg ha −1 ) and N stocks (3.23 and 5.31 mg ha −1 ) at 0–30 and 0–100 cm, respectively. Differences among land uses were observed mainly in the 0–100 cm layer, while variations in the 0–30 cm layer were not statistically significant. In the Aw site, C stocks ranged from 63.86 to 134.48 mg ha −1 and N stocks from 5.17 to 10.79 mg ha −1 , with no differences among land uses, a pattern consistent with the buffering capacity typically associated with clay-rich soils. The δ 13 C analysis indicated replacement of C 3 carbon by C 4 carbon down to 60 cm in the Af site, whereas in the Aw site this substitution was limited to the 0–10 cm layer. The δ 15 N patterns were consistent with more intense N cycling and organic matter processing in managed systems relative to forest. These results highlight the importance of sustainable land management adapted to edaphoclimatic conditions for conserving C and N stocks in Amazon soils. • Soil C and N stocks vary across land uses in Af and Aw climates of the Amazon. • Intensive pastures increase C and N in sandy soils under Af climate. • Clay-rich soils under Aw climate retain higher and more stable C and N. • δ 13 C and δ 15 N isotopes reveal shifts in C sources and N cycling processes. • Soil texture controls the resilience of C and N stocks to land use change in Amazon soils. • Soil texture controls the resilience of C and N stocks to land use change in Amazon soils.