Characteristics and influencing factors of N₂O emissions in typical forestland and tea plantations with different planting years in southern Hubei Province

Tea plantations, as important economic crops, have a significant impact on regional greenhouse gas emissions. To investigate the characteristics and influencing factors of N₂O emissions from typical forestlands and tea plantations with different planting years, we monitored N₂O emissions for one year using the static chamber method in low-year (5 years) and high-year (40 years) tea plantations, as well as in adjacent forestland (L) in Xianning, Hubei Province. Environmental factors such as rainfall, temperature, soil water-filled pore space (WFPS), dissolved organic carbon (DOC), microbial biomass carbon (MBC), ammonium nitrogen (NH₄⁺-N), and nitrate nitrogen (NO₃⁻-N) were analyzed for their effects on N₂O emissions. The results showed that soil acidification intensified with increasing plantation years, with the pH of the high-year tea plantation (T40) significantly lower than that of the low-year plantation (T5) and forestland. N₂O emissions from tea plantation soils were significantly higher than those from forestland, in the order of T5 ((5.43±0.30) kg/hm²）< T40（(2.59±0.31) kg/hm²）< L（(0.15±0.12) kg/hm²), which were 36.2 and 17.3 times greater than forestland for T5 and T40, respectively. Soil N₂O emissions showed significant seasonal variation, with the highest emissions in spring, followed by summer, and little change in autumn and winter. In the low-year tea plantation, N₂O emissions were mainly driven by soil DOC and NH₄⁺-N, while in the high-year plantation, NO₃⁻-N was the primary influencing factor. The study indicates that N fertilizer input and DOC accumulation significantly promote N₂O emissions in low-year tea plantations, whereas emissions in high-year plantations are mainly driven by long-term soil acidification and NO₃⁻-N. Therefore, fertilization practices and soil carbon-nitrogen components should be adjusted according to plantation year to effectively reduce greenhouse gas emissions from tea plantation soils in southern Hubei.