N-cycling functional genes and soil properties shape the heterogeneity of nitrous oxide emission pathways in tea plantation soils

Abstract

Tea (Camellia sinensis), one of the world’s most popular beverages, plays a vital role in socio-economic development. However, nitrous oxide (N₂O) emissions from tea plantation soils have become a serious environmental issue, largely due to soil acidification and excessive N fertilizer inputs. Despite this, there is still a knowledge gap in determining how much nitrification and denitrification contribute to overall N₂O emissions in tea plantation soils, which makes it difficult to make focused mitigation strategies. Here, we utilized ¹⁵N isotope labeling experiments to probe into the contribution of various microbial pathways to N₂O emissions of tea plantation soils across seven major tea-producing provinces in China. We assessed soil properties, microbial diversity and composition, N₂O production-and-reduction-related functional gene abundances, and keystone species abundances to probe into driving mechanisms influencing N₂O sources. The results revealed significant heterogeneity of N₂O emission intensity and pathways among different tea plantation soils. Co-denitrification and heterotrophic nitrification emerged as the primary contributors of N₂O emissions, accounting for an average of 34 % and 41 %, respectively. However, the mean contributions of denitrification and autotrophic nitrification were only 22 % and 3 %, respectively. Variance partitioning and correlation analyses indicated that this heterogeneity was predominantly driven by N-cycling gene abundances and soil properties (both contributed 71 % of the explanation) rather than microbial diversity and keystone species abundance. This study advances our understanding of the soil N-cycling process in acidic soils and provides a groundwork for formulating targeted measures to reduce N₂O emissions based on the dominant pathways in tea plantation soils.