Do long-term high nitrogen inputs change the composition of soil dissolved organic matter in a primary tropical forest?

作者：Guoxiang Niu, Gege Yin, Xiaohan Mo, Qinggong Mao, Jiangming Mo, Junjian Wang, X. L. Lu · 发表于：Environmental Research Letters · 年份：2022 · DOI：10.1088/1748-9326/ac8e87 · 被引用次数：18 · 研究领域：Soil Carbon and Nitrogen Dynamics、Geology and Paleoclimatology Research、Marine and coastal ecosystems

Abstract Dissolved organic matter (DOM) plays a key role in forest carbon biogeochemistry by linking soil organic carbon (SOC) sequestration and water fluxes, which is further shaped by elevated atmospheric nitrogen (N) deposition. Although enhanced SOC sequestration was evidenced in tropical forests due to rising N deposition, it remains unclear how long-term N inputs affect soil DOM composition, which regulates SOC sequestration capability due to its mobility and biological instability. Here, the quantity, optical properties, and molecular-level characteristics of soil DOM based on a simulative N deposition experiment with four N addition levels (0, 5, 10, and 15 g m −2 yr −1 ) were studied in a primary tropical forest in south China. Results showed that 18 year N additions significantly altered soil DOM composition, with an increasing trend in soil dissolved organic carbon content. Medium- (10 g m −2 yr −1 ) and high-N addition (15 g m −2 yr −1 ) markedly elevated DOM average molecular weight by 12% and aromaticity, with specific ultraviolet absorbance at 254 nm increasing by 17%, modified aromatic index by 35%, and condensed aromatics by 67%. Medium- and high-N addition also increased recalcitrant DOM components but decreased other DOM components, with increasing percentages of lignin-like, tannin-like, and carboxylic-rich alicyclic molecule-like compounds, and decreasing percentage of more bioavailable contributions with H/C ratio >1.5. Importantly, significant correl...