Speaker
Description
As the most active and bioavailable fraction of soil organic matter (SOM), dissolved organic matter (DOM) plays a key role in microbial transformations and the stabilization and accumulation of SOM. However, it remains unclear how nitrogen (N) deposition and alterations in plant resource alter soil DOM composition and their interactions with microbes, especially in old-growth tropical forest ecosystems. Here, based on a long-term (18 years) simulative N deposition experiment with four N addition levels (0, 5, 10, and15 g m-2 yr-1) and the adjacent short-term (eight months) manipulative Detritus Input and Removal Treatments (DIRT) experiment, the quantity, optical properties, and molecular-level characteristics of soil DOM were measured and the relationships of soil DOM with soil microbes were fully explored. Results showed that N additions significantly altered soil DOM composition, with an increasing trend in soil dissolved organic carbon (C) 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. Changes in plant inputs significantly altered soil DOM’s optical properties, and the most pronounced changes were observed in the humification index and fluorescent components. In litterfall removal and no-input plots, molecular characteristic values increased greatly, such as O/C, double-bond equivalent, aromaticity index, and proportion of carboxyl-rich alicyclic molecules, while bioavailable compounds decreased. Importantly, alterations in DOM composition significantly correlated with soil microbial activities, which reflected by soil microbial biomass C, N, phospholipid fatty acids, and enzyme activities, and further affected the formation of mineral-associated SOM and SOM heavy fraction through influencing recalcitrant DOM components. These findings suggest that long-term N additions and short-term DIRT may alter soil DOM composition in a way to benefit soil C storage in the primary tropical forests. It merits focusing on the mechanisms to association of DOM dynamics with C sequestration.
| Are you participating to the "AnaEE Environmental Rising Star Award "? | No |
|---|