Influence mechanisms of N addition on the concentration of soil dissolved organic matter in China

Abstract

Soil dissolved organic matter (DOM) plays a critical role in regulating the cycling of terrestrial biogeochemistry. However, the influence mechanisms of nitrogen (N) addition on soil DOM concentration are not well understood at the regional scale. We performed a meta‐analysis of 1004 paired observations from 115 literature to explore how N addition affected the soil DOM concentration, including dissolved organic carbon (DOC) and nitrogen (DON), in China. Overall, N addition markedly stimulated the soil DOC and DON concentrations by 5.2% and 33.1%, respectively. This implied that the stimulation by increased N availability than the suppression by decreased soil pH played a more important role in the soil DOM concentration under N addition. The N addition level showed a significantly positive correlation with the soil DOC and DON concentrations under N addition. The N addition influence on soil DOC concentration was decreased along with the increase in initial soil total nitrogen (TN). This demonstrated the microbial N mining theory in the low N soils and the stoichiometric decomposition theory in the high N soils at the regional scale. The mean annual precipitation (MAP) potentially facilitated the leaching out of soil DON and displayed a negative impact on the soil DON concentration under N addition. The increased soil depth and initial soil pH depressed the soil DOC concentration whereas stimulated the soil DON concentration under N addition. This indicated that DOC mostly accumulated in the top soil and DON largely leached to the deep soil. And the initial soil pH with high value perhaps promoted the uptake of DOC for microbes and the solubility of DON, and thus resulted in the opposite influences on the soil DOC and DON concentrations. Our study provided a mechanistic understanding on N addition influence on the C and N dynamics of terrestrial ecosystem at the regional scale.

Effects of nutrient addition on the composition and chemical characteristics of soil dissolved organic matter in a desert steppe in northern China

“…Soil DOM characteristics showed a strong dependence on environmental variables (Figures 8 and 9), wherein pH exhibited a significant effect on soil DOM characteristics. Some studies have reported that the increase in N availability played a more important role in soil DOM concentration than the reduction in the stimulus for inhibiting soil pH (Xu et al, 2023). In the present study, the pH value of each treatment decreased, and pH was positively correlated with E 2 /E 3 (Figures 8 and 9).…”

Simultaneous adsorption of fulvic acid and organic contaminants by KOH activated mesoporous biochar with large surface area

“…2 b), which indicated that the adsorption capacity and affinity of organic contaminants with higher hydrogen-bonding donor ability tend to be less suppressed by the competition of FA. At a given FA concentration of 50 mg TOC/L, a high concentration level of DOM in natural water and soil water [ [39] , [40] , [41] , [42] ], adsorption of these selected organic contaminants in a wide concentration range (the relative equilibrium concentrations C e / S w ranged from about 0.0001 to 0.75) on KAC were not significantly suppressed by FA ( Fig. 3 a–g).…”