Main content area

Different effects of single versus repeated additions of glucose on the soil organic carbon turnover in a temperate forest receiving long-term N addition

Wang, Qingkui, Chen, Longchi, Yang, Qingpeng, Sun, Tao, Li, Changmeng
Geoderma 2019 v.341 pp. 59-67
carbon dioxide, carbon sequestration, glucose, nitrogen, soil, soil organic carbon, stable isotopes, temperate forests
Labile organic C inputs from litter decomposition and root turnover may stimulate soil organic carbon (SOC) decomposition by a priming effect that strongly influences SOC dynamics. The direction and magnitude of this priming effect depends on the type and pattern of N and C addition. However, in which manner the type and pattern of N and C addition affect priming effect remains poorly understood. Thus, we conducted 90-day incubation to evaluate the effects of single and repeated addition of 13C-labeled glucose on SOC decomposition to soils collected from a long-term simulated N experiment with inorganic or organic N addition as the rate of 100 kg N hm−2 yr−1 as solution form. Respired CO2 and its δ13C value were measured to calculate the added glucose and native SOC decomposition, and consequently quantify primed C, and net C balance between primed SOC and retained glucose-C. We revealed for the first time that long-term N addition significantly decreased the cumulative primed C by an average of 23.0%, but this decrease was greater under organic N (29.7%) than under inorganic N (16.3%). Therefore, the suppression effects of atmospheric N deposition on primed C may be underestimated by solely adding inorganic N. The amount of cumulative primed C induced by single glucose addition was 2.92 times as high as that induced by repeated glucose addition. This finding suggests that the single addition with a high amount of labile organic C may overestimate primed C that naturally occurs in the field. A combined effect of glucose addition patterns and N addition on primed C was also observed. After the 90-day incubation, the amount of added glucose-C that remained in soils was substantially higher than the SOC loss due to positive priming effect, resulting in a net C increase. Taken together all data, we conclude that the repeated addition of labile organic C to soils under increasing atmospheric N deposition can increase SOC sequestration and stocks despite the positive priming effects in temperate forests.