Song Wei, Hu Chunsheng, Luo Yu, Clough Tim J, Wrage-Mönnig Nicole, Ge Tida, Luo Jiafa, Zhou Shungui, Qin Shuping
Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.
Hebei Provincial Key Laboratory of Soil Ecology, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei, China.
Front Microbiol. 2023 Feb 8;14:1120466. doi: 10.3389/fmicb.2023.1120466. eCollection 2023.
Numerous studies have investigated the effects of nitrogen (N) addition on soil organic carbon (SOC) decomposition. However, most studies have focused on the shallow top soils <0.2 m (surface soil), with a few studies also examining the deeper soil depths of 0.5-1.0 m (subsoil). Studies investigating the effects of N addition on SOC decomposition in soil >1.0 m deep (deep soil) are rare. Here, we investigated the effects and the underlying mechanisms of nitrate addition on SOC stability in soil depths deeper than 1.0 m. The results showed that nitrate addition promoted deep soil respiration if the stoichiometric mole ratio of nitrate to O exceeded the threshold of 6:1, at which nitrate can be used as an alternative acceptor to O for microbial respiration. In addition, the mole ratio of the produced CO to NO was 2.57:1, which is close to the theoretical ratio of 2:1 expected when nitrate is used as an electron acceptor for microbial respiration. These results demonstrated that nitrate, as an alternative acceptor to O, promoted microbial carbon decomposition in deep soil. Furthermore, our results showed that nitrate addition increased the abundance of SOC decomposers and the expressions of their functional genes, and concurrently decreased MAOC, and the ratio of MAOC/SOC decreased from 20% before incubation to 4% at the end of incubation. Thus, nitrate can destabilize the MAOC in deep soils by stimulating microbial utilization of MAOC. Our results imply a new mechanism on how above-ground anthropogenic N inputs affect MAOC stability in deep soil. Mitigation of nitrate leaching is expected to benefit the conservation of MAOC in deep soil depths.
众多研究调查了添加氮（N）对土壤有机碳（SOC）分解的影响。然而，大多数研究集中在深度小于0.2米的浅层表土（表层土壤），只有少数研究也考察了0.5 - 1.0米深度的深层土壤（底土）。研究添加氮对深度大于1.0米的深层土壤（深层土）中SOC分解影响的研究很少。在此，我们研究了添加硝酸盐对深度超过1.0米的土壤中SOC稳定性的影响及其潜在机制。结果表明，如果硝酸盐与O的化学计量摩尔比超过6:1的阈值，添加硝酸盐会促进深层土壤呼吸，此时硝酸盐可作为微生物呼吸中O的替代受体。此外，产生的CO与NO的摩尔比为2.57:1，接近将硝酸盐用作微生物呼吸电子受体时预期的理论比值2:1。这些结果表明，硝酸盐作为O的替代受体，促进了深层土壤中的微生物碳分解。此外，我们的结果表明，添加硝酸盐增加了SOC分解者的丰度及其功能基因的表达，同时降低了MAOC，并且MAOC/SOC的比值从培养前的20%降至培养结束时的4%。因此，硝酸盐可通过刺激微生物对MAOC的利用使深层土壤中的MAOC不稳定。我们的结果暗示了一种关于地上人为氮输入如何影响深层土壤中MAOC稳定性的新机制。减少硝酸盐淋失有望有利于深层土壤中MAOC的保护。
