Qiu Qingyan, Mgelwa Abubakari Said, Jin Shaofei, Hu Yalin
Forest Ecology and Stable Isotope Center, College of Forestry, Fujian Agriculture and Forestry University, Fuzhou, China.
College of Natural Resources Management and Tourism, Mwalimu Julius K. Nyerere University of Agriculture and Technology, Musoma, Tanzania.
Front Plant Sci. 2022 Jul 12;13:950367. doi: 10.3389/fpls.2022.950367. eCollection 2022.
Subtropical regions are currently experiencing a dramatic increase in nitrogen (N) deposition; however, the contributions of nitrification and denitrification processes to soil NO emissions and the underlying mechanisms under increasing N deposition remain unclear. Therefore, a N-tracing laboratory experiment with four N application rates (0, 12.5, 25, and 50 μg N g soil) was conducted to investigate the response of nitrification- and denitrification-derived NO to N additions in an evergreen broad-leaved forest (BF) and a forest (PF) in the Wuyi Mountains in southeastern China. Moreover, the abundance of functional genes related to nitrification (), denitrification (, , and ), and soil properties were measured to clarify the underlying mechanisms. Results showed that nitrification-derived NO emissions were generally decreased with increasing N input. However, denitrification-derived NO emissions were a non-linear response to N additions, with maximum NO emissions at the middle N application rate. Denitrification-derived NO was the dominant pathway of NO production, accounting for 64 to 100% of the total NO fluxes. Soil NH -N content and pH were the predominant factors in regulating nitrification-derived NO emissions in BF and PF, respectively. Soil pH and the abundance contributed the most to the variations of denitrification-derived NO emissions in BF and PF, respectively. Our results suggest that N application has the potential to increase the contribution of denitrification to NO production in subtropical forest soils. Changes in soil chemical properties induced by N addition are more important than the abundance of nitrification and denitrification functional genes in regulating soil nitrification- and denitrification-derived NO emissions.
亚热带地区目前正经历着氮（N）沉降的急剧增加；然而，硝化作用和反硝化作用过程对土壤一氧化氮（NO）排放的贡献以及氮沉降增加情况下的潜在机制仍不清楚。因此，在中国东南部武夷山的一片常绿阔叶林（BF）和一片针叶林（PF）中，进行了一项氮示踪实验室实验，设置了四个施氮量水平（0、12.5、25和50 μg N g土壤），以研究硝化作用和反硝化作用产生的NO对氮添加的响应。此外，还测量了与硝化作用（ ）、反硝化作用（ 、 和 ）相关的功能基因丰度以及土壤性质，以阐明潜在机制。结果表明，硝化作用产生的NO排放通常随着氮输入的增加而减少。然而，反硝化作用产生的NO排放对氮添加呈非线性响应，在中等施氮量时NO排放最高。反硝化作用产生的NO是NO产生的主要途径，占总NO通量的64%至100%。土壤铵态氮（NH -N）含量和pH值分别是调节BF和PF中硝化作用产生的NO排放的主要因素。土壤pH值和 丰度分别对BF和PF中反硝化作用产生 的NO排放变化贡献最大。我们的结果表明，施氮有可能增加亚热带森林土壤中反硝化作用对NO产生的贡献。在调节土壤硝化作用和反硝化作用产生的NO排放方面，氮添加引起的土壤化学性质变化比硝化作用和反硝化作用功能基因的丰度更重要。
