State Key Laboratory of Soil Erosion and Dry Land Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, 712100, Shaanxi, China.
Appl Microbiol Biotechnol. 2019 Feb;103(4):1939-1951. doi: 10.1007/s00253-018-09575-0. Epub 2019 Jan 3.
Denitrification accounts for the production of mobile forms of nitrogen (N) for plant uptake, N leaching, and gaseous losses. However, few studies have investigated the potential effects of the natural restoration age on denitrification rates and denitrifying microorganisms, especially in fragile ecosystems in semiarid regions. The potential N gas (NO and N) emissions and denitrification rates significantly decreased after abandonment (< 9 years) compared to those of active farmland and then steadily increased as the restoration proceeded, leading to an enhanced soil N loss. The total bacterial and napA gene abundances significantly decreased after abandonment (< 9 years) compared to that of farmland and then significantly increased as the restoration proceeded. The abundances of the narG, nirK, nirS, qnorB, and nosZ genes steadily increased with the restoration age of abandoned farmland. The community compositions of denitrifying bacteria exhibited different fluctuating patterns, suggesting different response patterns of community traits of N gas emission-related functional guilds to the restoration age of abandoned farmland. Changes in N gas emissions and in the abundance and diversity of denitrifying microorganisms exhibited similar patterns, suggesting an increased population and diversity of denitrifying bacteria are responsible for the enhanced N gas emissions. We observed clear patterns of plant coverage and denitrifying microorganisms that were associated with increases in the organic C, NH-N, and NO-N contents and decreases in the soil bulk density as well as increases in the abundance and diversity of denitrifiers with the restoration age of abandoned farmland that were linked to an increase in N gas emissions. It is therefore recommended that effective measures (i.e., modest levels of grazing) may be able to be undertaken to assist with decreasing greenhouse gas nitrous oxide (NO) and N loss after 32 years of farmland abandonment.
反硝化作用导致可被植物吸收、淋溶和气体损失的移动形式的氮（N）的产生。然而，很少有研究调查自然恢复年龄对反硝化速率和反硝化微生物的潜在影响，特别是在半干旱地区的脆弱生态系统中。与活跃农田相比，废弃后（<9 年）潜在的 N 气体（NO 和 N）排放和反硝化速率显著降低，然后随着恢复的进行而稳步增加，导致土壤 N 损失增加。与农田相比，废弃后（<9 年）总细菌和 napA 基因丰度显著降低，然后随着恢复的进行而显著增加。narG、nirK、nirS、qnorB 和 nosZ 基因的丰度随着废弃农田的恢复年龄而稳步增加。反硝化细菌的群落组成表现出不同的波动模式，表明与 N 气体排放相关功能类群的群落特征对废弃农田恢复年龄的响应模式不同。N 气体排放以及反硝化微生物的丰度和多样性的变化表现出相似的模式，表明反硝化细菌种群和多样性的增加是导致 N 气体排放增加的原因。我们观察到植物覆盖和反硝化微生物的明显变化模式，这些变化与有机 C、NH-N 和 NO-N 含量的增加以及土壤容重的降低有关，与反硝化微生物的丰度和多样性的增加有关，这与 N 气体排放的增加有关。因此，建议采取有效措施（即适度放牧），以减少农田废弃 32 年后温室气体氧化亚氮（NO）和 N 的损失。
