单 位：
Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China; Jiangsu Province Engineering Research Center for Agricultural Soil—Water Efficient Utilization, Carbon Sequestration and Emission Reduction, Nanjing 210098 (China);College of Agricultural Science and Engineering, Hohai University, Nanjing 210098 (China)
摘 要：
Coastal ecosystems are highly susceptible to salt-related problems due to their formation process and geographical location. As such ecosystems are the most accessible land resources on Earth, clarifying and quantifying the effects of saline-alkali conditions on N content and NH3 volatilization are pivotal to promoting coastal agricultural productivity. The challenge in establishing this effect is determining how saline-alkali conditions impact NH3 volatilization through direct or indirect interactions. Incubation experiments combined with the ‘element’ structural equation modeling (SEM) method revealed the net effects of salt-alkali on NH3 volatilization and the roles of environmental factors in mutual interaction networks. The specific experimental design consisted of 27 different treatments, including one control treatment (CK), 4 salt treatments (S1, S2, S3 and S4: 1, 3, 8 and 15‰ NaCl) and 4 alkaline treatments (A1, A2, A3 and A4: 0.5, 1, 3 and 8‰ NaHCO3), and each treatment had 3 urea concentrations (N1, N2 and N3: 0.05, 0.10 and 0.15 g N kg−1 soil, respectively) and 3 replicates. Under the 0.05‰, 0.10‰, and 0.15‰ urea treatments, NH3 volatilization increased by 9.31%–34.98%, 3.07%–26.92%, and 2.99%–43.61% as the salt concentration increased from 1‰ to 15‰, respectively. With an increase in the alkalinity from 0.5‰ to 8‰, NH3 volatilization significantly increased by 8.36%–56.46%, 5.49%–30.10% and 30.72%–73.18%, respectively (the increase was calculated by comparison to the corresponding CK treatment). According to the ‘element’ SEM, the direct promotion effects of salinity and alkalinity on NH3 volatilization were 0.4 and 0.19 (standardized path coefficients, positive effects), respectively. Considering the total effect (net positive and negative effects) in the SEM results, alkalinity had a greater influence than salinity (0.104 > 0.086, standardized impact coefficients). The N content in the incubation system showed a direct positive effect on NH3 volatilization (0.78), with an obvious decrease under elevated salinity and alkalinity. Additionally, the gene abundance of N-transforming microbes indirectly increased NH3 volatilization (0.40×0.78). Our results indicated that potential NH3 emissions from coastal saline areas could be enhanced more by soil alkalization than by salinization.
