盐度水平对不同盐渍化程度土壤氧化亚氮排放的影响

选取内蒙古河套灌区3种不同盐渍化程度土壤(盐土、重度盐渍化土壤和轻度盐渍化土壤),采用室内培养方法,用不同浓度KCl溶液调节不同盐渍化程度土壤盐含量分别为原土壤盐含量(对照)的2倍和3倍,研究盐分对不同盐渍化程度土壤氧化亚氮(N_2O)排放的影响.结果表明,盐分含量显著影响不同盐渍化程度土壤N_2O排放.无外源盐分加入时,不同盐碱程度土壤中盐土N_2O排放量最高,重度盐渍化土壤次之,轻度盐渍化土壤最低.外源盐加入后,随盐度梯度升高,与其对照相比,盐土N_2O排放量降低;重度盐渍化土壤N_2O排放量呈现先增加后降低趋势;轻度盐渍化土壤N_2O排放量升高.与其对照相比,土壤的盐分含量增加2倍时,盐土N_2O排放量减少90%;轻度盐渍化土壤N_2O排放量增加9倍.外源盐加入不同盐渍化程度土壤对N_2O排放的影响程度取决于土壤培养前后铵态氮含量差值,加入外源盐后,N_2O累积排放变化量的94.6%由土壤NH_4~+-N含量差值解释(R2=0.95,p0.01).

Effect of salinity gradient on nitrous oxide emissions from different salinization soil

Soils in different salinization degrees were selected (saline soil, severe salinized soil and light salinized soil) in Hetao irrigation area of Inner Mongolia for indoor culturing. Soils were regulated by KCl to have salt contents 2 and 3 times higher than the undisturbed soil. Effect of different degrees of salinization on N₂O emissions was investigated. The salt content is a sensitive factor of nitrous oxide (N₂O) emission. N₂O emissions were the highest from saline soil, followed by severe soil salinized soil and light salinized soil. Without addition of external salt, N₂O emission decreased with the increase of the salinity gradient. Soil salt content of light salinization increased by 2 times, N₂O emissions increased by 9 times compared with the original soil. The effect of salinization on N₂O emission depended on the difference of ammonium nitrogen content from the soil when external salt was added to the soils. A significant correlation was discovered between the N₂O accumulation variation (variation of N₂O emission between soils with and without addition of external salt) and difference of soil ammonium nitrogen content (difference of the measured values before and after cultured), and 94.6% of the N₂O cumulative emission variation could be explained by the difference of soil NH₄⁺-N content (R²=0.95, p<0.01).