模拟强酸雨对福州平原稻田土壤团聚体稳定性及碳氮分布的影响

Effects of simulated strong acid rain on soil aggregate stability and distribution of carbon and nitrogen in paddy fields in Fuzhou plain

以福州平原稻田为研究对象,设置模拟酸雨pH分别为2.5、3.5、4.5,以不做任何处理为对照(CK),探讨喷淋模拟酸雨后早、晚稻田土壤团聚体的分布特征及稳定性,测定并分析土壤碳氮含量变化。结果表明,早、晚稻田土壤团聚体均以微团聚体(<0.25 mm粒级团聚体)为主。酸雨对早稻田土壤团聚体平均质量直径(mean weight diameter, MWD)、平均几何直径(geometrical mean diameter, GMD)、>0.25 mm粒级团聚体(diameter of more than 0.25 mm, DR_(0.25))含量和分形维数(fractal dimension,D)影响不显著;但显著减少晚稻田土壤团聚体MWD、GMD和DR_(0.25)含量(P<0.05),显著增加土壤团聚体D值(P<0.05)。各酸雨处理对早稻田土壤碳含量影响均不显著,但促进土壤氮含量增加,其中pH4.5酸雨处理影响显著(P<0.05);各酸雨处理均增加晚稻田土壤碳氮含量,其中pH4.5酸雨处理影响显著(P<0.05)。土壤碳氮含量比主要集中在>0.25 mm粒级团聚体内,表明土壤大团聚体是碳氮含量的主要载体。

The distribution pattern and stability of soil aggregates in the early and late paddy fields on Fuzhou plain after spraying simulated acid rain were investigated with no treatment as the control (CK). The pH of simulated acid rain was set at 2.5, 3.5, and 4.5, respectively. Changes of carbon and nitrogen contents were also measured and analyzed. The results showed that:(1) The soil aggregates in early and late paddy fields were mainly micro aggregates (<0.25 mm agglomerates);(2) The mean weight diameter (MWD), geometrical mean diameter (GMD),>0.25 mm diameter agglomerates (DR 0.25 ) and fractal dimension ( D ) of soil aggregates were not significantly different under acid rain treatments in early paddy fields. However, in later paddy fields, the soil MWD, GMD and DR 0.25 were significantly decreased ( P <0.05);and the D value was significantly increased under acid rain treatments ( P < 0.05);(3) The acid rain treatments over early rice fields had no significant effect on soil carbon content, but increased the soil nitrogen content. The increase of nitrogen content was significant ( P <0.05) with pH4.5 acid rain;(4) In the late rice fields, the carbon and nitrogen contents were increased under each acid rain treatment, with significant increase ( P <0.05) from the pH4.5 acid rain treatment;and (5) The percentage of carbon and nitrogen in soil aggregates was mainly concentrated in DR 0.25 , indicating that soil macroaggregates are the main carriers of soil carbon and nitrogen.