崇明东滩围垦区芦苇湿地土壤盐分动态研究

2009~2013年对崇明东滩围垦区芦苇湿地10 cm和30 cm两个土层的土壤溶液电导率、水分、温度和相关微气象因子进行了为期5 a的原位同步连续监测,探讨了不同时间尺度的湿地土壤盐分动态。结果如下:(1)在年际动态方面,10 cm土层的土壤溶液电导率在5 a间逐年递减,年均降低8.10%,30 cm土层的土壤溶液电导率在前4 a逐年递减,年均降低6.06%,但2013年较2012年上升了16.34%。各个年份10 cm土层的土壤溶液电导率均值皆显著低于30 cm土层,且年均值的差异逐年递增。(2)在季节动态方面,各年份内,两个土层的土壤溶液电导率多表现为春、夏、秋升高,冬季下降的趋势,也多在秋季和冬季分别达到最大值和最小值。各年份间,10 cm土层春季和夏季以及30 cm土层春季的土壤溶液电导率呈逐年递减的趋势。(3)在日动态方面, 10 cm土层的土壤溶液电导率波动幅度大于30 cm土层,并且30 cm土层土壤溶液电导率日最大值和最小值出现的时刻较10 cm土层有一定的滞后性。综上所述,研究区在围垦后,耕层土壤每年都能以一定的速率脱盐,但在季节性气候影响下,严重的返盐现象仍可能在秋季发生,因而在秋季可以通过增加人工措施以防止土壤返盐。

SOIL SALINITY FLUCTUATIONS ON ENCLOSED TIDELAND OF CHONG-MING DONG-TAN WETLAND

We investigated the fluctuation of soil salinity in an enclosed tideland located in the east of Chongming Island. The soil solution electrical conductivity has been monitored at the depth of 10 cm and 30 cm below the ground for 5 years (from 2009 to 2013). The results are as follow: 1) annual fluctuation of soil salinity showed that there was a large yearly fluctuation of soil salinity. The annual average salinity at the 10 cm depth decreased by 8.31% each year during the last 5 years. At the 30 cm depth, the annual average salinity decreased by 6.06% each year during the first 4 years whereas the annual average salinity has significantly increased by 16.34% in the last year. The soil salinity at the 10 cm depth was significantly lower than the soil salinity at the 30 cm depth and the difference between them has increased with years. 2) The seasonal fluctuation showed that there was a significant difference among seasons every year. In general, the soil salinity tended to increase in spring, summer and autumn, then decrease in winter. This tendency resulted in the peak of soil salinity in autumn and the bottom of soil salinity in winter. Especially, the soil salinity at the 30 cm depth rose to the maximum among those five years in the autumn of 2013. Furthermore, the soil salinity in spring and summer at the 10 cm depth has decreased year by year while only the soil salinity in spring at the 30 cm depth has declined in the same patterns. 3) The daily fluctuation showed that the soil salinity at 10 cm depth has changed more intensively than the soil salinity at the 30 cm depth. The soil salinity at 30 cm depth appeared a time lag of daily minimum and maximum compared with the soil salinity at 10 cm depth. In conclusion, the topsoil salinity of our monitoring area tended to decrease to some extent every year after it had been diked. However, the phenomenon of severe salt accumulation could occur in autumn by the influence of seasonal climate. It implied that the salinity of the water table could still be high and it had better to take some measures in autumn to prevent the salt in the lower soil layer moving up.