江苏里下河不同湿地植被地下水水位动态及影响因素

目的]了解水资源丰富的里下河平原典型淡水湿地植被地下水水位的动态变化特征及主要影响因素,为该区淡水湿地植被的恢复和保护提供参考依据。方法]以江苏省里下河平原两种典型淡水湿地植被(池杉针叶林和杨树阔叶林)为研究对象,分别布设2个地下水水位观测井,并对井中地下水水位动态进行长期观测,分析其月际和季节动态变化特征;同时采集2016年9月至2017年8月1个水文年的降水量和气温数据,分析地下水水位动态变化与气温和降水量变化的相关性。结果]表明:两种典型淡水湿地植被地下水水位的动态变化存在显著的差异,池杉林几乎全年淹水,其月均地下水水位大于杨树林,而杨树林月际间地下水水位变化幅度相对较大,表现出季节差异;从季节动态看,池杉林和杨树林夏季的地下水平均水位相对于其他季节均明显要低。两种淡水湿地森林地下水水位的变化受降水量影响程度不同,杨树林地下水水位月动态表现出滞后于降水量变化约1个月,而这种滞后性未体现在池杉林中。杨树林和池杉林地下水的月均水位与月均气温间均呈现出极显著的负相关关系。结论]不同淡水湿地森林的地下水水位动态具有不同特征,受环境因素的影响程度也有差异。在水资源丰富的里下河平原,降水量大小并不是影响该区淡水湿地植被地下水水位动态变化的关键因子,而气温则是主要影响因素。

Dynamics of Groundwater Level and Its Affecting Factors under Different Wetland Vegetation of Lixiahe Plain,Jiangsu Province

Objective] To understand the dynamic characteristics of groundwater level in typical freshwater wetland vegetation in the Lixiahe Plain which is rich in water resources in Jiangsu Province. Method] Two groundwater depth monitoring wells were set respectively in two typical freshwater wetland vegetations(Taxodium ascendens coniferous forest and Poplar broadleaved forest) in Lixiahe Plain of Jiangsu province. The monthly and seasonal variation of groundwater level were analyzed based on the long-term observation data of groundwater level. In addition,the temperature and precipitation data of the forests during the hydrological year from September 2016 to August2017 were also collected. The correlations between the dynamics of groundwater level and the variation of temperature and precipitation were analyzed. Result] There were significant differences in the dynamics of groundwater level between the two freshwater wetland vegetations. T. ascendens forest was almost flooded all the year round, and its monthly mean groundwater level was higher than that of Poplar forest. The amplitude of monthly variation of groundwater level in Poplar forest was larger than that of T. ascendens forest, and it showed a seasonal variation. On the seasonal scale, the average groundwater level in T. ascendens forest and Poplar forest in summer was significantly lower than that in other seasons. The effects of precipitation on the variation of groundwater level of the two freshwater wetland vegetations were different. The change of groundwater level in Poplar forest lagged behind the amount of precipitation about one month, while this lag did not appear in T. ascendens forest. The average monthly groundwater level was negatively correlated with the mean monthly temperature in both vegetation types. Conclusion] It is concluded that there are differences in the dynamics of groundwater level and the influencing factors between the two types of freshwater wetland vegetation. In Lixiahe Plain with abundant water resources, temperature rather than the precipitation is the key factor affecting the change of groundwater level in the freshwater wetland vegetation.