Inner-annual variation of soil water content and groundwater level in a typical islet wetland of Lake Poyang

Abstract

湿地植被空间分布受多个水分因子共同影响,为了探求鄱阳湖典型洲滩湿地不同植被类型下地下水、土壤水的变化特征,本文选择鄱阳湖吴城湿地保护区内一个长约1.2 km的典型洲滩湿地为实验区,建立了气象-土壤-水文联合观测系统.对观测的气象、水文要素进行分析发现:(1)洲滩湿地地下水位年内呈单峰变化,季节性差异显著,最大埋深可达10 m,出现在1月份,丰水期8月份地下水位最高时可出露地表,且地下水位与湖泊水位变化具有高度一致性;(2)由远湖区高地至近湖区低地,不同植被带中地下水平均埋深变化为藜蒿带(4.76 m) >芦苇带(2.87 m) >灰化薹草带(1.61 m).地下水埋深小于50 cm的持续时间分别为:藜蒿带27 d、芦苇带112 d、灰化薹草带170 d;(3)土壤平均含水量沿不同植被带梯度变化为:藜蒿带最小(15.9%),芦苇样带(40.7%)和灰化薹草样带(43.7%)较大.土壤含水量年内变幅为:藜蒿带最大(2.5%~55.2%),芦苇带和灰化薹草带相对较小,分别为22.1%~48.1%和28.4%~54.1%;(4)不同植被带土壤含水量季节变化规律不同,藜蒿带土壤含水量年内呈单峰型,仅夏季土壤含水量较高,其余季节均在10%左右,而芦苇带和灰化薹草样带春、夏、秋季均维持较高含水量(42%以上),仅冬季水分含量较低.;The spatial distribution of wetland vegetation is influenced by a number of hydrological factors, such as groundwater level and soil water content. In order to reveal the characteristics of groundwater level and soil moisture in different vegetation communities, a typical islet wetland of 1.2 km long in Wucheng National Wetland Reserve was selected as our experiment area. In-situ monitoring system was established to collect data of meteorology, soil and hydrology data of the wetland. Observation data showed that groundwater level was in a significant seasonal variation. The largest groundwater depth was up to 10 m in January, while the smallest groundwater depth reached the ground surface in August. It was found that the groundwater level was closely correlated with the lake water level, which implied that the islet wetland aquifer could be in a good hydraulic connection with the lake. The groundwater depth was significantly different along the vegetation gradient, with the mean groundwater depths of 4.76, 2.87 and 1.61 m for Artemisia selengensis, Phragmites and Carex cinerascens communities, respectively. In addition, the numbers of days that the groundwater depth remained for less than 50 cm was 170 d for Carex cinerascens, 112 d for Phragmites and 27 d for Artemisia selengensis, respectively. The soil water content ranged from 2.5%-55.2%, 22.1%-48.1%, and 28.4%-54.1% for Artemisia selengensis, Phragmites and Carex cinerascens communities, respectively. The seasonal variation of soil moisture for Artemisia selengensis demonstrated a higher value in summer and lower ones in other seasons. While the soil content variation for Phragmites and Carex cinerascens communities was similar, with higher water content in spring, summer, and autumn, and lower in winter.