鄱阳湖湿地地下水埋深及其与典型植被群落分布的关系

地下水位直接影响土壤含水量,进而影响湿地植被生长、分布和演替。本研究以鄱阳湖湿地为研究区,基于2014—2018年地下水位野外定点观测数据,分析湿地地下水年内与年际动态变化特征,构建鄱阳湖湿地地下水数值模型,分析地下水流场空间特征以及地下水埋深分布,结合高斯回归方法分析地下水埋深与典型植被分布之间的关系。结果表明: 年内洲滩湿地地下水位呈明显的动态变化,且地下水位与湖水位变化高度一致。地下水埋深年内变化与降水量季节性分布之间存在1个月的滞后。年际洲滩湿地地下水位由上游向下游呈减小趋势,且上游洲滩湿地地下水埋深变幅较小(0.1～1.1 m),下游洲滩湿地地下水埋深变幅较大(0.1～5.6 m)。研究区地下水流场由上游丘陵地区指向下游地势相对平坦的湖区,其流向与地形高程变化一致。研究区平均地下水埋深为2.07 m,且由远湖区至近湖区,地下水埋深不断减小。苔草、芦苇、茵陈蒿群落生长的最适地下水埋深分别为1.1、3.7、5.7 m;典型植被的分布对地下水埋深梯度的响应差异显著;茵陈蒿群落的生态幅宽大于苔草和芦苇群落;3种植被群落在地下水埋深1.1～5.7 m范围内出现生态位重叠现象,其中,苔草植被分布指数迅速减小,芦苇植被分布指数先增大后减小,茵陈蒿植被分布指数持续增至最大值,在地下水埋深达到5.7 m后开始减小。

Groundwater depth and its relation with typical vegetation distribution in the Poyang Lake wetland,China

Groundwater level directly affects soil water content,which in turn impacts the growth,distribution,and succession of wetland vegetation.Based on the groundwater monitoring data during 2014 to 2018,we analyzed the inter-and intra-annual variations in groundwater level of the wetland in Poyang Lake.We set up a groundwater numerical model to investigate the spatial patterns of groundwater flow field and distribution of groundwater depth.The relationship between groundwater depth and distribution of typical vegetation was explored with Gaussian regression analysis.Results showed that groundwater level of the wetland showed inter-annual variation,with the trend highly consistent to the changes in lake water level.There was a lag of one month between the inter-annual change in groundwater depth and the seasonal distribution of precipitation.The annual groundwater level showed a decreasing trend from upstream to downstream.The range of groundwater depth in upstream area of the wetland was narrower(0.1-1.1 m)than that of the downstream area(0.1-5.6 m).The groundwater flow field was directed from the hilly upstream area to the relatively flat downstream lake area,with the flow direction consistent with the change in elevation.The ground-water depth decreased with decreasing distance to the lake water body,with an average value of 2.07 m in the study are.The optimal groundwater depths for the growth of Carex,Phragmites aus-tralis,and Artemisia capillaris communities were 1.1,3.7 and 5.7 m,respectively.The typical vegetation distribution showed different responses to groundwater depth.The ecological width of A.capillaris communities was larger than the Carex and P.australis communities.The three types of community were overlapped in ecological niche when the groundwater depth ranged 1.1-5.7 m.The vegetation distribution index of Carex decreased rapidly,that of P.australis increased firstly and then decreased,while that of A.capillaris increased continually to the maximum and began to decrease when the groundwater depth reached 5.7 m.