洪泽湖湿地杨树林土壤水分变化及其与气象因子的关系

在洪泽湖调蓄灌溉与南水北调常态化调水影响下，湖区水位显著波动对湿地土壤水分及植被生长产生深刻影响。以江苏洪泽湖湿地典型杨树林为对象，借助涡度相关及土壤水分监测系统，研究湿地土壤-杨树系统水分的时空动态变化特征，解析气象因子的影响，为洪泽湖湿地杨树林的水分管理和科学经营与保护提供理论依据。结果表明:湿地杨树林土壤水分的年内变化可以大致分为稳定期（10-2月，31.36%~36.07%），消耗期（3-4月，36.64%~37.46%），积累期（5-7月，39.22%~53.92%）和消退期（8-9月，40.38%~32.92%）等4个阶段；春、夏和冬3季的土壤含水量的日变化曲线呈单峰型特征，而秋季表现为不对称双峰曲线特征。土壤水分随着土壤深度（0~40 cm）的增加而逐渐增加。土壤水分变化与日降水量、日平均气温、日平均相对湿度、日平均土壤温度呈极显著正相关（P < 0.01），与日平均感热通量、平均风速呈极显著负相关（P < 0.01）。气象因子中，日平均土壤温度和日平均相对湿度对土壤水分的影响最为明显，其贡献率分别为10.73%~57.97%和18.62%~25.12%。

Soil moisture changes in a poplar forest and their relationship to meteorological factors in the Hongze Lake Wetland

With storage irrigation and normal diversion of water from south to north, water level fluctuations in Hongze Lake have had a profound impact on soil moisture and the growth of wetland vegetation. To provide a theoretical basis for water management along with scientific management and protection of the poplar forest in Hongze Lake Wetland, spatial and temporal variations of soil moisture on a wetland system of poplar and their correlation with meteorological factors were analyzed using the system of eddy covariance and soil moisture monitoring. Results showed that over a year in the Hongze Lake Wetland the change of soil moisture in the poplar plantation could be divided into a stable period (October-February: 31.36%-36.07%), a consuming period (March-April: 36.64%-37.46%), an accumulating period (May-July: 39.22%-53.92%), and a subsiding period (August-September: 40.38%-32.92%). The diurnal variation of soil moisture in spring, summer, and winter exhibited mono-peak curves; whereas, two-peak curves occurred in autumn. Also, soil moisture increased with an increasing soil depth (0-40 cm). In addition, soil moisture in the poplar plantation was highly significant (P < 0.01) and positively correlated with daily precipitation (r = 0.203-0.378), daily mean air temperature (r = 0.462-0.549), daily average relative humidity (r = 0.397-0.510), and daily mean soil temperature (r = 0.549-0.862); it was also highly significant (P < 0.01) and negatively correlated with daily mean sensible heat flux (r = -0.238--0.482) and average wind speed (r = -0.293--0.430). Among these variables, the most obvious effect on soil moisture was with daily mean soil temperature (contributing 10.73%-57.97% to soil moisture) and daily average relative humidity (contributing 18.62%-25.12%. Based on the above analysis, an advice when we plant poplar using the method of ditching and ridging is put forward.