| After 40 years of construction,the Three-North Shelter Forest Program has become an important ecological barrier in Beijing,Tianjin and Hebei.In recent ten years,poplar shelterbelts in the semi-arid Bashang plateau area of Hebei Province have been degraded to varying degrees,which has aroused the common concern of all walks of life.Soil moisture is the key limiting factor of vegetation growth in this area,which affects vegetation growth by controlling the availability of resources.Therefore,it is of great significance to study the interaction between soil moisture and plants for the health management and maintenance of three-north shelter forest.In order to examine the dynamic change of soil moisture and its response to vegetation types,poplar degradation and precipitation in Bashang area of Hebei Province,the study carried out location observations on soil moisture in six vegetation types and five degradation levels of poplar shelterbelts.The observation depth is 160 cm,and the observation is divided into 10 cm intervals.The observation frequency is once a month in winter,and once every half month in other seasons,among which,from June to September,it is appropriately encrypted according to the rainstorm.The research observation period is from January 2018 to December 2019,with 51 observations in total.Based on field investigation and experimental analysis,the results show that:(1)Soil moisture with the change of time,it had obvious seasonal characteristics,which could be divided into four periods: stable period(January to February),recovery period(March to May),fluctuation period(June to September)and decline period(October to December).Two years observations showed that the soil water storage of poplar was medium,and there was no obvious phenomenon of low soil moisture.Soil water storage of Ulmus pumila / Caragana korshinskii mixed plantation and grassland was significantly higher than that of other vegetation types,and that of Pinus sylvestris var.mongolica was significantly lower than that of other vegetation types(P < 0.05).The soil water content of the moderate degraded poplar trees was significantly lower than that of other degraded poplar trees(P < 0.05),and that of the slightly degraded poplar in summer and autumn was significantly higher than that of other degraded poplar trees(P < 0.05).(2)Soil moisture status of Ulmus pumila / Caragana microphylla was better,and the mixed tree/shrub plantations was suitable for vegetation restoration in the semi-arid area.During the rainy season from April to September,the increment of soil water storage in the whole profile of Ulmus pumila / Caragana korshinskii was higher,the compensation degree(68.28±52.41%)was the highest,and the deficit degree(14.81±18.05%)was the lowest,and the supplement range of rainfall to the soil water storage of Ulmus pumila /Caragana korshinskii sample plot(40-160 cm)was the largest.The soil water storage of Caragana korshinskii and Pinus sylvestris var.mongolica was in deficit all the time.Only 60-90 cm and 150-160 cm soil layers of poplar were fully supplemented by water,and most soil layers were in deficit.(3)During the rainy season from May to September,among the five degradation degrees,the compensation degree of soil water of lightly degraded poplar(34.90±37.51%)was significantly higher than that of moderately degraded poplar(1.11± 16.06%),and its deficit degree(33.79± 15.74%)was significantly lower than that of moderately degraded poplar(57.90±2.26%)(P < 0.05).Compared with other degradation degrees,the compensation degree of total degradation poplar is the highest,and its deficiency degree was less than that of healthy poplar,moderate degradation poplar and severe degradation poplar,and the soil moisture is improved.(4)The soil of the observation plot is mainly sand,and the average content of sand,silt and clay were 72.58±8.32%,25.32±7.54%,2.10±0.87%,respectively.Soil texture had a significant impact on soil water retention capacity.Soil moisture had a very significant positive correlation with clay particles and silt particles,and a very significant negative correlation with sand particles(P < 0.01).The study uses field soil moisture positioning observation methods to understand the main vegetation types and soil moisture dynamics of poplar shelterbelts with different degradation degrees in Bashang area,Hebei,and enhances understanding of the relationship between vegetation and soil moisture in this area.The research results have certain reference value for the renovation and healthy operation and maintenance of the Three-North Shelterbelt in Bashang area,Hebei. |
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