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Northwest A&F University (2017)

Spatial Variability of Water Transformation in Hillslope Transects on the Loess Gully Region

段良霞

Titre : Spatial Variability of Water Transformation in Hillslope Transects on the Loess Gully Region

Auteur : 段良霞

Grade : Doctoral Dissertation 2017

Université : Northwest A&F University

Résumé partiel
Vegetation restoration practices have been implemented to control soil and water loss in the Loess Plateau,but extensively afforestation has also produced some negative effects,such as soil desiccation.Soil moisture is a critical variable controlling hydrological and biological processes and hence plays an important role on vegetation restoration and ecological construction.Understanding the distribution and transformation characteristics of soil water on a typical slope in the loess gully region can therefore reveal the driving mechanisms of the water hydrological cycle and thus provide scientific evidence for efficient management of soil water resource and sustainable vegetation restoration.The 70 locations along two long transects were selected on a hillslope of the Loess Plateau,China.Also,eight experimental runoff plots(Bothriochloa ischaemum L.(BOI),Sea-buckthorn(SEB),Chinese pine(CHP),Chinese arbor-vitae(CHA),SEB+CHP,SEB+ Black locust(LOC),CHP+ LOC,and CHA+ LOC)were established on a natural steep slope(35°).Based on classical statistics,geostatistics,state-space approach,temporal stability analysis,water balance,and Hydrus-1D model methods,the objective of this study was to investigate the spatial-temporal evolutional patterns and temporal stability of soil water storage on a typical slope in the loess gully region,estimate soil water storage using a state-space approach,explore the distribution of actual annual and diary evapotranspiration along the hillslope,and to further quantify the changes of each component of a water balance model over time under eight different vegetation types.The main results are congregated as follows :(1)The soil water content exhibited a moderate variation at the hillslope.A significant difference was found among 0-1,1-2,and 2-3 m soil layers.The spatial pattern of soil water content along the hillslope was similar for 0-1,1-2,and 2-3 m soil layers,while soil water content of the 0-1 and 1-2 m layers had a greater coefficient of variation than that of 2-3 m layers.The soil water content of the 0-1,1-2,and 2-3 m soil layers were best fitted by Gaussian,Exponential,and Exponential semivariogram models,respectively(R2>0.90).A semivariogram of soil water content for 0-1 m soil layer indicated a moderate spatial dependence,while a strong spatial dependence was observed for 1-2 m and 2-3 m soil layers.Soil water content was significantly influenced by elevation,clay and silt content,bulk density,and leaf area index,and no statistical significant relationships were found between soil water content and sand content and saturated hydraulic conductivity.(2)Soil water storage had a strong spatial autocorrelation structure,and thus the sampling distance used in the present study for soil water storage was sufficient to identify their spatial representativity.At the 95% confidence level,soil water storage was positively cross-correlated with elevation,clay content,and fractal dimension and negatively cross-correlated with silt content

Mots clés : Hillslope; Vegetation type; Soil water; Evapotranspiration; Water balance; Gully region

Présentation (CNKI)

Page publiée le 21 janvier 2018