The interactions between groundwater depth and soil hydrological processes, play an important role in both arid and semi-arid ecosystems. The effect of groundwater depth on soil water variations were neglected or not ...The interactions between groundwater depth and soil hydrological processes, play an important role in both arid and semi-arid ecosystems. The effect of groundwater depth on soil water variations were neglected or not explicitly treated. In this paper, we combine a simulation experiment and a water flow module of HYDRUS-1D model to study the variation in soil evaporation under different groundwater depth conditions and the relationship between groundwater depth and evaporation efficiency in Horqin Sandy Land, China.The results showed that with an increase in groundwater depth, the evaporation of soil and the recharge of groundwater decrease. In this study, the groundwater recharge did not account for more than 21% of the soil evaporation for the depths of groundwater examined. The soil water content at 60 cm was less affected by the evaporation efficiency when the mean groundwater depth was 61 cm during the experimental period. In addition, the evaporation efficiency(the ratio of actual evaporation to potential evaporation) decreases with the increase in groundwater depth during the experiment. Furthermore, the soil evaporation was not affected by groundwater when the groundwater depth was deeper than 239 cm.展开更多
Aims:Space-for-time substitution(SFT)is often used for vegetation status estimation during the recovery process of deserts.However,the evaluated accuracy of SFT remains uncertain.An eight-year located observation was ...Aims:Space-for-time substitution(SFT)is often used for vegetation status estimation during the recovery process of deserts.However,the evaluated accuracy of SFT remains uncertain.An eight-year located observation was used to assess the validity of SFT for vegetation state prediction.Methods:This study analyzed a chronosequence of Caragana microphylla Lam.plantings using the located observation method to test the accuracy of SFT for vegetation state prediction in the mobile sand dunes of the Horqin Sandy Land in northeastern China from July 2005 to June 2013.Important Findings:According to SFT,simple vegetation parameters(density,coverage and biomass)were found to be unstable,while sophisticated veg-etation parameters(species diversity and evenness)were relatively stable across the experimental treatments during the study period.Conversely,both the simple and sophisticated parameters were found to be relatively stable when tested using the located obser-vation method.Furthermore,most simple vegetation parameters slightly increased,while sophisticated parameters slightly decreased after eight years of field observations.Thus,long-term restoration management facilitated improvements in the simple parameters,but may have adversely impacted the sophisticated parameters in the post-restoration community.Our results suggest that sophisticated vegetation parameter states can be predicted by SFT,while simple vegetation parameter states are not well predicted by SFT.in conclusion,located observations or other effective evaluation methods must be employed to offset the deficiency of the SFT method for the prediction of vegetation parameters.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.31770755,31670712)Key Projects of Chinese Academy of Sciences(No.KFZD-SW-305)。
文摘The interactions between groundwater depth and soil hydrological processes, play an important role in both arid and semi-arid ecosystems. The effect of groundwater depth on soil water variations were neglected or not explicitly treated. In this paper, we combine a simulation experiment and a water flow module of HYDRUS-1D model to study the variation in soil evaporation under different groundwater depth conditions and the relationship between groundwater depth and evaporation efficiency in Horqin Sandy Land, China.The results showed that with an increase in groundwater depth, the evaporation of soil and the recharge of groundwater decrease. In this study, the groundwater recharge did not account for more than 21% of the soil evaporation for the depths of groundwater examined. The soil water content at 60 cm was less affected by the evaporation efficiency when the mean groundwater depth was 61 cm during the experimental period. In addition, the evaporation efficiency(the ratio of actual evaporation to potential evaporation) decreases with the increase in groundwater depth during the experiment. Furthermore, the soil evaporation was not affected by groundwater when the groundwater depth was deeper than 239 cm.
基金This work was supported by the National Key Research and Development Program of China(2016YFC0500803).
文摘Aims:Space-for-time substitution(SFT)is often used for vegetation status estimation during the recovery process of deserts.However,the evaluated accuracy of SFT remains uncertain.An eight-year located observation was used to assess the validity of SFT for vegetation state prediction.Methods:This study analyzed a chronosequence of Caragana microphylla Lam.plantings using the located observation method to test the accuracy of SFT for vegetation state prediction in the mobile sand dunes of the Horqin Sandy Land in northeastern China from July 2005 to June 2013.Important Findings:According to SFT,simple vegetation parameters(density,coverage and biomass)were found to be unstable,while sophisticated veg-etation parameters(species diversity and evenness)were relatively stable across the experimental treatments during the study period.Conversely,both the simple and sophisticated parameters were found to be relatively stable when tested using the located obser-vation method.Furthermore,most simple vegetation parameters slightly increased,while sophisticated parameters slightly decreased after eight years of field observations.Thus,long-term restoration management facilitated improvements in the simple parameters,but may have adversely impacted the sophisticated parameters in the post-restoration community.Our results suggest that sophisticated vegetation parameter states can be predicted by SFT,while simple vegetation parameter states are not well predicted by SFT.in conclusion,located observations or other effective evaluation methods must be employed to offset the deficiency of the SFT method for the prediction of vegetation parameters.
