Reveal Different Scales Of Deep Soil Water Status On The Loess Plateau Of China

On the Chinese Loess Plateau(CLP),which is a typical water-limited ecosystem,soil-water is the main factor restricting plant growth and ecological environmental reconstruction.Little and uneven distribution of annual precipitation of this area can not fulfill the need of vegetation in growing season,which is harmful for plant growth.Therefore,soil water balance of the CLP is the key answer to ensure sustainable development and sable recovery of ecological problems.Understanding the regime of soil-water accumulation in different scales is thus necessary for the maintenance of regional water resources and for balancing water inputs and outputs on CLP.Based on the above mentioned,we chose a large transect(500 km)at regional scale and three typical watersheds as experimental areas and explored the space distribution of soil water content(SWC),soil water storage(SWS)and available soil water storage(ASWS),and investigated the effect of different environmental factors on soil water.Several main conclusions are obtained as follows:(1)We revealed the characteristic of soil water at transect and in two climatic zones.SWS5 m tended to decrease from southeast to northwest and was approximately 320 mm higher in the subhumid than the semiarid zone.SWS and ASWS in the 0-500 cm soil profiles were more variable in the semiarid than the subhumid zone.SWS1 m and ASWS1 m increased with soil depth in the semiarid zone and fluctuated slightly in the profile in the subhumid zone.(2)The profile distribution of SWS.SWS5 m and ASWS5 m in the deep soil layers(100-500 cm)was lower in the dry than the rainy season,implying that SWS was relatively stable during the measured period.SWS1 m and ASWS1 m tended to fluctuate considerably in the 0-100 cm layer,indicating that the shallow soil layers were highly influenced by environmental factors(e.g.precipitation,infiltration and evaporation).(3)We analysed the relationship between SWS and several factors.SWS5 m andASWS5m differed significantly among the land uses along the transect.SWS5 m and ASWS5 m were influenced by many factors but mostly by soil texture in the semiarid zone and by soil,elevation and latitude in the subhumid zone.Climatic conditions,topographies and soil properties played dominant roles in determining the status of SWS5 m and ASWS5 m at the large scale of the transect.(4)Characteristic of SWC in three watersheds.The SWCs at all sites ranged from 2.3 to 46.6%,with a mean of 11.2% and a CV of 53%.SWC in the gullies was about 11.6% higher than that on the slopes.The CVs were lower in the gullies than that on the slopes.The vertical distribution of SWC on the slopes exhibited different patterns among the four land uses.SWC was higher on shady than sunny slopes in all three watersheds.(5)Land filled gullies of the GLC possessed a large capacity to store water in the soil by increasing the infiltration of precipitation—the increased yield of soil water accounted for 19% and 18.9% of the total annual rainfall in NG and GT-T,respectively.