GEOGRAPHICAL RESEARCH ›› 2006, Vol. 25 ›› Issue (4): 649-658.doi: 10.11821/yj2006040011

• Earth Surface Processes • Previous Articles     Next Articles

Multi-scale spatial variations in soil salt in the Yellow River Delta

WANG Hong1, GONG Peng2, LIU Gao-huan3   

  1. 1. College of Water Resources &,Environment,Hohai University,Nanjing 210098,China;
    2. International Institute for Earth System,Nanjing University,Nanjing 210093,China;
    3. Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China
  • Received:2005-11-15 Revised:2006-04-24 Online:2006-08-15 Published:2006-08-15

Abstract:

The Yellow River Delta(YRD) is rich in land resource which has a great potential of development.However,soil salinization is serious in the coastal salinized land which accounts for 63.6% of the region′s total land area.Soil salinization has become the main factors restricting the regional economic development.In order to utilize the salinized soil resources and realize the sustainable development of agriculture in the YRD,it is important to clarify the distribution of salinized soil and the reasons for the formation and development of salinization. Based on the multi-scale samples,this paper determined the spatial variation of soil salinity at two depths using both statistical and geostatistical methods,comparing the correlation coefficients between soil salinity and three geomorphic factors(e.g.micro-geomorphologic type,slope gradient and elevation),and finally generating the distribution maps of soil salinity using ordinary kriging at multi-scales and two depths.The analysis revealed that there is higher soil salt content in the embanked former back swamps,salt marshes and tidal flats than in the contemporary flood plains,abandoned river channels and isolated depressions.The variations of soil salinity have three scales.At the small scale(sampling intervals are 0.040.2km),the soil has a higher value of salinity in the north east and the south west.At medium scale(1km),it is high in F1 in the north west,while in F2 it is higher in the east than in the west.At large scale(6km),the distribution of soil salinity is characterized by a low value in the central part,where the Yellow River flows through,but it rises gradually toward north and southeast in the upper and lower layers.By analyzing the parameter of spatial dependence(the ratio of spatial variance and sill) of soil salinity in the multi-scales,we found the spatial structure of soil salinity became obvious with the increase of sampling intervals and expanded areas.The paper demonstrates that all geomorphic variables have comparatively high spatial dependence.The distribution of soil total salt shows a clear structure when it is significantly impacted by factors which have high spatial dependence;contrarily,soil salinity has small spatial dependence,then it may be influenced by other environmental variables which have weak structure(e.g.human activities).Finally,reasonable soil sampling plan and research directions in the future were put forward.

Key words: soil salinity, geomorphic factors, spatial dependence, multi-scale, ordinary kriging, Yellow River Delta