Alfisols are
important soils in China. They occupy about 1.25 million km￣2 orabout 13% of the land area.
Dark
brown forest soils,burozems,yellow-brown earths,and drab soils in temperate China are
identified as four major great soil groups.According to the criteria given by soil
Taxonomy,these soils should belong to Alfi-sols.Additionally,Baijiang soil is identified as a
special kind of Alfisols,proba-bly Albaqualfs.These are mostly forested soils with a return of
organic matter,estimated at 5 13t/ha/yr,to the soils from a mixed temperate forest.In terms
ofclemental bio-cycling Ca is prominent. In a comparison of 30 profiles,the average rate of
clay(B/A)was 1.47 for cry-oboralfs and Eutroboralfs:1.88 for Hapludalfs and 2.53 for Paleudalfs.
From Eu-troboralfs to Paleudalfs there was a difference of 7 times in the average gain(orioss)in
clay during soil development.Hapludalfs,Cryoboralf and associated Crya-quepts differ
considerably in the moisture regimes,but the amount of water isalways enough to cause a
significant leaching.During the weathering andpedogenetic processes-TiO_2, Mgo and
Fe_2O_3 are accumulated,respectively,in both Aand Bt
horizons, But SiO_2 and Al_O_3 tend to
be leached from the solum.Probably owing to the influence of the monsoon climate Alfisols in
China havedeveloped to have some differences from those in the U. S.. First.the E horizonof
Alfisols in the U,S. is not as prominent as in China,Secondly,the movementof Fe_2O_3 and
Al_2O_3 in the profile as well as the relative accumulation of SiO_2 inthe surface might reflect
a long
pedogenic process.Thirdly,many B horizons inChina average 30 80cm in thicknes,
whereas in the U. S.the average is close to20 50cm.