Amorphous Aluminosilicates in Some Soil Clays of North West Himalayas as Affected by Biosequence and Climosequence

The amorphous mineral components in ninety one clay samples of eighteen soil profiles, from different locations of North-West Himalayas (Kangra district, Himachal Pradesh) revealed that amorphous silica varied from 3.9 to 23.6% and alumina from 1.3 to 7.0%, irrespective of the soil depth. Their distribution did not show a definite relationship with profile depth. SiO₂/Al₂O₃ molar ratios ranged from 2.18 to 9.2. The variation of SiO₂ centent followed the same trend within the biosequences indicating thereby less effect of vegetation on this constituent. However, on the basis of weighted average values the soils under grass and forest cover showed higher content. The amount of Al₂O₃ was unaffacted by the type of vegetation. Generally, the soil clays of the hot and less dry foot-hills, and hot and sub-humid low hill Siwalik climosequences showed lesser amount of SiO₂ and Al₂O₂ as compared with soil clays of other climosequences.