Abstract:

Humus composition is one of the basic characteristics of soil, which has important guiding significance for the evaluation of soil formation and evolution process. In this paper, the samples of bryophyte crust layers from sandy deserts in different climatic regions of Inner Mongolia, China were collected. The content of humus composition of bryophyte crust layers and the light absorption properties of humic acid were determined by potassium dichromate volumetric method and optical density method. The results showed that with the increase in the dryness index, bryophyte crust organic matter content was reduced from 14.93 to 9.89 g·kg^-1,total humic acid content was reduced from 5.1 to 2.0 g·kg^-1,humic acid content was reduced from 2.9 to 0.7 g·kg^-1,folic acid content was reduced from 2.2 to 1.3 g·kg^-1, HA/FA ratio was reduced from 1.32 to 0.45,and E₄/E₆ ratio was increased from 4.28 to 5.83.The content of humus in bryophyte crust and the light absorption properties of humic acid have a zonal trend, and it influences the development and evolution of biological crusts and aeolian sandy soils.

Key words: Times New Roman", ,serif, bryophyte crust layers')">">bryophyte crust layers, desert, organic matter, humus composition, zonality trend