A pedodiversity pattern: taxonomically established soil orders in China

Under the framework of Chinese Soil Taxonomy, all the 14 established soil orders including Histosols, Anthrosols, Spodosols, Andisols, Ferralisols, Vertisols, Aridisols, Halosols, Gleyosols, Isohumisols, Ferrisols, Luvisols, Cambisols and Primosols, forming a complicated pedodiversity pattern resulted from both various natural conditions and long history of human activities, are introduced with brief descriptions. At the end of the paper, the selected references in English are listed for foreign readers to get further information in detail if needed.

Soil bacterial depth distribution controlled by soil orders and soil forms

Human disturbances to soils can lead to dramatic changes in soil physical,chemical,and biological properties.The influence of agricultural activities on the bacterial community over different orders of soil and at depth is still not well understood.We used the concept of genoform and phenoform to investigate the vertical(down to 1 m depth)soil bacterial community structure in paired genosoils(undisturbed forests)and phenosoils(cultivated vineyards)in different soil orders.The study was conducted in the Hunter Valley area,New South Wales,Australia,where samples were collected from 3 different soil orders(Calcarosol,Chromosol,and Kurosol),and each soil order consists of a pair of genosoil and phenosoil.The bacterial community structure was analyzed using highthroughput sequencing of 16S rRNA.Results showed that bacterial-diversity decreased with depth in phenosoils,however,the trend is less obvious in genoform profiles.Topsoil diversity was greater in phenosoils than genosoils,but the trend was reversed in subsoils.Thus,cropping not only affected topsoil bacteria community but also decreased its diversity in the subsoil.Bacterial community in topsoils was influenced by both soil orders and soil forms,however,in subsoils it was more impacted by soil orders.Constrained Analysis of Principal Coordinates revealed that cropping increased the similarity of bacterial structures of different soil orders.This study highlighted the strong influence of agricultural activities on soil microbial distribution with depth,which is controlled by soil order.

Fractional description of mechanical property evolution of soft soils during creep

The motion of pore water directly influences mechanical properties of soils, which are variable during creep. Accurate description of the evolution of mechanical properties of soils can help to reveal the internal behavior of pore water. Based on the idea of using the fractional order to reflect mechanical properties of soils, a fractional creep model is proposed by introducing a variable-order fractional operator, and realized on a series of creep responses in soft soils. A comparative analysis illustrates that the evolution of mechanical properties, shown through the simulated results, exactly corresponds to the motion of pore water and the solid skeleton. This demonstrates that the proposed variable-order fractional model can be employed to characterize the evolution of mechanical properties of and the pore water motion in soft soils during creep. It is observed that the fractional order from the proposed model is related to the dissipation rate of pore water pressure.