Soil Archaeal Communities Can Be Influenced by Land-Use History in An Australian Vertisol.

Agriculture is one of the most important human activities that exert a large impact on soils and their biota. Most research on soil microorganisms has concentrated on bacteria and fungi; only recently has the diversity and dynamics of soil archaeal communities been considered. However, there is increasing evidence to show that they are playing a significant role in the cycling or carbon, nitrogen and plant-fungal interactions. Microorganisms in Vertisols are exposed to regular disturbances due to changes in physico-chemical properties from wetting-drying and crop management practices. Such changes alter the diversity and activity of soil organisms including bacteria, fungi and microfauna. We measured the diversity of soil archaeal communities, using a PCR-DGGE profiling of archaeal 16S rRNA gene, in an Australian Vertisol under cotton-wheat-cotton (CWC) or cotton-wheat-vetch-cotton (CWVC) rotations. Surface 10cm soils collected from within the cotton crop were exposed to stubble addition and / or wetting and drying regime and incubated at 25C for 8 weeks. Previous land use history had a significant influence on the archaeal community structure (PERMANOVA CV=23.8, P<0.001) and richness and diversity was higher under the CWVC rotation. Both the exposure to repeated wetting-drying regime or incubation with stubble significantly altered community structure in soils from both field treatments; cluster analysis grouping them into distinct groups. Species richness (Margalef’s index, d) and diversity (Shannon index H’) were significantly higher in soils incubated with added stubble or exposed to wetting-drying regime (d=4.51-4.65 and H’=3.41-3.46) compared to control field soils (d=3.9 and H’=3.27).  In conclusion, the effect of land-use history and stubble addition suggest that quantity and quality of C inputs can impact soil archaeal community. In a self-mulching Vertisol the effect of wetting and drying events could be due to the changes in physico-chemical characteristics. Implications of such changes in archaeal community structure to soil functions are yet to be fully understood.