Response of soils properties and archaea community to saline-sodic soils under long-term rice-based cropping system

Understanding the soil microbiology and physico-chemistry may contribute to efficient land utilization. A 10-year field experiment was conducted in Songnen Plain, China. High-throughput sequencing and quantitative PCR of 16S rRNA and methyl coenzyme M reductase A (mcrA) genes were performed to investigate the dynamic changes in archaeal community following long-term rice planting. Ten-year rice planting significantly decreased soil salinity and alkalinity, including pH (7.6%), electrical conductivity (23.9%), sodium absorption ratio (33.1%), and exchangeable sodium percentage (33.5%) and significantly increased soil organic carbon (70.5%) and mineral nutrient concentrations. Rice planting increased alpha-diversity, and reshaped the archaea community structure of saline-alkali soil. The archaea community compositions during the 10-year period were divided into three stages: 1) shift in abundance from ammonia-oxidizing archaea to methanogenic archaea, 2) methanogenic archaea (e.g. genera Methanosarcina, Methanosaeta, Methanobacterium, Methanocella, Methanomassiliicoccus) established superiority, and 3) methanogenic archaea genes copy numbers increased and the community became stable. Redundancy analysis showed that the decrease in pH caused by long-term flooding was the main factor responsible for the changes in archaea community structure. The results highlighted that the rice planting could be a beneficial approach for maintaining ecological stability and reclaiming severe saline-alkali soil.