Saline and alkaline stresses alter soil properties and composition and structure of gene-based nitrifier and denitrifier communities in a calcareous desert soil

Jiaxin Guo,Yongxue Zhou,Huijuan Guo,Wei Min

doi:10.1186/s12866-021-02313-z

Abstract

BackgroundSaline and alkaline stresses damages the health of soil systems. Meanwhile, little is known about how saline or alkaline stress affects soil nitrifier and denitrifier communities. Therefore, we compared the responses of gene-based nitrifier and denitrifier communities to chloride (CS), sulfate (SS), and alkaline (AS) stresses with those in a no-stress control (CK) in pots with a calcareous desert soil.ResultsCompared with CK, saline and alkaline stress decreased potential nitrification rate (PNR) and NO3-N; increased pH, salinity, water content, and NH4-N; and decreased copy numbers of amoA-AOA and amoA-AOB genes but increased those of denitrifier nirS and nosZ genes. Copies of nirK increased in SS and AS but decreased in CS. There were more copies of amoA-AOB than of amoA-AOA and of nirS than of nirK or nosZ. Compared with CK, SS and AS decreased operational taxonomic units (OTUs) of amoA-AOB but increased those of nirS and nosZ, whereas CS decreased nirK OTUs but increased those of nosZ. The numbers of OTUs and amoA-AOB genes were greater than those of amoA-AOA. There were positive linear relations between PNR and amoA-AOA and amoA-AOB copies. Compared with CK, the Chao 1 index of amoA-AOA and amoA-AOB decreased in AS, that of nirK increased in CS and SS, but that of nirS and nosZ increased in all treatments. The Shannon index of amoA-AOB decreased but that of nirS increased in CS and SS, whereas the index of nirK decreased in all treatments. Saline and alkaline stress greatly affected the structure of nitrifier and denitrifier communities and decreased potential biomarkers of nirS-type; however, AS increased those of nirK- and nosZ-type, and SS decreased those of nosZ-type. Soil water content, pH, and salinity were important in shaping amoA-AOA and denitrifier communities, whereas soil water and pH were important to amoA-AOB communities.ConclusionThese results indicate that the nitrifier and denitrifier communities respond to saline and alkaline stresses conditions. Communities of amoA-AOA and amoA-AOB contribute to nitrification in alluvial gray desert soil, and those of nirS are more important in denitrification than those of nirK or nosZ.

Highlights

Saline and alkaline stresses damages the health of soil systems
These results suggest that saline and alkaline stresses inhibit the conversion of NH4-N to NO3-N, the key microbial process associated with nitrification
Neutral salt (CS and SS) stress significantly increased the relative abundance of Pseudomonas. These results indicated that Azoarcus was strongly tolerant of saline and alkaline stresses and that Pseudomonas was strongly tolerant of neutral salt stress

Summary

Introduction

Saline and alkaline stresses damages the health of soil systems. Little is known about how saline or alkaline stress affects soil nitrifier and denitrifier communities. We compared the responses of gene-based nitrifier and denitrifier communities to chloride (CS), sulfate (SS), and alkaline (AS) stresses with those in a no-stress control (CK) in pots with a calcareous desert soil. In China, there are approximately 8.11 × 107 ha of saline or alkaline soils, accounting for 8 to 9% of the total land area [4]. Salt-affected soils are either saline or alkaline. The effects of saline stress (NaCl or Na2SO4) are generally osmotic and ionic, whereas alkaline stress (NaHCO3 or Na2CO3) results from higher pH. Saline or alkaline stress adversely affects soil physicochemical properties, soil microbiological processes, and plant growth [6, 7]

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