Soil salinity is a serious problem for agriculture in coastal regions. Nevertheless, the effects of soil salinity on microbial community composition and their metabolic activities are far from clear. To improve such understanding, we studied microbial diversity, community composition, and potential metabolic activity of agricultural soils covering non–, mild–, and severe–salinity. The results showed that salinity had no significant effect on bacterial richness; however, it was the major driver of a shift in bacterial community composition and it significantly reduced microbial activity. Abundant and diverse of microbial communities were detected in the severe–salinity soils with an enriched population of salt–tolerant species. Co–occurrence network analysis revealed stronger dependencies between species associated with severe salinity soils. Results of microcalorimetric technology indicated that, after glucose amendment, there was no significant difference in microbial potential activity among soils with the three salinity levels. Although the salt prolonged the lag time of microbial communities, the activated microorganisms had a higher growth rate. In conclusion, salinity shapes soil microbial community composition and reduces microbial activity. An addition of labile organic amendments can greatly alleviate salt restrictions on microbial activity, which provides new insight for enhancing microbial ecological functions in salt–affected soils.

/pdf/microbial-community-composition-and-activity-in-saline-soils-2lazpfft.pdf

Microbial Community Composition and Activity in Saline Soils of Coastal Agro–Ecosystems

Passivation of lead and cerium in soil facilitated by biochar-supported phosphate-doped ferrihydrite: Mechanisms and microbial community evolution.

Relationships between soil biodiversity and multifunctionality in croplands depend on salinity and organic matter

Soil salinity affects the microbial carbon use efficiency (CUE) that in turn regulates soil-atmosphere gas exchange and soil C sequestration. So far, little is known about CUE in salt-affected soils. Hereby, CUE across coastal soils with electric conductivity (EC) ranging from 0.14 dS m−1 to 13.65 dS m−1 was investigated using stoichiometric modeling. Contrary to the belief that CUE decreases with salinity increase, this present study showed that CUE follows a unimodal pattern along the saline gradient with the highest CUE observed at EC = 2 dS m−1. When EC > 2 dS m−1, both CUE and soil microbial growth rate significantly decrease with salinity indicating that microorganisms sacrifice growth for survival/adaptation to high salt stress. When EC < 2 dS m−1, CUE shows a significant positive correlation with EC, but microbial community growth rates remain stable. We also observed that microbial growth becomes limited by carbon scarcity and that the degree of carbon constraint is significantly aggravated with EC. This implies that elevating CUE can be the preferred mechanism for microorganisms to stabilize elemental stoichiometry and maintain growth rate. Our results revealed that along the saline gradient, the dominant factor of CUE shifted from the ecological stoichiometry to salinity, which provides an insight into the microbial-driven carbon cycling in salt-affected soils. 

Microbial Carbon Use Efficiency in Coastal Soils Along a Salinity Gradient Revealed by Ecoenzymatic Stoichiometry

With the increasing shortage of land resources and people’s attention to the ecological environment, the application of microbial fertilizer with natural soil microorganisms as the main component has attracted increasing attention in saline agriculture. In this study, two salt-tolerant strains, YL07 (Bacillus atrophaeus) and YL10 (Planococcus soli), were isolated from maize (Zea mays L.) rhizosphere soil with a saturated conductivity (ECe) of 6.13 dS/m and pH of 8.32 (Xinjiang, China). The effects of B. atrophaeus WZYH01 (YL07) and Planococcus soli WZYH02 (YL10) on the growth and development of maize (Zea mays L.) under salt stress (ECe = 5.9 dS/m) were further studied. The results showed that compared with uninoculation, inoculation with B. atrophaeus WZYH01 and Planococcus soli WZYH02 significantly improved maize growth performance, biomass yield, and antioxidant levels under salt stress, and the effect of Planococcus soli WZYH02 was more prominent than the effect of B. atrophaeus WZYH01. Moreover, inoculation with B. atrophaeus WZYH01 and Planococcus soli WZYH02 protected maize from salt stress by regulating plant hormone [IAA and abscisic acid (ABA)] levels and increasing nutrient acquisition. In addition, the tested strains were most efficient for maize growth and health, increasing the content of K+ accompanied by an effective decrease in Na+ in maize tissues. The transcription levels of salt tolerance genes (ZMNHX1, ZMNHX2, ZMHKT, ZMWRKY58, and ZMDREB2A) in inoculated maize were also dramatically higher than the transcription levels of the specified salt tolerance genes in uninoculated maize. In conclusion, B. atrophaeus WZYH01 and Planococcus soli WZYH02 can alleviate the harmful effects of salt stress on crop growth, thereby promoting sustainable agricultural development.

/pdf/bacillus-atrophaeus-wzyh01-and-planococcus-soli-wzyh02-1tsgont3.pdf

Y. Feng

Papers

Interactive effects of salinity and SOM on the ecoenzymatic activities across coastal soils subjected to a saline gradient