Saline 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. Compared 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. These 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.

中文翻译：

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盐碱胁迫改变了钙质沙漠土壤中基于基因的硝化菌和反硝化菌群落的土壤性质和组成和结构

盐碱胁迫损害土壤系统的健康。与此同时，人们对盐碱胁迫如何影响土壤硝化菌和反硝化菌群落知之甚少。因此，我们将基于基因的硝化菌和反硝化菌群落对氯化物 (CS)、硫酸盐 (SS) 和碱性 (AS) 胁迫的响应与无胁迫控制 (CK) 的钙质沙漠土壤盆中的响应进行了比较。与CK相比，盐碱胁迫降低了潜在硝化率（PNR）和NO3​​-N；增加 pH 值、盐度、水含量和 NH4-N；amoA-AOA 和 amoA-AOB 基因的拷贝数减少，但反硝化菌 nirS 和 nosZ 基因的拷贝数增加。nirK 的拷贝在 SS 和 AS 中增加，但在 CS 中减少。amoA-AOB 的拷贝数多于 amoA-AOA 和 nirS 的拷贝数多于 nirK 或 nosZ。与CK相比，SS 和 AS 减少了 amoA-AOB 的操作分类单位（OTU），但增加了 nirS 和 nosZ 的操作分类单位（OTU），而 CS 减少了 nirK OTU，但增加了 nosZ 的操作分类单位（OTU）。OTUs 和 amoA-AOB 基因的数量大于 amoA-AOA。PNR 与 amoA-AOA 和 amoA-AOB 拷贝之间存在正线性关系。与CK相比，AS中amoA-AOA和amoA-AOB的Chao 1指数在CS和SS中均降低，nirK在CS和SS中升高，但nirS和nosZ在所有处理中均升高。在CS和SS中，amoA-AOB的香农指数降低，但nirS的香农指数增加，而nirK的指数在所有处理中均降低。盐碱胁迫极大地影响了硝化菌和反硝化菌群落的结构，降低了nirS型的潜在生物标志物；然而，AS 增加了 nirK 型和 nosZ 型的，和 SS 降低了 nosZ 型。土壤含水量、pH 值和盐度对形成 amoA-AOA 和反硝化菌群落很重要，而土壤水和 pH 值对 amoA-AOB 群落很重要。这些结果表明硝化菌和反硝化菌群落对盐碱胁迫条件有反应。amoA-AOA和amoA-AOB群落对冲积灰漠土壤的硝化作用有贡献，nirS在反硝化作用中比nirK或nosZ更重要。