作物茬口对黑土农田土壤反硝化细菌数量及群落结构的影响

王璐; 刘俊杰; 刘株秀; 顾海东; 张兴义; 王光华; 刘晓冰

doi:10.11674/zwyf.2022038

作物茬口对黑土农田土壤反硝化细菌数量及群落结构的影响

Effects of crop stubbles in different cropping systems on the number and community structure of denitrifying bacteria in black soil farmland

摘要

摘要:
目的反硝化作用导致农田土壤氮素损失和温室气体N₂O的排放。研究不同作物茬口对土壤反硝化细菌群落结构的影响，旨在揭示作物茬口影响N₂O排放的相关机制。
方法定位试验位于黑龙江省海伦市前进乡光荣村(47°23′N，126°51′E)，种植方式包括玉米连作(CC)、大豆连作(SS)以及玉米–大豆轮作，每年一季。取样时，轮作体系玉米已倒茬三次、大豆两次。采集CC、SS以及轮作体系中的大豆茬口(SSC)和玉米茬口(CSC)的表层土壤(0—15 cm)样品，利用实时定量PCR (qPCR)和高通量测序技术，分析土壤中的nirS和nirK型反硝化细菌丰度和群落组成。
结果在4个作物茬口土壤中，CC处理的反硝化速率最高，玉米–大豆轮作体系中SSC和CSC处理的反硝化速率显著高于SS处理。轮作体系两个茬口SSC和CSC处理的nirS和nirK型反硝化细菌基因丰度多显著高于SS处理，而与CC处理多差异不显著。PCoA结果显示，SSC和CSC处理的nirS型反硝化细菌群落间差异显著，而CC和SS处理的nirK型反硝化细菌群落间存在显著差异。RDA分析结果表明，NO₃^–-N和C/N分别是nirS和nirK型反硝化细菌群落分异的最主要驱动因子。SEM分析结果显示，nirS型反硝化细菌群落与反硝化速率呈显著正相关(R²=0.92)，而nirS和nirK型基因丰度与土壤反硝化速率无显著相关关系。
结论作物茬口显著影响黑土农田土壤反硝化细菌群落和丰度组成。反硝化细菌群落组成而非反硝化细菌丰度是反硝化速率变化的决定性因素，nirS型反硝化细菌对土壤反硝化作用贡献更大。

Abstract:
Objectives Denitrification is an important process in soil nitrogen loss and greenhouse gas emissions. We studied the effects of crop stubbles in different cropping systems on soil denitrifying bacterial community structures, aiming to reveal the related mechanisms of crop stubbles affecting N₂O emission.
Methods The experiment was conducted in Hailun City, Heilongjiang Province (47°23′N, 126°51′E). Continuous cropping of corn, soybean, and corn–soybean rotation was set up in the experiment. At sampling, the corn was three years, and the soybean was two years old. Topsoil (0–15 cm) samples were collected after harvesting maize and soybean. The abundance and community composition of the soil nirS and nirK denitrification bacteria were analyzed using real-time quantitative PCR (qPCR) and high-throughput sequencing techniques.
Results The continuous corn (CC) plot soil had the highest denitrification rate. Rotation corn (CSC) and rotation soybean (SSC) had higher soil denitrification rate (P<0.05) than continuous soybean (SS). The abundance of nirS and nirK denitrifying bacterial genes in CSC and SSC was higher than that in SS, and there was no significant difference between CSC and CC (P>0.05). PCoA results showed variation in nirS denitrifying bacterial communities in SSC and CSC, while CC and SS had different nirK bacterial communities. RDA analysis showed that NO₃^–-N content and C/N were the main factors regulating the nirS and nirK denitrifying bacterial communities, respectively. SEM revealed that nirS denitrifying bacterial communities were positively (R²=0.92) correlated with the denitrification rate (P<0.05) , but the gene abundance of nirS and nirK did not correlate with the denitrification rate.
Conclusions The abundance and community composition of denitrifying bacteria vary among the farmlands under different crops. Denitrifying bacterial community composition, rather than their abundance, plays essential roles in determining the denitrification rate, while nirS denitrifying bacteria contributes more to soil denitrification.

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