Effect of conservation tillage on the abundance and diversities of soil diazotrophic communities in different soil layers of Mollisol
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摘要:
东北黑土由于近几十年持续性高强度的利用,已经出现肥力下降等问题。保护性耕作是防止土壤退化的有效措施,可影响土壤微生物的丰度和多样性,然而保护性耕作对东北黑土固氮菌群落结构的影响仍不清楚。本研究利用15年免耕和传统耕作试验,采用高通量测序方法,探讨东北地区免耕和传统耕作条件下0~5 cm和5~20 cm两个土壤深度的固氮菌群落的丰度、多样性和组成的差异,以及与土壤理化性质的相关关系。研究结果表明,免耕和传统耕作下土壤固氮菌在门水平上变形菌门相对丰度最大;属水平上慢生根瘤菌属的相对丰度最大。耕作方式、土壤深度对nifH基因拷贝数、Chao 1和Shannon指数均无显著影响,PCA分析表明,免耕和传统耕作显著影响土壤固氮菌群落的组成,土壤容重与PC1显著相关。Mantel test检验表明,固氮菌群落与土壤容重显著相关。本研究结果表明免耕通过影响土壤容重改变了土壤固氮菌的群落组成。本研究加深了保护性耕作对土壤固氮菌群落影响的理解,为东北黑土区保护性耕作的应用提供了理论依据。
Abstract:Due to the continuous high-intensity utilization in recent decades, the Mollisol fertility in Northeast China has declined.Conservation tillage is a good alternative to prevent soil degradation, which alters the abundance and diversity of soil microorganisms; however, the impact of conservation tillage on soil diazotrophic community in Mollisol of Northeast China is still unclear.We conducted an experiments including 15-year no tillage (NT) and conventional tillage (CT) treatments, and analyzed the differences in abundance, diversity and composition of soil diazotrophic community in 0~5 cm and 5~20 cm soil layers of Molloisols in Northeast China.The result showed that Proteobacteria was the most abundant phyla while Bradyrhizobium was the most abundant genus.Tillage and soil depth had no significant effects on the copy number of nifH gene, Chao 1 and Shannon index.PCA analysis showed that there were significant differences in the diazotrophic communities between NT and CT.Soil bulk density (BD) was significantly correlated with PC1.Mantel test revealed that soil diazotrophic community was significantly correlated with soil BD.The results showed that NT changed the community composition of soil diazotrophic by affecting soil BD.The study deepens our understanding of the impact of tillage regime on soil diazotrophic community and provides a theoretical basis for the application of conservation tillage in Mollisol zone of Northeast China.
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Key words:
- conservation tillage /
- microorganism /
- nifH /
- diversity /
- soil bulk density
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图 1 固氮菌基因丰度对耕作和土壤深度的响应
注:NT5代表免耕0~5 cm深度; NT20代表免耕5~20 cm深度; CT5代表传统耕作0~5 cm深度; CT20代表传统耕作5~20 cm深度。下同。
Figure 1. Soil nifH gene abundance response to tillage and soil depth
Note: NT5, no tillage at soil depths of 0~5 cm; NT20, no tillage at soil depths of 5~20 cm; CT5, conventional tillage at soil depths of 0~5 cm; CT20, conventional tillage at soil depths of 5~20 cm.The same is as below.
图 5 土壤理化属性与固氮菌群落的相关性
注:SOC代表土壤有机碳; DOC代表可溶性碳; TN代表总氮; TP代表总磷; AP代表有效磷; TK代表全钾; AK代表速效钾;BD代表容重;显著相关(**代表P < 0.01; *代表P < 0.05)。
Figure 5. Correlation between diazotrophic community and soil properties
Note: SOC indicates soil organic carbon; DOC indicates dissolved organic carbon; TN indicates total nitragen; TP indicates total phosphorus; AP indicates available phosphorus; TK indicates total potassium; AK indicates available potassium; BD indicates bulk density.Significant correlations (** indicates P < 0.01;* indicates P < 0.05).
表 1 土壤固氮菌群落与土壤理化属性Mantel test分析
Table 1. Mantel test analysis between soil diazotrophic community and soil properties
SOC DOC TN NO3--N NH4+-N TP AP TK AK BD pH r -0.129 -0.125 -0.122 0.030 -0.112 0.008 -0.058 -0.057 -0.055 0.455* 0.450 P 0.408 0.478 0.501 0.863 0.598 0.974 0.788 0.775 0.757 0.003 0.060 注:SOC代表土壤有机碳; DOC代表可溶性碳; TN代表总氮; TP代表总磷; AP代表有效磷; TK代表全钾; AK代表速效钾;BD代表容重;显著相关(**代表P < 0.01; *代表P < 0.05)。
Note: SOC indicates soil organic carbon; DOC indicates dissolved organic carbon; TN indicates total nitragen; TP indicates total phosphorus; AP indicates available phosphorus; TK indicates total potassium; AK indicates available potassium; BD indicates bulk density.Significant correlations (** indicates P < 0.01;* indicates P < 0.05). -
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