补播乡土禾豆牧草对宁夏荒漠草地土壤微生物群落结构的影响

Impacts of reseeding native grass and a legume on soil microbial community structure in the desert steppe of Ningxia

本研究在宁夏荒漠草地设计了3种补播处理,即蒙古冰草(Agropyron mongolicum)补播、牛枝子(Lespedeza potaninii)补播和蒙古冰草+牛枝子混合补播,以不补播放牧草地为对照,分析微生物群落结构的变化及其与土壤理化性质间的关系。结果表明:与放牧草地相比,3种补播处理对原核微生物群落物种组成有明显影响,可以显著提高0-20 cm土层土壤的优势细菌变形菌门的相对丰度(P<0.05)。与放牧草地相比,3种补播模式对真菌群落物种组成无明显影响,但牛枝子补播的土壤优势群落真菌子囊菌门相对丰度在0-20 cm土层显著低于蒙古冰草+牛枝子混合补播处理,在20-40 cm土层,显著低于蒙古冰草补播和蒙古冰草+牛枝子混播处理(P<0.05)。Pearson相关分析显示,在所有补播处理中变形菌门和子囊菌门的相对丰度与土壤活性有机碳呈显著正相关关系(P<0.05)。与放牧地相比,牛枝子补播处理下土壤原核微生物和真菌α多样性总体上表现出增加趋势,且土壤原核微生物α多样性与土壤全氮呈负相关关系,土壤真菌α多样性与土壤碳组分含量呈负相关关系。β多样性分析表明,蒙古冰草补播和蒙古冰草+牛枝子混合补播均显著改变了0-20 cm土层的原核微生物群落结构(P<0.05),牛枝子补播显著改变了20-40 cm土层的原核微生物群落结构(P<0.05),和放牧草地相比,3种补播处理均显著改变了0-40 cm土层真菌的群落结构(P<0.05)。RDA分析显示,土壤有机碳和全氮是影响原核微生物和真菌群落结构的关键因子。可见,补播乡土牧草可能会通过改变土壤微生物群落结构来影响退化荒漠草地的生态系统功能(如碳氮的循环),这在未来的草地恢复和管理工作中应予以重视。

This study implemented three treatments:reseeded Agropyron mongolicum,Lespedeza potaninii,and a combination of A.mongolicum and L.potaninii,within a desert steppe in Ningxia.A grazed steppe was chosen as the control.Subsequently,the soil microbial community structure and its correlation with soil physicochemical properties were assessed.The results showed that compared to the grazed steppe,the three reseeding treatments did not significantly affect the species composition of the fungal community.However,the relative abundance of the dominant fungal phylum Ascomycota differed.Specifically,in the 0-20 cm soil layer,the relative abundance was significantly lower under the L.potaninii reseeding treatment compared to the mixed reseeding treatment of A.mongolicum and L.potaninii.Additionally,in the 20-40 cm soil layer,the relative abundance was significantly lower compared to both the A.mongolicum reseeding and mixed reseeding treatments(P<0.05).Pearson correlation analysis revealed a significant positive correlation(P<0.05)between the relative abundance of Proteobacteria and Ascomycota and soil active organic carbon across all replanting treatments.Moreover,compared to the grazed steppe,reseeding with L.potaninii enhanced both prokaryotic and fungalα-diversities.Prokaryoticα-diversity was negatively correlated with total nitrogen,whereas fungalα-diversity was negatively correlated with carbon fractions.β-diversity analysis indicated that reseeding with A.mongolicum and A.mongolicum+L.potaninii altered soil prokaryotic community structure within the 0-20 cm depth range(P<0.05),while reseeding with L.potaninii altered soil prokaryotic community structure within the 20-40 cm depth range(P<0.05).Furthermore,all reseeding treatments altered soil fungal community structure across the entire 0-40 cm depth range(P<0.05).The RDA model indicated that soil organic carbon and total nitrogen are key factors affecting the structure of both prokaryotic microbial and fungal communities.As evident from the findings presented above,this study underscores that reseeding with native forages could potentially influence ecosystem functions within the desert steppe,particularly impacting carbon and nitrogen cycling through alterations in soil microbial community structure.These tentative changes emphasize the importance of researchers’vigilance in monitoring and understanding such ecological shifts.