桉树种植对林地土壤丛枝菌根真菌群落结构及多样性的影响

Diversity and structure of the soil arbuscular mycorrhizal fungal community are altered by Eucalyptus plantations

桉树(Eucalyptus spp.)种植所产生的生态争议已受到广泛关注。丛枝菌根真菌(Arbuscular Mycorrhizal Fungi, AM真菌)是土壤微生物的重要组成部分,与根系共生后可促进植物的养分运输、提高植物逆境生存能力等。然而,桉树种植对土壤AM真菌群落结构和功能的影响尚不清楚。研究比较了次生林改种桉树后不同年限(2年/5年/10年)的土壤理化性质、AM真菌种类、群落组成及多样性的变化。结果表明,桉树种植显著改变了土壤理化性质,具体表现为2年生和10年生桉树林中土壤pH和有机碳显著降低(P<0.05);AM真菌的孢子密度在桉树林土壤中显著低于次生林土壤(其中在5年生土壤中最低);AM真菌的种丰度随种植年份的增加逐渐下降,在10年生桉树林土壤中有所恢复; 5年生桉树的菌根侵染率最高,10年生桉树侵染率最低。AM真菌群落组成和结构发生显著变化,优势种Funneliforms geosporus的丰度在2年生和10年生林地中显著降低;而Septoglomus deserticola的丰度在2年生和10年生林地中显著增加。另外,冗余分析(Redundancy analysis, RDA)结果表明,土壤AM真菌群落结构主要受土壤pH值(解释率:89.88%)变化的影响。研究揭示了次生林改种桉树林后土壤AM真菌的群落变化特征,为桉树林的栽培管理和环境修复提供了数据支撑。

Eucalyptus plantations are controversial because of its complexed impacts on environments.Arbuscular mycorrhizal(AM)fungi in soil provide important ecological functions such as enhancing soil nutrient transportation and plant stress tolerance via symbiosis.Until recently,the influence of massive Eucalyptus planting on soil microbial communities,especially the AM fungi is yet to be investigated.Herein,we investigated into these effects by comparing the diversity and taxonomic composition of AM fungal community in soil between the secondary forest and Eucalyptus forests which involved two-,five-,and ten-year′s plantations.Our results provided evidence that the practices of Eucalyptus plantations significantly changed soil properties(P<0.05),e.g.,the soil pH and soil organic carbon significantly decreased in the two-and ten-year′s soil samples relative to the secondary forest.Importantly,spore density of AM fungi in soil declined by the Eucalyptus plantations,with the lowest level being observed in the five-year plantation.Species richness of AM fungi inclined to decrease within five years of Eucalyptus plantation,but recovered to a contain extent after ten years.In contrast,AM infection rate on the roots of Eucalyptus reached to the highest and lowest level in the five-year and ten-year plantation,respectively.Further,the composition and structure of AM fungi shifted significantly by Eucalyptus plantations.Noticeably,the dominant species Funneliformis geosporus and Septoglomus deserticola significantly decreased and increased in the two-and ten-year Eucalyptus plantations,respectively.Lastly,our redundancy analysis indicated that soil pH largely promoted the variation of the AM fungal community(explanation rate:89.88%).Collectively,our study revealed the shifts of AM fungi in the soil of the secondary forest after the practices of Eucalyptus plantations,which is necessary to shed light onto the strategies of environment restoration in Eucalyptus plantations.