The Characteristics Of AM Fungal Community In Eucalyptus Grandis Plantation At Different Stand Ages

Eucalyptus grandis plantation has strong climate adaptability and pest resistance in Southern Jiangxi.Arbuscular mycorrhizal fungi(AM fungi)can form symbiotic structures with the roots of E.grandis to help them adapt and grow in adverse environments.Understanding the composition and dynamic change of AM fungal community in E.grandis roots can provide reference for the sustainable management of plantation.We took the E.grandis plantations in Southern Jiangxi as the research object,firstly investigated the plant growth,soil properties and AM fungal colonization level of E.grandis plantations at different stand ages,and identified the composition of AM fungal community in roots by using highthroughput sequencing.Then we extracted the key factors of plant growth,soil properties and AM fungi community characteristics for correlation analysis.Finally,a structural equation model was established to reflect the causal relationship among the factors,which for exploring the inner link between the three of "E.grandis plantations-AM fungal community– soil properties".The main research results are as follows:1.Effects of stand ages on plant growth and soil propertiesOur results showed that the height and diameter at breast height(DBH)of trees increased quickly and then slowly from the early to the late stages of succession.Generally,1 to 5 years was a rapid growth period,and the stands tended to be mature in 5 to 7 years,while the height and DBH growth of 7 to 9 years stands have slowed down significantly.The major changes in soil properties were found in the contents of total P and total K,which firstly decreased and then increased with the increase of stand age.Therefore,the appropriate extension of rotation can ensure the integrity of nutrient cycle and is beneficial to the longterm sustainable management of E.grandis plantations.2.Effects of stand ages on the diversity of AM fungiThe diversity of AM fungal community in E.grandis plantations in Southern Jiangxi was not significantly different among different stand ages,indicating that the long-term planting of E.grandis did not significantly reduce the diversity of related microorganisms.The stability of AM fungal diversity can always maximize the benefits provided by mycorrhizal fungi in the dynamic changes of community structure,which is the direction of improving the plantation flora.Relatively,the abundance of young stand species is lower than mature stands species is relatively high,but the exact curve is not clear yet.3.Effects of stand ages on AM fungal community compositionA total of 8 genera,7 families,4 orders were identified by high-throughput sequencing of AM fungal community of E.grandis roots in Southern Jiangxi.Among them,the dominant genera were Paraglomus and Glomus,and their total relative abundance exceeded 90%.In general,the AM fungal community of E.grandis plantations in this region is mainly composed of two types of dominant flora with high abundance and a variety of lowabundance flora.The relative abundance of Paraglomus and Glomus changed significantly with stand ages.Therefore,in the long-term management of plantation,the dominant AM flora is not unchanged,and there is an obvious mutual competition between the flora.4.Relationships among plant growth,soil properties and AM fungal communityThere is a close interaction between plant growth,soil properties and AM fungal community.Changes in the relative abundance of Paraglomus and Glomus,the two dominant species,will directly or indirectly cause changes in soil properties,colonization level of AM fungi and diversity of AM fungi,change the nutrient cycle between plants and soil,and then affect plant growth.It indicates that the adjustment strategy of AM fungal community with stand ages is to change the community composition to achieve its functional diversity on the premise of maintaining the maximum diversity,so as to adapt to different physiological needs of plants and changes of soil environment.This adjustment strategy of AM fungal community is of great significance for the wide adaptability of E.grandis plantations in Southern Jiangxi.