Abstract: Haloxylon ammodendron is one of the widely planted species for sand stabilization in the arid regions of Northwest China. After long-term plantation, it has degraded due to soil environmental imbalances and severe root diseases. In this study, we investigated the structure and diversity characteristics of soil and root microbial communities of H. ammodendron plantation with different ages (0, 10, 30 and 50 years) in the margin of a desert oasis in the Hexi Corridor. The results showed that soil pH, total nitrogen, total phosphorus, and β-glucanase activity were significantly higher in 30 years plantation than those in other ages. The α diversity indices of soil and root fungal communities were also significantly higher in 30 years plantation than those in other ages. There was significant difference in soil fungal community structure between 30 and 50 years plantations. Root fungal community structure was significantly different between 30 and other years. The relative abundance of Coniophora (the pathogen of Basidiomycota) became the dominant fungal genus in 30 years plantation, and significantly increased by 9.4 times in soil and by 12.3 times in root compared with 10 years plantation. The relative abundance of Pseudomonas (the dominant bacterial group) in soil significantly decreased in 30 and 50 years plantations. The relative abundance of pathogenic Coniophora was significantly and positively correlated with soil pH, β-glucanase activity and total phosphorus, and was negatively correlated with the abundance of Pseudomonas in the soil. The increase of pathogenic Coniophora in 30 years was the key microbial factor for the degradation and death of H. ammodendron. Our results could provide valuable information on the prevention of diseases in H. ammodendron plantation.

Key words: high-throughput sequencing, root endophyte, soil microorganism, pathogen, Coniophora, Haloxylon ammodendron