Soil Bacterial Approach to Assessing Afforestation in the Desertfied Northern China

Abstract Large-scale afforestation is still controversial in desertified Northern China. The original and unremitting efforts mainly have been concentrating on ecohydrology and aeolian sediments. However, as the major divers of terrestrial ecosystem, variations in soil bacteria remain unclear. In the past 50 y, Pinus sylvestris var. mongolica has been extensively planted throughout China to combat desertification. Therefore, soil bacteria associated with P. sylvestris were investigated to assess the greening efforts in the Mu Us Desert. Soils samples were collected in half-mature (MUh), nearly mature (MUn), and mature (MUm) plantations, as well as in bare sandy land as a control (CK). High-throughput amplicon sequencing, PICRUSt platform, and RDA analysis were performed to identify soil bacterial community structure and function, and determine their correlation with soil properties. The dominant bacteria differed between P. sylvestris plantation and desert soil, but was not strongly influenced by stand age. RB41 was abundant in the plantations, whereas Pseudarthrobacter was the dominant genus in CK. P. sylvestris plantations increased soil bacterial diversity and led to greater bacterial dispersal. “Environmental Information Processing” was detected as the dominant function in the five functional categories. The dominant driving function was variational from “Genetic Information Processing” and “Cellular Processes” to “Metabolism”, “Organismal Systems” and “Environmental Information Processing” in P. sylvestris afforestation. Soil moisture, pH, organic matter; and total phosphorus were significantly correlated with soil bacteria in CK, MUh, MUn, and MUm, respectively. P. sylvestris planting increased the complexity of the bacterial community and changed the dominant bacterial function from microscopic to macroscopic. The soil characteristics driving the bacterial community changed from soil moisture to soil pH and nutrients following P. sylvestris afforestation. Thus, revegetation promoted soil nutrient cycling and soil improvement in sandy land, which enriched the diversity of soil bacterial community and changed bacteria functional expression. Through understanding these processes, soil bacteria would be a considerable indicator to assessing afforestation. This finding will substantially contribute to soil ecological remediation and soil improvement in a desert region.