Elucidating the impact of afforestation on soil bacterial community composition and its potential function in afforestation is imperative for comprehending the biochemical processes of land use change. This study employed high-throughput genomic sequencing to determine the bacterial phylogenetic assembly and assess functional groups following afforestation encompassing shrubland and woodland. Compared with non-afforested cropland, the soil organic carbon (SOC) remained unchanged, but significant alterations were observed in the bacterial composition and potential functions under afforestation. Afforestation enhanced bacterial diversity and even shifted the bacteria from the r- to K-strategy, as indicated by higher oligotroph/copiotroph ratios. Soil properties explained 66.45% and 68.9% of the total variation in bacterial community composition at the phylum level and the functional group. A 60.44% decrease in soil water content, a 3.82% increase in pH, a 7.5% increase in bulk density, and a 66.8% decrease in available phosphorus (AP) were the main soil factors affecting both bacterial community composition and functional traits in afforestation. In particular, lower available nutrients, AP, and nitrate nitrogen in afforestation drive the bacterial life history strategies. We conclude that changes in bacterial metabolic functions due to reduced soil available nutrients from dryland afforestation might be the main driver for microbial-inhibited SOC accumulation. These results could provide strong microbiological evidence to help further evaluate the importance of dryland afforestation.

Study region: A gravel desert in the middle reaches of the Heihe River Basin, northwestern China. Study focus: Lack of long-term monitoring of soil water and groundwater level (GL) limited accurately quantifying the interactions between soil water, groundwater, and the shrubs in the desert ecosystems. This study focused on clarifying the water movement in the groundwater-soil-plant-atmosphere continuum in the desert ecosystems. Hydrological processes of a shrub community were simulated by developing the HYDRUS-1D model based on the twelve-years monitoring in a gravel desert. New hydrological insights for the region Evapotranspiration of the shrub community was properly partitioned by the Penman-Monteith equation with the dual crop coefficient approach. Reaumuria songarica and Nitraria sphaerocarpa community relied on shallow soil water. Actual transpiration and evapotranspiration ranged from 33 mm and 80 mm in a dry year to 65 mm and 171 mm in a wet year, respectively. Only 39 % of evapotranspiration was used for shrub growth, and growing-season rainfall was more efficiently used in a dry year. Water rising from lower layers was dominant in the 0–10 m layer. The capillary fringe varied from 102 cm to 267 cm, averaging 205 cm above GL during the growing seasons. The rising groundwater is unavailable but promising for the shrubs’ utilization. The results of this study are valuable for developing sustainable management strategies for the similar gravel desert ecosystems.