Rhizosphere microorganisms play a pivotal role in biogeochemical cycles, particularly in relation to carbon (C) and nitrogen (N) cycles. However, the impact of stand age on the composition of rhizosphere microbial communities and the abundance involved in C and N cycling remains largely unexplored in restoration ecosystems dominated by shrubs of temperate deserts. This study focuses on revealing changes in microbial composition and functional genes in the rhizosphere soil of Caragana korshinskii after revegetation, as well as their response mechanisms to changes in environmental factors. The alpha diversity of bacteria tended to increase with stand age, whereas that of fungi decreased. The abundance of denitrification; dissimilatory nitrate reduction to ammonium, nitrification, and ammonium assimilation; and C fixation-related gene levels increased with stand age, whereas those related to the degradation of starch, pectin, hemicellulose, cellulose, and aromatics decreased. The parameters MBC, MBN, and TC were the key factors affecting the bacterial community, whereas the fungal community was regulated by TN, EC, pH, and MBC. Stand age indirectly regulated C and N cycling functions of genes through altered soil properties and microbial community structures. This study presents a novel approach to accurately evaluate the C and N cycling dynamics within ecosystems at various stages of restoration.

Gravel mulching is a widely employed strategy for water conservation in arid agricultural regions, with potential implications for soil carbon (C) sequestration and greenhouse gas emissions. However, soil respiration and CO₂-C emissions remain uncertain owing to less consideration of the influence of precipitation patterns and planting age. In this study, we investigated the soil respiration rate (R_soil) and cumulative CO₂-C emission (C_cum), both measured over a period of 72 h, along with soil properties and enzyme activities under different precipitation conditions based on gravel mulching with different planting ages. We analyzed the effects of planting ages on R_soil and C_cum and revealed the underlying mechanisms driving changes in environmental factors on R_soil and C_cum. The results demonstrated that the R_soil reached the maximum value at about 1 h, 0.5 h, and 0.25 h after rewetting in 1, 10, and 20 years of gravel mulching under the condition with 1 mm, 5 mm, and 10 mm of precipitation, respectively, whereas the R_soil exhibited its maximum at about 8 h after soil rewetting under precipitation of 30 mm. The C_cum induced by precipitation pulses tends to decrease with increasing years of gravel mulching. The C_cum was 0.0061 t ha⁻¹ in the 20-year gravel-mulched soil, representing a 53.79% reduction compared to the 1-year gravel-mulched soil. Soil organic matter (SOM), planting ages, and alkaline phosphatase (ALP) were the primary factors influencing the R_soil and C_cum in 0–20 cm, while SOM, planting ages, and soil porosity (AirP) were the key factors affecting the R_soil and C_cum in 20–40 cm. The R_soil and C_cum in the 0–20 cm soil were regulated by soil enzyme activities, while those of 20–40 cm soil were controlled by soil properties. This indicates that the decrease in R_soil and C_cum is caused by soil degradation, characterized by a decrease in SOM and ALP. This study offers a novel insight into the long-term environmental impact of gravel mulching measures in arid areas, which is helpful in providing a theoretical basis for dryland agricultural management. It is imperative to consider the duration of gravel mulching when predicting the potential for C sequestration in arid agricultural areas.