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.

Plants of the Clematis genus are attractive ornamental plants due to their various flower colors and patterns, and they play an important role as ground cover plants in landscaping. However, the application of Clematis plants in landscaping in arid and semi-arid areas is limited. This study used five common wild Clematis species in Gansu Province as experimental materials, including Clematistangutica, Clematis glauca, Clematis intricata, Clematis nannophylla, and Clematis fruticosa. By simulating different intensities of drought stress with polyethylene glycol (PEG), the germination behavior of seeds and the physiological and biochemical responses of seedlings of these five species to drought stress were observed. The results showed that 15% PEG stress significantly inhibited the seed germination of the five species, which was also the drought threshold for seed germination of C. fruticosa. C. tangutica exhibited the strongest tolerance to drought stress in seed germination. Seedlings of the five Clematis plants showed different levels of tolerance to drought stress, mainly demonstrating higher tolerance to 10% and 20% concentrations of PEG stress, while a 30% concentration of PEG stress caused varying degrees of damage to the seedlings of the five Clematis species. PCA analysis indicated that seedlings of C. intricata and C. glauca had higher scores under drought stress. These findings can provide a theoretical basis for the selection of urban landscaping plant species in arid and semi-arid regions of northwest China.

Echinops gmelinii Turcz. is a winter annual species of the Asteraceae family, distributed in sandy areas of northern China, and is crucial for wind avoidance and sand fixation. To understand the inter- and intra-annual population dynamics of E. gmelinii in its cold desert habitats, we conducted long- and short-term demographic studies to investigate the timing of germination, seedling survival, soil seed bank and seed longevity of natural populations on the fringe of the Tengger Desert. Cypselae (seeds) of E. gmelinii can germinate in both July and August, but this process is heavily affected by precipitation amount and timing. Early emerging seedlings died rapidly under the high temperature and drought stress, before completing their life cycle. Later emerging seedlings could survive to complete their life cycle due to more suitable conditions for plant growth. In short, seedling survival dynamics were affected by precipitation distribution, and the survival rates were low (<4%). In addition, we found that the high seed production (1328 seeds·m⁻²) of E. gmelinii depended mainly on the production of seeds by individuals rather than high plant density (35 individuals·m⁻²). The contribution of newly ripened seeds and soil seed banks to seedlings emergence was 57.7% and 42.3%, respectively. Thus, only a small amount of the newly matured seeds was depleted during the year. Only 23.6% of the annual seeds germinated, and the remainder accumulated in a persistent soil seed bank (seed longevity was ≥2 y). The amount and timing of precipitation distribution were the key factors affecting the population dynamics of E. gmelinii in our study area. This species can cope with the uncertain precipitation patterns though a “cautious” germination strategy, varying the timing of germination and forming a persistent soil seed bank.