Experimental sand burial and precipitation enhancement alter plant and soil carbon allocation in a semi-arid steppe in north China

Changes of soil carbon along precipitation gradients in three typical vegetation types in the Alxa desert region, China

The changes and influencing factors of soil inorganic carbon (SIC) and organic carbon (SOC) on precipitation gradients are crucial for predicting and evaluating carbon storage changes at the regional scale. However, people's understanding of the distribution characteristics of SOC and SIC reserves on regional precipitation gradients is insufficient, and the main environmental variables that affect SOC and SIC changes are also not well understood. Therefore, this study focuses on the Alxa region and selects five regions covered by three typical desert vegetation types, Zygophyllum xanthoxylon (ZX), Nitraria tangutorum (NT), and Reaumuria songarica (RS), along the climate transect where precipitation gradually increases. The study analyzes and discusses the variation characteristics of SOC and SIC under different vegetation and precipitation conditions. The results indicate that both SOC and SIC increase with the increase of precipitation, and the increase in SOC is greater with the increase of precipitation. The average SOC content in the 0-300cm profile is NT (4.13 g kg-1) > RS (3.61 g kg-1) > ZX (3.57 g kg-1); The average value of SIC content is: RS (5.78 g kg-1) > NT (5.11 g kg-1) > ZX (5.02 g kg-1). Overall, the multi-annual average precipitation (MAP) in the Alxa region is the most important environmental factor affecting SIC and SOC.

Functional Trait Responses of Sophora alopecuroides L. Seedlings to Diverse Environmental Stresses in the Desert Steppe of Ningxia, China

The seedling stage of plants is a crucial and vulnerable period in population and community dynamics. Despite this, studies on how plant traits respond to different environmental stresses often tend to overlook this early stage. Our study focused on Sophora alopecuroides L. seedlings in Ningxia Yanchi desert steppe, analyzing the effects of sand burial, salinity, and drought on their key aboveground and belowground traits. The results showed that sand burial significantly negatively affected stem biomass (SB), leaf biomass (LB), stem diameter (SD), leaf length (LL), leaf width (LW), leaf area (LA), and total root volume (RV), but positively influenced total root length (RL). As sand burial depth increased, SB, LB, SD, LL, LW, LA, RV, root biomass (RB), RV, and lateral root numbers (LRN) significantly decreased. Salinity stress negatively affected SB, LB, SD, LL, LW, LA, RB, RL, and RV, with these traits declining as the stress concentration increased. Drought stress had a positive effect on SD and LL, with both traits showing an increase as the intensity of the drought stress intensified; however, it adversely affected RL. In Ningxia Yanchi desert steppe, salinity stress had the most significant effect on the traits of S. alopecuroides seedlings, followed by sand burial, with drought having the least significant effect. This study provides essential theoretical support for understanding how S. alopecuroides seedlings cope with environmental stresses in their early life stages.

Sand burial helps regulate timing of seed germination of a dominant herb in an inland dune ecosystem with a semiarid temperate climate

Sand burial plays important role in the life history of species in sandy areas of arid and semi-arid temperate regions, by affecting seed germination, seedling growth and survival and plant community. However, few studies have focused on the effects of sand burial on the dynamics of seed dormancy in such areas. In this study, seed germination characteristics of Allium tenuissimum, a dominant perennial herb in the dune ecosystem in Ordos Plateau in northern China, was investigated. Dormancy dynamics were monitored for seeds buried at sand depths of 0, 2 and 5 cm in the natural habitats for 13 months. Freshly matured seeds of A. tenuissimum were conditionally dormant and germinated to high percentages at high but not low temperatures. Germination percentages were increased by incubation at summer temperature (15/25 °C) and dry storage, but GA₃ and cold stratification had no significant effects. These results suggested that seeds of A. tenuissimum were conditionally dormant, and incubation under warm, wet (but not cold, wet) conditions and dry after-ripening resulted in complete dormancy releasing. Seeds buried at 2 and 5 cm in the field for 13 months exhibited seasonal changes in germination, with an increase in spring and summer followed by decrease in autumn and winter. However, seeds on the soil surface (0 cm) gradually came out of dormancy beginning in January, and germinated percentage was highest in July, after which remained high. The peak of nondormancy for seeds buried in the field was in the summer, which corresponds to the period of highest annual precipitation. Sand burial helped mediate seeds dormancy dynamics of A. tenuissimum via seasonal dormancy cycling. Our finding contributes to a better understanding of how timing of seedling establishment is controlled in a semiarid dune ecosystem in temperate climate.