Stoichiometric features of C, N, and P in soil and litter of Tamarix cones and their relationship with environmental factors in the Taklimakan Desert, China

Purpose The main objectives of this study were to explore the soil and litter carbon (C), nitrogen (N), and phosphorus (P) stoichiometric features in the Tamarix cones across the Taklimakan Desert, China, and also to verify the relationships between soil C, N, and P stoichiometry and environmental factors, with the ultimate aim of finding out the driving factors for the stoichiometric characteristics of desert soils. Materials and methods The soils under Tamarix cones, from the surface to a depth of 500 cm, were sampled in four typical Tamarix habitats (at Qiemo, Qira, Aral, Tazhong) of the Tamarix cones along the periphery and in the hinterland of the Taklimakan Desert. Soil samples were collected to measure soil properties and the concentrations of soil and litter C, N, and P. Analysis of variance (ANOVA) and distance-based redundancy analysis (db-RDA) were used to analyze the vertical patterns of soil C, N, and P stoichiometry and to identify the critical environmental factors influencing soil stoichiometry. Results and discussion Soil and litter C and N concentrations decreased with increasing soil depth throughout the profiles, while P concentrations showed no significant differences with depth. Soil C and N concentration, C/P ratios, and N/P ratios were significantly higher at the saline desert site (Qiemo) than at the other sites. Soil C and N were negatively correlated with litter C, N, and P within the 0-500-cm layer. In contrast, soil P was not significantly influenced by litter composition as it is primarily derived from the parent material at the soil bottom. In addition, environmental factors explained > 98% and 68.6% of the total variance of soil and litter stoichiometry, respectively. The results also indicated that, at all sites, the impacts of environmental factors on soil stoichiometry were mainly caused by the soil litter content, silt, sand, and soil water contents. However, at Qiemo, soil stoichiometry was also affected by the clay content, and at Aral and Tazhong, the pH, electrical conductivity, and mean annual temperature also exerted a strong influence on soil stoichiometry. Conclusions It could be concluded that the soil properties (such as, soil clay, silt, and sand content) and litter content exert a great influence on the stoichiometry of soil C, N, and P in the Tamarix cones of the Taklimakan Desert. In saline areas, soil salinity (electrical conductivity) and alkalinity (pH) may also influence the soil stoichiometry. In addition, the formation process of Tamarix cones also affects soil stoichiometry. Considering the extremely low precipitation and intensive evaporation in the Taklimakan Desert, this study provides a deep insight into the patterns of soil stoichiometry within extreme arid desert ecosystems.