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Tamarix taklamakanensis, a dominant species in the Taklimakan Desert of China, plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability. This study aimed to determine the water use strategies of T. taklamakanensis in the Taklimakan Desert under a falling groundwater depth. Four typical T. taklamakanensis nabkha habitats (sandy desert of Tazhong site, saline desert-alluvial plain of Qiemo site, desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site) were selected with different climate, soil, groundwater and plant cover conditions. Stable isotope values of hydrogen and oxygen were measured for plant xylem water, soil water (soil depths within 0–500 cm), snowmelt water and groundwater in the different habitats. Four potential water sources for T. taklamakanensis, defined as shallow, middle and deep soil water, as well as groundwater, were investigated using a Bayesian isotope mixing model. It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation, but through the river runoff from snowmelt water in the nearby mountain ranges. The surface soil water content was quickly depleted by strong evaporation, groundwater depth was relatively shallow and the height of T. taklamakanensis nabkha was relatively low, thus T. taklamakanensis primarily utilized the middle (23%±1%) and deep (31%±5%) soil water and groundwater (36%±2%) within the sandy desert habitat. T. taklamakanensis mainly used the deep soil water (55%±4%) and a small amount of groundwater (25%±2%) within the saline desert-alluvial plain habitat, where the soil water content was relatively high and the groundwater depth was shallow. In contrast, within the desert-oasis ecotone in the Qira and Aral sites, T. taklamakanensis primarily utilized the deep soil water (35%±1% and 38%±2%, respectively) and may also use groundwater because the height of T. taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low, which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities. Consequently, T. taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources (deep soil water and groundwater), reflecting its adaptations to the different habitats in the arid desert environment. These findings improve our understanding on determining the water sources and water use strategies of T. taklamakanensis in the Taklimakan Desert.

Symbiotic plants might be able to regulate a limited nitrogen (N) pool, thus avoiding and reducing competition for resources, through the uptake of different chemical N forms. Our aim was to see whether coexisting herbs showed preference for different forms of N in a temperate desert. We conducted a situ experiment using the 15 N labeling method in the Gurbantunggut Desert of Northwestern China dominated by Erodium oxyrrhynchum, Hyalea pulchella, Nonea caspica and Lactuca undulata during their growing period (April and May). Four desert herb species preferentially relied on 15 N-NO3 for their N nutrition. Multi-factor analysis of variance (ANOVA) analysis results showed that species, N forms, months, and soil depths strongly affected N uptake rate. The uptake rate by herbs was higher in May than in April, and higher at 0-5 cm than at 5-15 cm soil layers. Erodium oxyrrhynchum, N. caspica and L. undulata showed different preference on N form over months. Erodium oxyrrhynchum and L. undulata changed their uptake preference from more 15 N-Glycine in April to more 15 N-NH4 in May. Although the N uptake rate of four desert herbs varied across different soil depths and months, all species absorbed more inorganic N compared with organic N. The higher preference for 15 N-NO3 and 15 N-NH4 over 15 N-Gly possibly reflects adaptation to different N forms in temperate desert.

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. 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. 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. 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.

Strong partially balanced $$t$$t-designs $$t$$t-$$(v,k,\lambda )$$(v,k,?) were introduced by Pei (in J Comb Des 6:417---419, 1998). They can be used to construct authentication codes, whose probabilities $$P_r$$Pr of successful deception in an optimum spoofing attack of order $$r$$r for $$0\le r\le t-1$$0≤r≤t-1, achieve their information-theoretic lower bounds. In this paper, we determine the existence of optimal strong partially balanced $$3$$3-designs $$3$$3-$$(v,4,\lambda )$$(v,4,?), which is based on candelabra quadruple systems.