Allocation of foliar-P fractions of Alhagi sparsifolia and its relationship with soil-P fractions and soil properties in a hyperarid desert ecosystem

Desert vegetation in the juncture of the Qira oasis and the Taklamakan Desert typically grows on phosphorus (P)-poor soils. Alhagi sparsifolia Shap. (A. sparsifolia), as widely distributed natural vegetation in this area, not only has crucial ecological effects of wind sheltering and sand fixation, but also is an excellent forage resource. Researchers are increasingly interested in the foliar-P utilization strategy of A. sparsifolia that allows it to survive in extremely P-impoverished soils. Therefore, A. sparsifolia growing in four different soil sites with differing availability of P in this area were studied, and leaves and 0-100 cm soils were collected. Foliar total nitrogen (N), total-P and P fractions (metabolic-P, nucleic acid-P, structural-P, and residual-P) were determined. Soil labile-P (resin-P, NaHCO3-Pi, and NaHCO3-Po), moderately labile-P (NaOH-Po and NaOH-Pi), stable-P (HCl-P and residual-P), and basic soil properties were determined. Our findings showed that A. sparsifolia growth was highly likely to be limited by soil-P in this area, and the concentrations of foliar total-P and young leaf metabolic-P increased with increasing soil-P availability, while foliar-N was relatively constant. Comparatively, A. sparsifolia allocated a higher proportion of foliar-P to nucleic acid-P and a lower proportion to structural-P, as soil-P availability decreased. Moreover, foliar metabolic-P, nucleic acid-P, and structural-P had the strongest positive response to soil labile-P in topsoil. Furthermore, soil electrical conductivity (EC), labile-P, and moderately labile-P influenced foliar-P fractions. Comprehensively, variation in foliar-P allocation patterns of A. sparsifolia varied across the four soils with differing available-P and were closely related to soil-P fractions and properties. These results will help us better understand A. sparsifolia foliar-P utilization strategy and their potential responses to environmental nutrients.