Patterns of nitrogen and phosphorus stoichiometry among leaf, stem and root of desert plants and responses to climate and soil factors in Xinjiang, China

Abstract

Nitrogen (N) and phosphorus (P) play essential roles in plant growth and deserve more attention in desert ecosystems. Nutrients stoichiometry patterns across various plant organs can reflect the plants' trade-offs to obtain resources and their growth strategy. However, it is still unclear how these nutrients are allocated among desert plant organs and how they are related to the arid climate conditions. This study aimed to examine how plant N and P stoichiometry varies among the organs of desert plants, and how they respond to climate and soil factors. Therefore, we analyzed N and P stoichiometry of leaves, stems, and roots collected from 29 desert sites in Xinjiang, China, to achieve this goal. Our studies indicated that the mean N and P concentrations in the stems (17.5 ± 0.2 and 1.0 ± 0.02 mg g−1, respectively) and roots (10.3 ± 0.2 and 0.7 ± 0.01 mg g−1, respectively) were significantly lower than those in leaves (21.4 ± 0.3 and 1.2 ± 0.02 mg g−1, respectively); the N:P ratio in stems (19.1 ± 0.3) was significantly higher than those in roots (17.6 ± 0.4), but N:P in leaves (18.2 ± 0.3) was not significantly different from those in stems and roots. Across plant life forms, N and N:P of both leaves and roots were respectively higher in shrubs than those in trees and herbs, P in three organs were significantly lower in trees than those in shrubs and herbs. Moreover, our results demonstrated that most soil factors had direct influences on N and P stoichiometry among different organs, and climate factors had indirect effect on N and P stoichiometry by affecting soil factors. This study provided the N and P stoichiometric characteristics of desert plant organs and explored their relationships with environmental variables, which can help understand nutrient stoichiometry patterns and utilization strategy of N and P and their potential responses to global climate changes in the desert ecosystems of central Asia.