Leaf-root-soil N:P stoichiometry of ephemeral plants in a temperate desert in Central Asia

Ephemeral plants are a crucial vegetation component in temperate deserts of Central Asia, and play an important role in biogeochemical cycle and biodiversity maintenance in desert ecosystems. However, the nitrogen (N) and phosphorus (P) status and interrelations of leaf-root-soil of ephemeral plants remain unclear. A total of 194 leaf-root-soil samples of eight ephemeral species at 37 sites in the Gurbantunggut Desert, China were collected, and then the corresponding N and P concentrations, and the N:P ratio were measured. Results showed that soil parameters presented no significant difference among the eight species. The total soil N:P was only 0.116 (geomean), indicating limited soil N, while the available soil N:P (4.896, geomean) was significantly larger than the total N:P. The leaf N (averagely 30.995 mg g^-1) and P (averagely 1.523 mg g^-1) concentrations were 2.64-8.46 and 0.93-3.99 times higher than the root N (averagely 8.014 mg g^-1) and P (averagely 0.802 mg g^-1) concentrations, respectively. Thus, leaf N:P (averagely 21.499) was 1.410-2.957 times higher than root N:P (averagely 11.803). Meanwhile, significant interspecific differences existed in plant stoichiometric traits. At the across-species level, N content scaled as the 3/4-power of P content in both leaves and roots. Leaf and root N:P ratios were mainly influenced by P; however, the leaf-to-root N or P ratio was dominated by roots. Leaf and root N, P contents and N:P were generally unrelated to soil nutrients, and the former presented lower variation than the latter, indicating a strong stoichiometric homeostasis for ephemerals. These results demonstrate that regardless of soil nutrient supply capacity in this region, the fast-growing ephemeral plants have formed a specific leaf-root-soil stoichiometric relation and nutrient use strategy adapting to the extreme desert environment.