Foliar carbon, nitrogen and phosphorus stoichiometry of typical desert plants across the Alashan Desert

Abstract

Carbon (C), nitrogen (N) and phosphorus (P) play an important role in plant growth and regulate various physiological functions. Leaf C, N and P stoichiometry varies with many aspects of plant biology. The ratios of C/N and C/P may reflect the balance between the plant demand and N and P availability and constrain various processes. Previous data from soils in China pointed to a shortage of P. Shortage of N was also reported from the Alashan Desert. We therefore assumed that plant stoichiometry may reflect the low levels of N and P in the Alashan Desert soils. To find the ecological stoichiometry characteristics of C, N and P of the plants of the Alashan desert, we examined 54 typical desert species, which included three groups of plants: perennial shrubs (PS), perennial herbs (PH) and annual herbs (AH). A total of 25, 15 and 14 plants were sampled from PS, PH and AH, respectively. Our findings indicate that C, N, P in the plant leaves ranged from 236.48 to 513.54 (with an average of 379.01±55.42) mg/g for C, 1.2 mg/g to 37.37 (with an average of 10.65±7.91) mg/g for N, and 0.11 mg/g to 4.5 (with an average of 1.04±0.81) mg/g for P. Whereas C and P, and N and P were positively correlated in agreement with previous publications, no significant relation was found between C and N, in disagreement with previous publications. As for N and P, these values were substantially lower for PS. The average values for PH and AH were 11.55 (± 7.34) and 10.88 (± 7.17), mg/g for N, and 1.47 (± 0.94), and 1.41 (± 0.94) mg/g for P. As for PS, they were 10.38 (± 8.24) and 0.84 (± 0.65) mg/g for N and P, respectively. The average values found for N and P in the Alashan Desert were substantially lower than the typical values reported from other desert regions in China having on average 24.4 (± 8.10) and 1.74 (± 0.88) mg/g of N and P, respectively. Furthermore, out of all plants examined, 71% of the plants had a ratio of N/P < 14 which implies that plant growth is primary limited by N. Interestingly, the lowest values were found in leaves at the new shoots and we presume that nutrients are transferred from leaves at the older branches to leaves at the younger shoots. Our data thus imply that the Alashan desert plants are adapted to substantially low values of N, and also, following the low ratio of N/P, to low amounts of P.