Spatial patterns of leaf carbon, nitrogen stoichiometry and stable carbon isotope composition of Ranunculus natans CA Mey. (Ranunculaceae) in the arid zone of northwest China

Leaf carbon concentrations (C%), nitrogen concentrations (N%), carbon-nitrogen ratio (C:N) and stable carbon isotope composition (delta C-13) are key foliar traits with great ecological importance, but few studies have attempted to document the pattern of leaf C%, N%, C:N and delta C-13 value for aquatic macrophytes. In this study, we examined the pattern of leaf C%, N%, C:N and delta C-13 value of Ranunculus natans collected from 26 sites across northwest China, and tried to explore how different environmental conditions affect leaf C%, N%, C: N stoichiometry, and delta C-13 value. Results showed that leaf N%, C:N ratios and delta C-13 varied significantly among the 26 R. natnas collection sites, but leaf C% did not differ significantly. Our study found weak relationships between foliar N% and C: N of R. natans and altitude, latitude and longitude, which indicated that variability in foliar N%, C:N stoichiometry across diverse habitats may result from plant growth, development, metabolism, phenological and life history traits, rather than from variation in geographic environment. We also demonstrated that leaf delta C-13 values displayed a linear increase in altitudinal direction. The differences in delta C-13 values were likely caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency because delta C-13 values in R. natans were not correlated with foliar N concentrations. Our data support the previously proposed temperature-plant physiology hypothesis because there is a negative relationship between leaf N% of R. natans and temperature of water body where R. natans inhabits. (C) 2015 Elsevier B.V. All rights reserved