内蒙古典型草原植物叶片碳氮磷化学计量特征的季节动态

Aims Exploring the seasonal dynamics in leaf carbon (C), nitrogen (N) and phosphorus (P) concentrations and their ecological stoichiometric characteristics will enhance our understanding about physiological and ecological processes such as plant growth and development and nutrient uptake and utilization as well as dynamic equilibrium relationship among plant stoichiometry. Methods Here, we collected leaf samples of 18 dominant plant species semimonthly through growing season (i.e. from June 2nd to Sept. 2nd) from a long-term fenced site in a typical steppe in Xilinhot of Nei Mongol, China. Leaf C, N and P concentrations were measured. Seasonal changes in leaf C, N and P concentrations and their ratios were explored and their differences between different species groups were analyzed using one-way ANOVA. The relationships between leaf C, N and P concentrations and their ratios were analyzed using correlation analysis. Lastly, the allometric relationships between the concentrations of different elements were analyzed using Standardized Major Axis. Important findings Seasonal trends in leaf C, N and P concentrations and their ratios were not consistent with each other and also differed between different functional groups. Specifically, the variation of leaf N and P concentrations for all functional groups showed obvious dilution effect. Monocotyledons and perennial grasses had lower leaf N and P concentrations but much higher leaf C:N and C:P mass ratio than dicotyledons and perennial forbs, respectively. Leaf N concentration was positively correlated with leaf P concentration while leaf C:N and C:P mass ratios were negatively correlated with leaf N and P concentrations respectively, indicating the internal coupling mechanism between nutrient elements in plants. Allometric analyses showed that leaf N concentration and C:N mass ratio, leaf P concentration and C:P mass ratio as well as leaf N and P concentrations all maintained the same growth rate respectively among species through most time of growing season.