Background and aims

Plant nutrient-acquisitive traits and clonal demographic traits can influence plant productivity under changing environments. However, it remains unclear how these traits of different clonal growth forms respond to changes in water and nitrogen availability, and how such responses in turn affect plant productivity.

Methods

We used a 17-year nitrogen and water addition experiment in a temperate steppe to examine their effects on nutrient-acquisitive traits (root traits and leaf nutrient resorption efficiency), clonal demographic traits (shoot density and bud density), and above-ground net primary productivity (ANPP) of clumper, rhizomatous, and stoloniferous clonal growth forms.

Results

We found that nitrogen addition increased ANPP of clumper and rhizomatous plants but decreased that of stoloniferous plants. Conversely, water addition decreased ANPP of clumper plants, while increased that of rhizomatous and stoloniferous plants. Furthermore, water- and nitrogen-induced changes in shoot density were the main driver of ANPP variations, rather than changes in bud density and nutrient-acquisitive traits. Moreover, we found that nitrogen-evoked shifts in shoot density were positively correlated with changes in specific root length and root nitrogen content, but were negatively with root average diameter and root tissue density. Water-induced changes in shoot density displayed positive and negative correlations with leaf nitrogen and phosphorus resorption efficiency.

Conclusion

Our results demonstrate that ANPP responses of different clonal growth forms to long-term water and nitrogen addition are closely related to clonal demographic traits and nutrient-acquisitive traits, with nitrogen effects linked to root traits and water effects to leaf nutrient resorption efficiency.