Nitrogen allocation, partitioning and use efficiency in three invasive plant species in comparison with their native congeners

In this study, we hypothesized that invasive species may allocate a higher fraction of leaf nitrogen (N) to photosynthesis than phylogenetically related native species. To test this hypothesis, we determined N allocation and other ecophysiological traits of three invasive species in comparison with their respective native congeners by measuring response curves of photosynthesis to intercellular CO2 concentration. The invasive species of Peperomia and Piper indeed allocated a higher fraction of leaf N to photosynthesis and were more efficient in photosynthetic N (N-P) partitioning than their native congeners. The two invasive species partitioned a higher fraction of N-P to carboxylation and showed a higher use efficiency of N-P, while their native congeners partitioned a higher fraction of N-P to light-harvesting components. The higher N allocation to photosynthesis and the higher N-P partitioning to carboxylation in the two invaders were associated with their higher specific leaf area. Nitrogen allocation and partitioning were the most important factors in explaining the differences in light-saturated photosynthetic rate and photosynthetic N use efficiency (PNUE) between the two invasive species and their native congeners. The differences in N allocation-related variables between the invasive and native species of Amaranthus could not be evaluated in this study due to the method. Except PNUE, resource capture- and use-related traits were not always higher in all three invasive species compared to their native congeners, indicating that different invasive species may have different syndrome of traits associated with its invasiveness.