Abstract: Biological invasion is one of the most important threats to global biodiversity and ecosystem functioning. In this study, we measured carbon, nitrogen, and phosphorus content and their ratios in alien species Mikania micrantha with three invasive degrees and native species Siegesbeckia orientalis to explore the nutritional strategy of M. micrantha. The results showed that for M. micrantha, soil N and P contents in the three habitats were high. The contents of soil C, N, AN, and AP with mild invasion were higher than that in the other two habitats, showing that soil nutrients reduced with the increasing invasion. Leaf N content in M. micrantha under three invasive degrees were significantly greater than that of root and stem. Under severe and median invasion degrees, stem P content was significantly higher than root P and leaf P, indicating that more P was allocated to stem with increasing invasion. In contrast, more N was allocated to leaf. N∶P in root and stem of the three invasion degrees were lower than that in leaf. In particular, stem N∶P of mildly invasive M. micrantha was significantly lower than that of the other two invasion degrees, suggesting that the greatest relative growth may occur in stem and root during invasion. Ratios of N∶P and C∶P in root and stem of M. micrantha were significantly lower than that of native species S. orientalis, implying that M. micrantha may grow faster than native species with a “growth competition strategy”. Significant negative correlations were found between C∶N and N∶P in both root and stem for M. micrantha, showing a tradeoff between growth and storage. There was a significant positive correlation between stem P of M. micrantha and soil C and N (0-10 cm), and between root P and soil AP (10-20 cm), indicating that M. micrantha may increase the absorption and utilization of P with increasing soil nutrition. Growth and nutrient strategies varied under different resource conditions (e.g., growth competitive strategy), as well as fundamental tradeoffs between growth and storage, which all contribute to the successful invasion of M. micrantha.

Key words: Quercus aliena var. acuteserrata,  water, spectral reflectance., throughfall elimination, photosynthetic pigment