Simulated nitrogen deposition induces shifts in growth and resource-use strategies during range expansion of an invasive plant

An appropriate resource-use strategy contributes to the invasion success of exotic plants. During range expansion, population density and nitrogen availability are two important factors that exert significant influences on resource-use-associated traits. As population density decreases and resource availability increases, invasive species are likely driven to be increasingly quicker in resource-use return. By far, it remains unclear how resource-use-related traits shift in response to simultaneous changes in population density and N deposition, and how the shift in resource-use strategy is related to growth in invasive plants. Here we investigated the intraspecific variation in growth and leaf-level resource-use-related traits across invasive populations of different covers under contrasting N levels using a worldwide invasive perennial vine, Mikania micrantha. N addition greatly increased the growth and leaf physiological parameters of M. micrantha. At low N level, the resource-use strategy shifted to be more conservative with decreasing population cover, which was primarily correlated with increasing leaf investment; at high N level, on the contrary, the resource-use strategy shifted to be more acquisitive, which was primarily correlated with increasing carbon assimilation capacity. In addition, M. micrantha growth performance was less related to population cover, and it did not associate with leaf physiology. These results suggest that resource-use strategy shifts from conservative to acquisitive towards range edges during range expansion of M. micrantha. This work reveals the pattern of resource-use strategy in long-term plant invasion, and can provide insights into how invasive species will fare in the context of nitrogen deposition.