Effects of nutrient on competition between invasive species Bidens frondosa and native congener B. tripartita.
Bidens frondosa L. is an exotic annual herb native to North America, which often co-occurs with native congener B. tripartita L. in habitats, such as abandoned arable land, farmland etc. In order to understand the invasiveness of B. frondosa, the effects of compound fertilizer on competitive response of B. frondosa and B. tripartita were studied. The results showed that the competitive response of B. frondosa declined with nutrient increment, while that of B. tripartita increased. Furthermore, the competitive response of B. frondosa was greater than that of B. tripartita under low nutrient level and on the contrary under high nutrient level. The growth of B. frondosa was suppressed by competitor under low nutrient, while did that of B. tripartita under high nutrient. Therefore, it was suggested that the competitive ability of B. frondosa was enhanced with nutrient increasing, meanwhile that of B. tripartita decreased. Human activities cause nutrient increase, which increase the competitive capacity of B. frondosa to B. tripartita, and then improved the exotic species invasion.