Nitrogen Influence to the Independent Invasion and the Co-Invasion of Solidago canadensis and Conyza canadensis via Intensified Allelopathy
The allelopathy of alien plants is critical to their successful invasion. In nature, two alien plants can co-invade the same habitat. Changes in the forms of nitrogen may have the potential to alter the invasion process of alien plants by causing alterations in their allelopathy. This study aimed to evaluate the individual and combined allelopathy of two alien plants from theAsteraceaefamily,Solidago canadensisL. andConyza canadensis(L.) Cronq. This study examined the effects of aqueous leaf extracts of the two alien plants with different nitrogen forms (NO3−N, NH4−N, and CO(NH2)2−N, and the mixed nitrogen forms at a 1:1:1 ratio) on the seed germination and seedling growth of the horticulturalAsteraceaespeciesLactuca sativaL. using a germination bioassay. The allelopathy of the two alien plants significantly reduced the seed germination and seedling growth ofL. sativa. Extracts fromS. canadensisproduced stronger allelopathy on the seed germination and seedling growth ofL. sativacompared with those fromC. canadensis. The mixture of extracts from the two alien plants produced an antagonistic effect when compared with the effects of extracts from each plant species. The addition of nitrogen intensified the allelopathy of the two alien plants on the seed germination and seedling growth ofL. sativa. The degree of influence of nitrogen on the individual and combined allelopathy of the two alien plants was similar. Thus, nitrogen deposition may facilitate the independent invasion and co-invasion of the two alien plants via intensified allelopathy.Keywords:alien plant;allelochemicals;aqueous leaf extracts;nitrogen deposition;Lactuca sativaL.
危险品化学品经营许可证（带存储）