"Soaked in rainwater" effect of Ageratina adenophora on seedling growth and development of native tree species in Nepal.
Ageratina adenophora is considered as one of the most problematic invasive species spreading worldwide and replacing native vegetation. There is hardly any information of its effect on native dominant tree species. Many tests on its effect on native vegetation have used crushed and ground leaves to estimate chemical inhibition. The grinding affects the chemical composition and leads to exposure that does not exist on soil surface. To avoid these disadvantages, we simulated soaking of A. adenophora leaves in rainwater as it happens in nature at times of native tree seed germination in Nepal. Seedlings of two native trees (Schima wallichii and Alnus nepalensis) were exposed to entire A. adenophora leaves or extract made from the entire leaves in pots containing native soil. Seedling length and dry weight were inhibited by A. adenophora fresh leaves and leaf extract. The effects remained over the 7-12 weeks exposure periods. In conclusion, A. adenophora leaves can suppress growth of these native tree species. This may create problems in the establishment and survival of the native tree seedlings in invaded areas.