Responses of native and invasive woody seedlings to combined competition and drought are species-specific

A greenhouse experiment was conducted to evaluate the effects of drought on the interactions between native and invasive tree species. Organic and inorganic net N uptake capacity and total soluble protein as well as total soluable amino acid contents were quantified in leaves and fine roots of the native species Fagus sylvatica L., Quercus robur L. and Pinus sylvestris L.) and the invasive species Prunus serotina Ehrh. and Robinia pseudoacacia L.. We used a fully orthogonal design with the factors ´water availability´ (i.e. control or drought) and ´competitor´ (i.e. interspecific competition with two or three different competitors). For each species combination, half of the pots did not receive any irrigation for the duration of the experiment, while the other half was watered with tap water every second day. Organic and inorganic net N uptake capacity was quantified using 15N/13C, N metabolites were quantified photometrically. Growth was reduced as a result of competition. Inorganic an...