Seed germination niche for common ragweed (Ambrosia artemisiifolia L.) populations naturalized in Turkey

Common ragweed (Ambrosia artemisiifolia L.) is an invasive species, and is currently spread in different habitats over several regions in Turkey. However, no information exists on the seed germination biology of Turkish populations. Therefore, the seed germination niche (upper and lower limits of environmental conditions for seed germination) was determined for common ragweed populations in two climatic regions (Thrace and Black Sea) of Turkey. Seed germination was evaluated under different photoperiods, constant temperatures and levels of water stress, salinity and pH. Seedling emergence was recorded from various seed burial depths. Significant differences were observed among populations for the seed germination niche and seedling emergence. Seed germination niche helps explain the occurrence of the species in the diverse environmental conditions found across Turkey. Seeds from the Thrace populations were more tolerant to water and salinity stress and germinated under relatively higher pH levels than those from the Black Sea populations. Further, seeds from the Thrace region germinated to higher percentages at all temperatures than those from the Black Sea populations. Seeds from all populations germinated to higher percentages in light/dark than in dark. Seedling emergence was significantly retarded by a seed burial depth > 4 cm. The results suggest that the species has extensive range expansion potential in the country and that immediate management of the naturalized populations is needed. In agricultural habitats, the species can be managed by shallow tillage and subsequent management of emerging seedlings to reduce the soil seed bank. Management strategies such as appropriate mowing time and mowing frequency need to be developed for control of roadside populations.