Plant-soil interactions of range-expanding plants

Abstract

In this thesis, I investigated plant-soil interactions of range-expanding plant species. Range-expanding plant species are increasingly present in the Netherlands as a result of climate warming. Similarly to exotic plant species, the arrival of range-expanding plants may alter the composition of microbial communities in the soil, nutrient availability and important ecosystem functions such as decomposition. I show that differences in plant and soil chemistry of range-expanding plants and related natives were linked to plant species identity rather than origin. I found that range-expanding plant species recruited similar bacterial rhizosphere communities as native species when both species are grown in the same soil, and that all communities were functionally similar. However, communities in soils of range-expanding plant species in the field may be different from communities in the soils of native species. Furthermore, I show that in some specific cases range-expanding plant species may benefit from high nutrient availability in the soil and positive plant soil feedbacks from the decomposition of their own litter. Finally, in a mesocosm outdoor experiment I show that plant-soil interactions of range-expanding plants may differ most from natives under climate extreme events such as drought. Overall, the results of my thesis suggest a limited role of plant origin and specialist decomposer communities on indirect plant-soil interactions of range-expanding plant species. While it seems unlikely that range-expanding plant species may alter soil communities and their functioning when compared to congeneric natives species, local effects in the field may need to be quantified.