Extreme drought or heavy rainfall drives plant-soil feedbacks of range-shifting and congeneric native plant species

One of the consequences of climate change is the frequency of extreme weather incidences, such as extreme drought or heavy rainfall increase. At the same time, climate warming enables certain plant species to expand to higher latitudes. The question is how the frequency of extreme drought or heavy rainfall affects plant-soil interactions of range-shifting plants in the new habitat compared to native residents. We conducted an outdoor mesocosm experiment to study how an extreme drought influenced biomass production of range-shifting and co-occurring congenetic native plant communities in the next year by plant-soil feedback. We found that in soils with a history of extreme drought range-shifting plants produced more shoot biomass. To explore mechanisms in more detail, we set up a greenhouse experiment to condition soils under extreme drought and heavy rainfall. Then, we tested plant-soil feedbacks using Centaurea jacea as native and Centaurea stoebe as range expander. Our results showed during soil conditioning under extreme drought the shoot biomass was decreased, and under extreme wet conditions was increased. This applied to both range expander and native species. At the same time, soil N, P, and K and soil microbial communities had changed in a different manner. Consequently, these soil biotic and abiotic changes might be the main drivers of negative, neutral, positive plant-soil feedbacks of range expanders and natives under extreme weather events, with an impact on plant quality changes and plant-associated herbivore responses. Thus, we show that climate change may influence both plant biomass and aboveground herbivory through altering plant-soil biota interactions.