Temporal dynamics of range-expander and congeneric native plant responses during and after extreme drought events

Current climate change causes range shifts of many species to higher latitudes and altitudes, and enhances their exposure to extreme weather events. It has been shown that range shifting plant species may perform differently in the new soil than related natives, however, little is known about how extreme weather events influence range-shifting plants compared to related natives. Here, we used outdoor mesocosms to study how range-shifting plant species respond to extreme drought in live soil from a habitat in the new range with and without live soil from a habitat in the original range. During summer drought, shoot biomass of the range-expanders was reduced. In spite of this, in the mixed community range-expanders produced more shoot biomass than congeneric natives. In mesocosms with a history of range-expanders in the previous year, native plants produced less biomass. Plant legacy or soil origin effects did not change the response of natives or range-expanders to summer drought. During rewetting, range-expanders had less biomass than congeneric natives, but had higher drought resilience (survival) in soils from the new range where in the previous year native plant species had grown. The biomass patterns of the mixed plant communities were dominated by Centaurea species, however, not all plant species within the groups of natives and of range expanders showed the general pattern. Drought reduced litter decomposition, microbial biomass and abundances of bacterivorous, fungivorous and carnivorous nematodes. Their abundances recovered during rewetting. There was less microbial biomass, fungal biomass and there were fewer fungivorous nematodes in soils from the original range (Hungary) where range-expanders had grown in the previous year. We conclude that in mixed plant communities of range-expanders and congeneric natives, range-expanders performed better, both under ambient and drought conditions, than congeneric natives. However, when considering the responses of individual species, we observed variations among couples of congenerics, so that under the present-mixed community-conditions there was no uniformity in responses to drought of range expanders versus congeneric natives. Range-expanding plant species reduced soil fungal biomass and numbers of soil fungivorous nematodes, suggesting that effects of range-expanding plant species can trickle up in the soil food web.Funding provided by: ERC-Advance*Crossref Funder Registry ID: Award Number: 32302