Drought legacy influences plant invasion through plant-soil feedback dependent on the origin and lifespan of conditioning species

Alien plant invasion is one of the key factors of global change. Soil legacies from previous plant species can affect the alien plants that are later introduced. Moreover, it is suggested that drought, as a common environmental factor, often influences plant-soil interactions. However, little is known about how drought and plant-soil feedback jointly affect the growth of subsequent alien and native plants of different lifespans.

We conducted a two-phase plant-soil feedback experiment. Firstly, we conditioned the soil using each of the 32 species (eight native annuals, eight native perennials, eight alien annuals and eight alien perennials) with or without drought treatment. Thereafter, each of 20 species were grown on their conspecific and heterospecific soils to test the various soil-legacy effects.

Plants grew better in soil with heterospecific legacies than with conspecific legacies. The alien and perennial plants exhibited superior growth compared to the native and annual plants. Alien perennials achieved the relatively best growth in drought-treated soils compared to all other plant species. Moreover, perennial plants were less negatively affected than annuals when grown on drought-treated soils conditioned by native species, particularly by native perennials.

Our study suggests that alien perennials have an advantage in coping with the negative effects of complex soil legacies. This may accelerate the invasion process of communities and ecosystems dominated by perennials with drought conditions.