Is there local adaptation in plant species to soil reaction? A lesson from a multispecies experiment

Abstract

Seed sourcing for restoration measures is a currently highly debated issue in conservation ecology. Where to take the seeds from, if reintroduction of plant species is necessary? In many countries, seed transfer zones have been defined to preserve genetic variability and to provide locally adapted plants. However, delineation of seed transfer zones mostly relies on climatic gradients, ignoring other abiotic factors, such as bedrock and soil conditions. One of the main soil properties is soil reaction (pH), yet it is still unclear whether pH is an important driver for local adaptation in plants. In this study, we tested whether plants are adapted to soil reaction across five common grassland species. For each species, we sampled seeds from two provenances, and within each provenance from two populations—one coming from basic and one from acidic soil. We grew the plants in a common garden in an artificial substrate with manipulated pH, which allowed us to test for the effect of soil reaction, isolated from other soil properties. All species produced more biomass on acidic substrate, in most cases independently of their original soil and provenance. Only one out of five species showed weak local adaptation to soil reaction. The experimental substrate by far explained most of the biomass production in all species. This suggests that adaptation to soil reaction is rare and of low importance in common species of temperate grasslands.