Soil biota and chemical interactions promote co‐existence in co‐evolved grassland communities

Abstract

1. Plant populations can exhibit local adaptation to their abiotic environment, such as climate and soil properties, as well as biotic components such as the chemical signatures of dominant plant species and mutualistic and pathogenic microbial populations. While patterns of local adaptation in individual species are widely recorded, the importance of microevolutionary processes for plant community assembly and function is poorly understood.2. Here, we examined how a history of long-term co-existence, and thus potential for local co-adaptation, influenced the process of plant community assembly.Soil inocula and seeds of eight plant species were collected from three calcareous grasslands with a long history of grazing within a single geographical region.Mesocosm communities were established using local genotypes from a single site or an artificial mixture of genotypes from two different sites. To investigate the role of root exudates and local ('home') and non-local ('away') soil biota as mediators of plant species co-existence, the population origin treatment was combined with the addition of activated carbon, which is known to adsorb exudates from soil, and sterilization of soil inocula. Individual-, species-and mesocosm-level responses were measured over the course of three growing seasons.3. We found that root exudates promoted seedling survival, species co-existence and productivity in assemblages of genotypes originating from the same community but had a weak impact in mixed, novel communities. Soil biota promoted the growth of subordinate forbs and restrained the growth of dominant graminoids, particularly in communities composed of local genotypes. The effects of population origin were significant in the first 2 years of the experiment but were not detectable in the third year when interbreeding and new seedling establishment took place. Plant genotypes coupled with 'home' microbial inoculum experienced a stronger reduction in growth compared with genotypes exposed to 'away' inoculum, indicating that plants experienced home-field disadvantage in interactions with soil biota. Synthesis.Our study demonstrates that the mechanisms of initial grassland community assembly depend on community history, with below-ground chemical 2612 | Journal of Ecology SEMCHENKO Et al.

Soil chemical legacies trigger species-specific and context-dependent root responses in later arriving plants

“…Our findings reveal that the modification of the composition of the rhizosphere metabolome by early species can create historical contingency effects that affect root foraging by later arrivers in a species-specific and contextdependent manner. Our results contribute to current scientific knowledge showing that soil chemical cues can mediate plant-plant interactions and affect species coexistence (Delory et al, 2016;Semchenko et al, 2019). Fig.…”

Plant community composition steers grassland vegetation via soil legacy effects

“…This microbial signature can remain as a legacy in the soil after the plant is gone, and in turn affect other plants growing later in the same soil (Kulmatiski et al 2008; Van der Putten et al 2013; Teste et al 2017; Eppinga et al 2018). It is often speculated that soil legacy effects created by plants play an important role in regulating plant community dynamics and plant coexistence (Lekberg et al 2018; Semchenko et al 2019). It was recently shown that inoculation of soils with biotic legacies can change plant community development under natural conditions (Wubs et al 2016; Wubs et al 2019).…”

Stability of species and provenance performance when translocated into different community assemblages

“…Studies focusing on plant interactions include the role that species mixtures and nurse effects play in building complex ecosystems (Padilla & Pugnaire ; Bucharova et al ), including age trends in interactions transiting from facilitation to competition (Forrester et al ). At the provenance level, locally co‐evolved neighboring plants can mutually benefit each other in terms of survival and performance when growing in close proximity, taking advantage of sympatric interactions (Grady et al ; Semchenko et al ). Even within provenances of the same species, “social” interactions among plants may have a genetic basis (referred to as indirect genetic effects), and can affect the performance of neighboring plants through, for example, competition and disease spread (Costa e Silva et al ).…”