Plant–microbial interactions facilitate grassland species coexistence at the community level

Abstract

Interspecific competition and plant–soil feedbacks are powerful drivers of plant community structure. However, across a range of edaphic conditions the interactive effects of these drivers on complex plant communities remain unclear. For example, plant–soil feedback studies focus on soil trained by a single plant species. We developed a method to assess effects of plant–microbial interactions (PMI) on a complex plant community. We established mesocosms with 13 grassland species, grown individually or together, in overgrazed or restored soil, with or without soil microbial inoculum collected from a productive and diverse native grassland. We assessed biomass production as influenced by edaphic conditions, interspecific competition and PMI. Furthermore, we assessed potential influences of interspecific competition and edaphic conditions on strength and direction of PMI. Our results indicate PMI drives negative growth responses for graminoids while forbs experience positive growth responses. Generally, interspecific competition did not alter the magnitude or direction of PMI‐mediated growth responses. Edaphic conditions altered the influence of soil microbial communities on individual plant growth while PMI facilitated plant evenness. In plant community mesocosms, PMI‐associated benefits were observed in overgrazed soil. However, interspecific competition overwhelmed plant growth benefits associated with soil microbial communities when plant communities were grown in restored soil. In mesocosms containing dominant grass species, interspecific competition had negative effects on species coexistence, but both positive and negative PMI partially counterbalanced this influence on plant species evenness. Understanding these mechanisms may improve our capacity to manage diverse and productive grasslands by enabling prediction of plant community composition following disturbance and subsequent restoration.

AM fungi and pathogen dissimilarity predicting plant-microbial interactions strength in graminoids and forbs

“…At the level of plant functional group, forbs suffered a more pronounced positive PMI compared to graminoids. This phenomenon could be attributed to the absence of speci c pathogen that target forbs in the soil, as well as the relatively weaker nutrient competition ability of forbs (Li et al 2020), which result in a greater reliance on mutualistic microorganisms for nutritional support.…”

“…The inoculation soil was collected from restored grassland. The restored soil exhibited relatively higher soil nutrient levels compared to the overgrazed soil (Li et al 2020). All soils were excavated from the top 20 cm, and the substrate soil and the inoculum soil used as controls were sterilized in an autoclave (120 min, 121°C, 103 kPa).…”

“…The experiments described here are based on our previous study (Li et al 2020). We selected 13 grass species (4 graminoids and 9 forbs) commonly found in the steppe of China, with Leymus chinensis as the dominant species.…”

“…Positive PSF occurs when plants perform better in soils conditioned by themselves vs another species or sterilized soil, and negative PSF occurs if plants in uence soil communities to suppress conspeci c plants (Bever 2003). Positive and negative PSF are commonly linked to plant species co-existence, since dominant plants in a stable community often suffer from negative PSF, while other rare species bene t from positive plant-soil microbial feedbacks (Li et al 2020). In PSF framework, symbionts, enemies and decomposers are considered as the main biotic mechanisms of PSF effects (van der Putten et al 2016).…”

Assessing soil microbes that drive fairy ring patterns in temperate semiarid grasslands

“…Numerous biotic or microbial-induced abiotic changes likely drive fairy ring dynamics, such as soil physical, chemical, and/or biological properties; however, these complex interactions have not been disentangled in controlled studies. Plant–microbial interactions (PMI) have received substantial attention in recent decades [ 14 ], and soil inoculation methods used in PMI experiments can help elucidate soil biotic and abiotic factors contributing to fairy ring dynamics. We utilized these controlled experimental methods to gain insight into grassland fairy ring patterns observed in the field.…”