Effects of Intra- and Interspecific Plant Density on Rhizosphere Bacterial Communities

Abstract

There have been very few studies on the effects of plant competition on the rhizosphere bacterial community. To investigate the impacts of intra-and interspecific plant competition, we analyzed the responses of rhizosphere bacterial communities to plant density as determined by 16S rRNA gene targeted sequencing. We included five weedy plant species growing in field soil in monocultures and mixed cultures at three densities in a greenhouse experiment. The rhizosphere bacterial community of each species changed more with density in a mixture of all five plant species than in monocultures, so intra-and interspecific plant competition had different effects on the bacterial community. For the dominant plant competitor, Centaurea cyanus, neither intra-nor interspecific competition had major effects on the composition of its rhizosphere bacterial communities. In contrast, the bacterial communities of the weakest competitor, Trifolium repens, were affected differently by intra-and interspecific competition. During increasing intraspecific competition T. repens maintained a highly specialized bacterial community dominated by Rhizobium; while during interspecific competition, the relative abundance of Rhizobium declined while other nitrogen fixing and potentially plant growth promoting taxa became more abundant. Contrary to previous observations made for soil microbial communities, the bacterial rhizosphere community of the weakest competitor did not become more similar to that of the dominant species. Thus, the process of competition, as well as the plant species themselves, determined the rhizosphere bacterial community. Our results emphasize the role of plant-plant interactions for rhizosphere bacterial communities. These effects may feedback to affect plant-plant interactions, and this is an important hypothesis for future research.

Influence of Peanut, Sorghum, and Soil Salinity on Microbial Community Composition in Interspecific Interaction Zone

“…Mixed cultivation can significantly impact the soil microbial communities, and the interaction across host plant species plays a major role in shaping the soil microbial communities by modifying the rhizosphere microenvironment ( Wahbi et al, 2016 ; Cavalieri et al, 2020 ). Due to the differences in the root system architecture and exudates of different plant species, the impact of shaping microbial communities in II also differs.…”

“…In the intercropping system, roots of different types of plants are in direct contact with the soil, and they directly or indirectly affect the development of soil microbiota in the rhizosphere and in bulk soil by means of root exudates ( Haichar et al, 2014 ). In addition, interspecific root interaction can create a relatively stable microhabitat through resource competition and mutual promotions ( Aguilera et al, 2017 ; Cavalieri et al, 2020 ). The beneficial soil eco-quality and ecosystem services in the intercropping model are mainly driven by soil microbial activities ( Granzow et al, 2017 ; Nivelle et al, 2018 ).…”

Invasive grass dominance over native forbs is linked to shifts in the bacterial rhizosphere microbiome

“…Forbs also contributed a higher percentage of ASVs from this family to the joint grass-forb rhizosphere microbiome, further supporting close associations between native forbs and this group. Invasive grass dominance may therefore be partially due to a decrease in locally adapted microbes similar to Cavalieri et al [31].…”

“…Conversely, competition with a novel plant, such as an invader, may bring resident plants into contact with novel pathogens [30]. These competitive interactions can lead to the loss of specialized microbes in the inferior competitor [31] and drive the resulting microbial community to resemble that of the dominant competitor [18,19]. Furthermore, microbial community changes can feed back to affect plant competitive ability [19], with the potential to drive either coexistence or exclusion [32].…”

“…Plants may also indirectly compete for beneficial plant-growth-promoting microbes [7,27,28] or come into contact with novel pathogens through competition with a novel plant, such as an invader [29]. These interactions can lead to the loss of specialized microbes in the inferior competitor [30] and drive the resulting microbial community to resemble that of the dominant competitor [18,19]. Shifts in the microbiome are a potentially important contributor to the dominance of invasive plants.…”