Rhizosphere microbe populations but not root traits induced by drought in Populus euphratica males

Abstract

How sex-related root traits and soil microbes and their interactions respond to drought remains unclear. Here, we investigated how fine root traits and the composition of rhizosphere microbial communities in Populus euphratica females and males respond to drought in concert in 17-year-old plantations. Females increased specific root length (SRL) in response to drought. However, males showed no changes in their roots but significant increases in arbuscular mycorrhizal hyphal biomass and population of Gram-negative bacteria in the rhizosphere. Also, fungal symbiotroph communities associated with root systems in males differed from those in females under drought. We further demonstrated that the Gram-positive to Gram-negative bacteria ratios positively correlated with the SRL, while fungi to bacteria ratios were negatively correlated. Meanwhile, the relative abundance of symbiotrophs was negatively correlated with the SRL, while saprotroph abundance was positively correlated. Nevertheless, the relative abundance of symbiotrophs was positively correlated with the root carbon content (RCC). These findings indicate that microbial responses to drought depend highly upon the sex of the plant and microbial group and are related to root trait adjustments to drought. This discovery also highlights the role of plant-microbial interactions in the ecosystems of P. euphratica forest plantations. [Figure not available: see fulltext.]