Soil mutualisms potentially determine the reintroduction outcome of an endangered legume

Abstract

Successful recovery of populations of endangered plant species requires conservation of existing populations as well as the creation of new populations through reintroduction. However, the ecological requirements of many rare plant species are poorly understood, and many reintroduced populations are unable to survive long term. Effective reintroduction of rare plants, such as the federally endangered Astragalus bibullatus, may depend on developing a greater understanding of the symbiotic relationships that these rare species form with the soil microbiome, as well as determining whether these are species-and site-specific. We inoculated seedlings of A. bibullatus, its more widespread congener A. tennesseensis, and the common grass Schizachyrium scoparium, with soil biota collected from five glade sites where A. bibullatus is historically present (HP) and four glade sites where the species is historically absent (HA). We examined the impacts of soil microbes from HP and HA glade sites as well as from each species on the growth, arbuscular mycorrhizal fungi (AMF) colonization, and formation of root nodules of A. bibullatus and its congener A. tennesseensis. Astragalus bibullatus grew significantly larger when grown in soil from HP glade sites compared to its growth in soil from HA glade sites. Astragalus bibullatus also formed significantly more root nodules when grown in HP soil, but no difference was detected in AMF colonization based on glade history. Our findings suggest that the successful establishment of rare plant species may depend on species-specific associations with soil mutualists such as nitrogenfixing rhizobial bacteria and should consider whether essential microbes are present.

Does restoration of plant diversity trigger concomitant soil microbiome changes in dryland ecosystems?

“…removing unwanted plants) is less effective in achieving restoration goals than targeted microbiome restoration (e.g. removing topsoil; Resch et al., 2021), or even that the lack of essential soil micro‐organisms might deter successful plant establishment (Becknell et al., 2021; Koziol & Bever, 2017). Moreover, other studies have attempted unsuccessfully to predict soil microbial diversity and composition as a function of plant species composition and plant functional traits (Barberán et al., 2015; Prober et al., 2015).…”

“…cheatgrass changed microbial community composition within 2 years; Belnap & Phillips, 2001) gain advantages in early establishment. In contrast, the reintroduction of late successional plants often failed unless certain microbial symbionts were inoculated (Becknell et al, 2021;Koziol & Bever, 2017). Thus, targeted microbiome restoration should be considered to improve revegetation outcomes if the revegetated plants are unlikely to be well established before the concomitant changes in soil microbiome are completed.…”

Microbiome transfer from native to invasive species may increase invasion risk and shorten invasion lag

“…In the previous section, we have already discussed how the presence of native mycorrhizal fungi in the soil may facilitate the establishment of newly introduced plants (Dickie et al, 2017; Becknell et al, 2021; Parepa et al, 2013). Experimental work is in progress to explore how specific microbiome can contribute not only to soil health and plant fitness, but also to animal reproductive success and in increasing their resilience against environmental stress (Peixoto et al, 2021; Comizzoli and Power, 2019), uncovering promising new venues for the successful management of reintroduced populations (Trevelline et al, 2019; Redford et al, 2012; Bahrndorff et al, 2016).…”