Soil Microbes Boost Trees' Resilience to Climate Change Stress

Soil microbiota transplanted from more stressful environmental conditions – drought or excessive heat or cold, for example – can enhance tree tolerance to changing climates, researchers report. The findings suggest that management of soil microbiota, especially during forest restorations, could be a valuable strategy for increasing forest resilience to climate change. Climate change is forcing many species outside of their evolved range of environmental tolerances, forcing them to acclimate, adapt, or migrate to avoid extinction. For long-lived sessile plant species like trees, neither adaptation nor migration may happen fast enough to keep up the pace of climate change. However, research shows that diverse assemblages of microbes that live on and around plants, including mycorrhizal fungi in the soil surrounding their roots, can enhance plant tolerance to environmental stress. And since microbial taxa are likely to adapt faster than their host plants and disperse farther, microbial associations may offer an alternative, underappreciated source of plant community resistance to climate change. To evaluate this possibility, Cassandra Allsup and colleagues sampled soil microbial communities from 12 locations in the northern U.S along gradients of temperature and precipitation. In both field and controlled greenhouse experiments, they tested how soil inoculation with these variable microbiotas influenced a tree seedling's ability to tolerate different environmental stresses. Allsup et al. found that soil microbiota that had experience with certain climate stressors were better able to promote tree survival under those specific conditions. For example, microbiota from drier environments were better able to improve drought tolerance in saplings. Inoculated microbe species persisted in the seedling's rhizosphere even after three years of growth. The authors found that microbe-mediated drought tolerance was associated with increased diversity of arbuscular mycorrhizal fungi, while cold tolerance was associated with lower fungal richness. "The findings that stress-experienced microbiomes can ameliorate climate stress raises hope for ecosystem resilience, but a comprehensive gene-to-ecosystem understanding of microbial roles in climate change resilience is needed before active management of soil microbial communities can be taken," writes Michelle Afkhami in a related Perspective.