BayCEER Workshop 2021

Long-term soil warming alters fine root dynamics and morphology, and their ectomycorrhizal fungal community in a temperate forest soil

Climate warming is predicted to affect temperate forests severely, but the response of fine roots, key to plant nutrition, water uptake, soil carbon and nutrient cycling is unclear. Understanding how fine roots will respond to increasing temperature is a prerequisite for predicting the functioning of forests in a warmer climate. We assessed the response of fine roots and colonizing ectomycorrhizal (EcM) fungal and root-associated bacterial communities to soil warming by 4 °C in a forest soil in the Austrian Limestone Alps after 8 and 14 years of soil warming, respectively. Fine root biomass and fine root production were 17% and 128% higher in the warmed plots after 14 years, respectively. The increase in fine root biomass (13%) was not significant after 8 years of treatment, whereas specific root length, specific root area, and the number of root tips increased in warmed plots at both sampling occasions. Soil warming did not affect EcM exploration types and diversity, but changed their community composition, with an increase in the relative abundance of Cenococum at 0 – 10 cm soil depth, a drought-stress tolerant genus, and an increase in short and long-distance exploration types like Sebacina and Boletus at 10 – 20 cm soil depth. Warming increased the root-associated bacterial diversity but did not affect their community composition. Soil warming did not affect nutrient concentrations of fine roots, but there was an indication of limited phosphorus (P) and potassium (K) availability in the soil. Our findings suggest that, in the studied ecosystem, global warming could persistently increase fine root growth as well as biomass, and could simultaneously alter fine root morphology and EcM fungal community composition towards improved nutrient forage. Increased carbon input by higher fine root production has the potential to partially offset the warming-induced carbon losses by enhanced carbon mineralization.