How Does Whole-Ecosystem Warming Alter Plant Fine-Root and Fungal Mycelium Dynamics in a Boreal Peat Bog?

Abstract:

Soil fungi influence the storage of carbon in peat soils of the boreal landscape. Thus, their responses to climate change must be understood to quantify the future contribution of boreal peatlands to global climate regulation. We peered into the unseen belowground world of a peat bog using first of its kind, high-resolution minirhizotron technology. Our goal was to capture the response of plant fine-root and fungal mycelium dynamics to elevated temperatures after 4 to 6 years of whole-ecosystem warming and exposure to elevated carbon dioxide concentrations in the Spruce and Peatland Responses Under Changing Environments experiment (northern Minnesota). We show that whole-ecosystem warming has changed the abundance of vascular plant fine roots and altered the morphology of fungal mycelium. In particular, warming has increased ericaceous shrub root and fungal rhizomorph abundance, but decreased the abundance of tree fine roots, ectomycorrhizas and fungal hyphae. Warming has also extended the belowground active season by 62 days and increased root and fungal growth. Ericaceous shrubs and trees may have shifted their soil resource acquisition strategies with warming: shrubs appeared to rely more on fine roots while trees appeared to rely more on costly fungal rhizomorphs. Alterations in the functional composition of fungal communities and lengthening of belowground activity in a warmer future may reduce long-term carbon storage while potentially aggravating the impact of climate changes on boreal peatlands.