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Contributed Talk

Session: : Wetlands 2

COS 295-6 - Peat loss collocates with a threshold in plant-mycorrhizal associations in drained peatlands encroached by trees

Thursday, August 10, 2023
2:45 PM – 3:00 PM PDT
Location: E145
Abstract: The response of soil microbial communities is key to a mechanistic understanding of the effects of drainage-induced encroachment by trees on northern peatlands carbon balance.

Here, we profiled the soil fungal community and estimated its genetic potential for lignocellulose decay (class II peroxidase potential) along drainage gradients stretching from interior (undrained, open locations) to ditch (drained, forested locations).

Mycorrhizal fungi dominated the soil fungal community across the gradients. The dominant type of mycorrhizal association abruptly shifted from ericoid to ectomycorrhizal at approximately 120 m from the ditches. This distance corresponded with increased peat loss, from which more than half was attributable to oxidation. The ectomycorrhizal genus Cortinarius dominated at the drained end of the gradients and its higher class II peroxidase potential was positively associated with peat humification and carbon-to-nitrogen ratio.

Our study is consistent with a plant-soil feedback mechanism, driven by a shift in the mycorrhizal type of vegetation, that potentially mediates changes in aerobic decomposition during post-drainage succession. Such feedback may have long-term legacy effects upon post-drainage restoration efforts and implication for tree encroachment onto carbon-rich soils globally.