Anthoxanthum odoratum (Poaceae) as a bioindicator of arbuscular mycorrhizal fungi abundance prior to native revegetation on agricultural soils

Abstract

ABSTRACT Mycorrhizal fungi, which form symbiotic associations with plant roots, can be critical to the successful establishment of plants. Up to 90% of land plant species form associations with arbuscular mycorrhizal fungi (AMF), which develop fungal structures inside host roots. Common site preparation practices prior to ecological restoration, such as soil disturbance and herbicide application, may lessen the availability of AMF, potentially jeopardising plant establishment. However, the state of the soil microbiome can be difficult to assess directly. This study examines the potential of the widespread pasture grass Anthoxanthum odoratum (Sweet Vernal, Poaceae) as a bioassay of AMF abundance in soils. We present a rapid clearing and staining protocol for visualising AMF structures in the roots of A. odoratum. We then compare % colonisation on roots of naturally established A. odoratum plants collected from undisturbed pastures vs. sprayed and tilled pastures. Roots of A. odoratum collected from sprayed and tilled pastures showed a significantly lower average AMF colonisation at 43.8% compared with 57.6% on roots from undisturbed pastures. However, all plants sourced from the sprayed and tilled pastures still showed some AMF structures. Our results strongly suggest that A. odoratum can be a useful bioindicator of AMF presence and abundance in soils, offering a promising tool for seed-based restoration on retired agricultural land.