Plant-fungal symbiosis affects litter decomposition during primary succession

Microbial symbionts of plants can affect decomposition by altering the quality or quantity of host plant tissue (substrate) or the micro-environment where decomposition occurs (conditioning). In C3 grasses, foliar fungal endophytes (Clavicipitaceae) can increase plant resistance to drought and/or produce alkaloids that reduce herbivory – effects that may also influence host litter composition and subsequent litter decomposition. We studied the effect of the endophyte Epichloë sp. on litter decomposition in the Great Lakes dunes (USA) using a reciprocal design altering endophyte presence/absence in both American beachgrass Ammophila breviligulata substrate (litter bags) and its conditioning of the decomposition microenvironment. Symbiont treatments were crossed with rain-out shelters that altered growing season precipitation. The first year of decomposition, senesced leaf substrate from A. breviligulata with Epichloë decomposed 21% faster than endophyte-free substrate. By the third year,...