Post-fire Quercus alba fitness in a stressed plant community

Prescribed burns are widely used for managing North American deciduous forests due to their ability to positively affect plant community structure and composition. This study examines the effects of neighboring herbaceous plants on the recruitment of Quercus alba (white oak) seedlings in fire-managed parts of Shawnee National Forest (Illinois, USA). Herbs were clipped to induce plant community stress and relative growth rates (RGRs) of planted white oak seedlings were assessed to determine if a competitive or facilitative dynamic is present. In addition to RGR, we observed the mycorrhizal network via fungal colonization in mesh bags to quantify belowground activity for our experimental plots. Our results supported fires positive effects on tree recruitment and herbaceous growth. Clipping combined with fire management decreased RGR. This finding suggests that a facilitative dynamic is at play and herbaceous neighbors help white oak seedlings persist due to protection from environmental stressors (p = 0.017). Soil moisture played a large role in promoting tree fitness on each of our sites. Lower hyphal biomass was observed in areas where herbs were clipped. We further speculate that the stress caused by clipping may have suspended or eliminated the need for mycorrhizae to form, possibly due to herb mortality. Knowing how herbs and trees interact will lead to purposeful forest community planning especially in fire-managed forests where herbs are likely to dominate post-prescribed burn.