Midwestern forests are currently invaded by the insect emerald ash borer (EAB, Agrilus planipennis) and the shrub Amur honeysuckle (Lonicera maackii). EAB induced loss of the once prominent ash (Fraxinus spp.) trees coupled with the gain of honeysuckle is changing understory plant composition and likely altering forest nutrient cycling. While plant responses to invasive species have been largely explored, few have investigated effects on microbial processes such as changes in fungal driven decomposition due to variation in available leaf litter. To assess these changes, we ran two independent 100-day decomposition culture experiments (monoculture and plates diluted 50:50 with native litter and L. maackii litter). Three fungal guilds (brown rot, white rot and ectomycorrhizal) were cultured on Acer spp., Quercus spp., F. americana, F. nigra, F. pennslycanica, F. quadrangulata, Lindera benzoin, and L. maackii litter as a representation of common species within Midwestern forests. Individual monocultures contained a single litter species and a single fungal guild totaling 24 treatments (7 replicates: n = 168). Dilution cultures consisted of L. maackii with Acer spp., Quercus spp., and L. benzoin with a single fungal guild for 9 treatments (7 replicates: n = 63). We measured fungal hyphal growth, litter decay rate, fungal biomass.
Results/Conclusions
In monoculture, L. maackii had the fastest decomposition rate (~2 times faster, P < 0.0001) followed by Fraxinus spp., Quercus spp., L. benzoin and Acer spp. In dilution cultures, L. maackii increased decomposition rates ~1.5 times faster than compared to monocultures of the corresponding individual litter species (L. benzoin, P < 0.0001; Quercus spp., P < 0.0001; and Acer spp., P < 0.0001). Of the three fungal guilds, litter with brown rot had the slowest decay rate across litter species. Litter with Ectomycorrhizal (ECM) fungi and white rot fungi had faster decay rates, although they were not different from each other (P < 0.0001). Brown rot fungi had the fastest hyphal growth rate at ~1.15 times faster growth than white rot and ~1.44 times faster growth than ECM (P < 0.0001). White rot fungi had the largest fungal biomass at ~ 2.5 times greater than brown rot and ~2.67 times greater than ECM (P < 0.0001). Each fungal guild produced higher overall biomass on each dilution culture than the respective monoculture of each native species. These results suggest that L. maackii causes an increased litter decay rate that is possibly driven by an increase in fungal growth across fungal guilds.