Exploring Quercus rubra seedling growth under manipulated soil conditions

Background/Question/Methods

Global change is altering forests composition and productivity and thus litter inputs both above and belowground. Over time, these changes in leaf and root inputs will change the soil environment and thus impact seedling growth. To assess how long-term soil litter manipulations will affect future seedling growth, we grew Quercus rubra seedlings in four soil treatments from a 20 year Detrital Inputs and Removal Treatments (DIRT) soil manipulation experiment located at the University of Michigan Biological Station (45.5587° N, 84.6775 ° W). To explore how litter inputs shape seedling growth, we collected soil from four of the DIRT treatments: control (no litter manipulation) exclusion of both above and belowground litter input, exclusion of aboveground litter input, and exclusion of belowground litter input. We grew 75 seedlings per treatment for 60 days after which we harvested above and belowground biomass.

Results/Conclusions

Overall, we found that there was 27% more seedling biomass (above and belowground) in the aboveground litter exclusion treatment than the total litter exclusion treatment. Further, there was 32% more aboveground seedling biomass in the belowground litter exclusion treatment than the total litter exclusion treatment. We similarly found differences in soil nutrients; both ammonium and nitrate concentrations varied across soil treatments, notably between the belowground litter exclusion treatments compared to other treatments. Legacy soil effects from long-term litter manipulations affect seedling growth, and seedlings reciprocally affect soil nutrients – these results illustrate an intimate connection between forest composition and litter inputs both above and belowground which will become increasingly important for future forest trajectories.