Quercus (oak) is a dominant genus in many forest ecosystems across the United States that contribute vital ecosystem services through water and nutrient cycling. The recent decline of Quercus, largely due to fire suppression and forest mesophication, has the potential to alter forest hydrological and biogeochemical cycling. Given the prevalence, persistence, and diversity of Quercus crowns in forest ecosystems, it is likely that this species strongly mediates nutrient cycling when present. The objective of this study was to (1) quantify canopy-derived nutrients contributed to forest ecosystems and (2) determine interspecific temporal distribution of Quercus leaf fall in a Quercus-Carya forest in Mississippi. Beginning in Fall 2014, throughfall quantity and chemistry were sampled during individual storm events under four Quercus species and two non-Quercus (Carya) species. During Fall 2014 and 2015, canopy litterfall was collected weekly to quantify changes in leaf area index (LAI) and timing of species-specific leaf fall rates. After leaf fall, leaf litter was sampled weekly from the forest floor to quantify biogeochemical changes in the litter layer.
Results/Conclusions
Throughfall volumetric flux was altered by seasonal changes in vegetative cover rather than interspecific differences between species. Ion concentrations were generally higher during the growing season. Throughfall ion and dissolved organic carbon (DOC) concentrations were significantly higher than precipitation suggesting the importance of deciduous foliage in modifying precipitation chemistry. Slower leaf loss in Quercus species has the potential to increase ion concentrations during leaf fall. Higher C:N ratios and slower decay rates in Quercus litter indicate a slower nutrient release throughout the dormant and growing seasons. The results of this study indicate Quercus as an important contributor to forest hydrology and nutrient cycling. Further investigation should be done to reveal the ecological significance of Quercus to forest health.