THE INFLUENCE OF ROCK AND SOIL NUTRIENTS ON THE FOLIAR NUTRIENT RESORPTION EFFICIENCY: A COMPARISON BETWEEN NEW ENGLAND AND VIRGINIA

As forest harvesting needs intensifies, the acquisition and retention of nutrients by trees becomes increasingly important to meet long-term nutritional demands. In this study, we investigate foliar, soil, and rock nutrient pools, and resorption efficiencies among tree genera along lithological gradients in Virginia and New England. We chose three sites in Virginia (MOR, PAC, and BEE) and three sites in New England (COR, SCG, BEF) ranging from high to low nutrient content based on the composition of soil and their parent material. At each site, we replicated three plots each with a radius of 11.3 m, and collected the species at each site, green leaves from dominant tree species, soils from depths 0cm-50cm, rocks, and fall leaf litter. Green leaves and litterfall were digested using nitric and hydrochloric acids, while soils and rocks were totally digested using hydrofluoric acid. The soil exchangeable nutrients were extracted using ammonium chloride. Specifically, we quantified essential macro (Ca, Mg, K, P) and micronutrients (Mn, Ni, Zn) in the soils, rocks, green leaves, and litterfall of each site. We found that nutrient rich sites (MOR and COR) had higher concentrations of Ca, Mg, and P in its soils, while PAC and BEF had the highest amount of K. We found that sites lower in soil nutrients tend to result in lower nutrient concentrations in the greens leaves of trees but higher resorption efficiencies. In addition, sites with lower concentrations of nutrients in its soils had green leaves with higher concentrations nutrients. These results suggest that in nutrient-limited environments, trees may have strategies to conserve nutrients through efficient resorption. Understanding the relationship between soil elements and tree nutrient dynamics is essential for determining effective long-term forest management.