Litter Decomposition and Nitrogen Fluxes Following Fertilization and Rainfall Exclusion Treatments.

Forest litter has been shown to be both a source and sink for carbon and nitrogen in pine plantations at different points within a rotation. Major factors that have been correlated to litter decomposition include sun light, temperature, moisture, and litter nutrient status. In this experiment, three meter by three meter throughfall excluders were constructed using ten centimeter wide troughs evenly spaced to cover thirty percent of the ground area. These excluders were installed in the treated buffer of the control and fertilized treatments of the Virginia Fertilization by Throughfall Exclusion Experiment. Under each excluder and in the adjacent buffer area, twenty-one 10 cm by 25 cm litter bags were filled with 14g each of both brown litter collected in litter traps during the Fall of 2013 and green litter collected from live branches from each treatment in the main experiment. Three litter bags with each tissue type will be collected at installation, 2, 4, 6, 8, 12 and 18 months. Mass loss and nutrient content will be determined after each collection. In addition, brown litter and green foliage from trees that were grown after fertilization with 15N enriched urea fertilizer were placed in one meter square sub-plots adjacent to the litter decomposition bags. We will sample soil 0 - 5 cm and 5 – 10 cm depths as well as litter and duff after one year to attempt to track where 15N enriched nitrogen is being transported. Our hypotheses include: 1) Green foliage will decompose at a faster rate due to more favorable C:N ratio. 2) Decomposition rates will be slower under throughfall exclusion due to lower moisture and light levels. 3) 15N enriched tissue will provide a viable means for tracking nitrogen dynamics in this system.