PARENT SESSION
Wednesday, August 9, 5:00-6:30 pm
Poster Session 18 - Forest ecology and management
Exhibit Hall, Ballroom Level, Cook Convention Center
The role of fungi in movement of nitrogen within leaf litter mixtures.
Gartner, Tracy*,1, 2, Treseder, Kathleen2, Mack, Michelle3, 1 Carthage College, Kenosha, WI2 University of California, Irvine, Irvine, CA3 University of Florida, Gainesville, FL
ABSTRACT- Leaves from many different species mix together on the forest floor in natural ecosystems, and many recent experiments have shown that decomposition rates may be altered as a result of mixing a variety of leaf types. One of the dominant hypotheses for why decomposition rates change in leaf mixtures is that nitrogen could be transferred from litter types that contain high amounts of nitrogen to adjacent litter that has little nitrogen. Such a transfer of nitrogen, which would result in overall increases in decomposition rates, could be mediated by water films between the litter types or by fungal hyphae connecting the litter. Here, we present the results of an experiment designed to test whether transfer of nitrogen actually occurs in litter mixtures and to assess the importance of the presence of fungal hyphae for this process. Using litterbags and microcosms containing Festuca altaica (grass) labeled with 15N (mean delta N = 150) and Vaccinium vitis-idaea (cranberry) with natural abundance nitrogen levels (mean delta N = -3), we observed that levels of 15N increased in the cranberry and decreased in the grass when the two leaf types were mixed. This supports the hypothesis of nitrogen transfer; however, significant transfer only occurred when fungal hyphae were present. Therefore, nutrient transfer as a mechanism for changes in decomposition may be important as fungal hyphae establish later in the decomposition process. Improving our understanding of the mechanisms involved in interactions among adjacent litter will greatly enhance our ability to predict carbon fluxes and nutrient dynamics at larger spatial scales.
Key words: litter mixtures, decomposition, boreal forests