Characterization of Soil Organic Matter in Planted and Plant-Free Pots with the Use of Lignin Biomarkers.

Inputs of labile organic substrates to soils are commonly associated with elevated soil organic carbon mineralization rates; this process is known as the priming effect. Plant presence and soil conditions (i.e. water regime, nutrient status) are known to be interacting factors governing priming. In this study, we examine the role of differing species, loblolly pine (Pinus taeda L.) and nuttall oak (Quercus texana B.), and moisture regimes (low and high) upon the soil priming effect. We explore whether there is depletion of original soil carbon and concurrent replacement of original carbon through addition of fresh organic matter from the planted tree species. By employing a series of planted and plant-free pots in a greenhouse mesocosm study, we were able to characterize the composition of soil organic matter and its carbon with the use of CuO oxidation products (e.g. lignin, cutin/suberin biomarkers). Carbon was elevated on the low moisture samples relative to all other treatments. The C:N ratio suggests that newly produced plant carbon is replacing original soil carbon. The soil lignin content of the planted treatments was lower than the plant-free treatments suggesting that lignin present in the original soil may have been preferentially degraded by priming.  CuO oxidation products have utility for exploring mechanisms behind preferential replacement of lignin in these soils. Understanding the role of species and soil moisture is important for predicting the response of soil carbon to land use and climate change.

See more from this Division: SSSA Division: Forest, Range & Wildland Soils
See more from this Session: Forest, Range & Wildland Soils: III

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