1. Hypotheses Lower elevations have less biomass input compared to upper elevations. Shrubs at lower elevations have higher amounts of Lignin and C:N ratios compared to higher elevations. Soil Sampling Stratified random sampling (three canopy and three Inter canopy areas (Fig.2))of soil in five plots up to 0-30cm (at 0-5, 5-10, 10-20 and 20-30 depth intervals(Fig.3)), at each elevation. Litter Trapping Litter traps (Fig.4) are custom made for the three randomly chosen shrubs within each plot to cover the entire canopy. Litter is collected over a period of one year. Soil Fractionation SOC associated with silt and clay are higher in the degree of stabilization compared to SOC associated with CPOM and FPOM. Percentages of these SOC will be used to determine its stability (labile or recalcitrant (Fig.5)) Laboratory Incubations Temperature sensitivity of SOC decomposition is evaluated via exposure of the soils to a temperature gradient ((15, 20, 25, 30) o C) in controlled (constant soil moisture - 50% water holding capacity) laboratory incubations (Fig.6). Methods Litter Quantity and Quality Collected litter will be measured in terms of concentrations of, biomass total C total N lignin CPOM Recalcitrant SOC Labile SOC ClaySiltFPOM Soil Sample Shrub Litter traps Soil sampling spot (canopy) Soil sampling spot (inter- space) Fig.2 Soil sampling scheme Fig.3 Soil core Fig.6 Laboratory soil incubations Fig.5 Schematic diagram of soil fractionation Fig.4 Litter trap design Soil organic carbon and its temperature sensitivity along an elevational gradient in a semi-arid ecosystem Hasini Delvinne, Kevin Feris, Alejandro Flores, Shawn Benner, Marie-Anne de Graaff Boise State University Background: Semi-arid ecosystems are an important component of the global carbon (C) cycle as they store a significant amount of soil C due to large extents of land. Rising temperatures may alter the amount of soil organic C (SOC) currently stored in these ecosystems. A proper consensus has not yet emerged on the temperature sensitivity of SOC decomposition posing an uncertainty in predicting C cycle feedback to rising temperatures. This study will provide improved insights to the sensitivity of SOC stores to global warming in semi arid ecosystems. Objective: To elucidate how litter input affects soil structure and SOC quality along an elevational gradient in a semi-arid ecosystem and assess impacts of these characteristics on the temperature sensitivity of SOC decomposition. Introduction Acknowledgements Fig XX Study Site Study site: Reynolds Creek Experimental Watershed in the Owyhee Mountains of Southwestern Idaho (Fig.1). Field sites : Flats, Nancy Gulch, Lower Sheep Creek, Reynolds Mountain (Table 1). Site Dominant Vegetation Elevation (m) MAP (mm) MAT ( o C) Flats Artemisia tridentata subsp. wyomingensis 118024010.22 Nancy Gulch Artemisia tridentata subsp. wyomingensis 14172808.86 Lower Sheep Creek Artemisia arbuscula 16533108.52 Reynolds Mountain Artemisia tridentata subsp. vaseyana 2111 7955.56 This research was supported by NSF RC CZO Cooperative Agreement #EAR 1331872 and USDA ARS. Advisors: Dr. Marie-Anne de Graaff, Dr. Kevin Feris, Dr. Alejandro Flores, Dr. Shawn Benner, all de Graaff lab members and especially Trevor Thornton, Billy Bringman, Megan Bijan and Rhet Stewart for their assistance in the field. Question 1 Question 2Question 3 How does the quantity and quality of SOC input change along an elevational gradient? How does the physical distribution (silt, clay, coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM) of SOC change along an elevational gradient? How do these changes affect soil carbon decomposition under different temperatures? Table. 1 Field sites descriptions Reynolds Mountain Fig. 1 Field sites at Reynolds Creek 10m Flats Nancy Gulch Lower Sheep Creek T2G Hypotheses More labile SOC incorporated into CPOM and FPOM fractions at upper elevations, and more recalcitrant SOC associated with silt and clay at lower elevations - less precipitation Hypotheses SOC pools at lower elevations: larger positive feedback to temperature rise (greater amount of CO 2 emission) due to recalcitrant being more temperature sensitive than the labile SOC pools at upper elevations.