2012 Annual Report 1a.Objectives (from AD-416): 1. Quantify the differences in soil carbon sequestration potential within the Clear Creek Amana Hydrologic Observatory (a second-order watershed) under different agricultural management practices; especially, we will measure the short-term dynamic fluxes of carbon as a function of crop, tillage management, antecedent water content, and a wide range of runoff conditions. 2. Through 12C/13C isotope ratio measurements in Eastern Iowa, resolve the relative effects of soil respiration, land cover (C3 or C4 plants), and crop rotation on soil and canopy carbon isotope ratios. 3. Refine spatially distributed models and make predictions of carbon transport and fluxes over larger, integrated watersheds and over decadal periods. In this way, we will determine the sensitivity of regional-scale carbon observation networks to the range of carbon fluxes found in objective 1. We will use what is learned in objectives 1 and 2 to relate changes in biogeochemical processes of production, decomposition, preservation, and burial of carbon in landscapes with a variety of chemical and biological characteristics, and changes in these processes with time. 4. Complement the on-the-ground measurements with remote sensed CO2 (from satellite and LIDAR) to in-situ samples from tall tower and aircraft, and to state-of-the-art atmospheric CO2 simulation results; the CO2 fluxes are necessary to capture terrestrial carbon cycle responses to climate variability and to improve carbon model simulations. 1b.Approach (from AD-416): Studies will be conducted to compare the carbon balance across the Clear Creek and Walnut Creek watersheds in Iowa. These two different sites represent two different landforms within Iowa and different erosion characteristics. The studies will address the carbon exchange through direct measurements of the carbon balance along with indirect measurements through the C12/C13 ratios to compare with the soil respiration and CO2 exchange in plant canopies. The coupling of the ground-based measurements with the aircraft and satellite measurements of CO2 fluxes will be compared with spatial and temporal models for these two areas. 3.Progress Report: The goal of this experiment is to evaluate the change in the carbon dynamics across a landscape utilizing historical data observed from a long-term corn-soybean field site with simulation models capable of estimating the carbon fluxes from different soils. Experimental data collected from the field site included flux data of carbon dioxide (CO2) throughout the year above both corn and soybean crops, soil carbon analysis and spatial distribution of soil carbon across these fields, an analysis of the spatial variation of soil CO2 fluxes, and meteorological data required to evaluate the performance of the carbon transport and flux models. These data are being used to validate the carbon flux data and soil carbon storage across landscapes to determine if the level of accuracy is sufficient for longer term estimates across time and space and to estimate the impact of erosion on the soil carbon changes.