Dataset: 1999 CO2xCommunity Experiment Belowground Biomass

Abstract
Belowground biomass for 20 of the 45 experiment plots in the "CO₂xCommunity" experiment taken in August 1999. Samples were taken after 13 years of continuous treatment with elevated CO₂ at an approximate CO₂ concentration of 750 ppm. Two soil cores were taken from each ambient CO₂ and elevated CO₂ plot in two plant communities, the C3 and C4 communities. A third plant community in the experiment was not sampled. The soil cores were 5.1 cm in diameter and 100 cm in length, extracted with a piston corer in three sections at target intervals of 0-33 cm, 34-66 cm, and 67-100 cm. The soil cores were sub-sectioned horizontally by depth. All belowground biomass was recovered from the top 15 cm of the soil core. At depths greater than 15 cm some soil sub-sections were used to estimate belowground biomass while others were used to estimate bulk density. Belowground biomass was sorted into the morphological categories living roots, rhizomes, and culms, and litter (i.e., dead roots and detritus), and color categories that can be interpreted as coming from C4 grasses or C3 sedges to a rough approximation. The data were gap-filled for depth sub-sections with no belowground biomass data, and modeled to provide estimates of whole-profile root biomass to a depth of 1 m. Total below ground biomass was significantly (p=0.017) and positively affected by the experimental treatment. Spartina patens had significantly less below ground biomass than Schoenoplectus americanus (p<0.0001). Detailed methods and other metadata are provided in the Read Me file. The dataset is composed of 11 files including the disaggregated data, the derived data for total biomass, and replicable workflow in R for calculating the derived data from disaggregated data.