This archive contains all data and code used by the following publication: Field, J. L., Sloan, B. P., Craig, M. E., Calloway, P., Ottinger, S. L., Mead, T., Abramoff, R. Z., Venegas, M. P., Chhetri, H. B., Haiby, K., Kalluri, U. C., Muchero, W., Schadt, C. W., & Mayes, M. A. (2025). Which plant traits increase soil carbon sequestration? Empirical evidence from a long-term poplar genetic diversity trial (p. 2025.02.17.638464). bioRxiv. https://doi.org/10.1101/2025.02.17.638464 Our analysis combined several soil and root data sets collected by Oak Ridge National Laboratory (ORNL) researchers/collaborators from the Clatskanie Poplar Common Garden in Clatskanie, OR by from 2009-2024. The raw data data files are located */02-data/01-raw/* which we harmonized using the codes in */01-codes/01-harmonize-clatskanie-data-pub.qmd*. The final processed data set used in the paper is found at */02-data/02-processed/clatskanie-c-fit-data.csv* and its columns are described in the table below. Variable Description Units ord Order of gentoypes used for manuscript plotting tree Unique ID for all poplar trees across these data sets (max of 66 trees) genotype ID for genotypes contained across these data sets (max of 23 genotypes) block ID for replicate blocks (max of 3 replicates) Depth Soil core depth at each tree. Primarily use 15 cm for manuscript, see raw data for deeper samples (max 60 cm for select trees) cm latitude Latitude of tree degrees longitude Longitude of tree degrees cop_id Flag to indicate if a given year is before or after coppicing. height Tree height cm dbh Tree diameter at breast height cm agb Estimated aboveground biomass growth rate from @truax2014 based on dbh kg/yr root_CN Root carbon to nitrogen ratio Lig Root lignin percentage % BD Soil bulk density g/cm$^3$ pH_soil Soil acidity taken from LDRD soil chemistry data. CEC Cation exchange capacity milliequivalents per 100 grams base_sat Soil base saturation of CEC % Sand, Silt, Clay Percent sand, silt or clay % POMC, MAOMC, TotC Particulate (POM), mineral-associated (MAOM), and Total soil organic matter C concentrations mg C/g soil POMC_st, MAOMC_st, TotC_st Particulate (POM), mineral-associated (MAOM), and Total soil organic matter C stocks tonnes C/ha POMC_CN, MAOMC_CN, soil_CN Particulate (POM), mineral-associated (MAOM), and Total soil organic matter carbon to nitrogen ratios % TotC_30, TotC_st_30 Total SOC concentration and stock from 0-30 cm rather than 0-15 cm as the other observations. mg C/g soil or tonnes C/ha C_chk_rel, C_chk_id Percentage mass balance error in POMC + MAOMC versus TotC, with less than 30% error being acceptable. % Al_ppm, B_ppm, Cu_ppm, Fe_ppm, Mn_ppm, Mo_ppm, Na_ppm, Ni_ppm, Zn_ppm Aluminum, Boron, Copper, Iron, Manganese, Molibdinum, Sodium, Nickel, and Zinc concentrations. parts per million (ppm) pCa, pK, pMg, pP, pS Calcium, Potassium, Magnesium, Phosphorus, Sulfur percentages % _root, _soil, _diff Suffix indicating either the root or soil elemental or nutrient quantity or the difference in root and soil quantity. Finally, the analysis and figure generation codes for the manuscript are located in the */01-codes/01-gcb-pub-analysis.qmd* file, while the figure files are located in */03-figs/*. These *Quarto* notebooks have corresponding rendered markdown files (*.md*) stored in the same location. *R* version 4.4.1 was used for all analysis. Full Changelog: https://github.com/sloan091/gcb-clatskanie-soil-c/commits/initial-release-gcb