Metadata – Date (at beginning and end of data collection) (year, month, date) – Growing season? (yes or no) – GPS location (in decimal degrees) – In situ or pot? – Species ID (family, genus, species) – Plant functional type – Growth form – C3/C4/Cyad – Angiosperm/ gymnosperm – Deciduous/evergreen – Contributor – Citation – Site ID – Root order – Functional classification – Soil depth ( upper and lower) (cm) – Depth of field (mm) – Treatment, extent of treatment, and unit for extent – Collection method – Soil block dimensions (length, width, height) (cm) – Calculation method – Latitude, longitude – Stand age (yr) – Location notes – notes

Morphology – Root diameter (mm) – Specific root length (SRL) (m g -1 ) – Root tissue density (RTD) (g cm -1 ) – Branching intensity (# roots per higher order root) – Branching architecture (root length per higher order root) – Type of mycorrhizae (AM or EM) – % EM colonization (% tips colonized) – % AM colonization (% length colonized) Anatomy – Stele diameter (µm) – Cortex diameter (µm) – Root porosity (aerenchyma area) – Vessel diameter (µm) – Phellem Standing Biomass – Absolute biomass (g m -2 ) – % total biomass (by order, diameter, and functional class) – Annual production (g m -2 ) – Annual mortality (g m -2 year -1 ) – Biomass turnover (g m -2 a -1 )

Chemistry – Root C, N, K, P, Al, Ca, Mg (mg g -1 ) – Root Cr, Ni, Cu, Zn, As, Cd, Pb (mg kg -1 ) – C:N ratio – C storage (kg C hm -2 ) – Ion concentration (Na + and Cl - ) (mg g d.wt -1 ) – Lignin – Cellulose – Hemi-cellulose – Carbohydrates (TNC)(mg g -1 ) – Isotopic concentration Mean root stable δ 15 N (%) Dynamics – Survivorship (roots year -1 ) – Growing season survivorship (% growing season -1 ) – Phenology production – Phenology mortality – Lifespan (days) – Turnover rate (% growing season -1 ) Function – Respiration rate (nmol O 2 g -1 s - 1 ) – Respiration rate by mass (nmol s -1 m -2 ) – Nutrient uptake – Water uptake – Exudate rate – Oxygenation rate – Enzyme production – Conductance

Soil dynamics – Soil temperature (°C) – Volumetric soil water content (%) – Oxygen availability – Soil respiration – Mineralization rate Climate – Mean annual precipitation (mm) – Min & max monthly temperature (°C) – Mean annual temperature (°C) – Chamber temperature (day, night) (°C) Other site characteristics – Elevation (m above sea level) – Slope (°) Soils – pH – Textural class – Soil horizon – % sand, silt, clay, and SOM – Bulk density (g cm -3 ) – Soil N and P (g kg -1 ) – Al:Ca ratio – Cation exchange capacity (CEC) (meq cg -1 ) – % base cation saturation – Elemental concentration (total and exchangeable) – Redox potential (mV) Vegetation – Basal area (total and by species) – LAI (total and by species) – Photosynthesis