Foliar contributions to methane and nitrous oxide exchange in urban green roof systems

This dataset contains multi-season measurements of foliar and substrate greenhouse gas (GHG) exchange from experimentally established extensive urban green roof systems. The primary purpose of the dataset is to quantify methane (CH₄), nitrous oxide (N₂O), carbon dioxide (CO₂), and water vapor (H₂O) fluxes at the plant (foliar) and substrate (soil) levels, and to evaluate the effects of biochar amendment and plant functional type on these fluxes. The study was designed to assess the contribution of plant-mediated processes within the soil–plant–atmosphere continuum and to determine how engineered substrate modification influences methane uptake and nitrous oxide emission under field conditions.

Observations were collected across multiple seasons (Fall 2023, Spring 2024, Summer 2024, and Autumn 2024) from replicated green roof modules. Each record represents an individual plant pot or experimental unit and includes identifiers for season, species, treatment category, and treatment number (0 = control; 1 = biochar-amended substrate). The dataset integrates foliar gas flux measurements (co2_flux, ch4_flux, n2o_flux, h2o_flux), substrate gas flux measurements (soil_co2, soil_ch4, soil_n2o, soil_h2o), environmental covariates (gas_temperature, ambient_temperature), substrate physicochemical properties (soil_temp, soil_moisture, soil_ph, soil_ec, soil_c_percent, soil_nitrogen_percent), and plant tissue chemistry (leaf_c_percent, leaf_nitrogen_percent).

Flux values are reported as area- and time-normalized exchange rates, where negative CH₄ values indicate net uptake and positive N₂O values indicate net emission. The dataset supports analyses of seasonal variability, treatment effects, plant functional differences, and mechanistic linkages between substrate properties and GHG exchange. It is suitable for statistical modeling, structural equation analysis, comparative urban ecosystem studies, and scaling assessments of green roof contributions to urban greenhouse gas budgets. Missing values are coded as NA where laboratory measurements were unavailable.