Urban tree channeling of soil methane and nitrous oxide and its mitigation using biochar

This dataset comprises seasonal measurements of foliar- and soil-atmosphere exchanges of CO₂, CH₄, N₂O, and H₂O from urban trees, alongside associated leaf traits, soil properties, tree structural attributes, and site characteristics. The data were collected to evaluate how urban trees and their underlying soils function as a coupled biogeochemical system, with particular emphasis on canopy-mediated greenhouse gas exchange and its environmental and biological controls. Foliar gas fluxes (CO₂, CH₄, N₂O, H₂O) were measured at the leaf level and are linked to individual trees, species identity, seasonal conditions, and experimental treatments. Concurrent soil gas fluxes were measured beneath the same trees, enabling direct comparison between aboveground and belowground pathways of greenhouse gas exchange. Supporting variables include soil temperature, soil moisture, pH, and electrical conductivity, which characterize edaphic controls on gas fluxes. Leaf functional traits—such as specific leaf area (SLA) and optical indices (chlorophyll, flavonoids, anthocyanins, and nitrogen balance index [NBI])—are included to assess relationships between leaf structure, physiology, and trace-gas exchange. Tree-level structural and health metrics (e.g., DBH, height, crown dimensions, dieback, chlorosis, and crown transparency) provide context for evaluating how tree size, vigor, and canopy architecture influence foliar and soil greenhouse gas dynamics. Spatial coordinates (x, y), planting year, mulch cover, and treatment information allow analyses of management history, spatial variability, and urban site effects. Together, these data support investigations of urban carbon and nitrogen cycling, species- and trait-based controls on greenhouse gas fluxes, and the role of urban green infrastructure in climate mitigation and ecosystem modeling.