Tree stem methane flux, tomography, and microtopography data from Harvard Forest upland and wetland sites, 2023-2025

This data package contains tree stem methane (CH4) and carbon dioxide (CO2) flux measurements, wood tomography assessments, and microtopography classifications from Harvard Forest, Petersham, Massachusetts, USA. Data were collected from June 2023 to October 2025 at two contrasting forest sites: the Black Gum Swamp (BGS) wetland and the Environmental Measurement Station (EMS) upland forest on the Prospect Hill tract. Stem greenhouse gas fluxes were measured on 60 trees (30 per site) spanning four species: black gum (Nyssa sylvatica), red maple (Acer rubrum), eastern hemlock (Tsuga canadensis), and red oak (Quercus rubra). Fluxes were quantified using static closed chambers coupled to a Los Gatos Research Ultra-Portable Greenhouse Gas Analyzer (UGGA). The dataset includes 1,640 quality-controlled flux observations with associated R-squared values, standard errors, and measurement metadata. CH4 flux units are reported in nmol m-2 s-1 and CO2 fluxes in micromol m-2 s-1. Internal wood condition was assessed non-destructively for all 60 study trees using PiCUS sonic tomography (SoT) and electrical resistance tomography (ERT) at breast height (1.37 m). Summary statistics of resistivity and sound wood percentage are provided alongside cross-section images for each tree. Microtopographic position (hummock, hollow, or intermediate) was classified for the 30 wetland trees based on field assessment of tree base elevation relative to the surrounding peat surface.本数据包包含来自美国马萨诸塞州皮茨哈姆市哈佛森林的树干甲烷（CH₄）与二氧化碳（CO₂）通量实测数据、木材层析成像评估结果以及微地形分类数据。数据采集于2023年6月至2025年10月，覆盖两处对比林分：黑胶沼泽（BGS）湿地与展望山地块的环境测量站（EMS）高地林。研究人员对60棵树木（每处站点30棵）开展树干温室气体通量测定，受试树种涵盖4种：黑胶树（Nyssa sylvatica）、红枫（Acer rubrum）、东部铁杉（Tsuga canadensis）以及红栎（Quercus rubra）。通量测定采用静态密闭箱联用Los Gatos Research超便携式温室气体分析仪（UGGA）完成。本数据集包含1640条经质量管控的通量观测数据，附带对应的R²值、标准误差以及测量元数据。其中甲烷通量单位为nmol·m⁻²·s⁻¹，二氧化碳通量单位为μmol·m⁻²·s⁻¹。研究人员对全部60棵受试树木在胸高（1.37m）位置，采用PiCUS声波层析成像（SoT）与电阻层析成像（ERT）开展无损内部木材状况评估，同时提供了每棵树木的电阻率与健全木材占比的统计汇总结果，以及对应的横截面图像。针对30棵湿地树木，研究人员基于树基海拔相对于周围泥炭表面的野外实测结果，对其微地形位置（丘状、洼陷或中间型）进行了分类。