Dataset: Spatiotemporal variability and origin of CO2 and CH4 tree stem fluxes in an upland forest

The exchange of multiple greenhouse gases (i.e., CO2 and CH4) between tree stems and the atmosphere represents a knowledge gap in the global carbon cycle. Stem CO2 and CH4 fluxes vary across time and space and is unclear which are their individual or shared drivers. This dataset contains information of CO2 and CH4 fluxes at different stem heights combining manual (biweekly; n=678) and automated (hourly; n>38,000) measurements in a temperate upland forest.This study was performed in an upland forested area at the St. Jones Reserve [39°5’20”N, 75°26’21”W], a component of the Delaware National Estuarine Research Reserve (DNERR).The dominant vegetation species are bitternut hickory (Carya cordiformis), eastern red cedar (Juniperus virginiana L.), American holly (Ilex opaca (Ashe)), sweet gum (Liquidambar styraciflua L.) and black gum (Nyssa sylvatica (Marshall)), with an overall tree density of 678 stems ha-1 and mean diameter at breast height (DBH) of 25.7±13.9 cm (mean±sd). We studied bitternut hickory, which is one of the most important species in the study site, accounting for 24.9% of the total basal area.For code

树木茎干与大气间多种温室气体（即二氧化碳CO₂、甲烷CH₄）的交换过程，是全球碳循环研究中一处尚未厘清的知识盲区。茎干CO₂与CH₄通量存在显著时空异质性，目前尚不明确其各自的驱动因子与共同驱动因子。
本数据集涵盖温带山地森林中不同茎干高度下的CO₂与CH₄通量数据，整合了人工观测（每两周一次，样本量n=678）与自动连续观测（每小时一次，样本量n>38000）两种测量方式的结果。
本研究在特拉华国家河口研究保护区（Delaware National Estuarine Research Reserve, DNERR）下属的圣琼斯保护区（St. Jones Reserve）山地林区开展，地理坐标为39°5'20"N, 75°26'21"W。
研究区优势植被物种包括灰胡桃（Carya cordiformis）、北美圆柏（Juniperus virginiana L.）、美国冬青（Ilex opaca (Ashe)）、枫香（Liquidambar styraciflua L.）与蓝果树（Nyssa sylvatica (Marshall)）；林区整体树木密度为678株·ha⁻¹，平均胸径（Diameter at Breast Height, DBH）为25.7±13.9 cm（平均值±标准差）。
本研究聚焦于灰胡桃，该物种为研究区内最重要的物种之一，其胸高断面积占总断面积的24.9%。
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