Sapflow and xylem water isotopes from Snodgrass Mountain, East River Watershed, Colorado USA

This dataset includes sapflux and stable water isotopes of soil water and xylem water for aspen, fir and spruce trees along the Snodgrass Mountain transect in the East River Watershed, Colorado USA. The purpose of generating this dataset was to understand: (1) the total flux of water being used by trees in the watershed, (2) separate the component of transpiration that was derived from recent precipitation vs. older water such as winter precipitation of groundwater and (3) understand how total water use and water sources for the trees varies between species and position on a hillslope. The data were collected from May 2019 until October 2022. The sap flux data were collected using ICT SFM1 sensors and are presented in both units of cm hr-1 and as mm hr -1 by multiplying the sap flux by the sapwood area of the tree. All sap flow data has been been corrected using estimates of wounding diameter, water content of wood and sap wood depth. The xylem water isotope data were collected approximately weekly from each of the trees instrumented with sap flux. The stems were collected and the water extracted using classic cryogenic methods. Isotope measurements were done using a Picarro 2140i analyzer. We provide an estimate of the Seasonal Origin Index for each measurements following Allen et al., 2019 (10.5194/hess-23-1199-2019) where values of -1 equate to trees relying on winter precipitation and +1 tree relying on summer precipitation. We also provide the simultaneous sap flux for each isotope measurement when this data was available. Please note this is an update to an earlier data repository with the same name that only included 2019 data. The new dataset was posted in January 2023 and is inclusive of the original 2019 data but now includes 2021 and 2022 data.

本数据集涵盖美国科罗拉多州东河汇水区斯诺格拉斯山样带上的美洲山杨、冷杉与云杉的树干液流（sapflux）以及土壤水、木质部水的稳定水同位素数据。构建该数据集的核心目的为解析以下三项科学问题：（1）明确该汇水区内树木的总耗水通量；（2）区分树木蒸腾的水源组分，即甄别来自近期降水的水分与冬季降水、地下水等较老水源对应的蒸腾占比；（3）明晰不同树种以及山坡不同位置的树木总耗水量与水源的差异。数据采集周期为2019年5月至2022年10月。树干液流数据采用ICT SFM1传感器采集，提供两种单位的结果：cm hr⁻¹，以及通过将液流值乘以树木边材面积得到的mm hr⁻¹。所有树干液流数据均已通过伤径、木材含水率以及边材深度的估算值完成校正。木质部水同位素数据约每周采集一次，采样对象为所有安装了液流传感器的树木。采集茎干样本后，采用经典低温冷凝法提取水分，随后使用Picarro 2140i同位素分析仪完成同位素测定。本数据集提供了基于Allen等人2019年研究（DOI: 10.5194/hess-23-1199-2019）提出的季节来源指数估算值，其中取值为-1代表树木依赖冬季降水水源，取值为+1代表树木依赖夏季降水水源。当对应数据可获取时，本数据集还提供了与每一次同位素采样同步的树干液流数据。请注意，本数据集为同名早期数据仓库的更新版本，早期版本仅包含2019年的采集数据。新版数据集于2023年1月发布，保留了原始2019年的全部数据，并新增了2021年与2022年的采集数据。