This dataset includes isotopic values of bulk soil water and stem water samples collected from four different sampling sites within the Pallas catchment. Two sampling sites (SF1 and SF2) were set in forested areas with mineral soils, and another two (FP1 and FP2) in forested peatlands. The bulk soil samples were collected on 8 occasions between May 2019 and June 2020, while the stem samples were collected during the snow-free periods, 6 times overall. Bulk soil was sampled from 1 m deep soil cores, at 5 cm increments up to 50 cm of depth and at 10 cm increments from 50 - 100 cm depth. 1- 4 replicates per sampling site were collected during each sampling campaign, depending on field conditions. Stem samples were collected from 2 different mature trees of each of the present tree species at 2.5 - 3 m height. An extendable pruner was utilized to sample healthy, suberized stems with mature bark of 10–15 cm length and diameter larger than 2 cm, which were subsequently placed in 50 ml Eppendorf tubes made of biobased plastic, wrapped in laboratory film (Parafilm®) and stored in the cooling box. Isotopic composition of bulk soil water was measured by the direct equilibration method, using a cavity ring-down spectroscopy analyzer (Picarro L2140-i model, Picarro Inc., Santa Clara, CA, USA). The water from stem samples was extracted by cryogenic vacuum distillation method, and subsequently measured on Picarro L2130-i CRDS analyser. The main goal of the study was to examine spatiotemporal variability and seasonal origin of soil water at the soil-vegetation interface in Pallas catchment, and to assess how soil water isotopic seasonality is reflected in stem water of local tree species. The findings were published in https://onlinelibrary.wiley.com/doi/10.1002/hyp.14811

2023