In this study, aridity data and tree ring data were collected in Northern Serbia, in Southeast (SE) Banat, a subregion within Vojvodina, and Vojvodina at large. They were each investigated independently. The De Martonne Aridity Index and the Forestry Aridity Index are derived from examining the relationship between precipitation and surface air temperature data sets sourced from seven meteorological stations in SE Banat, and from 10 meteorological stations located in Vojvodina as a whole. Vojvodina is a large territory and used as the control area, for the period 1949–2017. The Palmer Drought Severity Index was derived for the period 1927–2016, for both SE Banat and the totality of Vojvodina. The results of the Tree Ring Width Index were obtained from samples collected in or around the villages of Vlajkovac and Šušara, both located in SE Banat, for the period 1927–2017. These tree ring records were compared with three previous aridity and drought indices, and the meteorological data on the surface air temperature and the precipitation, with the objective being to evaluate the response of tree growth to climate dynamics in the SE Banat subregion. It was noted that the significant positive temperature trends recorded in both areas were too insufficient to trigger any trends in aridity or the Tree Ring Width Index, as neither displayed any change. Instead, it appears that these climatic parameters only changed in response to the precipitation trend, which remained unchanged during the investigated period, rather than in response to the temperature trend. It appears that the forest vegetation in the investigated areas was not affected significantly by climate change in response to the dominant temperature increase.

We present the first Greenlandic tree ring oxygen isotope record (δ¹⁸O_GTR), derived from four birch trees collected from the Qinguadalen Valley in southwestern Greenland in 1999. Our δ¹⁸O record spans from 1950–1999 and is significantly and positively correlated with winter ice core δ¹⁸O from southern Greenland. δ¹⁸O_GTR records are positively correlated with southwestern Greenland January–August mean temperatures. North Atlantic Oscillation (NAO) reconstructions have been developed from a variety of proxies, but never with Greenlandic tree rings, and our δ¹⁸O_GTR record is significantly correlated with NAO (r = −0.64), and spatial correlations with sea-level pressure indicate a classic NAO pressure seesaw pattern. These results may facilitate a longer NAO reconstruction based on long time series of tree ring δ¹⁸O records from Greenland, provided that subfossil wood can be found in areas vacated by melting glaciers.

Hydroclimate variability across the East European Plain plays a critical role in regional ecosystems and climate dynamics, yet moisture-sensitive tree-ring proxies remain scarce in this region, particularly at high latitudes where tree-ring width (TRW) and density are primarily controlled by temperature. Tree-ring cellulose oxygen isotopes (δ¹⁸O_TRC) have the potential to serve as a useful hydroclimate proxy, but their climatic signal in this region remain poorly understood. Here, we developed three δ¹⁸O_TRC chronologies of Scots pine (Pinus sylvestris L.) from the northern, central, and southern East European Plain to assess their climate signals. The δ¹⁸O_TRC chronologies from the three sites show similar response to summer moisture condition. The northern δ¹⁸O_TRC shows the strongest relationship with vapor pressure deficit (VPD), the central δ¹⁸O_TRC records both hydroclimate variability and precipitation oxygen isotopes (δ¹⁸O_p) signals, and the southern δ¹⁸O_TRC mainly reflects the Standardized Precipitation Evapotranspiration Index (SPEI). In contrast, TRW shows weak hydroclimate sensitivity at the northern and central sites, whereas at the southern site it mainly reflects soil moisture. Overall, compared with TRW, δ¹⁸O_TRC better captures regional summer hydroclimate signals, particularly capturing signals related to atmospheric drought.

Hydroclimate variability across the East European Plain plays a critical role in regional ecosystems and climate dynamics, yet moisture-sensitive tree-ring proxies remain scarce in this region, particularly at high latitudes where tree-ring width (TRW) and density are primarily controlled by temperature. Tree-ring cellulose oxygen isotopes (δ¹⁸O_TRC) have the potential to serve as a useful hydroclimate proxy, but their climatic signal in this region remain poorly understood. Here, we developed three δ¹⁸O_TRC chronologies of Scots pine (Pinus sylvestris L.) from the northern, central, and southern East European Plain to assess their climate signals. The δ¹⁸O_TRC chronologies from the three sites show similar response to summer moisture condition. The northern δ¹⁸O_TRC shows the strongest relationship with vapor pressure deficit (VPD), the central δ¹⁸O_TRC records both hydroclimate variability and precipitation oxygen isotopes (δ¹⁸O_p) signals, and the southern δ¹⁸O_TRC mainly reflects the Standardized Precipitation Evapotranspiration Index (SPEI). In contrast, TRW shows weak hydroclimate sensitivity at the northern and central sites, whereas at the southern site it mainly reflects soil moisture. Overall, compared with TRW, δ¹⁸O_TRC better captures regional summer hydroclimate signals, particularly capturing signals related to atmospheric drought.