Search Results (230)

Stable oxygen isotopes in tree rings (δ¹⁸O) serve as important proxies for climate change and offer unique advantages for climate reconstruction in arid and semi-arid regions. We established an annual δ¹⁸O chronology spanning 1964–2023 using Juniperus excelsa tree-ring samples collected from the Alborz Mountains in Iran. We analyzed relationships between δ¹⁸O and key climate variables: precipitation, temperature, Palmer Drought Severity Index (PDSI), vapor pressure (VP), and potential evapotranspiration (PET). Correlation analysis reveals that tree-ring δ¹⁸O is highly sensitive to hydroclimatic variations. Tree-ring cellulose δ¹⁸O shows significant negative correlations with annual total precipitation and spring PDSI, and significant positive correlations with spring temperature (particularly maximum temperature), April VP, and spring PET. The strongest correlation occurs with spring PET. These results indicate that δ¹⁸O responds strongly to the balance between springtime moisture supply (precipitation and soil moisture) and atmospheric evaporative demand (temperature, VP, and PET), reflecting an integrated signal of both regional moisture availability and energy input. The pronounced response of δ¹⁸O to spring evaporative conditions highlights its potential for capturing high-resolution changes in spring climatic conditions. Our δ¹⁸O series remained stable from the 1960s to the 1990s, but showed greater interannual variability after 2000, likely linked to regional warming and climate instability. A comparison with the δ¹⁸O variations from the eastern Alborz Mountains indicates that, despite some differences in magnitude, δ¹⁸O records from the western and eastern Alborz Mountains show broadly similar variability patterns. On a larger climatic scale, δ¹⁸O correlates significantly and positively with the Niño 3.4 index but shows no significant correlation with the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO). This suggests that ENSO-driven interannual variability in the tropical Pacific plays a key role in regulating regional hydroclimatic processes. This study confirms the strong potential of tree-ring oxygen isotopes from the Alborz Mountains for reconstructing hydroclimatic conditions and high-frequency climate variability. Full article

Water availability is a major constraint on socioeconomic development in northeastern Mexico, highlighting the need for effective water resource planning that accounts for the variability and extremes of precipitation. In this study, seasonal precipitation reconstructions were developed using tree-ring chronologies from spruce species (Picea spp.). A representative chronology for Picea mexicana Martínez was developed from two populations and spans the period 1786–2020, while a chronology for Picea martinezii T.F. Patterson was established from three populations covering 1746–2020. Both species exhibited significant positive correlations with January–May precipitation (r = 0.65 and 0.71, respectively; p < 0.01) and negative correlations with maximum temperature over the same period (r = −0.52 and −0.59, respectively). Two January–May precipitation reconstructions were produced for periods with adequate sample depth (EPS > 0.85): 1851–2020 for P. mexicana and 1821–2020 for P. martinezii. Both reconstructions revealed pronounced interannual variability, with recurrent droughts and persistently dry conditions, particularly evident in the P. mexicana series. Spatial correlation analyses indicated a historical link between reconstructed precipitation and the El Niño–Southern Oscillation (ENSO). These results highlight the value of spruce species for dendroclimatic reconstruction and their sensitivity to precipitation variability, especially as rising maximum temperatures may compromise their persistence in the Sierra Madre Oriental. Full article

Ponderosa pine (Pinus ponderosa Lawson & C. Lawson) forests in the western United States have experienced reduced fire frequency since Euro-American settlement, usually because of successful fire suppression policies and even without such human impacts at remote sites in the Great Basin and Mojave Deserts. In an effort to improve our understanding of long-term environmental dynamics in sky-island ecosystems, we developed tree-ring chronologies from ponderosa pines located in the Sheep Mountain Range of southern Nevada, inside the Desert National Wildlife Refuge (DNWR). After comparing those dendrochronological records with other ones available for the south-central Great Basin, we analyzed their climatic response using station-recorded monthly precipitation and air temperature data from 1950 to 2024. The main climatic signal was December through May total precipitation, which was then reconstructed at annual resolution over the past five centuries, from 1490 to 2011 CE. The mean episode duration was 2.6 years, and the maximum drought duration was 11 years (1924–1934; the “Dust Bowl” period), while the longest episode, 19 years (1905–1923), is known throughout North America as the “early 1900s pluvial”. By quantifying multi-annual dry and wet episodes, the period since DNWR establishment was placed in a long-term dendroclimatic framework, allowing us to estimate the potential drought resilience of its unique, tree-dominated environments. Full article

Tropical trees represent an important potential archive of climate and ecological information, but their dendrochronology based on conventional techniques has been challenging. We conducted a pilot study of the wood anatomy and dendroclimatological potential of Juglans neotropica Diels (Juglandaceae), an IUCN Red List species, using 225 radii sampled from 57 trees in Piura (4°55′ S, 79° 56′ W), northern Peru. A total of 112 radii from 40 trees passed quality control and are included in the tree-ring width chronology for this species. J. neotropica has demonstrably annual rings, and results are consistent with reports that the species has a dormant period during the dry season, which locally is approximately June–November. Local precipitation is correlated (p = 0.10, 1-tailed test) with tree-ring growth, lagged by one year, consistent with other studies of tropical tree species. The age distribution of the sample collection of J. neotropica is young and invariant, probably because of selective cutting by local villagers. To supplement ring-width analysis, we conducted the first oxygen isotopic (δ¹⁸O) and radiocarbon (∆¹⁴C) analysis for this species on radii from two individuals; results are preliminary given sample size limitations, but consistent with dendrochronological dating, within uncertainties, in all three chronometric analyses. A two-sample composite annually-averaged δ¹⁸O anomaly data series is correlated significantly with gridded regional growing season (December–May) precipitation (1973/74–2005/06). Qualitatively consistent with simulation of ring width and δ18O, responses to El Niño events are manifested in positive ring-growth anomalies and negative isotopic anomalies following known event years. The combination of tree-ring, radiocarbon, stable isotopic analyses, and the application of sensor and chronological modeling provides a degree of confidence in the results that would not have been possible by relying on any single approach and indicates the potential for further investigation of this and other tropical tree species with uncertain ring boundaries. Full article

Dendrochronological analysis was carried out at the archaeological settlement of Gran Carro, located in Lake Bolsena (Italy). According to the most recent archaeological evidence, the site dates back to the period spanning from the Middle Bronze Age (15th century BC) to the Early Iron Age (8th century BC). In the excavation of the archaeological area, wooden piles from deciduous oak species (Quercus section robur and Quercus section cerris) were found, species still common in the area. The analysed trees, aged 15–50 years, likely came from managed forests, though agamic regeneration is possible. Relative felling dates provide initial insights into the duration of the settlement phases, revealing modifications to the original structure over an interval year ranging from 9 to 23 years. Absolute dating using wiggle matching indicates that most of the analysed piles date between 934 and 810 BC, though calibration curve slope limits precision. Nonetheless, dendrochronological analysis suggests that the settlement associated with an individual dendrogroup can likely be placed more precisely within this time range from 907 to 885 BC. From a broader perspective, the excavated area so far indicates that the settlement can be dated with 95% probability to the period 1054–810 BC and with 68% probability to the period 1017–817 BC. The results represent a significant milestone and may offer valuable insights for future investigations and developments. Full article

A deeper understanding of growth–climate relationships in natural forests (NFs) and planted forests (PFs) is crucial for the prediction of climate change impacts on forest productivity. Yet, the mechanisms and divergences in climatic responses between these forest types remain debated. This study investigated P. tabulaeformis NFs and PFs in China using tree-ring chronologies to analyze their radial growth responses to climatic factors and associated temporal–spatial dynamics. The results reveal significant negative correlations between radial growth and mean temperatures (Tmean) in August of the previous year and June of the current year, and positive correlations were observed with the September standardized precipitation evapotranspiration index (SPEI) of the previous year and May precipitation (PPT) and SPEI of the current year. Compared with NFs, PFs exhibited a heightened climatic sensitivity, with stronger inhibitory effects from prior- and current-year growing-season temperatures and greater SPEI influences during the growing season. Moving window analysis demonstrated higher temporal variability and more frequent short-term correlation shifts in PF growth–climate relationships. Spatially, NFs displayed latitudinal divergence, autumn Tmean shifted from growth-suppressive in southern regions to growth-promotive in the north, and winter SPEI transitioned from positive to negative correlations along the same gradient. However, PFs showed no significant spatial patterns. Relative importance analysis highlighted water availability (PPT and SPEI) as the dominant driver of NF growth, whereas temperature, moisture, and solar radiation co-regulated PF growth. These findings provide critical insights into climate-driven growth divergences between forest types and offer scientific support for the optimization of NF conservation and PF management under accelerating climate change. Full article

This study evaluated the long-term hydroclimatic trend through a reconstruction procedure of precipitation variability in central Greece (1657–2020), using eight tree-ring chronologies (Pinus sp. and Abies sp.). Through the combination of gridded climate datasets with tree-ring width (TRW) and earlywood width (EWW) chronologies, we created three precipitation reconstructions, (1) April–August (AMJJA) and (2) May–June (MJ) using TRW and (3) EWW chronologies, utilizing both measured and gridded precipitation data. Chronologies were standardized using ARSTAN, while principal component analysis (PCA) was used for the development of the reconstructions. Verification and calibration of the derived time series (split-period tests, RE > 0, R = 0.62–0.67) confirmed a strong reconstruction that explained 15%–45% of the variability in precipitation. The results revealed strong growth–precipitation relationships throughout spring–summer (AMJJA/MJ). Multi-decadal variability is captured by TRW chronologies, while higher-frequency signals are reflected by EWW. Significant time intervals (19.6-, 12.5-, and 2.2-year cycles) were found by spectral analysis, indicating climatic impacts on tree-ring chronologies. Extremely wet (e.g., 1885, 1913) and dry (e.g., 1894–1895) episodes were confirmed against regional paleoclimate data and were consistent among previous reconstructions (72%–92% agreement). Despite the fact that sample depth reduced after 1978, the EPS was constantly higher than the threshold (EPS > 0.85 post-1746), showing the reliability of the reconstruction. This study expanded the hydroclimatic record of the southeast Mediterranean and highlighted that tree-ring chronologies are reliable variables to predict the historical precipitation. Full article

Tree ring chronologies (tree ring width—TRW, earlywood—EW, latewood—LW) were constructed to investigate fir’s (Abies borisii-regis Mattf.) response to key hydrometeorological factors, namely precipitation, temperature and drought (12-month Standardized Precipitation Evapotranspiration Index, SPEI-12). There has been only one previously published study conducted in the northern area of the species’ expansion (Albania). The current study was conducted in the southern area of the species’ expansion (Central Greece). Precipitation was the most important factor that affected tree growth. May precipitation was positively correlated with LW, while June and July precipitation was positively correlated with both EW and LW. Previous September precipitation was positively correlated with EW and LW. Interestingly, the current September precipitation was negatively correlated with EW. High temperatures in April showed a positive relation with LW, high temperatures in June negatively affected all chronologies, while high temperatures July and August were negatively related with LW. High autumn temperatures in the previous year significantly (negatively) influenced all tree ring chronologies. The SPEI index revealed that wet conditions during May and June positively correlated with high tree growth for both EW and LW, while wet conditions in July and August significantly affect LW formation. Wet conditions in the previous September also had a positive effect on tree growth. SPEI showed similar behavior with precipitation, showing that precipitation is the driving factor in fir growth. The results highlight the importance of summer rainfall and temperature in controlling tree growth in Mediterranean regions. The study revealed significant knowledge on the susceptibility of Abies borisii-regis Mattf. to climate variability and highlighted its consequences for future forest management plans. Full article

Trees mediate critical biogeochemical cycles involving nutrients, pollutants, water, and energy at the interface between terrestrial biosphere and atmosphere. Forest ecosystems significantly influence the global cycling of mercury (Hg), serving as important sinks and potential sources of re-emission through various biotic and abiotic processes. Anthropogenic Hg emissions, predominantly from industrial activities, mining, and fossil fuel combustion, have substantially altered the natural Hg cycle, intensifying ecotoxicological concerns and establishing forests as primary routes for atmospheric Hg deposition into terrestrial reservoirs. This perturbation profoundly affects global atmospheric Hg concentrations, residence times, and spatial distribution patterns. While early investigations focused on forest stands near heavily polluted areas, contemporary research has expanded to diverse ecosystems, revealing that trees provide tissues that function as temporal archives for atmospheric-terrestrial Hg exchange. Leaves capture high-resolution records of contemporary Hg dynamics at sub-annual timescales, whereas annual growth rings preserve multi-decadal chronologies of historical atmospheric exposure. Incorporating this dual temporal perspective is crucial for analysing Hg deposition trends and assessing the efficacy of environmental policies designed to control and mitigate Hg pollution. This review critically evaluates recent developments concerning the ecophysiological determinants of Hg accumulation in trees, highlighting how combined foliar and dendrochemical analytical methods strengthen our mechanistic understanding of vegetation-atmosphere Hg exchange. To enhance biomonitoring approaches, we emphasised the need for methodological standardisation, deeper integration of ecophysiological variables, and consideration of climate change implications as priority research areas. Furthermore, integrating Hg measurements with functional markers (δ¹³C and δ¹⁸O) and Hg isotope analyses strengthens the capacity to differentiate between physiological and environmental influences on Hg accumulation, thereby refining the mechanistic framework underlying effective tree-based Hg biomonitoring. Full article

This study revealed a significant reduction in tree growth across northern Fennoscandia following the 1600 AD eruption of Huaynaputina in Peru, the most powerful volcanic event in South America over the past two millennia. In the analysis, we utilized six tree-ring chronologies, which included the Finnish super-long chronology (5634 BC–2004 AD), the Kola Peninsula chronology (1445–2004 AD), and historical chronologies derived from old wooden churches in Finnish Lapland and Karelia, Russia. Using a superposed epoch analysis across these chronologies revealed a significant 24% (p < 0.01) decline in tree-ring growth in 1601 compared to the previous six years. The northernmost records, the Finnish super-long chronology (72%, p < 0.001) and the Sodankylä Old Church chronology (67%, p < 0.001), showed the most pronounced decreases. Statistical analysis confirmed significant (p < 0.05) similarities in tree-ring responses across all chronologies from 1601 to 1608. These findings underscore the reliability of using the 1600 Huaynaputina eruption as a chronological marker for dating historic wooden churches in northern Fennoscandia that were likely built between the late 17th and early 18th centuries. Additionally, analyzing church wood may provide insights into past climate patterns and environmental conditions linked to the eruption. Full article

Climate change may induce regional climate shifts, profoundly affecting plant growth, distribution, and ecosystems. This study collected 37 Sabina chinensis (Sabina chinensis (L.) Ant. cv. Kaizuca) tree cores (74 samples) from a site in the Yangtze River Delta (YRD) coastal region. Utilizing traditional dendrochronological principles and methods, a standardized tree-ring width chronology was developed to detect climate shift points and explore the differences in Sabina chinensis radial growth responses to climate factors, before and after these shifts. The findings are as follows: (1) Between 1967 and 2020, temperature emerged as the main climate factor influencing the radial growth of Sabina chinensis in the study area. (2) There are differences in the correlations between the tree radial growth of Sabina chinensis and climate factors in different months and seasons, before and after climate change. (3) Moving correlation analysis indicated that the relationships between radial growth and precipitation and temperature gradually altered. The study reveals the intricate influencing mechanisms of different climate factors on Sabina chinensis radial growth, before and after climate shifts, offering valuable references for other similar dendrochronological studies. Full article

Desert and semi-desert ecosystems cover a large proportion of global land area, but their tree-ring materials had traditionally been studied less intensively than that of forest ecosystems. In this study, we presented the time series of growth rings from eight typical shrub species of the semi-desert region in the northern foot of Yinshan Mountain, Inner Mongolia, China. The results showed that all those shrub species had recognizably demarcated annual rings of main stems, and tree-ring chronologies could been constructed successfully. The climate-growth analysis indicated that the chronologies was positively correlated with precipitation and PDSI but negatively correlated with temperature variables, indicating that drought stress had primary importance in the control of the relative ring width from year to year for those shrub species. Interestingly, the annual growth rate of those shrub species had no noticeable downward trend in recent decades, indicating that shrub growth had not negatively impacted the recently developed warm–dry climate in the sample sites. Our results provide evidence that growth rings in the main stems of shrub species in the northern foot of Yinshan Mountain should be a reliable proxy of annual fluctuation in the semi-desert environment of China. Full article

To study the long-term hydroclimate variability in the Satluj Basin, streamflow data was reconstructed using tree-ring width datasets from multiple taxa available from the Kullu Valley, western (Indian) Himalaya. Five ring-width tree-ring chronologies of three conifer tree taxa (Abies pindrow, Cedrus deodara, and Pinus roxburghii) significantly correlate with the streamflow during the southwest monsoon season. Based on this correlation, a 228-year (1787–2014 CE) June–August streamflow was reconstructed using average tree-ring chronology. The reconstruction accounts for 34.5% of the total variance of the gauge records from 1964 to 2011 CE. The annual reconstruction showed above-average high-flow periods during the periods 1808–1811, 1823–1827, 1833–1837, 1860–1863, 1876–1881, and 1986–1992 CE and below-average low-flow periods during the periods 1792–1798, 1817–1820, 1828–1832, 1853–1856, 1867–1870, 1944–1947, and 1959–1962 CE. Furthermore, a period of prominent prolonged below-average discharge in the low-frequency streamflow record is indicated during the periods 1788–1807, 1999–2011, 1966–1977, 1939–1949, and 1854–1864. The low-flow (dry periods) observed in the present streamflow reconstruction are coherent with other hydroclimatic reconstructions carried out from the local (Himachal Pradesh and Kashmir Himalaya) to the regional (Hindukush mountain range in Pakistan) level. The reconstruction shows occurrences of short (2.0–2.8 and 4.8–8.3 years) to medium (12.5 years) periodicities, which signify their teleconnections with large-scale climate variations such as the El Niño–Southern Oscillation and the Pacific Decadal Oscillation. Full article

Warm-season mean maximum temperature changes over mid-latitude regions have been attracting increasing attention amid the background of global warming. In this study, we present three tree-ring width chronologies: Tongbai Mountain (TBM; 1916–2014), Shimen Mountain (SMM; 1663–2014), and Xinlong (XL; 1541–2014), derived respectively from the eastern Qinling Mountains, north–central China, and the eastern Tibetan Plateau. Therein, TBM and SMM are newly developed, while XL is a reanalysis. Correlation analysis with climatic factors reveals that these three chronologies exhibit the highest correlation with the May–July mean maximum temperature. Based on these chronologies, we conducted reconstructions of the May–July mean maximum temperature. Spatial correlation analysis of each reconstruction with concurrent observed data, as well as comparisons with nearby temperature reconstructions, indicates their large-scale representativeness. However, during the common period of 1916–2014, the three chronologies show weak correlations with each other at the interannual timescale. Furthermore, the 11-year running correlation coefficients among the three reconstructions fluctuated during this common period. Additionally, fluctuations were observed between the reconstructions from SMM and XL during the overlapping period of 1668–2009, suggesting that tree-ring-based temperature reconstructions may be inconsistent when compared over mid-latitude China. These inconsistent changes can be attributed to the regional differences in the May–July mean maximum temperature change, the influence of different precipitation signals on the maximum temperature, and the El Niño–Southern Oscillations. Full article

The response of trees to climate is crucial for the health assessment and protection of forests in alpine regions. Based on samples of Pinus tabuliformis and Abies fargesii, two typical evergreen coniferous species with distinct elevation differences in the vertical vegetation zones of the Qinling Mountains, we have developed two tree-ring width chronologies for the southern slope of the central Qinling Mountains in central China. The correlation analysis results showed that the radial growth of P. tabuliformis and A. fargesii responded to different climatic factors. Water stress caused by temperature in May of the current year was the main limiting factor for radial growth of P. tabuliformis, while precipitation in September of the previous year and the current year had a negative impact on A. fargesii, with lag effects of temperature and precipitation during the previous growing season. Spatial correlation and comparative analysis indicated that the P. tabuliformis chronology responded to extreme dry and wet events on a regional scale. Interannual and multidecadal periodic signals recorded by tree rings suggested that the hydrological and climatic changes on the southern slope of the central Qinling Mountains were teleconnected with the Pacific and Atlantic Oceans, including El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO). Our results provide new evidence for a hydroclimatical response study inferred from tree rings on the southern slope of the central Qinling Mountains. Full article