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... On longer (decadal and greater) timescales, a number of non-climate factors can influence tree growth. For example, any stand-wide disturbance event that affects growth among a majority of trees within a chronology will result in the presence of a shared trend of varying length (Cook, 1985(Cook, , 1987. In addition, in the early stage of development, juvenile trees typically create wide rings of less-dense wood as the tree devotes resources to rapid growth, such that the early part of tree-ring chronologies are dominated by age effects (Fritts, 1976). ...
... It is also possible that local climatic differences could cause independent variance at the site-level that would be mischaracterized as noise by our method. While the PAGES database was curated to maximize temperature-sensitivity, some sites might be limited by precipitation as well as temperature, or could be sensitive to temperature within different parts of the growing season ( environmental and climate conditions, and ecological interactions all could create emergent trends that become integrated with slow climate variations (Cook, 1985;Cook & Kairiukstis, 2010). ...
... This result speaks to the fundamental challenge of recovering climate variations that occur over longer than the typical lifespan of a tree-a constraint known as the "segment length curse" (Cook et al., 1995). This age-related constraint is exacerbated by the detrending process that inevitably removes some low-frequency climate variability (Briffa et al., 1996;Cook, 1985). The converse problem is also expected-that even as low-frequency climate information could be removed during detrending, some influence of life history will remain in final chronologies. ...
Tree rings are the most widely‐used proxy records for reconstructing Common Era temperatures. Tree‐ring records correlate strongly with temperature on an interannual basis, but studies have found discrepancies between tree rings and climate models on longer timescales, indicating that low‐frequency noise could be prevalent in these archives. Using a large network of temperature‐sensitive tree‐ring records, we partition timeseries variance into a common (i.e., “signal”) and non‐climatic (i.e., “noise”) component using a frequency‐resolved signal‐to‐noise ratio (SNR) analysis. We find that the availability of stored resources from prior years (i.e., biological “memory”) dampens the climate signal at high‐frequencies, and that independent noise reduces the SNR on long timescales. We also find that well‐replicated, millennial‐length records had the strongest common signal across centuries. Our work suggests that low‐frequency noise models are appropriate for use in pseudoproxy experiments, and speaks to the continued value of high‐quality data development as a top priority in dendroclimatology.
... To eliminate the age-related growth component from a specific tree-ring series, we implemented the negative exponential curve method implemented in ARSTAN (Cook 1985). This approach allowed us to separate climate signals from age-related growth patterns in tree-ring data (Blasing and Fritts 1976;Cook, Edward R., and Leonardas A. Kairiukstis 2013). ...
... By combining each individual tree-ring series and constructing a regional chronology, we obtained a standardized chronology using ARSTAN. The standardized chronology represents tree-ring variations closely associated with climate change and served as a key component in our analysis (Cook 1985). ...
... These findings indicate synchronized variations in NPP due to similar climatic conditions experienced by the trees within the plots. Notable, low NPP values were observed in 1957, 1963, 1974, 1985, 1992, 1997, 2001, 2008, and 2014, whereas notably high NPP values were observed in 1970, 1989, 1994, 1999, 2002, 2010 (Fig. 3 (a)) in each plot. The overall forest NPP trend was determined by calculating the average NPP of the four plots and analysing the 5-year moving average results (Fig. 3 (b)), ZS sample plots could not be included in the mean analysis due to temporal inconsistencies with the other sample plots. ...
Climate warming has pronounced impacts on high-elevation regions, including arid Central Asia, and has multiple impacts on the environment. Forests in these mountainous areas provide essential services by regulating regional climate, sequestering carbon, and supporting soil and water conservation. However, trends in forest productivity and their response to climate change remain unclear. To address this knowledge gap, we collected tree cores from five sample plots in the western Tianshan region. We used tree-ring widths to reconstruct net primary productivity (NPP) and investigated the sensitivity of forest NPP to climate change by analysing weather station data and employing LASSO regression to identify climatic factors influencing forest growth. Our results demonstrate that the reconstructed forest NPP effectively captured significant carbon shifts and revealed a non-significant increase in forest productivity associated with climate warming and higher precipitation between 1970 and 2020 at low and middle elevations in the Tianshan mountains. Humidity is the primary limiting factor affecting forest growth in this region. Conversely, the relationship between temperature and forest growth is not consistent as precipitation increases. Our findings suggest that continued warming will exacerbate water stress in forests.
... from 24 trees. This program incorporated several approaches of tree-ring chronology computation that are new to dendrochronology (Cook, 1985). The techniques of cubic spline curve-fitting, two-stage removal of growth trend, biweight robust estimation of the mean value function, autoregressive modeling, and return of the common pooled persistence to the residuals, are used to enhance the common signal contained in an assemblage of tree-ring series while reducing noise and nonsynchronous variance to a minimum (Cook, 1985). ...
... This program incorporated several approaches of tree-ring chronology computation that are new to dendrochronology (Cook, 1985). The techniques of cubic spline curve-fitting, two-stage removal of growth trend, biweight robust estimation of the mean value function, autoregressive modeling, and return of the common pooled persistence to the residuals, are used to enhance the common signal contained in an assemblage of tree-ring series while reducing noise and nonsynchronous variance to a minimum (Cook, 1985). ...
... In addition, we subtracted the LWBI from the EWBI to generate the ΔBI data (Björklund et al., 2014). To remove age-related growth trends, we employed the ARSTAN program, which conservatively detrend the tree-ring sequences by fitting a negative exponential curve or a line with an arbitrary slope or a Hugershoff curve (Cook, 1985). The standard chronology was generated by calculating the double-weighted mean of individual sequences for each tree-ring series ( Figure 3). ...
... The reliability of the reconstruction model was assessed using a split-sample calibration and verification approach. Statistical parameters including the reduction of error (RE), coefficient of efficiency (CE) and sign test (ST) were used to evaluate the reliability of the reconstruction model (Cook, 1985;Fritts, 1976). Additionally, a multi-taper method (MTM) spectral analysis was used to identify periodicity in the reconstructed sequences (Mann & Lees, 1996), and spatial correlation analysis was performed to explore the spatial representation of the reconstructed series by using the KNMI climate explorer (http://climexp.knmi.nl). ...
Tree‐ring blue intensity (BI) is well known as a relatively new proxy, which has been utilized for temperature reconstructions over some regions of the worldwide, and has great research potential. In this study, based on tree‐ring data from Pinus massoniana in northwestern Wuyi Mountains in southeastern China, we established a series of tree‐ring width (TRW), earlywood BI (EWBI), latewood BI (LWBI) and delta BI (ΔBI) chronologies. The correlation analysis results indicated that BI chronologies are better than TRW chronology in relation to climate factors; EWBI chronology is a positive correlation with three temperatures (Tmean, Tmax and Tmin), whereas ΔBI and LWBI chronologies almost are negative correlations with temperatures. The LWBI chronology exhibited the highest correlation in July–August Tmin during 1955–2021 (r = −0.61, p < 0.01) and for the reconstruction. The reconstruction model could explain 36.64% of the observed variance. The reconstructed series spanned from 1843 to 2021 and documented three warm periods (1843–1863, 1874–1888 and 1992–2021) and one cold period (1911–1991), and Tmin rapidly warming since 1950s, which is similar to variation in the surrounding temperature reconstruction and is also consistent with the rate of global warming published by the IPCC. The result shows that the summer Tmin anomaly in southeast China is related significantly to the quasi‐biennial oscillation in the western Pacific and Indian Ocean.
... The chronology was established using the ARSTAN program (Cook 1985). To remove the influence of non-climatic factors, spline functions were initially applied to detrend the tree-ring width data from individual cores (Cook 1985). ...
... The chronology was established using the ARSTAN program (Cook 1985). To remove the influence of non-climatic factors, spline functions were initially applied to detrend the tree-ring width data from individual cores (Cook 1985). The standard deviation among the data was 0.169. ...
Vegetation productivity on the southern edge of the Inner Mongolian Plateau, which plays a vital role in the ecological environment and in the arable and pastoral production in this region, can be characterized by the NDVI (normalized difference vegetation index). However, the observed NDVI data span only the last ~ 40 years. The growth of Pinus tabulaeformis Carr. is strongly correlated with the NDVI, making it a valuable proxy for extending the length of observed NDVI datasets. In this study, we reconstructed an NDVI series for 1776-2021 for the Daqing Mountains, based on a tree-ring width chronology. The reconstructed data accounted for 55% of the variance in the observed data, and its statistical characteristics and validation indicate that the reconstruction is dependable. Spatial correlation analysis demonstrated the consistency of climate signals in central Inner Mongolia in both the arable and pastoral zones. The results of superposed epoch analysis revealed a good temporal consistency between drought and flood events and the reconstructed NDVI sequence in this region. and pastoral zones. The results of superposed epoch analysis revealed a good temporal consistency between drought and flood events and the reconstructed NDVI sequence in this region.
... We standardized the data using the ARSTAN software (Cook 1985) to optimize the climatic signal in the radial growth of tree rings. In this procedure, each sequence of tree rings is first subjected to a standard negative exponential curve or a straight or horizontal line with a negative slope. ...
... In this procedure, each sequence of tree rings is first subjected to a standard negative exponential curve or a straight or horizontal line with a negative slope. A single standard (STD) chronology (Cook 1985) was then created by calculating a bi-weighted robust mean from the raw measurements of each ring divided by the value of the fitted curve for the corresponding year. ...
Purpose
Climate change, largely caused by elevated carbon dioxide (CO2) concentrations, is a driver of lasting disturbances that cause changes in forest ecosystem functioning. This study aimed to investigate how Japanese cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria japonica D. Don) plantations in the subtropical forests of China respond to disturbances in tree growth under climate change.
Materials and methods
In this study, 23 canopy gaps were selected from two species in the Lushan National Nature Reserve of Jiangxi Province, China. Increment cores were obtained from trees retained near the edges of gaps and within the forest. Tree-ring chronologies were established, and the basal area increment (BAI) was calculated. The growth averaging method was used to detect growth release and analyze two key parameters of tree radial growth: magnitude and time lag. Moving correlation analyses were used to assess the long-term relationship between tree growth and climate, and regression analyses were used to quantify the relationship between the BAI and atmospheric CO2 concentrations.
Results and discussion
Species characteristics, tree distance from the gap center, gap size, and elevation all influenced tree growth release which was greater for Japanese cedar than Japanese cypress, and decreased with increasing distance from the gap center. Diameter at breast height (DBH) and pre-release growth influenced the time lag in growth release. The time-lag effect was more significant with smaller DBH and pre-release growth and did not differ between the two species. The correlations among growth, temperature, and precipitation were altered by the microclimatic environment created by the gaps. The BAI of Japanese cypress and Japanese cedar responded quadratically with increasing CO2 concentration (Ca), and the BAI increased with rising Ca, peaking at 360–380 ppm, followed by a decreasing trend. Due to the effect of the disturbance, there was a BAI increase of approximately 400 ppm (2015) for trees at the gap edge.
Conclusions
Growth characteristics were influenced by tree- and gap-level variables. Disturbance altered the link between tree growth and climate responses, increasing tree growth sensitivity to climatic influences, shifting the quadratic relationship between BAI and CO2 concentration, and providing growth potential to trees that crossed the CO2 tipping point.
... Ring widths were detrended using a 40-year cubic smoothing spline to generate a radial growth index (RGI) by using the program ARSTAN (Version 6.05P) [29]. The rationale for this was that the ring widths were standardized in order to eliminate size-and age-related effects on ring widths. ...
The overall objective of our study was to examine the influence of climatic factors and tree-based competition on the radial growth of jack pine (Pinus banksiana) forests affected by the fungal pathogen, Diplodia pinea. Our study utilized dendroclimatic techniques to examine how past annual diameter growth can be influenced by the historical climate of the region. Twenty jack pine sites were sampled in Michigan within the Upper Peninsula (UP) and the Lower Peninsula (LP) region. Furthermore, two condition levels of forest health (D. pinea-affected vs. healthy reference stands) were considered between two levels of stand density (i.e., high vs. low density). The relationships between radial growth and climate identified in this study indicated that jack pine radial growth was typically affected by the climatic moisture index, whereas the response to temperature variables was weak to non-existent. In the Upper Peninsula region, crown damage likely sustained during harsh winters could have made jack pine stands prone to D. pinea by facilitating a point of entry for infection; furthermore, higher-density stands infected by D. pinea were influenced by moisture stress that occurred during the summer of the prior year. In the LP region, regardless of stand density, D. pinea was sensitive to moisture stress in the summer of the prior growing season; furthermore, negative relationships with precipitation in the spring may have improved spore dispersion in D. pinea-affected stands. Overall, our study provides improved understanding of the interactive role of climatic stress and forest pathogens on jack pine productivity.
... Site chronologies were developed in the program ARSTAN (Cook & Holmes, 1986) for all tree ring records within each climate footprint following the methods in Hunter et al. (2020). In creating the chronologies, raw-ring measurements were detrended using a 2/3 cubic smoothing spline with a 50% frequency cutoff (Cook, 1985;Cook & Peters, 1981), a common tree ring detrending technique which removes the age-related growth trend while preserving other higher frequency variations (e.g., climate signal). This smoothing method is suggested as a reasonable method for paleoclimate analysis (Cook & Kairiukstis, 1990). ...
Groundwater level records in North America are relatively short (<60 years), preventing long‐term analysis of historical changes in groundwater levels associated with drought. In this study, tree ring widths are used to reconstruct groundwater levels in three regions in the North American Cordillera: Central British Columbia (BC), Canada, the Southern Interior Region of BC, and the San Luis Valley in Colorado, USA. Periods with severe drought conditions, identified using regime shift and threshold analyses were: 1890–1900 and 1950–1970 in Colorado, around 1920–1940 in the BC Interior, and 1935–1945 in Central BC. The groundwater level reconstructions are correlated with several climate indices and have similar regime shifts as identified in streamflow and drought records. The groundwater level reconstructions are strongly related to winter snowpack, suggesting that the observed trend of declining snowpack in recent years may lead to declining groundwater availability in these regions.
... Following the measurement and cross-dating of tree rings, a total of 232 tree-ring width series were derived from 84 trees in Meili Snow Mountain and 128 trees in Baxoila Ling ( Figure S2). To eliminate age-related growth trends, negative exponential curves or negatively sloped straight lines were fitted to each tree-ring sequence, and the resulting annual tree-ring width indices were utilized to construct a tree-ring chronology for each site along the two transects, employing bi-weight robust averaging (Cook, 1985) ( Figure S2). Owing to the presence of shared signature years (characterized by extremely narrow or wide rings), the tree-ring samples were aggregated into two composite chronologies for the two transects ( Figure 2), in addition to the site-specific chronologies. ...
Tree‐growth stability is crucial in upholding forest ecosystem services. Despite extensive research on the correlation between tree growth and climate, the influence of forest understorey on tree‐growth stability remains understudied.
We surveyed forest plots and collected tree‐ring samples along two elevational gradients, ranging from 3600 to 4400 m a.s.l., in the southeastern Tibetan Plateau. An index was developed to quantify individualistic growth stability of trees, and its linkage with the complexity of forest understorey structure was examined.
We found that tree‐growth stability is more pronounced in complex forest communities. In forests with higher understorey complexity, the proportion of trees experiencing growth release increased during wet years, while those with growth suppression augmented during dry years. Interestingly, a subset of trees exhibits abnormal growth increases even during the driest years, whereas another subset shows abnormal growth reductions during the wettest years. Furthermore, forests with more complex understorey structures exhibited a higher proportion of trees showcasing these two types of ‘anti‐phase’ growth statuses.
Synthesis. Our study underscores the linkage between individualistic growth stability of trees and the complexity of understorey structures. The growth stability of the overstorey layer is conveyed at the expense of individual‐level growth stability and synchrony in forests with complex understorey structures. These findings emphasize the necessity for attention to the interplay between tree growth and understorey community structures when assessing the impacts of future climate change on forest dynamics.
... For this purpose, we primarily used a negative exponential function, but in cases where this did not fit the data adequately we applied a linear regression function. To investigate the relationship between tree growth, climate, and runoff, and to develop a streamflow reconstruction for the Kura River, we built a standard regional tree-ring width chronology using the ARSTAN software from Cook (1985). The expressed population signal (EPS) for the chronology was 0.967, indicating a high level of reliability, and the mean inter-series correlation (RBAR) was 0.418, reflecting the degree of coherence among the individual tree-ring series. ...
In this paper, we conduct a dendrochronological study in the Western Transcaucasia region of Georgia to elucidate the relationship between tree growth and climatic variables (temperature, precipitation, and streamflow) in order to reconstruct the paleohydrology of the Kura River and to assess the impacts of climate change on water resources. We analyzed tree-ring chronologies from 1720 to 2021 CE, and analysis of July–August streamflow revealed five wet phases (1739–1753, 1764–1807, 1811–1831, 1962–1988 and 2000–2019 CE ranging in duration from 11 to 49 years) when streamflow exceeded the long-term mean, and four dry phases (1720–1738, 1832–1881, 1936–1961 and 1989–1999 CE) when streamflow was below average. The most extreme wet and dry years were 1771 and 1851 CE, respectively. Spatial correlation patterns of Kura River reconstructed runoff against sea level pressure (SLP) are negative in the Arctic and positive in mid- to high-latitude Eurasia. The Arctic Oscillation (AO)/North Atlantic Oscillation (NAO), and solar activity are important drivers of hydroclimatic conditions in the Mediterranean region, by modifying the location of high-pressure areas and large-scale atmospheric circulations. Comparison of our Kura streamflow reconstructions and data in the Old World Drought Atlas (OWDA) reveals a moderately positive correlation (0.40) throughout the study period, being strongest over the Southern Caucasus and Eastern Turkey. This validates the drought signals and emphasizes the importance of using multi-proxy approaches, supported by spatially resolved data, to enhance understanding of regional hydroclimatic variability and drought patterns. We additionally conducted future streamflow scenarios, most notably under the high-emission SSP585 scenario, in line with global trends in CMIP6 projections. Our streamflow results indicate a trend towards increasing drought severity, which highlights the need for urgent adaptation and mitigation strategies in water resource management in this region. Ultimately, this study provides valuable information on historical hydroclimatic conditions in the Kura River Basin, which help to develop strategies to mitigate the hydrologic impacts of climate change in the Western Transcaucasia Caucasus region. We further highlight the importance of regional and global teleconnections for understanding regional hydrological dynamics.
... --. [17,18]. ...
The intensive development of urbanized territories causes a change in the local climate and last impact to the growth and development of trees. The results of a study of the impact of the so-called “urban heat island” effect on the dynamics of tree-rings of Scots pine growing in the forest park “Slepyanka” in Minsk are presents. The active growth of the city and the development of large industrial enterprises began in the post the Second World War years. By the 1960s, the Minsk weather station, which was previously located outside the city, found itself on its border, and by the 1980s – within the city. At the same time, a large forest area has been preserved not far from it. The control object is pine trees growing in the same type of forest and of a similar age on the territory of the Pukhovichi forestry enterprise not so far from the Maryina Gorka weather station, located 60 km to the southwest of Minsk. Urban warming has increased radial growth by 9 to 16% compared to control stands since the 1980s. However, trees become more sensitive to summer droughts and the relationship between radial growth and winter-early spring air temperatures increases. The results confirm that global warming can increase the productivity of pine forest in Belarus but make them more susceptible to unfavorable climatic factors. This makes it possible to use trees that grow in large urban forest parks to predict changes in the productivity and sustainability of forest stands outside the city in the same region with further climate change.
... Ring-width series showing poor cross-dating and low correlation were discarded. Then we standardized the raw series to develop ring-width chronologies following methods devised by Fritts (1976) and Cook (1985). A nonlinear model (modified negative exponential curve) was fitted to the raw ring-width series to remove the biological growth trend from all individual series while preserving climate signals. ...
High mountain forests are notably sensitive to climate variability. The most significant relationships between tree radial growth and climate factors are often observed at altitudinal treelines, making them valuable for dendroecological studies. Cedrus deodara, commonly known as Himalayan cedar, is a key conifer species found at elevations between 2,400 and 4,000 meters in the temperate and sub-alpine zones of western Nepal Himalaya. A dendrochronological study was conducted to assess and examine the growth-climate response using tree cores from two cedar forests in the temperate zone of Nepal’s Rara National Park (RNP) and adjacent regions namely Mugu and Jumla in western Nepal. Tree cores were obtained from selected trees using an increment borer to reconstruct stand age structure, analyze growth-climate relationships, and assess above ground biomass production trends, indicated by Basal Area Increment (BAI) of trees. Growth-climate analysis was undertaken to establish correlations between climate variables and cedar growth, utilizing annual ring width index chronologies along with the historic climate data. Results revealed significant negative impacts of early growing season’s temperatures and positive impacts of late growing season’s temperatures on the radial growth at both sites. However, the negative influence of spring season temperatures was only observed at the Mugu site. Additionally, both sites exhibited a positive correlation between annual rainfall and radial growth of C. deodara. Basal Area Increment (BAI) analysis indicated a healthy forest stand of Himalayan cedar despite higher levels of human disturbance and increasing drought trends. The study underscores the importance of considering warming temperatures and alterations in precipitation patterns, as these factors are likely to significantly impact forest productivity in mountain ecosystems in the future.
... Trees improve the natural environment, enrich the ecosystems, and provide the aesthetic nourishment in urban and forest areas. With age they start to senesce with the onset of decay, breakage, and windthrow sometimes caused by hurricanes, thunderstorms, microorganism decay, or animal activities [1,2]. Certain defects such as cracks and holes are often indicative of this process, which remain in a tree trunk or its branches. ...
Trees’ structural defects are responsible for the reduction in forest product quality and the accident of tree collapse under extreme environmental conditions. Although the manual view inspection for assessing tree health condition is reliable, it is inefficient in discriminating, locating, and quantifying the defects with various features (i.e., crack and hole). There is a general need for investigation of efficient ways to assess these defects to enhance the sustainability of trees. In this study, the deep learning algorithms of lightweight You Only Look Once (YOLO) and encoder-decoder network named DeepLabv3+ are combined in unmanned aerial vehicle (UAV) observations to evaluate trees’ structural defects. Experimentally, we found that the state-of-the-art detector YOLOv7-tiny offers real-time (i.e., 50–60 fps) and long-range sensing (i.e., 5 m) of tree defects but has limited capacity to acquire the patterns of defects at the millimeter scale. To address this limitation, we further utilized DeepLabv3+ cascaded with different network architectures of ResNet18, ResNet50, Xception, and MobileNetv2 to obtain the actual morphology of defects through close-range and pixel-wise image semantic segmentation. Moreover, the proposed hybrid scheme YOLOv7-tiny_DeepLabv3+_UAV assesses tree’s defect size with an averaged accuracy of 92.62% (±6%).
... Subsequently, we used the detrend function from the dplR package in R (Bunn, 2008) to fit a modified negative exponential curve (ModNegExp) to each raw tree-ring series for detrending. Following detrending, standardized indices were calculated for each ring by dividing the original measured ring widths by the corresponding fitted values from the detrended model (Cook, 1985). These indices were then combined into a single F I G U R E 2 Climatograph of the study area for the period 1957-2017. ...
Vegetation growth is affected by past growth rates and climate variability. However, the impacts of vegetation growth carryover (VGC; biotic) and lagged climatic effects (LCE; abiotic) on tree stem radial growth may be decoupled from photosynthetic capacity, as higher photosynthesis does not always translate into greater growth. To assess the interaction of tree‐species level VGC and LCE with ecosystem‐scale photosynthetic processes, we utilized tree‐ring width (TRW) data for three tree species: Castanopsis eyrei (CE), Castanea henryi (CH, Chinese chinquapin), and Liquidambar formosana (LF, Chinese sweet gum), along with satellite‐based data on canopy greenness (EVI, enhanced vegetation index), leaf area index (LAI), and gross primary productivity (GPP). We used vector autoregressive models, impulse response functions, and forecast error variance decomposition to analyze the duration, intensity, and drivers of VGC and of LCE response to precipitation, temperature, and sunshine duration. The results showed that at the tree‐species level, VGC in TRW was strongest in the first year, with an average 77% reduction in response intensity by the fourth year. VGC and LCE exhibited species‐specific patterns; compared to CE and CH (diffuse‐porous species), LF (ring‐porous species) exhibited stronger VGC but weaker LCE. For photosynthetic capacity at the ecosystem scale (EVI, LAI, and GPP), VGC and LCE occurred within 96 days. Our study demonstrates that VGC effects play a dominant role in vegetation function and productivity, and that vegetation responses to previous growth states are decoupled from climatic variability. Additionally, we discovered the possibility for tree‐ring growth to be decoupled from canopy condition. Investigating VGC and LCE of multiple indicators of vegetation growth at multiple scales has the potential to improve the accuracy of terrestrial global change models.
... Prewhitening allowed us to remove the trend and low-frequency oscillations but retain the high-frequency ones. At this step, Pearson's coefficient r for the series was calculated using the leave-one-out method after prewhitening, which is a wellelaborated method of detrending (Cook 1985). ...
The four-eyed fir bark beetle Polygraphus proximus Blandford, 1894 (Coleoptera, Curculionidae: Sco-lytinae) is an invasive species that originates from the Far East. Since early 2000s, it became known as an aggressive pest causing massive dieback of Siberian fir (Abies sibirica Ledeb.) in Siberia and, to some extent, in the European part of Russia. Here, we report the first record of P. proximus in Sverdlovsk Region (the Middle Urals, Russia). In summer 2023, A. sibirica trees colonized by the pest were discovered on the territory of the "Olenyi Ruchyi" Natural Park. The dendrochronological analysis of the cores of fir trees killed by the beetle indicated that the majority (72%) of these trees died in 2021-2022, while the earliest tree death occured already in 2007 and 2009, meaning that the pest was present in the Natural Park for at least two decades. Mycological analysis of bark and wood samples of infested trees revealed the fungus colonies assigned to Grosmannia aoshimae (Ohtaka, Masuya & Yamaoka) Masuya & Yamaoka. Associated with P. proximus, this Far Eastern fungus species has spread with the beetle to Siberia and the Urals, contributing to tree mortality. Siberian fir is present on 69% of the forested area in the “Olenyi Ruchyi”. The colonization of fir trees by P. proximus recorded in the park in 2023 alarms about the high risk of the pest outbreak in the coming years, which may lead to subsequent tree death over a huge territory of the park affecting its ecological, cultural, and recreational values. To prevent the dramatic impact, it is highly urgent to take all the necessary measures to suppress the distribution and combat this alien pest.
... To preserve the potential effects of changes in permafrost conditions on radial shrub growth, while minimize any age-related growth trends, the ring-width series for each individual shrub were standardized (detrended, Fritts 1976) by fitting either negative exponential curves or straight lines using the ARSTAN software (Cook et al., 2017). Mean ring-width indices for each year were computed as the biweight robust estimate (Cook 1985) used to produce a standard chronology from all individual ring-width series (non prewhitened) for each site. Both H.W. Linderholm et al. ...
... Tree cores exhibiting poor cross-dating and correlation, displaying minimal year-toyear growth variability, unusual growth trends, breaks, or being identified as very young were excluded before the establishment of the chronology. The corrected ring-width data were standardized by using the computer program ARSTAN (Cook 1985). A negative exponential curve was used to detrend the tree-ring series to remove the biological growth trend related to the tree's age. ...
A dendrochronological study was carried out to investigate the relationship between the growth of chir pine (Pinus roxburghii) and climatic variables in the subtropical forest of western Nepal. Using tree ring analysis and meteorological data gathered from a nearby meteorological station, a 78-year (1944 to 2021) long chronology has been created. Temperature and precipitation were found to have a substantial impact on P. roxburghii radial growth. Although there were positive correlations between precipitation and tree growth in January, December, and February to April, these relationships were not statistically significant. According to the correlation analyses, there was a negative relationship between the tree growth and the precipitation in September and August of the current year as well as the September of the previous year. Notably, temperature was crucial, as there were significant positive relations found between the minimum and maximum temperatures and tree growth. The temperature of the previous year (September, November, and December) as well as the current year (June to November) had a positive correlation with the growth of tree rings. The results indicated that while temperature was favorable for chir pine radial growth practically all months and seasons, summer to post-monsoon precipitation limited tree growth. Furthermore, the increasing average minimum temperature had a more significant relation with the tree ring growth than the average maximum temperature. Our result demonstrated that the growth of subtropicalP. roxburghiiresponded positively to the present scenario of rising temperature and falling precipitation in the study area. This research contributes valuable insights into the complex dynamics of forest ecosystems and their responses to changing environmental conditions.
Keywords:
Climate change; dendrochronology; tree ring analysis; precipitation; Nepal Himalaya region
... We used the program COFECHA for data quality control of our tree-ring measurement series (Holmes 1983). The chronology was generated using the ARSTAN program (Cook 1985). To filter out non-climatic influences in the ring width series, we applied a negative exponential function. ...
Unstable environments intensify the frequency of extreme disasters. Long-term climate changes can lead to agricultural and ecological degradation that threatens population sustainability. To better understand past climatic events and consequences, here we present a reconstruction of the self-calibrating Palmer drought severity index (scP-DSI) from September to August for the desert margins of northern China, dating back to 1742. The reconstruction accounts for 42.9% of the variation of meteorological data between 1951 and 2020. Our spatial correlation analyses showed significant correlations between scPDSI, runoff, and precipitation. Over the past 279 years, the study area has undergone nine dry and eight wet periods, with the most severe climate extremes between the 1850s and 1890s. This period of prolonged drought in northeastern China coincided with the combined impacts of climatic factors and human influences, contributing to the fall of the Qing Dynasty. Analysis of periodicity and anomalies in sea surface temperatures indicate a strong association between wet and dry cycles and El Niño-Southern Oscillations. Our findings offer insights into long-term dry and wet fluctuations at the desert margins in northern China and elucidate the relationship between drought and the dynamics of civilizations. They also highlight the potential impact of extremes in climate on modern society, especially under the four projected shared socioeconomic pathways climatic scenarios, which predict worsening droughts in northern China.
... Moreover, the series were pre-whitened to remove the remaining autocorrelation (Cook et al., 1990b). Pre-whitening of the series prior to cross-dating is frequently recommended (Cook, 1985;Monserud and Yamaguchi, 1989;Grissino-Mayer et al., 2010). The Tavastia and Åland master chronologies were produced by averaging the standardized tree-ring series into the respective mean chronologies. ...
Archaeological and living tree data were used to construct tree-ring chronologies over the medieval (AD 1183–1430) and recent (AD 1812–2020) periods in Turku, which is historically an important population centre in Southwest Finland and the country. Comparisons between the two tree-ring assemblages, and between the previously built chronologies from the Åland (historical timber) and Tavastia (lacustrine subfossils and living trees) sites, provided ways of understanding the growth patterns and their linkages to climatic, environmental, and edaphic factors. Tree growth in and around Turku was affected by warm-season precipitation and winter temperature. Similar relationships were previously evident also in the Åland tree rings, whereas the data from a wetter Tavastia site did not exhibit similar precipitation signal. The site conditions influence also the correlations which are higher between Turku and Åland than between Turku and Tavastia chronologies. Construction of long continuous chronology is impaired by human-related activities, the Great Fire of Turku in 1827 and logging, which have diminished the availability of dead and living-tree materials, respectively. These conditions lead to hardships of filling the gap between the medieval and recent periods and updating the archaeological datasets with compatible living-tree data, which are both demonstrated by our results.
... Tree chronologies included series with high confidence in crossdating and ≥ 30 yr length. Series were standardized to ring-width indices via ARSTAN (Cook 1985) using a cubic smoothing spline with a 50% frequency cutoff at 32 yr (32-yr spline) to remove geometric growth trends and low-frequency variation. Standard (STD) tree chronologies were combined into nine respective location chronologies and one composite chronology with no further detrending and used a biweight robust mean to reduce the influence of outliers (Cook and Kairiukstis 1990). ...
Key message
Dendroclimatic sensitivity varies by axial position for Sequoiadendron giganteum: negative correlations with June temperature strengthen with height, while positive correlations with snow water are strongest in the lower trunk.
Increment cores collected along trunks of mature Sequoiadendron giganteum provide new and updated ring-width chronologies ideal for assessing how height above ground affects sensitivity of radial growth to climatic variation. Chronologies from 61 living trees at nine locations across the geographic distribution span 1973 yr. Analyses of subsets of 18–44 trees reveal that correlations between radial increments and climate (temperature, water availability) vary with axial position. Negative correlations with maximum and minimum June temperature intensify with height and are strongest at the highest position analyzed (60 m above ground). Sensitivity to the hydroclimate variable of April-1 snow water equivalent is stronger at lower trunk positions (10 m) compared to breast height or the upper trunk, and a similar relationship is identified for the standardized precipitation evapotranspiration index using a 12-month window ending in September. Drought-induced low-growth years computed as radial increment relative to the mean of 10 yr before and after are more weakly expressed at breast height compared to higher on the trunk (10–60 m). Analysis of regional upper (maximum core height = 87 m) versus lower trunk (above buttress) chronologies corroborate differing inter-annual correlations with climate depending on height above ground. Accounting for axial variation in dendroclimatic sensitivity can maximize the quality of environmental reconstructions using tree rings and improve biophysical understanding of Sequoiadendron, especially in the context of an increasingly arid climate.
... Raw ring width sequences were detrended by fitting a negative exponential curve or linear regression function (ModNegExp) with the "dplR" package (Bunn 2008) in R software (R Core Team 2021). All tree-ring indices from each site were then combined into a single standard chronology using Tukey's biweight robust mean to minimize the effects of abnormal values (Fig. 3) (Cook 1985). The arithmetic mean method was used to calculate the regional tree-ring chronologies of P. massoniana for young (YOUNG) and old (OLD) age classes. ...
Trees progress through various growth stages, each marked by specific responses and adaptation strategies to environmental conditions. Despite the importance of age-related growth responses on overall forest health and management policies, limited knowledge exists regarding age-related effects on dendroclimatic relationships in key subtropical tree species. In this study, we employed a dendrochronological method to examine the impact of rapid warming on growth dynamics and climatic sensitivity of young (40–60 years) and old (100–180 years) Pinus massoniana forests across six sites in central-southern China. The normalized log basal area increment of trees in both age groups increased significantly following rapid warming in 1984. Trees in young forests further showed a distinct growth decline during a prolonged severe drought (2004–2013), whereas those in old forests maintained growth increases. Tree growth was more strongly influenced by temperature than by moisture, particularly in old forests. Spring temperatures strongly and positively impacted the growth of old trees but had a weaker effect on young ones. Old forests had a significantly lower resistance to extreme drought but faster recovery compared to young forests. The “divergence problem” was more pronounced in younger forests due to their heightened sensitivity to warming-induced drought and heat stress. With ongoing warming, young forests also may initially experience a growth decline due to their heightened sensitivity to winter drought. Our findings underscore the importance of considering age-dependent changes in forest/tree growth response to warming in subtropical forest management, particularly in the context of achieving “Carbon Peak & Carbon Neutrality” goals in China.
... The trees were excluded for the chronology development in a few cases when anomalous growth trends occurred. The tree-ring indices were calculated as ratios between raw measurements and the fitted growth values, and then merged to develop a biweight robust mean chronology of die-back and healthy groups, respectively (Cook, 1985). We then averaged all of the standardized tree-ring series to obtain the final TRW index for each group (Fig. 2a). ...
... Finally, we employed a double-weighted mean method to obtain a standardized tree ring width index series for each sampling site (Che et al., 2023). This process was implemented using the ARSTAN program (Cook, 1985). ...
Quantitative assessment of tree responses to the local environment can help provide scientific guidance for planted forest management. However, research on the climate-growth relationship of Korshinsk peashrub (Caragana korshinskii Kom.) under different land preparation and post-management (irrigation) conditions is still insufficient. In this study, we collected 223 tree-ring samples from Korshinsk peashrubs using dendroecological methods and systematically quantified the relationships between shrub growth and climatic factors under different management practices in the western Loess Plateau of China. Our findings demonstrated that drought stress caused by scarce precipitation from April to August was the primary factor limiting the growth of Korshinsk peashrubs in the northern and southern mountains of Lanzhou. The “climwin” climate model results showed a weak correlation between natural Korshinsk peashrub growth and drought stress, whereas planted Korshinsk peashrub under rain-fed conditions in the southern mountain was significantly (p<0.05) limited by drought stress from April to August. Moreover, planted Korshinsk peashrub growth under irrigated conditions in the northern mountain was limited only by drought stress in January. Drought model explained 28.9%, 38.3%, and 9.80% of the radial growth variation in Xiguoyuan (XGY), Shuibaozhan (SBZ), and Zhichagou (ZCG) sites, respectively. Artificial supplementary irrigation alleviated the limitation of drought on planted forest growth, which may be implemented for Korshinsk peashrubs planted on sunny slopes, while planted Korshinsk peashrubs under natural rain-fed conditions can be planted on shady slopes through rainwater harvesting and conservation measures such as horizontal ditches and planting holes.
... The crossdating was further validated using the program COFECHA. Site chronologies were derived by averaging individually standardized cores using the program ARSTAN [31], which applied a cubic spline with a 50% response frequency cut-off at the half length of the series to preserve high-frequency growth variance while removing agerelated growth trends. The early section of chronologies was truncated with the threshold of 0.85 in expressed population signal (EPS) to denote sufficient strength of the signal for use in paleoclimate reconstruction. ...
The climate in the source region of the Yangtze River, Yellow River, and Mekong River is of great research interest because of its sensitivity to global change and its importance in regulating water resources to densely populated and vast areas downstream. A five-century long record of spring (May–June) for the Palmer Drought Severity Index (PDSI) was reconstructed for this region using tree-ring width chronologies of Qilian juniper (Juniperus przewalskii Kom.) from five high-elevation sites. The reconstruction explained 46% variance in the PDSI during the instrumental period 1955–2005. The reconstructed PDSI showed that the occurrence of dry extremes became frequent during the last century relative to the previous four centuries. The standard deviation of the reconstructed PDSI in the 100-year window showed that the recent century held apparent high values of standard deviation in the long-term context. Sustained droughts occurred in periods 1582–1631, 1737–1757, 1772–1791, 1869–1891, 1916–1939, and 1952–1982, whereas relatively wet intervals were observed in 1505–1527, 1543–1564, 1712–1736, 1792–1816, 1852–1868, 1892–1915, and 1983–2008. Notably, in the context of the past five centuries, the study region showed an increased inter-annual variability in the recent century, suggesting an intensified hydroclimatic activity possibly associated with global warming. Moreover, through diagnostic analysis of atmospheric circulation, we found that the negative phase East Asian–Pacific teleconnection pattern may be likely to trigger drought in the study region.
... To obtain well-replicated chronologies, the tree-ring samples were grouped into three altitudes, treeline (4200 m a.s.l.), middle elevation (3900-4100 m a.s.l.) and lower elevation (3600-3800 m a.s.l.). A standard tree-ring chronology was developed for each elevation group by fitting a negative exponential curve or a straight line of negative slope to the tree-ring sequences to remove any biological growth trends and computing bi-weight robust means of the resulting ringwidth indices (Cook 1985). ...
standardized precipitation-evapotranspiration indices (SPEI) strengthened in the mid-and lower-transect. Comparison between growth and vegetation data showed that tree growth was more sensitive to drought in stands with higher species richness and greater shrub cover. Drought stress on growth may be increased by heavy competition from shrub and herb layers. These results show the non-stationary nature of tree growth-climate associations and the linkage to forest community structures. Vegetation components should be considered in future modeling and forecasting of forest dynamics in relation to climate changes.
... ARSTAN program was used in the creation and standardization of regional chronologies. The standardization process was performed with the ARTSAN program by tting a 67% cubic smoothing spline with a 50% cutoff frequency (Cook, 1985). Many years of data are needed to analyze climate-annual ringwidth relations. ...
This study aims to determine the effect of monthly average temperature and monthly total precipitation on tree ring growth and to reveal the possible effects of climate change by using gridded data from the lower and upper growing limits of Scots pine, fir and black pine in the Küre Mountains National Park. Küre Mountains National Park is an essential natural protected area in Türkiye's Black Sea Region. This park is one of the 9 Hotspots in Turkey. For dendrochronological analyses, samples were taken from the lower and upper growing limits of Scots pine, fir and black pine trees, using increment borer, from locations determined within the national park's borders. Measurements of the samples taken were made using the LINTABTSAP measurement system with a sensitivity of 0.01 mm. In analyzing climate-tree ring relations, gridded data taken from the World Meteorological Organization Regional Climate Center website was used for areal precipitation totals and temperature averages, as it has longer-term data. Response Functions were calculated with the help of DENDROCLIM2002 to reveal the statistical relationships between climate data and tree ring growth. According to our results, tree ring growth on trees in the research area is positively affected by the increases in monthly total precipitation in June and July for all site all chronologies and negatively affected by November of the previous year and January, February, September and October of the current year.
To understand and manage Mediterranean forested ecosystems under a changing climate, forest managers require improved knowledge of forest plantations ability to adaptat to drought stress. This paper analyses the radial growth dynamics (earlywood width, EW; latewood width, LW; tree-ring width, TRW; basal area increment, BAI) and vegetation activity (normalized difference vegetation index, NDVI; enhanced vegetation index, EVI) of Pinus nigra plantations growing on two sites (lower, upper) with contrasting edaphic conditions, in eastern Albania, and evaluates the growth responses to climate (temperature and precipitation) and drought (standardized precipitation index, SPI; standardized precipitation evaporation index, SPEI). P. nigra plantations showed pronounced differences in growth and response to climate (drought) and soil variations between sites. Trees at the lower site, located on poor soils, showed lower growth rates and higher response to June-July precipitation, August temperatures and drought index SPI (< 8 months) in summer as compared to trees at the upper site distributed on rich soils which remained more buffered. At the upper site, the high vegetation activity in July (EVI) and August (NDVI) affected considerably the radial growth rate, whereas at the lower site, only July EVI showed significant relationship with EW, LW and TRW. Vegetation indices at the lower site showed the strongest association with drought. We conclude that future management of P. nigra plantations should be properly adapted to modulate variations in climate and to sustain tree growth and productivity, triggered by local site conditions.
Against the background of climate warming and humidification, the so-called ‘divergence problem’ reduces the stability of tree rings in response to climate, and affects the reliability of tree-ring reconstruction. Investigation of the divergence problem is crucial to improve our understanding of the response patterns of trees to climate warming, and provide a scientific basis for accurate climate reconstruction. Based on tree-ring width data for Siberian larch (Larix sibirica Ledeb.) growing at low elevations in the eastern Altay Mountains, we analyzed the relationship between radial growth of trees and climatic factors in the context of abrupt climate change in this region. We calculated the proportional contribution of five climatic factors to the radial growth of trees, and discussed the response mechanism of radial growth of L. sibirica in combination with large-scale atmospheric circulation patterns. The radial growth of L. sibirica was mainly constrained by water availability. Before climate warming (1961–1990), the radial growth of L. sibirica was mainly limited by temperature in the previous June. After abrupt climate warming (1991–2020), there was a significant positive correlation between growth and soil moisture in the previous winter, suggesting that high temperatures in the following spring would limit tree radial growth if water availability was low. The attribution analysis results revealed that, before 1990, the proportional of relative contribution of temperature to radial growth of trees exceeded 60%. Since 1990, the proportional of relative contribution of water (precipitation and volumetric soil water) to growth of L. sibirica increased. This might reflect the combined effects of local climatic conditions and changes in large-scale atmospheric circulation.
Although recent warming affects the high-northern latitudes at an unprecedented rate, little is known about its impact on boreal forests because in situ observations from remote ecosystems in Siberia are sparse. Here, we analyse the radial growth and climate sensitivity of 54 Cajander larches (Larix cajanderi Mayr.) from three sites across the northern treeline ecotone within the Omoloy river basin in northeastern Siberia. Three independent tree-ring width chronologies span 279–499 years and exhibit distinct summer temperature signals. These records further reveal evidence for sufficiently earlier onsets of growing seasons since the middle of the 20th century. This phenological shift coincides with rapidly increasing May temperatures and associated earlier snowmelt. Our findings reinforce the importance of high-precision ground measurements from remote regions in Siberia to better understand how warming-induced changes in the functioning and productivity of the boreal forest influence carbon, nutrient, and water cycle dynamics.
Extreme climate events have increased in terms of their amplitudes, frequency and severity, greatly affecting ecosystem functions and the balance of the global carbon cycle. However, there are still uncertainties about how extreme climate change will affect tree growth. This study characterized the responses of tree growth to extreme climate on the northeastern Tibetan Plateau from 2000 to 2020. Meanwhile, a back propagation neural network was used to predict tree growth trends under two future emission scenarios from 2020 to 2050. This study revealed that: (1) the tree-ring width index (RWI) showed a decreasing trend (− 0.04/decade) in the eastern region, but the enhanced vegetation index (EVI) showed an increasing trend (0.05/decade) from 2000 to 2020. While both RWI and EVI in the middle and western regions showed increasing trends. (2) The responses of RWI and EVI to extreme climate were regionally asymmetric. In the eastern region, extreme precipitation inhibited tree radial growth, while extreme warm nights promoted tree canopy growth. In two other regions, both extreme precipitation and extreme warm nights promoted tree growth. (3) The model predicts that there was no significant change in RWI and EVI in the western region, but both RWI and EVI showed an increasing trend in the middle and eastern regions under the low emission scenario. Under the high emission scenario, the growth of tree stem and canopy in all three regions shows a general decreasing trend. The results of this study both improved the understanding of the differences in carbon allocation between tree stem (RWI) and canopy (EVI) and identified vulnerability thresholds for tree populations.
Across much of Europe, climate change has caused a major dieback of Norway spruce (Picea abies L.), an economically important tree species. However, the southeasternmost fringe of this tree species-the Eastern Carpathians-has not yet suffered large-scale dieback. Studying temporal shifts of climate sensitivity (TSCS) over time may elucidate the degree to which Norway spruce may be vulnerable to climate-change induced decline in upcoming decades. Under this framework, we analyzed a regional tree-ring network comprising >3000 trees, with the aim of quantifying TSCS since 1950. We mathematically defined TSCS as the slope parameter of the regression of climate sensitivity (the correlation coefficient) over time. Given the often-observed contrasting shift of climate sensitivity at low versus high elevations, we were particularly interested in studying potentially divergent TSCS along elevational and spatial gradients. Our analyses revealed several indications of TSCS for Norway spruce in the Eastern Carpathians. First, at high elevations (>1100 m a.s.l.), we found that the positive link between summer temperature and spruce growth decreased significantly over the study period. In turn, these trees, over time, featured an increasing positive relationship with late winter temperatures. At low elevations (<800 m a.s.l.), the signal of positive summer Standardised Precipitation-Evapotranspiration Index (SPEI) correlation became more frequent among sites towards 2021, while the strength of the positive winter SPEI correlation from the previous growing season weakened. Our results revealed that TSCS was driven significantly by an elevational climate gradient and a longitudinal continentality gradient. Overall, our findings indicate that Norway spruce is increasingly affected by water limitations under climate change at low elevations, highlighting a potentially rising risk of decline of this species in the Eastern Carpathians.
Tree growth is a multifaceted process influenced by various factors at different spatial and temporal scales, including intrinsic tree traits and environmental conditions. Climate factors have a significant impact on tree growth dynamics, while geological controls can also play a crucial role. However, our understanding of the interplay between these factors concerning tree growth is currently limited. This study focuses on Norway spruce (Picea abies [L.] Karst.), one of the economically most important coniferous tree species in Europe, to investigate the interplay of growth, climate, and environment at the forest and corresponding treeline sites in the High Tatra Mountains of Slovakia. Specifically, we developed chronologies of tree-ring width (TRW) and late-wood density (MXD) for different tree size classes across two limestone and granitic sites. Growth rates of Norway spruce trees have been increasing in forests since the 1930s and from the 1950s at treelines. Growth rates were consistently higher on limestone bedrock compared to granitic bedrock conditions. Variability of radial growth is primarily driven by climate at both geological settings with trees on granitic bedrock displaying more pronounced responses to climatic variables. We observed weakening (non-stationarity) in climate signals over time and across all size classes in both geological settings. The magnitude of these effects is small, but varies across size classes, with larger trees generally displaying stronger climate sensitivities compared to smaller ones. Therefore, our findings accentuate the potential implications of geological settings, climate, and environmental factors on the absolute growth and growth dynamics of Norway spruce, highlighting the need for further research to fully understand and manage forest ecosystems in mountainous regions.
The Himalayas are undergoing significant changes in temperature and moisture availability due to global climate change. Understanding how these changes affect tree growth is critical for conserving and managing this biodiverse region. To investigate the growth-limiting climatic factors, we collected tree-ring data from Abies pindrow old-growth mountain forests across 3190 to 3700 m a.s.l. in the inner valleys of the Garhwal Himalayas. This area faces significant temperature increases, reduced summer monsoon activity, and decreased winter precipitation. We found that over the past century, tree growth suffered from warm and dry springs and benefited from cool and moist springs, particularly at lower elevations (< 3400 m a.s.l.). Conversely, summer climate dynamics had minimal impact on radial growth. The sensitivity of Abies growth to spring climate can be attributed to the inner valleys’ continental climate, marked by spring water deficit. Additionally, higher elevation trees (> 3400 m a.s.l.) showed positive correlations with dormant period temperatures in prior October and January, with the positive effect of October warmth strengthening over time. A dynamic analysis of the impact of spring (March–May) temperature, precipitation and Standardized Precipitation-Evapotranspiration Index revealed a recent unification (the 1980–2010s) of the climate–growth relationship across elevations. Specifically, the low-elevation trees have become less sensitive to warm springs, while the high-elevation trees have only recently become sensitive to warm and dry springs. The varying growth responses along the elevation gradient highlight the necessity of site-dependent differentiation when assessing the impacts of global climate change on species performance and geographic range shifts.
Spring precipitation in southeastern China and Bengal, occurring during the transitional phase from winter to summer monsoons, serves as a critical window into the dynamics of large-scale circulations and the subsequent summer monsoon. While many studies have analyzed spring precipitation in southeastern China and Bengal, their interconnections and implications for the summer monsoon have remained relatively under explored. We utilized the Empirical Orthogonal Function of spring precipitation to reveal Synchronous Spring Precipitation (SSP) in southeastern China and Bengal. This synchronicity is bridged by the East Asian Subtropical Jet (EASJ) that extends from Bengal to southeastern China. The EASJ was predominantly correlated with precipitation in southeastern China prior to the 1990s, while it developed a more profound connection with precipitation in Bengal after the 1990s. Notably, SSP anomalies occurred during the developing phase of the El Niño-Southern Oscillation (ENSO). The predictive capacity of SSP for the Indian summer monsoon (ISM) amplifies during periods of the intensified SSP-ENSO correlations and positive phase of the North Pacific Meridional Mode. Tree-ring based reconstructions spanning the past two centuries further corroborate the persistent linkages among the SSP, ISM, and ENSO. Our research sheds light on the intricate interplay of these factors and their significance in understanding and predicting the monsoon dynamics in the region.
The dating of landslide movements is a unique opportunity to learn about their past in the absence of archival data. Dendrogeomorphic methods, based on the study of tree rings, offer an exceptional combination of accuracy and temporal range of dating. However, most landslide studies to date have been based on the analysis of macroscopic growth disturbances in trees. In doing so, the use of anatomical growth responses may be more advantageous in some aspects. Thus, this study aims to introduce the spectrum of anatomical growth responses in trees induced by landslide movements for their dating, substantiating their advantages and limitations, and comparing them with each other. Samples from roots and trunks of sycamore maple (Acer pseudoplatanus L.) growing on a landslide of known time of occurrence (May 2010) were used. Geophysical ERT measurements were performed to test the assumption of subsurface influence of landslide movements on tree growth. Based on the results focused on the intensity of changes in vessel lumen area (VLA) and percentage changes of VLA within the tree ring, anatomical changes identified in four different geomorphic situations on the landslide with expected different effects of landslide movements on tree growth were compared with each other. Responses in tree roots were generally significantly stronger compared to those in tree trunks. However, the short time series and difficult cross-dating of roots can be considered as a disadvantage. On the other hand, the identification of anatomical responses in trees with straight trunks (until now practically not used in landslide research) allows a significant expansion of the number of trees usable for landslide dating in the future.
We analyzed the influence of the local climate and three large-scale climatic phenomena on primary (crown) and secondary (radial) growth of 35 Pinus oocarpa trees in the Los Tuxtlas Biosphere Reserve in southeastern Mexico. Whereas local satellite data of the Normalized Difference Vegetation Index (NDVI) was employed to analyze primary growth, annual tree-ring widths were measured and averaged across trees to quantify secondary growth for the site. For primary growth, a monthly time series of 26 years (1982–2008) resulted for the site. For secondary growth, the annual time series of tree-ring widths was for 45 years (1965–2008). The NDVI positively correlated with precipitation for March to May (r = 0.56), and tree-ring widths for January to June (r = 0.63). Maximum temperature correlated negatively with the NDVI for June to July (r =− 0.55) and tree ring widths for June (r = − 0.55). The results from correlation analysis and spatial correlation maps highlight the negative influence of the Pacific Ocean and the positive influence of the Atlantic Ocean on both types of growth, by causing large-scale climatic phenomena that affect the regional climate. The NDVI and radial growth positively correlated from April to July (r = 0.44), when both growth types resume concurrently, suggesting that carbohydrates produced in the crown lead to increased radial growth at the beginning of the growing season. Our study highlights the differential effects of large-scale climate phenomena on primary and secondary tree growth in a widespread tropical pine species in Mexico.
We found many narrow or missing annual tree-rings during the period from 1996 to 1998 in most of fir trees sampled in the Diazas forest (Torla; 42º 37’ 50’’ N, 0º 05’ 40’’ W, 1528 m a.s.l.). These tree-rings were synchronic with attacks in that area of the leaf miner Epinotia subsequana Hw. (Lepidoptera). This temporal coincidence motivated this dendroecological study. The radial growth in Diazas was compared with that observed in other 13 fir forests sampled across the Aragón Pyrenees and not affected by E. subsequana. During the 1996-98 period, the radial growth in Diazas was 12-22 % with respect to the mean growth in the rest of stands. The decrease of radial growth during these three years was the cause of the high frequency of missing rings. These were rarely found in others fir forests. This fact suggested that some local factor have caused the growth reduction. The lower radial growth was produced by the intense defoliations done by E. subsequana. The most pronounced reduction of growth was observed in 1997, one year after the maximum level of defoliation was reached (1996). This temporal lag may be due to the fact that the defoliation observed in 1996 reduced the reserves and growth potential to form the tree-ring in the next year. In fact, the radial growth did not increase notably until 3 years (1999) after the first intense growth reduction (1996) was observed
The effect of temperature and precipitation on the change in the radial growth of wood of Berlin poplar (Populus × berolinensis Dipp.) and small-leaved linden (Tilia cordata Mill.) in Saint Petersburg was studied. Cores were taken from old trees in the Forestry Technical University park, in the Palevsky square, in the city of Pushkin (poplar trees) and in the Moscow Victory Park (linden trees). To eliminate the influence of the samples’ age factor on the change in its growth rings’ width, the generally accepted detrending methods were used; the calculations were carried out in the Arstan software. Precipitation and temperature fluctuations during the winter period do not significantly affect the growth of poplar and linden in Saint Petersburg. Summer precipitation has a positive, but overall not a decisive effect, in some cases, the radial growth increases with increasing rainfall. Temperature has no significant effect on standardised (age-adjusted) growth rates. Non-standardised average values of growth under the increasing temperature conditions in July–September significantly decrease. The effects of temperature and precipitation appear to be indirect, exacerbating or offsetting the effects of other factors, especially the air pollution. The impact of pollutants increases with the increase in temperatures at the end of the growing season, because they accumulate on the leaves’ surface. Precipitation washes away pollutants, reducing the intensity of their impact. Growth decline in poplar trees in the second half of the 1990s, in the absence of such an occurrence in linden, can be explained by the consequences of a prolonged outbreak of the poplar moth (Phyllonorycter populifoliella) mass reproduction in 1991–1999. The above assumptions require additional research; in particular, determining the level of leaf contamination during the growing season and taking into account the impact of other factors.
The increasing number of climate-associated disasters in the Himalayan region causing a huge impact on human life and the ecosystem are the bellwethers of climate change. Weather records from the high Himalayas, though sparse and limited to the past few decades, show its sensitivity to global climate change. However, short observational records preclude our understanding of long-term climate variation over the topographically controlled Himalaya. In view of this, tree-ring data of Himalayan birch trees from the cold-arid Lahaul-Spiti, Himachal Pradesh, western Himalaya is analyzed in the present study. The response function analysis of Himalayan birch chronologies with climate variables revealed a significant impact of February–March minimum temperature in radial growth of Himalayan birch. Taking this relationship as a guide, we developed the first record of winter/spring (February–March) minimum temperature for this region. The reconstructed minimum temperature record reveals annual to decadal scale variability associated with several prolonged cold and warm periods. A strong association of warm/cold phases of February–March temperature with low/high snow water equivalent of western Himalaya, as well as seasonal snow and glacial derived streamflow of the upper Indus River basin was identified. The observed hydrological linkages were further tested using river flow records of the Satluj and Indus Rivers of the western Himalaya. The observed opposite relationship between winter–spring minimum temperature and the summer hydro-climatic records can be of immense use to policymakers, agriculture stockholders, and hydropower project officials to take precautionary measures in advance.
Deformation and failure of the talus slope in the cold region significantly threaten engineered structures. Its driving mechanism of the deformation process is the most challenging issue. In this study, we try to explore these issues using tree ring characteristics. Fifty samples from 21 trees of Pinus densiflora growing on the talus slope in the Huanren area of Northeast China are tested to investigate the characteristics of tree rings and their relation to climate change. The deformation and its driving mechanism of this talus slope are then studied by combining the analysis of tree-ring width and mutation identification with the local meteorological data. The results present that the studied talus slope in Huanren has deformed to varying degrees at least 60 times since 1900. It is reasonable to speculate that the deformation mode of this slope is probably of a long-term and slow type. The local precipitation and seasonal temperature difference are the vital inducing factors of the mutation of tree-ring width and slope deformation. Repeated freezing and thawing are believed to be the driving factors of this talus slope in the cold region. A theoretical model is proposed to capture and predict the deformation of the talus slope. This work presents a new perspective and insight to reveal the deformation and its driving mechanism of similar talus slopes in the cold region. It is of great significance to practical engineering treatment and disaster prevention for this kind of cold region environment.
The role of the temperate mixed broadleaf-Korean pine forest (BKF) in global biogeochemical cycles will depend on how the tree species community responds to climate; however, species-specific responses and vulnerabilities of common trees in BKF to extreme climates are poorly understood. Here we used dendrochronological methods to assess radial growth of seven main tree species (Pinus koraiensis, Picea jezoensis, Abies nephrolepis, Fraxinus mandshurica, Phellodendron amurense, Quercus mongolica, and Ulmus davidiana) in an old-growth BKF in response to climate changes in the Xiaoxing’an Mountains and to improve predictions of changes in the tree species composition. Temperature in most months and winter precipitation significantly negatively affected growth of P. jezoensis and A. nephrolepis, but positively impacted growth of P. koraiensis and the broadleaf species, especially F. mandshurica and U. davidiana. Precipitation and relative humidity in June significantly positively impacted the growth of most tree species. The positive effect of the temperature during the previous non-growing season (PNG) on growth of F. mandshurica and Q. mongolica strengthened significantly with rapid warming around 1981, while the impact of PNG temperature on the growth of P. jezoensis and A. nephrolepis changed from significantly negative to weakly negative or positive at this time. The negative response of radial growth of P. jezoensis and A. nephrolepis to precipitation during the growing season gradually weakened, and the negative response to PNG precipitation was enhanced. Among the studied species, P. koraiensis was the most resistant to drought, and U. davidiana recovered the best after extreme drought. Ulmus davidiana, P. jezoensis and A. nephrolepis were more resistant to extreme cold than the other species. Climate warming generally exacerbated the opposite growth patterns of conifer (decline) and broadleaf (increase) species. Deciduous broadleaf tree species in the old-growth BKF probably will gradually become dominant as warming continues. Species-specific growth-climate relationships should be considered in future models of biogeochemical cycles and in forestry management practices.
Europe experienced severe heat waves during the last decade, which impacted ecological and societal systems and are likely to increase under projected global warming. A better understanding of pre-industrial warm-season changes is needed to contextualize these recent trends and extremes. Here, we introduce a network of 352 living and relict larch trees (Larix decidua Mill.) from the Matter and Simplon valleys in the Swiss Alps to develop a maximum latewood density (MXD) chronology calibrating at r = 0.8 (p > 0.05, 1901–2017 CE) against May–August temperatures over Western Europe. Machine learning is applied to identify historical wood samples aligning with growth characteristics of sites from elevations above 1900 m asl to extend the modern part of the chronology back to 881 CE. The new Alpine record reveals warmer conditions in the tenth century, followed by an extended cold period during the late Medieval times, a less-pronounced Little Ice Age culminating in the 1810s, and prolonged anthropogenic warming until present. The Samalas eruption likely triggered the coldest reconstructed summer in Western Europe in 1258 CE (-2.32 °C), which is in line with a recently published MXD-based reconstruction from the Spanish Pyrenees. Whereas the new Alpine reconstruction is potentially constrained in the lowest frequency, centennial timescale domain, it overcomes variance biases in existing state-of-the-art reconstructions and sets a new standard in site-control of historical samples and calibration/ verification statistics.
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