An unstable tree-growth response to climate in two 500 year chronologies,North Eastern Qinghai-Tibetan Plateau

Two new Juniper tree-ring-width (TRW) chronologies spanning more than 500 years were developed in the Yellow River source area, North Eastern Qinghai-Tibetan Plateau (NE-QTP). For the two studied sites, located approximately 50 km apart, split correlation and coherence analysis reveal unstable tree-growth responses to local moisture availability. While significant correlations are obtained with April–June local precipitation, Palmer Drought Severity Index (PDSI) and river flow from 1948/1954 to 1998 and from 1948/1954 to 1970s, these correlations vanish for the time period 1970s-1998. The local instrumental climate data (precipitation, PDSI and river flow) exhibit opposite correlations with large scale modes of variability (El Niño Southern Oscillation, ENSO, and Pacific Decadal Oscillation, PDO) before and after the 1977 PDO shift. One tree-ring chronology is coherent and anti-phased with instrumental ENSO/PDO indices at 5.2-year frequency. On the longer time span, this TRW chronology is compared with PDO reconstructed from historical Chinese data. This comparison also exhibits unstable multi-decadal relationships, notably in the mid 19th century. Altogether, the comparison between our two chronologies, local instrumental climate records, and ENSO/PDO indices suggest a cautious use of local TRW records for paleoclimate reconstructions. Further studies are needed to explore both the spatial coherency of tree-ring records and the temporal stability of their response to local and large scale climate variability.     

Tree-ring based spring precipitation reconstruction in western Nepal Himalaya since AD 1840

Spring (March–June) precipitation has been reconstructed since AD 1840 for the Rara National Park (RNP), western Nepal Himalaya using Abies spectabilis tree-ring width. The reconstruction accounts for 35.8% of the total variance of the instrumental precipitation from 1958 to 2012 and captured distinct wet and dry variability. The longest wet periods occurred during 1850–1862, 1878–1886, 1909–1917, 1971–1984 and 2000–2008 while dry periods were usually shorter and occurred during 1873–1877, 1921–1923, 1925–1929, 1951–1956, 1958–1962 and 1994–1996. Spectral analysis of the reconstruction shows significant peaks at periodicity ranging 2.4–6.5 year, suggesting a covariation in inter-annual variability similar to that of El Niño-Southern Oscillation (ENSO). Spectral analysis of the reconstruction shows significant quasi–cyclic (2.4–3.4 year) and multidecadal (24.8–39.2 year) periodicity, suggesting a potential association with El Niño-Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO).     

High-elevation inter-site differences in Mount Smolikas tree-ring width data

We present the longest high-elevation tree-ring width dataset in the Mediterranean reaching back to the 6th century CE. The network includes 101 living and 92 relict Pinus heldreichii Christ trees from four differently exposed sites in the 2100–2200 m a.s.l. elevation range of Mt. Smolikas in the Pindus Mountains in Greece. Though the sites were all sampled within a distance of <1 km, inter-site correlations are surprisingly low (r_1550–2014 = 0.65–0.87), indicating site exposure might affect tree-ring formation. We here explore the consequence of exposure differences on the climate signals in an eastern Mediterranean treeline ecotone. Temporally stable growth/climate relationships reveal similar seasonal patterns among the four sites, but differences in signal strength. P. heldreichii growth at Mt. Smolikas is significantly controlled by temperature in April (r_1951–2014 = 0.33–0.50) and precipitation in June-July (r_1951–2014 = 0.23–0.42), which emphasizes the overall importance of an early growth onset and subsequent moisture conditions. The association between stem growth and April climate is strongest in the South-facing stand, supporting the significance of higher insolation rates at this thermally privileged site. Strongest summer precipitation signals are found in the NE-facing stand, where trees seem to benefit least from an early growth onset and where reduced meltwater supply may enhance the dependency on early summer precipitation. The significance of spring temperature on tree growth in all four sites constrains the emergence of a distinct summer precipitation signal in the Mt. Smolikas high elevation ecotone. Exploration of the site-specific influences on a new millennium-long tree-ring width dataset is an important step towards an improved understanding of long-term climate variability in the Eastern Mediterranean. Site-related differences in climate sensitivity in the high-elevation tree-ring network at Mt. Smolikas indicate that both temperature and precipitation during different seasons could potentially be reconstructed if distinct site exposures (S versus NE) are considered.     

Process-based modeling of tree-ring formation and its relationships with climate on the Tibetan Plateau

Response of climate warming on tree-ring formation has attracted much attention during recent years. However, most studies are based on statistical analysis, lacking understanding of tree-physiological processes, especially in the mountainous regions of the Tibetan Plateau (TP). Herein, we firstly use an updated new version of the tree-ring process-based Vaganov-Shashkin model (VS-oscilloscope) to simulate tree-ring formation and its relationships with climate factors during the past six decades. Our analyses covered 341 sampled trees growing within elevations ranging from 2750 to 4575 m a.s.l. at five sampling sites across the TP. Simulated tree-ring width series are significantly (p < 0.01) correlated with actual tree-ring width chronologies during their common interval periods. Starting dates of tree-ring formation are determined by temperature at all five sampling sites. After the initiation of tree stem cambial activity, soil moisture content has a significant effect on tree radial growth. Ending dates of cambial activity are driven by temperature over the whole study region. Simulated results indicate differences between wide and narrow tree-rings are mostly induced by soil moisture content, especially during the first half of the growing season, when effects from temperature variations are minor. Interestingly, we detected significantly (p < 0.001) increased relative growth rates due to higher soil moisture content after the year 1985 at the five sampling sites. However, the variability of mean relative growth rates due to temperature is negligible before and after that. Based on the successful application of VS-oscilloscope modeling on the high-elevation tree stands on the TP, our study provides a new perspective on tree radial growth process and their varying relationships to climate factors during the past six decades.     

Influence of climatic conditions and industrial emissions on spruce tree-ring Pb isotopes analyzed at ppb concentrations in the Athabasca oil sands region

This study investigates Pb isotope ratios at low concentrations (parts per billion; ppb) in tree rings and soils in the Northern Athabasca Oil Sands Region (NAOSR), western Canada, to evaluate if: (1) climatic conditions influence on tree-ring Pb assimilation; and (2) such low Pb content allows inferring the regional Pb depositional history.Our results reflect the influence of winter snow cover and the importance of minimum temperature and precipitation in spring and summer on the bioavailability of Pb and its passive assimilation by trees in sub-arctic semi-humid climatic conditions. Winter conditions can influence the state of root systems that subsequently impacts the following growth period, while spring and summer conditions likely control microbial processes and water source, and may thus impact Pb assimilation by trees. Thus, the results of tree-ring Pb concentrations show interesting correlation with cumulated snow from November of the previous year to February (ρ = 0.53; P < 0.01; n = 36). Likewise, the ²⁰⁶Pb/²⁰⁷Pb ratios inversely correlate with minimum temperature from April to September (ρ = −0.67; P < 0.01; n = 40) and precipitation from May to August (ρ = −0.42; P < 0.01; n = 36). The isotopic results also suggest that the effects of climatic variations are superimposed by regional industrial Pb deposition: Western North American Aerosols (WNAA) and fugitive dust from the oil sands mining operations appear to be the most likely sources.Importantly, this study suggests that even at low Pb concentrations, tree-ring Pb isotopes are modulated by climatic conditions and potential input of regional and long-range transport of airborne Pb. These interpretations open the possibility of using Pb isotopes as an environmental tool for inferring the pollution history in remote regions, and improving our understanding of its natural cycle through the forest environment.     

Growing-season precipitation since 1872 in the coastal area of subtropical southeast China reconstructed from tree rings and its relationship with the East Asian summer monsoon system

Tree rings from temperate zones of the world have provided abundant palaeo- ecological and paleo-hydroclimatic information. However, tree rings from subtropical to tropical regions remain relatively scarce, which greatly limit our fully understanding about the climate change issues. In the present work, tree-ring-width (TRW) measurements of Masson pine from Fujian province, the coastal area of subtropical southeast China were successfully crossdated and a TRW STD chronology was developed from 1854 to 2012. Significantly positive correlation was identified between the tree rings and April–November total precipitation (r = 0.71, p < 0.01). The reconstructed April–November precipitation exhibited two comparatively wet (1876–1886 and 1957–1962) and one comparatively dry (1986–2004) periods. An evident drying trend since 1959 was seen and it was mitigated after 1993. Most of the extreme low-precipitation years in the reconstruction were supported by the historical records. As revealed by the spatial correlation patterns, our precipitation reconstruction was also consistent with other hydroclimatic records along the coastal areas of southeast China, proving its ability to capture the large-scale hydrological signal in southeast China (mainly refers to the south of the middle-lower reaches of Yangtze River). The reconstructed precipitation showed significant correlation with the East Asian summer Monsoon (EASM) index. Moreover, it also indicated simultaneous variation with the monsoon precipitation in North China on a decadal scale, implying that growing season precipitation variations in both regions were influenced by the EASM strength. This work highlights the potential of using tree-ring width to reconstruct precipitation in subtropical southeast China, while the relevant issues about precipitation variation in this region is far from resolved.     

June–September temperature reconstruction in the Northern Caucasus based on blue intensity data

Although long-lived trees grow in the Northern Caucasus, no single tree-ring chronology has been reported thus far from this area in the International Tree-Ring Data Base (ITRDB), neither has one been published in international journals. Extensive tree-ring studies were conducted over the last decade, and a tree-ring network was developed for the investigated area. The data on the minimum blue intensity based on 33 series of pine (Pinus sylvestris L.) and fir (Abies nordmanniana (Steven) Spach) is presented in this study. The minimum blue intensity (BI) chronology covers the period 1596–2011 with EPS value ≥0.85. The BI chronology strongly correlates with the mean June-September temperature (R = 0.74; p < 0.05) from the weather station “Kluhorskij Pereval” (1951–2011). Mean June-September temperature anomalies were reconstructed using the rescaling method. Based on the reconstruction provided in this study the twentieth century is characterized by highly increased June-September temperature. According to this study, the minimum blue intensity approach demonstrates a great potential for paleoclimatic research in the Caucasus. Vast spatial coverage of the new BI-based reconstruction based on data from only two locations in the Northern Caucasus provides prospects for reconstruction of temperature variations for a great region in the Middle East and Northern Africa.     

Precipitation reconstruction for the southern Altay Mountains (China) from tree rings of Siberian spruce,reveals recent wetting trend

We developed six tree-ring width chronologies of Siberian spruce (Picea obovata) from the low elevation forest of the southern Altay Mountains in northern Xinjiang, China. Although the six chronologies come from different sampling sites, significant correlations existed among the chronologies (r ≥ 0.477), and the first principal component (PC1) accounted for 72.2% of total variance over their common period 1825–2010. Correlation response analysis revealed that radial growth of Siberian spruce is mainly limited by a 12-month precipitation starting from July of the previous year to June of the current year. We therefore developed a July–June precipitation reconstruction spanning 1825–2009, which explained 65.5% of the instrumental variance for the period 1962–2009. The information of our precipitation reconstruction suggested that dry conditions existed for the periods 1829–1838, 1852–1855, 1876–1888, 1898–1911, 1919–1923, 1932–1936, 1943–1955, 1963–1968, 1973–1984 and 2007–2009, and wet conditions for the periods AD 1825–1828, 1839–1851, 1856–1875, 1889–1897, 1912–1918, 1924–1931, 1937–1942, 1956–1962, 1969–1972 and 1985–2006. Spatial climate correlation analyses with gridded land surface data revealed that our precipitation reconstruction contains a strong precipitation signal for the Altay Mountain ranges. Our reconstruction agreed with the moisture-sensitive tree ring width series of Siberian larch from the Altay Mountains of Mongolia on a decadal timescale. In addition, in contrast to a drying trend in north central China, a clear wetting trend has occurred in the southern Altay Mountains since 1980s.     

Characterization of spatial variability of soil physicochemical properties and its impact on Rhodes grass productivity

Characterization of soil properties is a key step in understanding the source of spatial variability in the productivity across agricultural fields. A study on a 16 ha field located in the eastern region of Saudi Arabia was undertaken to investigate the spatial variability of selected soil properties, such as soil compaction ‘SC’, electrical conductivity ‘EC’, pH (acidity or alkalinity of soil) and soil texture and its impact on the productivity of Rhodes grass (Chloris gayana L.). The productivity of Rhodes grass was investigated using the Cumulative Normalized Difference Vegetation Index (CNDVI), which was determined from Landsat-8 (OLI) images. The statistical analysis showed high spatial variability across the experimental field based on SC, clay and silt; indicated by values of the coefficient of variation (CV) of 22.08%, 21.89% and 21.02%, respectively. However, low to very low variability was observed for soil EC, sand and pH; with CV values of 13.94%, 7.20% and 0.53%, respectively. Results of the CNDVI of two successive harvests showed a relatively similar trend of Rhodes grass productivity across the experimental area (r = 0.74, p = 0.0001). Soil physicochemical layers of a considerable spatial variability (SC, clay, silt and EC) were utilized to delineate the experimental field into three management zones (MZ-1, MZ-2 and MZ-3); which covered 30.23%, 33.85% and 35.92% of the total area, respectively. The results of CNDVI indicated that the MZ-1 was the most productive zone, as its major areas of 50.28% and 45.09% were occupied by the highest CNDVI classes of 0.97–1.08 and 4.26–4.72, for the first and second harvests, respectively.     

Climatic potential of δ18O of Abies spectabilis from the Nepal Himalaya

A 50-year tree-ring δ¹⁸O chronology of Abies spectabilis growing close to the tree line (3850 m asl) in the Nepal Himalaya is established to explore its dendroclimatic potential. Response function analysis with ambient climatic records revealed that tree-ring δ¹⁸O is primarily governed by rainfall during the monsoon season (June–September), and the regression model accounts for 35% of the variance in rainfall. Extreme dry years identified in instrumental weather data are detected in the δ¹⁸O chronology. Further, tree-ring δ¹⁸O is much more sensitive to rainfall fluctuations than other tree-ring parameters such as width and density typically used in dendroclimatology. Correlation analyses with Niño 3.4 SST reveal time-dependent behavior of ENSO–monsoon relationships.     

Annual precipitation variability inferred from tree-ring width chronologies in the Changling–Shoulu region,China, during AD 1853–2007

On the basis of a significant correlation between the tree-ring width series from Changling–Shoulu (CLSL) in north-central China and observed instrumental data, the annual total precipitation of the previous July to the current June was reconstructed since 1853 for the studied region, with the predictor variables accounting for 41.2% of the variance in the precipitation data. Distinct wet periods with precipitation levels greater than the mean (315 mm) occurred in 1864–1876 and 1934–1960. Notable dry periods with precipitation less than the mean occurred in 1877–1888 and 1923–1933. The precipitation fluctuated dramatically during 1940–1970, and became relatively stable around the mean value from 1960. The CLSL precipitation series showed significant correlations with precipitation reconstructions from Mt. Xinglong, Mt. Helan, Ningwu and eastern China, suggesting that these five rainfall curves represent the general precipitation variations in the western-central environmentally sensitive zone of northern China. The calculations of the CRU grid points also indicate the existence of significant spatial correlation among these sites. Periodicity analysis showed clear 23.33-, 8.24-, 2.64- and 2.59-year cycles at a 99% confidence level for the reconstructed series during the past 155 years.     

Spatial reorganisation of muscle activity correlates with change in tangential force variability during isometric contractions

The aim of this study was to quantify the effects of spatial reorganisation of muscle activity on task-related and tangential components of force variability during sustained contractions. Three-dimensional forces were measured from isometric elbow flexion during submaximal contractions (50 s, 5–50% of maximal voluntary contraction (MVC)) and total excursion of the centre of pressure was extracted. Spatial electromyographic (EMG) activity was recorded from the biceps brachii muscle. The centroids of the root mean square (RMS) EMG and normalised mutual information (NMI) maps were computed to assess spatial muscle activity and spatial relationship between EMG and task-related force variability, respectively. Result showed that difference between the position of the centroids at the beginning and at the end of the contraction of the RMS EMG and the NMI maps were different in the medial–lateral direction (P < 0.05), reflecting that muscle regions modulate their activity without necessarily modulating the contribution to the task-related force variability over time. Moreover, this difference between shifts of the centroids was positively correlated with the total excursion of the centre of pressure at the higher levels of contractions (>30% MVC, R² > 0.30, P < 0.05), suggesting that changes in spatial muscle activity could impact on the modulation of tangential forces. Therefore, within-muscle adaptations do not necessarily increase force variability, and this interaction can be quantified by analysing the RMS EMG and the NMI map centroids.     

Climate-growth relationships for Rocky Mountain juniper (Juniperus scopulorum Sarg.) on the volcanic badlands of western New Mexico,USA

We sampled Rocky Mountain junipers (RMJ) to produce a multi-century tree-ring chronology from a relict lava flow, the Paxton Springs Malpais (PAX), in the Zuni Mountains of western New Mexico. Our objective was to assess crossdating potential for RMJ growing on the volcanic badlands of the region, investigate potential relationships between climate and RMJ growth, and investigate temporal variability in relationships identified between climate and RMJ growing at our site. We hypothesized that, similar to other drought stressed-conifers growing on the lava flows, RMJ responds to climate factors that influence and indicate moisture availability. We found a high average mean sensitivity value (0.53), which indicated the PAX chronology exhibited enough annual variability to capture fluctuations in environmental conditions. The average interseries correlation (0.74) indicated confident crossdating and a significant association of annual growth among trees within the stand. The positive correlation between the PAX chronology and total precipitation for the local water year was significant (r = 0.53; P < 0.001). Significant positive correlations also were identified between monthly PDSI, monthly total precipitation, and RMJ radial growth. Analyses of temporal stability indicated that the positive relationship between RMJ growth at the PAX site and monthly PDSI was the most stable relationship during the period of analysis (1895–2007). More importantly, we identified a unique inverse relationship between radial growth and monthly mean temperature during periods of the preceding year and current growing year, the first such finding of a strong temperature response for a low-mid elevation tree species in the American Southwest. Our results confirm that RMJ samples collected on the Paxton Springs Malpais are sensitive to climate factors that affect moisture availability, further suggesting that RMJ may be suitable for use in dendroclimatic research at additional locations across the broad distribution of the species.     

Age-dependent tree-ring growth responses of Schrenk spruce (Picea schrenkiana) to climate—A case study in the Tianshan Mountain,China

For both its climatic and ecological importance, Schrenk spruce (Picea schrenkiana) is a crucial tree species living at mid-altitude on the western area of the Tianshan Mountains. It plays a key role on understanding climatic change in the Tianshan Mountains in the past 500 years. However, whether the relationship between tree growth and limiting climate factors is stable over time is still not well-known. In this study, standard and residual chronologies of four 100-year age classes (AC1 < 110a, 110a < AC2 < 210a, 210a < AC3 < 310a and AC4 > 310a) were established for detecting divergence in climate–growth relationships as well as comparing low-frequency and high-frequency variations. The results show that climate can account for a high amount of variance in tree-ring width and higher climate sensitivity was detected in younger trees. Younger trees (<210a) exhibit significantly negative growth responses to mean monthly air temperature of previous June and positive relationship with total monthly precipitation of current April and May, while mean monthly air temperature of current March may inhibit growth of older trees (>210a). Tree-ring chronology statistics and response function reveal that the age-growth patterns are non-monotonic. Our results together with previous studies demonstrate that the age effects on tree-ring growth–climate response is attributed to a combination of genetic characteristics and site microclimate, which suggests that it is necessary to consider both age-dependent and species-specific climate responses when using tree-ring measurements as a proxy for valid climate reconstructions.     

Landscapes as gradients: The spatial structure of terrestrial ecosystem components in southern Ontario,Canada

The conventional view of the environment – consisting of discrete patches that repeat themselves across the landscape – has seldom been tested. Across a wide spatial scope in southern Ontario, Canada, we investigated the spatial structure of physical and biological features of the environment: vegetation communities, moisture, pH, and organic content of soil at local scales (10–1250 m), and mammalian communities, mean annual temperature and precipitation at regional scales (10–650 km). Spatial structure was quantified using log–log regression of variance (V) with distance (D), according to the power formula, V = aD^z. All these ecosystem components exhibited gradients. Slopes (z) of log–log regressions were positive (0.065 < z < 0.703) and were significantly steeper at the regional scale than the local scale. Variance appeared to increase without bound as distance between sampling locations increased. The results support the view of landscapes as continua and gradients. These patterns represent a challenge to the conventional view of how the natural environment is organised.     

A multivariate analysis integrating ecological,socioeconomic and physical characteristics to investigate urban forest cover and plant diversity in Beijing,China

Understanding the factors driving the variation in urban green space and plant communities in heterogeneous urban landscapes is crucial for maintaining biodiversity and important ecosystem services. In this study, we used a combination of field surveys, remote sensing, census data and spatial analysis to investigate the interrelationships among geographical and social-economic variables across 328 different urban structural units (USUs) and how they may influence the distributions of urban forest cover, plant diversity and abundance, within the central urban area of Beijing, China. We found that the urban green space coverage varied substantially across different types of USUs, with higher in agricultural lands (N = 15), parks (N = 46) and lowest in utility zones (N = 36). The amount of urban green space within USUs declines exponentially with the distance to urban center. Our study suggested that geographical, social and economic factors were closely related with each other in urban ecological systems, and have important impacts on urban forest coverage and abundance. The percentage of forest as well as high and low density urban areas were mainly responsible for variations in the data across all USUs and all land use/land cover types, and thus are important constituents and ecological indicators for understanding and modeling urban environment. Herb richness is more strongly correlated with tree and shrub density than with tree and shrub richness (r = −0.472, p < 0.05). However, other geographic and socioeconomic factors showed no significant relationships with urban plant diversity or abundance.     

Toward consistent measurements of carbon accumulation: A multi-site assessment of biomass and basal area increment across Europe

The use of tree-ring data in carbon cycle research has so far been limited because traditional study designs are not geared toward quantifying forest carbon accumulation. Existing studies that assessed biomass increment from tree rings were often confined to individual sites and used inconsistent sampling schemes. We applied a consistent biomass-oriented sampling design at five managed forest sites located in different climate zones to assess the annual carbon accumulation in above-ground woody tissues (i.e. stems and branches) and its climate response. Radial growth and biometric measurements were combined to reconstruct the annual biomass increment in individual trees and upscaled to the site level. In addition to this, we estimated that 32–60 trees are required at these five sites to robustly quantify carbon accumulation rates. Tree dimensions and growth rates varied considerably among sites as a function of differing stand density, climatic limitations, and management interventions. Accordingly, mean site-level carbon accumulation rates between 65 g C m⁻² y⁻¹ and 225 g C m⁻² y⁻¹ were reconstructed for the 1970–2009 period. A comparison of biomass increment with the widely used basal area increment (BAI) revealed very similar growth trends but emphasized the merits of biomass assessments due to species-specific BAI/biomass relationship. Our study illustrates the benefits and challenges of combining tree-ring data with biometric measurements and promotes the consistent application of a standardized sampling protocol across large spatial scales. It is thus viewed as a conceptual basis for future use of tree-ring data to approach research questions related to forest productivity and the terrestrial carbon balance.     

Responses to climate change in radial growth of Picea schrenkiana along elevations of the eastern Tianshan Mountains,northwest China

Tree growth is largely driven by climate conditions in arid and alpine areas. A strong change in climate from warm-dry to warm-wet has already been observed in northwest China. However, little is known about the impacts of regional climate variability on the radial growth of trees along elevations of the eastern Tianshan Mountains. Consequently, we developed three tree-ring width chronologies of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) ranging in elevation from 2159 to 2552 m above sea level (a.s.l.), which play an important role in the forestry ecosystem, agriculture, and local economy of Central Asia. In our study, the correlation analyses of growth-drought using the monthly standardized precipitation-evapotranspiration index (SPEI) at different temporal scales demonstrated that drought in growing season was the main factor limiting tree growth, regardless of elevation. The relationships between radial growth of Schrenk spruce and main climate factors were relatively stable by moving correlation function, and the trend of STD chronologies and basal area increment (BAI) also showed a synchronous decline across the three elevations in recent decades. And meanwhile, slight differences in responses to climate change in radial growth along elevations were examined. The drought stress increased as elevations decreased. Radial growth at the higher elevation depended on moisture availability due to high temperature, as indicated by the significant negative correlation with mean temperature in the late growing season of the previous year (August-September, p < 0.001). However, radial growth at the lower elevation were restricted by drought stress due to less precipitation and higher temperatures, as demonstrated by the significant negative correlation with mean temperature but positive with total precipitation in the early growing season of the current year (April-May, p < 0.05). In addition, the decline of radial growth (BAI) at the higher elevation (3.710 cm² yr⁻¹/decade, p < 0.001) was faster than that of the middle elevation (2.344 cm² yr⁻¹/decade, p < 0.001) and the lower elevation (3.005 cm² yr⁻¹/decade, p < 0.001) since 2000, indicating that the trees at higher elevation of a relatively humid environment were more susceptible to the effects of climate change due to their poor adaptability to water deficit. Therefore, the forest ecosystems would be suppressed as a result of increasing drought stress in the future, especially in the high-elevation forests of arid and semi-arid areas.     

Evaluating the dendroclimatological potential of Taxus baccata (yew) in southwest Ireland

Tree-ring research in Ireland has typically been dominated by Quercus species, particularly Quercus petraea and Quercus robur. Recent years have seen a greater focus on multi-species reconstructions in Ireland but, due to difficulties with the hardness of the wood, missing/pinched rings and fused stems, Taxus baccata has not been included in these investigations. Despite these difficulties, a 31-tree, 204-year T. baccata chronology was successfully constructed from Killarney National Park, southwest Ireland. The chronology exhibits promising dendroclimatological potential, with climatic responsiveness equivalent to that of the other major Irish tree taxa, including Quercus. The chronology shows the strongest relationship with May–June precipitation from Muckross House synoptic station (1970–2007; r = 0.521, p < 0.01) and Valentia Observatory (1941–2007; r = 0.545, p < 0.01). November–April temperatures also exhibited a strong relationship with the chronology post-1970 (r = 0.605, p < 0.01 for Muckross House, r = 0.567, p < 0.01 for Valentia Observatory), but this relationship is not time stable and breaks down for the pre-1970 Valentia Observatory record. The long-lived nature of T. baccata, the exceptional preservation of wood and rings in this hard softwood species, as well as its prominence in Irish archaeology, all point to the potential to expand this chronology both spatially and temporally, and demonstrate T. baccata's potential in multi-site and multi-species tree-ring studies in the region.