Annual Tree-ring Width Research Articles

Climatic effects on primary and secondary growth of Pinus oocarpa trees in southern Mexico

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.

Enhanced interannual drought resilience in mixed stands: unveiling possible complementarity effects between tree species of the Spanish Northern Plateau

AbstractClimate change is expected to intensify drought in the Mediterranean region. Previous studies indicate that tree species mixing may reduce the water stress. Our study investigates the response to past drought events of four co-occurring Mediterranean species: Pinus pinea L. (stone pine), Pinus pinaster Ait. (maritime pine), Juniperus thurifera L. (Spanish juniper) and Quercus ilex L (holm oak). The study was performed at an interannual scale, both in monospecific and mixed stands. Annual tree ring widths data measured on increment cores and stem discs obtained from 281 trees were used to quantify the responses to drought events using complementary resilience indices. Additionally, we assessed tree intra- and inter-specific competition impact over the past 25 years. We fitted and compared generalised linear mixed models to determine the influence of species identity, stand composition as intra-specific and inter-specific competition on complementary resilience indices and annual basal area increment. The co-existence with other species enhanced the resistance to drought of the stone pine as the resilience capacity of the Spanish juniper. Conversely, maritime pine’s drought resistance declined considerably in mixed stands. Notably, only the anisohydric species Spanish juniper and holm oak were able to return to pre-disturbance growth rates after the drought. The influence of competition on tree growth was found to differ according to the hydrological conditions of each year and varied based on the specific source of competition. Our study showed that mixed stands in the Spanish Northern Plateau, especially with holm oak and Spanish juniper, are more resilient to prolonged droughts due to spatio-temporal complementarity and subsequent competition reduction. That is another reason for which such composed mixed stands should be promoted in the arid conditions of the Spanish Northern Plateau.

Tree-ring hydrological research in the Himalaya: State of the art and future directions

Recent developments in tree-ring research offer great potential for reconstructing past climate changes; determining the frequencies of natural hazards; and assessing the availability of freshwater resources over timescales that extend well into the pre-instrumental period. Here, we review the state of dendrochronological research in the Himalaya and outline future directions for tree-ring-based hydrological reconstructions in a region that has a pressing societal need to understand the causes and consequences of past, present and future changes in the hydrological cycle. We used ‘tree ring’ and ‘Himalaya’ as keywords to identify scholarly articles from the Web of Science that were published between 1994 and 2022. The resulting 173 publications were separated by their spatial coverage into the western, central and eastern Himalaya, as well as their scientific purpose (e.g. reconstructing growth-climate relationships, temperature, precipitation, streamflow, floods, droughts, etc.). Our analysis shows that dendrochronological research in the Himalaya primarily focused on understanding growth-climate relationships using annual tree-ring widths measurements obtained for coniferous species, and their application in climate reconstructions. Reconstructions of hydrological processes such as streamflows, and extremes such as glacial and landslide lake outburst floods, have received less attention. Recent advances in dendrochronology, including blue intensity (BI), quantitative wood anatomy (QWA), and tree-ring stable isotopes (TRSI) should be combined to improve the resolution and accuracy of hydrological reconstructions in all parts of the Himalaya. Such studies may allow us to better understand the effects of climate change and the Himalayan water resources for its lowland surroundings. They may also facilitate decision-making processes for mitigating the impacts of climate change on natural hazards, and for better managing water resources in the region.

Long-Term Climate Sensitivity of Resin-Tapped and Non-Resin-Tapped Scots Pine Trees Based on Tree Ring Width and Blue Intensity

The resin tapping of pine trees in Poland ended in the early 1990s. However, we can still find individual trees, and sometimes larger groups of trees, that were tapped. This study focused on the effect of the mechanical wounding of trees during resin tapping on the growth and climatic sensitivity of pine trees. The study concerned a 160-year-old pine stand in northwestern Poland in which resin tapping was last performed in the 1970s. All the trees had remained standing because of their high quality, which had destined them for seed collection. The stand included both resin-tapped (RT) and non-RT (NRT) trees. Our study was based on a dendrochronological analysis of two signals—annual tree ring widths (TRWs) and their delta blue intensity (DBI). We observed a significant increase in annual TRW after resin tapping had ceased, alongside a decrease in the DBI. The temporal stability in growth response was examined using daily climatic correlations from 1921 to 2021. It was found that the climatic sensitivity of RT and NRT pines was similar. There were differences in only some of the years, most while resin tapping was occurring, and then approximately 20 years after the resin tapping had ceased. However, these were small differences that mainly related to the strength of the correlation. It was also discovered that we can obtain different types of information from the study of TRWs and DBI.

Forest growth responds more to air pollution than soil acidification.

The forests of central Europe have undergone remarkable transitions in the past 40 years as air quality has improved dramatically. Retrospective analysis of Norway spruce (Picea abies) tree rings in the Czech Republic shows that air pollution (e.g. SO2 concentrations, high acidic deposition to the forest canopy) plays a dominant role in driving forest health. Extensive soil acidification occurred in the highly polluted "Black Triangle" in Central Europe, and upper mineral soils are still acidified. In contrast, acidic atmospheric deposition declined by 80% and atmospheric SO2 concentration by 90% between the late 1980s and 2010s. In this study we oserved that annual tree ring width (TRW) declined in the 1970s and subsequently recovered in the 1990s, tracking SO2 concentrations closely. Furthermore, recovery of TRW was similar in unlimed and limed stands. Despite large increases in soil base saturation, as well as soil pH, as a result of repeated liming starting in 1981, TRW growth was similar in limed and unlimed plots. TRW recovery was interrupted in 1996 when highly acidic rime (originating from more pronounced decline of alkaline dust than SO2 from local power plants) injured the spruce canopy, but recovered soon to the pre-episode growth. Across the long-term site history, changes in soil chemistry (pH, base saturation, Bc/Al soil solution ratio) cannot explain observed changes in TRW at the two study sites where we tracked soil chemistry. Instead, statistically significant recovery in TRW is linked to the trajectory of annual SO2 concentrations or sulfur deposition at all three stands.

Comparison of carbon content between plantation and natural regeneration seedlings in Durango, Mexico.

Forest plantations and natural forests perform a relevant role in capturing CO2 and reducing greenhouse gas concentrations. The objective of this study was to compare the diameter increment, biomass and carbon accumulation in a plantation of Pinus durangensis and a naturally regenerated stand. The data were collected from 32 circular plots of 100 m2 (16 plots in the planted site and 16 in naturally regenerated area). At each plot, the diameter at the base (cm) and height (m) of all seedlings were measured using a Vernier and tape measure, and a seedling was destructively sampled collecting one cross-section at the base of the stump. The annual ring-width increment of each sampled seedling was recorded to obtain its diameter at the base and estimate annual aboveground biomass and carbon accumulation through allometric equations. The response variables were evaluated using mixed-effects ANOVA models. Results indicated that there were significant differences (P ≤ 0.05) on annual tree-ring width growth, biomass and carbon accumulation. The plantation seedlings showed significantly higher growth rates, biomass and carbon accumulation at most evaluated years. After 7 years of growth the lines of current annual increment (CAI) and mean annual increment (MAI) in basal diameter for both the plantation and the natural regeneration have not yet intersected. Both forest plantations and naturally regenerated stands of the studied tree species may be suitable alternatives to promote CO2 capture and increase timber production.

Investigation of Trees' Sensitivity to Drought: A Case Study in the Opole Region, Poland

<i>Pinus sylvestris</i> L. is the most common tree species growing in Poland. Trees of this species are considered to be resistant to difficult meteorological conditions; however, in the past decades, many of them have died and been cut down by foresters. The measurements of the annual tree ring width can provide information on how trees respond to drought events. This study aimed to investigate the potential differences between healthy and declining trees (identified as trees to be cut down by foresters). For this purpose, we collected samples of five trees from each group and analysed them using dendrochronological and quantitative wood anatomy approaches. We measured ring width index (RWI) chronologies for healthy and declining trees and compared them with climate data. Additionally, we compared some anatomical features of trees from both groups as cell wall thickness (CWT) and lumen area (LA). The conducted analyses showed significant differences between healthy and declining trees. In particular, declining trees were characterised by lower RWI, LA and CWT values, especially in the past 20 years, and showed greater sensitivity to changes in temperature and humidity than healthy trees.

Mismatch between Annual Tree-Ring Width Growth and NDVI Index in Norway Spruce Stands of Central Europe

Presently, the forests of one of the most economically important tree species in Europe—Norway spruce [Picea abies (L.) Karst.]—have been disrupted and are in rapid decline due to a combination of several natural factors: extreme drought, heatwaves, and secondary damage caused by bark beetle outbreaks. The vulnerability of these forests has increased considerably over the past decade, and remote sensing methods can theoretically improve the identification of endangered forest stands. The main objective was to determine the relationship between remotely sensed characteristics of vegetation (using the normalized difference vegetation index—NDVI) and annual tree-ring growth in 180 trees through precipitation and air temperature. The research was conducted at six research plots in lowland spruce forests (319–425 m a.s.l.) in the central Czech Republic. No significant correlation between NDVI and annual ring width was observed. The primary factor limiting radial growth was lack of precipitation in the growing season; subsequently, spruce trees reacted negatively to air temperatures. A higher correlation with NDVI was observed on sites susceptible to drought, but overall, NDVI and RWI did not show similarities. This result describes that NDVI is a poor indicator for identifying low radial growth in Norway spruce stands on non-native localities in the studied area.

New tree-level temperature response curves document sensitivity of tree growth to high temperatures across a US-wide climatic gradient.

Temperature is a key climate indicator, whose distribution is expected to shift right in a warming world. However, the high-temperature tolerance of trees is less widely understood than their drought tolerance, especially when it comes to sub-lethal impacts of temperature on tree growth. I use a large data set of annual tree ring widths, combined with a flexible degree day model, to estimate the relationship between temperature and tree radial growth. I find that tree radial growth responds non-linearly to temperature across many ecoregions of the United States: across temperate and/or dry ecoregions, spring-summer temperature increases are beneficial or mostly neutral for tree growth up to around 25-30°C in humid climates and 10-15°C in dry climates, beyond which temperature increases suppress growth. Thirty additional degree days above the optimal temperature breakpoint lead to an average decrease in tree ring width of around 1%-5%, depending on ecoregions, seasons, and inclusion or exclusion of temperature-mediated drought impacts. High temperatures have legacy effects across a 5-year horizon in dry ecoregions, but none in the temperate-humid South-East or among temperature-sensitive trees. I find limited evidence that trees acclimatize to high temperatures within their lifetime: local variation in early exposure to high temperatures, which stems from local variation in the timing of tree birth, does not significantly impact the response to high temperatures, although temperature-sensitive trees acquire some heightened sensitivity from early exposure. I also find some evidence that trees adapt to high temperatures in the long run: across humid ecoregions of the United States, high temperatures are 40% less harmful to tree growth, where their average incidence is one standard deviation above average. Overall, these results highlight the strength of a new methodology which, applied to representative tree ring data, could contribute to predicting forest carbon uptake potential and composition under global change.

Enhanced leaf turnover and nitrogen recycling sustain CO2 fertilization effect on tree-ring growth.

Whether increased photosynthates under elevated atmospheric CO2 could translate into sustained biomass accumulation in forest trees remains uncertain. Here we demonstrate how tree radial growth is closely linked to litterfall dynamics, which enhances nitrogen recycling to support a sustained effect of CO2 fertilization on tree-ring growth. Our ten-year observations in two alpine treeline forests indicated that annual (or seasonal) stem radial increments generally had a positive relationship with the previous year's (or season's) litterfall and its associated nitrogen return and resorption. Annual tree-ring width, annual litterfall and annual nitrogen return and resorption all showed an increasing trend during 2007-2017, and most of the variations were explained by elevated atmospheric CO2 rather than climate change. Similar patterns were found in the longer time series of tree-ring width index from 1986-2017. The regional representativeness of our observed patterns was confirmed by the literature data of six other tree species at 11 treeline sites over the Tibetan Plateau. Enhanced nitrogen recycling through increased litterfall under elevated atmospheric CO2 supports a general increasing trend of tree-ring growth in recent decades, especially in cold and nitrogen-poor environments.

Temperature rather than individual growing period length determines radial growth of sessile oak in the Pyrenees

Tree growth and leaf phenology are both affected by global warming. Mountain ecosystems are of paramount importance for studying phenological and growth responses of trees to the gradual variation of temperature. However, the relationship between growing season length and tree growth has been little studied at the level of individual trees. Here, we investigated the relationships between leaf phenology, growing degree-days and radial growth of sessile oaks growing in nine populations along an elevational gradient of 1500 m in the French Pyrenees. In each population, leaf unfolding in spring and leaf coloration in autumn were monitored between 2005 and 2015 on 25-30 trees having contrasting spring phenology (i.e. early vs. late flushing trees). These trees were cored in 2013 to analyse annual tree-ring widths. While trees displayed consistent phenological ranks for both leaf unfolding and leaf coloration within their population over the years, the growing period length decreased with increasing elevation, from about 210 days at the lowest elevation (131 m a.s.l.) to 140 days at the highest elevation (1630 m a.s.l.). For a given year, individual leaf coloration dates correlated positively with leaf unfolding dates at lower elevations, but negatively at higher elevations. Radial growth was positively correlated with growing degree-days at higher elevations, but negatively correlated at lower elevations, likely because higher temperatures are often associated with severe droughts in the lowlands of this region. No clear relationship was found between growing period length and radial growth of oaks within their population. This indicates that climatic conditions during the growing period have a more important impact on the secondary growth of sessile oaks than the growing period length. Our findings suggest that the lengthening of the growing period of trees in response to global warming does not necessarily lead to higher radial growth and productivity.

Co-Occurring Wyoming Pinus Species Exhibit Differing Climate–Growth Relationships

The North American Dendroecological Field week (NADEF) is an intensive dendrochronology workshop, funded in part by the National Science Foundation. The 2019 Introductory Group at NADEF developed two precisely dated tree-ring width chronologies for Pinus contorta (lodgepole pine) and Pinus flexilis (limber pine) at the Wolf Knob site ca. 5 km west of Beartooth Lake, WY, within the bounds of the Shoshone National Forest (SNF), in the Greater Yellowstone Ecosystem (GYE). Wolf Knob is a semi-arid, S- to SW-facing, mid- to high-elevation site, making it an ideal location to examine the climate sensitivity of annual tree-ring width increments. Here, we show that two co-located Pinus species exhibit differing climate–growth relationships, with P. contorta exhibiting relatively weak correlations with precipitation (r = 0.37; p < 0.01) and temperature (r = –0.23; p < 0.05) during the late summer, and P. flexilis exhibiting stronger overall correlations with both cool-season (r = 0.48; p < 0.01) and warm-season precipitation (r = 0.51; p < 0.01) as well as with snowpack records (r = 0.45; p < 0.05). Our results suggest these two Pinus species may face disparate threats in the face of regional climate change, with P. flexilis being particularly vulnerable to drought conditions and declining snowpacks in the GYE. The differing seasonal climate sensitivities of the two species is likely caused by microsite conditions (e.g. soil moisture capacity, incoming solar radiation) and distinct species-climate responses, underscoring the importance of not only site selection, but also microsite and individual selection in dendroclimatological sampling. Finally, this work contributes to identifying Snow Water Equivalent (SWE)-sensitive tree-ring proxies in the GYE, critical for understanding ongoing warming-induced snowpack declines across western North America, particularly given the projections of a largely snow-free (April 1) GYE by 2075.

Factors affecting the radial growth of Juniperus foetidissima Willd. and J. excelsa M. Bieb. in central Anatolia

Central Anatolia is one of the semi-arid regions of Turkey that does not offer very suitable conditions for the growth of trees. Tree growth is a process controlled by genetic, environmental and climatic factors. Trees record these signals, which provide valuable scientific data for dendrochronological research. We used raw annual tree-ring width (taken from trees under the age of 100 years) as one of the dendrochronological parameters to compare Juniperus foetidissima and J. excelsa in terms of affecting factors. We compared the annual tree-ring width of both species considering species, locations and research sites of the altitude range of 677–1 400 m a.s.l.. Environmental signals (longitude and latitude, altitude, slope, exposure, human impact and nearest settlement distance), as well as climatic factors (precipitation, temperature, moisture) affecting growth were examined. Results indicate that there is an obvious difference in raw annual tree-ring widths depending on species. J. foetidissima differs from J. excelsa in wider annual tree-ring widths and preferences to a low slope and altitude. While the annual tree-ring width of J. excelsa did not respond to the environmental signals, the annual tree-ring width of J. foetidissima was notably correlated with longitude, latitude, altitude and slope. The most remarkable variables affecting the growth of both species were summer temperatures and moisture.

Importance of the legacy effect for assessing spatiotemporal correspondence between interannual tree-ring width and remote sensing products in the Sierra Nevada

Carbon uptake and tree growth are important factors for assessing productivity and long-term carbon storage. Measurements of radial stem growth are mainly performed at the individual tree scale and can be used to infer ecosystem net primary productivity (NPP). However, these measurements are spatially limited, and remote sensing provides a promising tool to track vegetation function and productivity across spatial scales, making it a viable technique for assessing variation in interannual tree growth and carbon storage. In this study we examined the correspondence between in-situ annual tree-ring width across four dominant evergreen species in the Sierra Nevada and a wide range of remotely sensed products linked to carbon uptake including NPP, gross primary productivity (GPP), net photosynthesis (PSN), normalized difference vegetation index (NDVI), near infrared reflectance of vegetation index (NIRV), and chlorophyll/carotenoid index (CCI) from MODIS (Moderate resolution Imaging Spectroradiometer) as well as downscaled solar-induced fluorescence (SIF) products, using a 14 year dataset (2000–2014) across 62 forest sites. We show that variation of annual tree-ring width was best captured by the annual sum of MODIS GPP, with a legacy effect (5-month backwards shift). Across all forest sites, MODIS GPP with a 5-month legacy effect showed moderate correspondence with tree-ring width (r = 0.60). Within each individual site, however, the interannual correspondence between MODIS GPP with a legacy effect and tree growth was stronger (median r = 0.70 vs 0.14 without a legacy effect). The importance of legacy effects in explaining tree growth variation within sites indicates that tree growth each year is influenced by carbon uptake during the latter part of the previous growing season. Additional local environmental factors also explained annual variation in tree-ring width, including (in descending order of importance) local tree density, latitude, slope, DBH, elevation and aspect.

Stationarity of climate-growth response is only marginally influenced by the soil moisture regime in Western Siberia

Stationary (time-stable) relationships between a tree-ring proxy and climatic drivers are a prerequisite for using tree rings as paleo-climatological archives, but non-stationarity has been detected worldwide. Here we use a classical, temperature-sensitive treeline site in Western Siberia to specifically test the influence of micro-site conditions (wet versus dry) on the stationarity of climate-growth relationships in three co-existing conifer species: Larix sibirica Ledeb., Picea obovata Ledeb., and Pinus sibirica DuTour. We test two commonly used tree-ring proxies, annual tree-ring width (TRW) and maximum latewood density (MXD), using moving windows and the bootstrapped transfer function stability test (BTFS). Summer temperature is the main driver of tree growth in all three species, but non-stationarities exist in all species and both tree-ring proxies. For TRW, we found stationarity only for larch from both micro-sites, while for MXD, we found stationarity for spruce from both micro-sites, and for pine from the wet micro-site. Micro-site variability did not seem to affect stationarity in any systematic way. We highlight the necessity to systematically test the influence of different methods of stationarity tests, since BTFS was more sensitive than moving-window analysis. Taken together, our results underscore the importance of testing the assumption of stationarity for diverse micro-sites, different species and proxies at all sites prior to any tree-ring based temperature reconstruction, since even within one site results can be drastically different.

The European Beech Annual Tree Ring Widths Time Series, Solar–Climatic Relationships and Solar Dynamo Regime Changes

In this study, the results from the analysis of annual ring widths (‘Dm’) time series of two “very sensitive” to the climate and solar–climate relationships of long lived European beech (Fagus sylvatica) samples (on age of 209 ± 1 and 245 ± 5 years correspondingly) are discussed. Both series are characterized by very good expressed and relating to the solar magnetic Hale cycle 20–22-year oscillations. A good coincidence between the changes of ‘Dm’ and the growth or fading of the solar magnetic cycle is found. The transition effects at the beginning and ending of the grand Dalton (1793–1833) and Gleissberg minima (1898–1933) are very clearly visible in the annual tree ring width data for the one of beech samples. Some of these effects are also detected in the second sample. The problem for the possible “lost” sunspot cycle at the end of 18th century is also discussed. A prediction for a possible “phase catastrophe” during the future Zurich sunspot cycles 26 and 27 between 2035–2040 AD as well as for general precipitation upward and temperature fall tendencies in Central Bulgaria, more essential after 2030 AD, are brought forth.

Growth-defence trade-offs in tapped pines on anatomical and resin production

Resin harvesting is a traditional forestry activity that provides economic revenue along with crucial ecosystem services (i.e., fire protection and employment) thus contributing to the socio-economic development of rural areas. In the Iberian Peninsula, Pinus pinaster Aiton has traditionally been exploited for resin to complement the profitability of timber harvesting. Trade-offs between resin yield and radial growth are not fully understood, however. Resin ducts, the anatomical structures that produce and transport resin within the tree, have been used as a proxy for resin yield or resistance to pathogens as they represent the tree’s investment on resin defences throughout its lifespan. It is not yet clear if these structures can be linked to growth or how well the resin duct network correlates with resin yield in tapped trees. To answer these questions, we investigate annual tree-ring width, resin duct traits (absolute and standardized), and resin yield of two maritime pine stands tapped for resin extraction in the North of Portugal (VPA and PCO). Resin duct features are assessed before and during tapping periods as may show the constitutive investment, as well as the combination of constitutive and induced ones. Before resin tapping, average tree-ring width in PCO and VPA was ~2.25 and ~1.13 mm year−1, respectively. During tapping, standardized growth rates increased by ca. 40% in VPA, the population living under lower water availability and shorter growing seasons, while growth rates were almost unaffected in PCO. Median resin production in 2016 was 2.9 kg (PCO) and 1.8 kg (VPA), but inter-tree variance was high in both sites. Resin duct production increased exponentially with tree-ring width similarly in the different sites and for the same periods, but wider rings and ducts in PCO resulted in greater areas occupied by resin ducts. Within the population, constitutive anatomical resin-based defences did not trade-off with radial growth, although, lower growth rates were related to higher resin duct investments in response to tapping. Despite this, annual resin production did not correlate with resin duct density or relative area. Conversely, resin yield was positively associated with trunk perimeter, average growth, and absolute resin duct traits. These variables will thus be the most valuable when trying to identify the best resin producers in a stand. Differences in growth sensitivity to resin tapping between sites suggested that the impact of resin harvesting on radial growth is site-dependent and may not be as negative as previously thought.

A multi-century July-August streamflow reconstruction of Metro Vancouver's water supply contribution from the Capilano and Seymour watersheds in southwestern British Columbia, Canada

Recent summer water shortages in Metro Vancouver are the result of unanticipated changes in the timing of regional snowmelt and rising summer temperatures. Continuing shortfalls over the next century would pose a significant challenge for water supply management decisions. To understand the magnitude of recent drought events in the context of those that happened in the past, we developed a tree-ring reconstruction of regionalised July–August streamflow to 1711 for Metro Vancouver’s Capilano and Seymour watersheds. We used the annual tree-ring widths of mountain hemlock (Tsuga mertensiana (Bong.) Carr.) and Pacific silver fir (Abies amabilis Douglas ex J. Forbes) trees exhibiting a relationship to the seasonal snowpack as proxies for the nival component of streamflow in a regression model. The model indicates that more multi-year, below-average, streamflow departures occurred during the instrumental record than over the 1711–1992 reconstruction period. The El Niño-Southern Oscillation was significantly (p < 0.05) associated with both reconstructed and measured streamflow for the study region. Similarly, seasonal Pacific Decadal Oscillation demonstrated strong statistical relationships (p < 0.05) with measured streamflow. Over the duration of the reconstruction, significant decadal and multi-decadal periodicities were also observed. The research places the Metro Vancouver water supply in a longer-term context than was previously possible and offers a basis for advancing water supply planning decisions in the context of a rapidly changing climate.

Different drought sensitivity traits of young sessile oak (Quercus petraea (Matt.) Liebl.) and Turkey oak (Quercus cerris L.) stands along a precipitation gradient in Hungary

This paper analyses the drought-induced growth responses of two ecologically and economically important broadleaf tree species, namely sessile oak (Quercus petraea (Matt.) Liebl.) and Turkey oak (Quercus cerris L.) in south-western Hungary. Although both have been described as drought‐tolerant species, our understanding of their growth responses to drought extremes is still limited. Forest stands of younger ages of the target species were sampled along a precipitation gradient under similar soil conditions. 136 tree-ring samples were used to build six species- and site-specific chronologies. We also applied several dendroecological metrics to assess the drought sensitivity of the species. Water deficit was estimated by various drought indices including the soil water-budget based water stress index. The results indicated a strong dependency of annual tree-ring width of both species on the water availability of summer months in the actual year of ring formation. However, we found markedly different reaction of the two species against drought conditions. Turkey oak responded more sensitively to droughts than sessile oak revealed by the significantly lower resistance and higher recovery potential of this species. The more plastic behaviour of Turkey oak could be also perceived by the higher sensitivity of its tree-ring chronologies and by the observed relationship between resistance and recovery that showed a closer fit to the line of full resilience in case of this species. Regarding the precipitation gradient, a linearly proportional increase of growth reduction with rising water stress was found for Turkey oak while the growth response of sessile oak decreased considerably with increasing aridity indicating lower growth plasticity of sessile oak to droughts there. Based on our findings it seems that Turkey oak copes better with droughts than sessile oak and may gain competitive advantages under the projected climate change in Hungary.

Dendro-anthracological tools applied to Scots type pine forests exploitation as fuel during the Mesolithic-Neolithic transition in the southern central pre-Pyrenees (Spain)

This work focuses on the reconstruction of fuelwood procurement during the Mesolithic-Neolithic transition in the southern central Pre-Pyrenees (Spain). The study combines wood charcoal identification with the application of dendro-anthracological approaches in the archaeological sequence of Esplugón (9.4–6.8 kyr cal BP) (Sabiñanigo, Huesca). Scots type pine (Pinus sylvestris tp.) reaches in this record around 90% of exploited firewood in line with its abundance in the inner Iberia mountainous areas during the onset of the Holocene. The classification of pine wood fragments in anthraco-groups is based on the combination of different dendro-anthracological tools: i) pith location tool and wood diameter estimation based on the trigonomethric method tool (ADmodel), ii) the study of growth rate based on the annual tree-ring width measurements, and iii) a modern dendrological dataset. There are hardly any differences observed in firewood procurement between the last hunter-gatherers and the first farmers in the long sequences from rock-shelters with recurrent human occupations. First results from this site point to the exploitation of whole trees but a high use of small pine branches probably from the gathering of branch shedding.