Dendrochronology and extreme pointer years in the tree-ring record (AD 1951-2011) of polar willow from southwestern Spitsbergen (Svalbard, Norway)

Greater warmth and precipitation over the past several decades in the High Arctic, as recorded in meteorological data, have caused shrub expansion and affected growth ring widths. The main aim of the study was to develop a tree-ring chronology of polar willow (Salix polaris Wahlenb.) from southwest Spitsbergen, attempt to explain its extreme pointer years (extremely low value of growthring widths) and to demonstrate the dendrochronological potential of this species. This plant is a deciduous, prostrate, creeping dwarf shrub that produces anatomically distinct annual growth rings with the consistent ring width variation. After using serial sectioning we developed rigorously cross-dated ring width chronology covering the period 1951–2011. Since the beginning of the 1980s an increase of the mean and maximum growth ring width has been observed which is consistent with the increase of both temperature and precipitation in the Arctic reported from meteorological sources. Nine negative extreme years were distinguished and explained by complex hydroclimatic drivers, which highlight the importance of availability of moisture from snowpack and spring precipitation. An additional negative factor present in the years with very low dwarf shrubs growth is rapid thawing and fast freezing during winter as well as low sunshine duration. Our results contradict the prior assumption that inter-annual tree growth variability of dwarf shrubs from polar regions is controlled simply by temperature

Use of Ornamental Trees in Dating of Abandoned Cemeteries on the Example of Thuja Occidentalis and Thuja Orientalis

Due to the lack of maintenance, abandoned cemeteries are often incorporated into the landscape. In many cases the information about the age of the cemetery is unavailable. To find out the approximate time of the formation of the cemetery the information recorded in the annual tree and shrub rings can be used. One of the most common tree species, planted for ornamental and symbolic purposes on the cemeteries, are Thuja orientalis and Thuja occidentalis. Alien to the Polish flora, these species adapted well to the local habitat and climatic conditions. The paper presents an attempt to apply dendrochronological dating to determine the age of the abandoned cemeteries in the region of the Great Masurian Lakes, part of the Masurian Lake District (north-eastern Poland). The study included five abandoned cemeteries. In total, 15 cores were taken from the trees. After applying the standard dendrochronological method, local chronologies for the studied species were established. The research indicated that the oldest found specimens - over 70 yrs old - are Thuja occidentalis individuals growing at the Słabowo cemetery. At the other sites the specimens of both Thuja species date back to the 1960s and early 1970s. Compared to the historical information regarding the age and origin of the studied objects, thujas growing there are much younger than the age of the cemeteries foundation. The presented method proved to be very helpful in understanding the time of Thuja occidentalis and Thuja orientalis introduction at the investigated cemeteries

Last 1100 yr of precipitation variability in western central Asia as revealed by tree-ring data from the Pamir-Alay

We developed a 1108 yr chronology of tree-ring widths, based on 64 Himalayan pencil juniper (Juniperus semiglobosa Regel) trees, for the Pamir-Alay Mountains, central Asia. Dendroclimatological analysis demonstrates that precipitation has significant effects on tree growth in the semiarid mountainous area of northwestern Tajikistan located on the edge of the great midlatitude Karakum and Kyzylkum deserts. The highest level of linear correlation (r= 0.67) is observed between tree growth and seasonalised winter (previous December–February) precipitation. Our studies also show that moisture (precipitation/Palmer Drought Severity Index) from the previous June to the current September was the dominant climatic factor accounting for interannual variations in tree-ring width, suggesting that this should be considered in climate reconstruction. Using the transfer function method, we reconstructed the region’s drought history over the period AD 908–2015. The results of this moisture reconstruction showed that the most recent millennium was characterised by series of dry and wet stages. The driest periods occurred before 1000, 1200–1250, and at the end of the eighteenth century and beginning of the nineteenth century. The wettest conditions existed in 1650–1700 and after 1990

Influence of climatic conditions on growth rings of Salix uva-ursi Pursh from the southeastern shore of Hudson Bay, Subarctic Canada

Over the past decades, warmer air temperature and spatiotemporal changes in the amount andpatterns of precipitation have been observed at high latitudes. Such interannual variability inclimatic conditions has a strong influence on the dynamics of biological processes regulatingterrestrial ecosystems. Dendroclimatology can improve our understanding of the impacts ofclimate change on vegetation. Based on ring width and frost rings of bearberry willow (Salix uva-ursi) individuals sampled on the southeastern shore of Hudson Bay, Nunavik (Subarctic Québec,Canada), we built a reliable 105-year growth chronology. A complex dendroclimatological analy-sis, using the standard approach (mean temperature and precipitation sums), extreme variables,and various climatological indices based on daily data, was conducted in order to preciselydescribe the relationship between annual variations in growth rings and climatic conditions.The growth of Low Arctic willows in the Hudson Bay region is determined by changes in airtemperatures as well as precipitation during the summer. However, temperature increases andreductions in amounts of rainfall may intensify drought stress, which is unfavorable for thisspecies. We found that analysis of daily amounts and intensity of precipitation improved ourunderstanding of the factors conditioning the growth of the studied species in an extremehabitat

An attempt to dendroclimatic reconstruction of winter temperature based on multispecies tree-rings widths and extreme years chronologies (example of Upper Silesia, Southern Poland)

This study aims at investigating pre-instrumental tree-ring based winter thermal conditions from Upper Silesia, southern Poland. The Scots pine, pedunculate oak and sessile oak ring widths and the extreme index were used to reconstruct winter mean temperature back to A.D. 1770. The climate response analysis showed that the pine is the most sensitive to February (0.36) and March (0.41) temperature, the oaks were found to be sensitive to the previous December (0.27) and January (0.23) temperature. It was found out that the combination of temperature sensitive species and an additional extreme index in regression can improve the reconstruction, with an emphasis on more reliable reconstruction of extreme values. The elimination of variance reduction and precise reconstruction of actual values of temperature is possible by scaling. The obtained calibration/verification results suggest that, through the application of the long-term composite chronologies a detailed study of the climate variability in Upper Silesia in past centuries can be provided

Dendrochronological potential of Ephedra Equisetina from Zaravshan Mountains (Tajikistan) in climate change studies

Samples from Mongolian Ephedra (Ephedra equisetina Bunge) was collected in the Zaravshan Mountains (the Fann Mountains), Tajikistan. The wood of Ephedra is ring-porous with well-defined growth rings. Annual ring widths were measured, individual series were first cross-dated and then averaged as a standard chronology. Correlations were calculated between the standard ring-width chronology and monthly climate data recorded in the weather station Iskanderkul. Dendroclimatological analysis showed that July temperature is the growth limiting factor of this species. Our study has shown high dendrochronological potential of Ephedra

The 443-Year Tree-Ring Chronology for the Scots Pine from Upper Silesia (Poland) as A Dating Tool and Climate Proxy

An annually resolved and absolutely dated ring-width chronology spanning 443 years has been constructed using the historical and living-tree Scots pine samples from the Upper Silesia, south of Poland. The constructed regional chronology, based on six object chronologies, covers the period of 1568–2010. It is composed of 178 wood samples with the mean correlation of 0.51, mean series length of 104 years and mean EPS of 0.85. In total, 65 extreme years were distinguished. Their independent verification, based on the historical and meteorological data, showed significant correlation with the exceptionally cold/mild winters as well as severe droughts. The comparison of the extreme years with the other Polish pine chronologies showed similarities in the years with the anomalous winter conditions. Some extreme years can be associated with the exceptional pluvial conditions; these years are common in the Central European hydroclimatic tree-ring records. The construction of this regional pine chronology enables for the absolute dating of many architectural monuments from investigated region. The application of the new chronology for the dating of local wood can support interpretations of changes in the environment of the Upper Silesian region. In the future it can also be used as the basis for climate reconstruction

Warunki klimatyczne na Górnym Śląsku w okresie 1645-2009 na podstawie analizy lat wskaźnikowych Abies alba, Pinus sylvestris, Larix decidua, Fagus sylvatica i Quercus spp.

Pointer years were identified for tree-ring chronologies of silver fir, Scots pine, european larch, common beech, sessile oak, pedunculate oak, nor-thern red oak and then related to weather records (documentary and instrumental data) during the 17th- 20th centuries. The strongest pointer years occurred throughout a range of taxa and were compared with other regions. Exceptional years (dry, wet and frosty) in Upper Silesia particularly often appear in the periods: 1645-1720, 1834-1876, 1940-1976

Post-1980s shift in the sensitivity of tundra vegetation to climate revealed by the first dendrochronological record from Bear Island (Bjørnøya), western Barents Sea

Tundra vegetation dynamics are an excellent indicator of Arctic climate change. In many places in the Arctic, greening of tundra has been observed since the 1980s due to rapid increases in temperature. However, in some areas the opposite process has taken place in connection with a reduction in biomass production. The spatial patterns of tundra ‘greening’ and ‘browning’ constitute important issues in the contemporary analysis of polar ecosystems. The aim of our study was to assess recent tundra vegetation dynamics on the basis of changes in annual growth ring widths of the polar willow. Bjørnøya (Bear Island), located in the western part of the Barents Sea is an important site in the transition zone between the high and low Arctic. No dendrochronological studies have been conducted to date due to the island’s isolation, which makes access very difficult. In 2012 and 2016, 43 samples of Salix polaris Wahlenb. were taken from the south-eastern part of Bear Island. An average chronology of the 29 most closely correlated measurement series was then compiled, covering 95 years (1922–2016); however, the time span 1946–2016 was used for the climate-growth analysis. Beginning in the mid-1980s, an increase in the width of annual increments was observed, whereas over the last decade (since 2005) the growth rate has declined rapidly. Simple correlation analyses showed that temperatures in spring and summer had the positive influence on the radial growth of the polar willow; however, the results of the moving correlation analysis made it possible to conclude that this relationship is more complex and time-dependent. Sensitivity of radial growth to temperature was strongest in the years 1955–2005, whereas the decrease in the strength of positive correlation with temperature since 2005 has been accompanied by a significant increase in the importance of summer precipitation