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Because of the eccentric radial growth for shrubs, climatic signals recorded by their ring-width series tend to be distorted. We hypothesized that measured Basal Area Increment (BAI) can overcome such a weakness. We used the desert shrub Zygophyllum xanthoxylum, with eccentric radial growth to test this hypothesis. RWI (mRWI) and BAI standard chronologies were established based on the ring-width data. Then, we converted BAI into RWI and created a transformed RWI (tRWI) standard chronology. Both BAI and tRWI showed higher correlation with climate records than mRWI, although their correlation coefficients were not significantly different from each other. Based on the comparison between tRWI and mRWI chronologies, mRWI overestimates the radial growth of Z. xanthoxylum caused by eccentric form. BAI can be applied to increase accuracy in dendrochronological studies for shrubs with eccentric growth.
Over the recent decades, a many oak tree-ring width chronologies have been used for archaeological, climatological and ecological studies, particularly across western, southern and central Europe. However, a general summary of research in the easternmost distribution of European oaks, represented mainly by Quercus robur L. and Quercus petraea (Matt.) Liebl., has been missing. Therefore, we herein overview the current state-of-the-art of oak dendrochronology in Eastern Europe. Many tree-ring width chronologies were created across this area mostly from living trees and applied in the investigation of climate-growth relationships or dendroecological studies, especially in Baltic States. In contrast, dendrochronological dating is fairly rare in the Baltic area because of a low occurrence of oak wood in historical constructions. The only long multi-centennial tree-ring width (TRW) chronology compiled using living trees as well as historical buildings exists in western Ukraine, though many preserved historical buildings still remain unexplored in some regions (e.g. Transcarpathia). The general lack of long and well-replicated TRW chronologies resulted in usage of radiocarbon methods or TRW chronologies representing distant regions for dating purposes. Nevertheless, some regions show great dendrochronological potential for compilation of long tree-ring width chronologies and its usability in dendroarchaeology or paleo-climatology.
Edmund Schulman is rightly honored for quantifying the age of bristlecone pines and discovering individuals significantly older than giant sequoias (Sequoiadendron gigantea), previously thought to be the oldest living things. However, George Engelmann inferred the potential for great age in his description of bristlecone pine (Pinus aristata) almost a century before, in 1863. Staff from Inyo National Forest re-made Engelmann's inference, and publically asserted that White Mountain bristlecones might outlive giant sequoias before Schulman had published any results of his bristlecone research.
Schulman sampled White Mountains pines after seeing a photograph and caption associated with an article by founders of the University of California White Mountain Research Station. Although Schulman's correspondence and publications make this clear, incorrect theories regarding his decision to come to the White Mountains have been published and are promulgated at the Schulman Grove Visitor Center in the White Mountains. This paper places Schulman's work in its historic context by recovering forgotten information about attempts by Inyo National Forest staff and White Mountain Research Station to call attention to the trees. It also recovers details of Schulman's and C. Wesley Ferguson's activities in the White Mountains range as documented in field notes and Thomas Harlan's Bristlecone Pine Project database.
Paleoclimate reconstructions from tree rings have so far been restricted to the western and northern Caucasus, and there have been no published tree-ring studies on any topic from the Republic of Azerbaijan in the eastern Caucasus. Here we report the first tree-ring study conducted in Azerbaijan and show that, in the southern part of the country, the common yew (Taxus baccata L.) has potential to provide annually-resolved paleoclimate information on temperature variability during winter. During the summers of 2016 and 2017, we obtained single cores from 23 yews in the Hyrcanian forests of southern Azerbaijan, near the village of Hamarat (Lerik district). The oldest yew had an inner ring date of C.E. 1867, but most other trees at this location began growing in the early 20th Century. Growth at the Lerik site is primarily and positively influenced by winter temperatures and, to a lesser degree, precipitation during summer and early autumn. Future collections of tree-ring widths from T. baccata in Azerbaijan could fill important geographic and seasonal gaps in our current paleotemperature network, and also provide useful information regarding the pace and potential impacts of wintertime warming in this region.