This paper is concerned with examining the degree of correlation between monthly climatic variables (multicollinearity) within data sets selected for their high quality. Various methods of describing the degree of multicollinearity are discussed and subsequently applied to different combinations of climate data within each site. The results indicate that higher degrees of multicollinearity occur in shorter data sets. Data consisting of 12 monthly variables of a single parameter (temperature or precipitation) have very low degrees of multicollinearity. Data set combinations of two parameters and lagged variables, as commonly used in tree-ring response function analysis, can have significant degrees of multicollinearity. If no preventative or corrective measures are taken when using such multicollinear data, erroneous interpretations of regression results may occur.

Three different response-function programs are applied to three tree-ring chronologies, two of Pinus ponderosa Laws. and one of Juniperus occidentalis Hook. These data were analyzed before and after ARMA modeling was applied. The results are described and compared to one another as well as to those obtained from all-steps multiple regression, stepwise multiple regression, ridge regression, and simple correlation. In spite of methodological differences all multivariate methodsproduced remarkably similar results. The results from simple correlation differed the most. Some differences among the response functions were apparent, especially in the coefficients associated with prior growth. The response-function results have smaller error estimates than ridge regression. According to Cropper (1985) this error in the response-function results is underestimated by approximately 40 %. The rationale for the different response-function solutions is discussed.

An exploratory investigation of tree growth and climate relationships in Abies religiosa from Michoacan, Mexico, produced the first crossdated and standardized tree-ring chronology from the North American tropics. Pearson correlation coefficients and principal components response function analysis were employed. Results indicate that ring-width series from this species have moderately high signal-to-noise ratio (S/N = 13.42). A substantial percentage of the ring-width signal can be explained by instrumented monthly climate data, particularly spring precipitation and winter temperature. Although correlation between climate data and the tree-ring measurements indicate that growth of Abies religiosa is highly influenced by year-to-year climate variation, longer climate records and tree-ring chronologies are needed from this tropical region to improve understanding of climate -tree growth relationships, and for dendroclimatic reconstruction.

The bootstrap procedure provides a way to test the significance of the regression coefficients and the stability of the estimates in response functions generated by regression on principal components. A subroutine RESBO, which calculates a bootstrapped response function, has been added to Fritts' program PRECON.

Tree-ring chronologies are widely used to reconstruct high-to low-frequency variations in growing season temperatures over centuries to millennia. The relevance of these timeseries in large-scale climate reconstructions is often determined by the strength of their correlation against instrumental temperature data. However, this single criterion ignores several important quantitative and qualitative characteristics of tree-ring chronologies. Those characteristics are (i) data homogeneity, (ii) sample replication, (iii) growth coherence, (iv) chronology development, and (v) climate signal including the correlation with instrumental data. Based on these 5 characteristics, a reconstruction-scoring scheme is proposed and applied to 39 published, millennial-length temperature reconstructions from Asia, Europe, North America, and the Southern Hemisphere. Results reveal no reconstruction scores highest in every category and each has their own strengths and weaknesses. Reconstructions that perform better overall include N-Scan and Finland from Europe, E-Canada from North America, Yamal and Dzhelo from Asia. Reconstructions performing less well include W-Himalaya and Karakorum from Asia, Tatra and S-Finland from Europe, and Great Basin from North America. By providing a comprehensive set of criteria to evaluate tree-ring chronologies we hope to improve the development of large-scale temperature reconstructions spanning the past millennium. All reconstructions and their corresponding scores are provided at www.blogs.uni-mainz.de/fb09climatology. (C) 2016 Elsevier Ltd. All rights reserved.

Tree-ring records from long-lived trees are instrumental for understanding climate variability during the Common Era. Some of the oldest and most valuable conifers used to reconstruct past climate exhibit strip-bark morphology, in which vertical segments of the tree have died in response to environmental stress. This form of localized stem mortality, also referred to as partial cambial dieback, is particularly common on conifers growing in xeric, cold, or exposed environments. Some studies note that strip-bark trees have increasing ring-width trends relative to trees with a fully living stem circumference, but there is substantial uncertainty as to what extent partial cambial dieback can influence tree-ring records and subsequent climate reconstructions. This dissertation explores the environmental drivers of partial cambial dieback on Siberian pine (Pinus sibirica Du Tour) from Mongolia, the effect of cambial dieback on the radial growth and physiology of affected trees, and methods for reducing strip-bark biases in tree-ring records. Chapter 1 assesses the causes and radial growth impacts of partial cambial dieback on Siberian pine trees growing on an ancient lava flow in central Mongolia. Using a combination of field observations and dendrochronological methods, this chapter demonstrates that strip-bark trees from this site exhibit dieback primarily on the southern side of stems, and that dieback was most common during a cold and dry period in the mid-19th century. Given the directionality and timing of dieback on these strip-bark trees, it is hypothesized that localized mortality events are linked to physiological injuries spurred from solar heating combined with unfavorable climatic conditions. This chapter also reveals that strip-bark trees from this site have increasing radial growth trends relative to trees with a full circular morphology (“whole-bark” trees). Strip-bark trees showed an especially rapid increase in ring widths following the cambial dieback period in the mid-19th century, providing initial evidence that dieback events can lead to increasing ring widths in strip-bark Siberian pine. Chapter 2 seeks to discern the physiological mechanisms of increasing radial growth trends in the Siberian pine strip-bark trees using stable carbon and oxygen isotopes from tree rings. One simple hypothesis is that strip-bark trees show increasing ring-width trends because radial growth is restricted to a smaller stem area after cambial dieback events. Conversely, some studies have hypothesized that increasing ring widths in strip-bark trees reflect a CO2 fertilization effect on growth that is not readily apparent in whole-bark trees. This chapter finds that strip-bark and whole-bark trees responded similarly to increasing atmospheric CO2 and climate variability in their radial growth and leaf-level gas exchange inferred from tree-ring stable isotopes. However, strip-bark and whole-bark trees showed notably different behavior following documented cambial dieback events. After dieback events, strip-bark trees exhibited an increase in ring widths and an enrichment in stable carbon and oxygen isotopes that was not apparent in whole-bark trees. These results further support the notion that partial cambial dieback leads directly to increasing ring widths in strip-bark trees, and that this response could reflect an increase in the ratio of leaf to live stem area after dieback occurs. Chapters 1 and 2 demonstrate that partial cambial dieback events and morphological changes impact the radial growth and physiology of strip-bark trees. Therefore, prior to developing climate reconstructions, it is necessary to remove variance associated with these non-climatic, morphological changes in tree-ring series. Chapter 3 outlines two chronology development methods for reducing strip-bark biases in tree-ring records. These methods, applied to Siberian pine and Great Basin bristlecone pine (Pinus longaeva Bailey), successfully reduce a strip-bark bias without removing low-to-medium frequency climate variance inferred from whole-bark trees, which were not impacted by dieback activity. While one approach directly corrects the bias in strip-bark series using a whole-bark chronology as a target, another method is based on the development of a low-percentile chronology, which can be applied to a site collection where the stem morphology of individual trees is unknown. Some limitations and caveats of these methods are discussed in context of the analyzed tree species. The findings from this dissertation have significantly contributed to our understanding of the radial growth and physiological responses of Siberian pine to partial cambial dieback and environmental changes. This dissertation also provides new methods for removing strip-bark biases in tree-ring chronologies. The conclusions presented here have important implications regarding the potential effects of partial cambial dieback on tree-ring records from other tree species and climate reconstructions derived from them. Continued and detailed study of the causes and impacts of partial cambial dieback on other tree species will be critical for understanding the interactions between ancient trees and their environment, and for improving the reliability of climate reconstructions based fully or partly on strip-bark trees.

Climate on earth is getting warmer, which effects earth’s energy balance and so forth the ocean and atmospheric circulation.  In many sub-polar regions on the northern hemisphere changes due to warming of the climate can be observed. Some examples that already have been observed are shifts in tree line, towards higher altitudes and latitudes, increased ablation of Swedish glaciers and melting of the permafrost on the Siberian tundra. In Sweden climate change scenarios tell us that it will become warmer and that a higher amount of precipitation in form of rain will be an effect from this. To study climate changes in Sweden, transition zones are useful in order to observe changes in distribution of species and animal populations. This study uses tree rings from Scots Pine (Pinus sylvestris L.) that grow at the tree line in Grövelsjön that is part of the mountains in Dalarna County. By measuring the width of the tree rings, a chronology that is representative for July temperature is made over this area. The method is called dendroclimatology and has generally been used to reconstruct past climate for the last 1000 years.  The results of this study show that the tree ring chronology don’t show a clear increase in temperature for the last century, which could have been expected from an area like this. But the result also show that when instrumentally measured temperature were plotted month by month, the only month with significant up going trend in temperature in this area is April. A temperature change in April does not leave a signal in the tree rings because it is too cold for them to grow that early in the season.

Prepared for U.S. Army Corps of Engineers, Los Angeles District Office, Contract No. DACW-09-80-C-0071

Contract #DACW 72-78-Q-0046 / US Army Coastal Engineering Research Center Requisition Purchase Request #IWR-B-78-119 / The objectives of this report are, first, to summarize the findings to date of the dendroclimatic work performed by our research team at the University of Arizona with respect to the broad patterns of climatic variations over North America since 1600 AD. A secondary objective, as stated in the contract, is to select set(s) of those past climatic patterns which most closely resemble or provide a perspective for conditions of climatic variability expressed as possessing a substantial degree of mobility of occurrence by the National Defense University (1978) study of climatic changes.

This thesis presents research that improves our understanding of the relationship between climate and tree-ring stable isotopes in New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F). As a whole, this research creates a framework from which future investigations of stable isotope dendroclimatology can pursued at high temporal resolution across longer term temporal intervals. Such a framework is required to realize the full potential of New Zealand tree-ring records as archives of palaeoclimatic information. In the Southern Hemisphere, mid-to-high latitude terrestrial climate proxy records are sparse; the long-lived endemic conifers of New Zealand present a rare opportunity to gain valuable insight into Late-Quaternary and Holocene climatic change. A major barrier to long stable isotope dendroclimatic proxy records has been the time-and-resource intensive nature of associated sample preparation and analytical processes. Through experimental assessment of the SBrendel α-cellulose extraction method, this research demonstrates that this simple processing method can, with some caveats, be successfully applied to resinous conifers, facilitating rapid chemical preparation of samples. Further efficiency gains are documented in through use of dual element low temperature pyrolysis of cellulose, providing carbon and oxygen stable isotope determinations on a single sample, rather than the traditionally separate analyses. These preliminary investigations into methodological efficiency enabled the ~3000 stable isotope determinations on kauri and cedar, on which the following investigations into isotopic variability, chronology quality and climate-isotope relationships are based. Both kauri and cedar exhibit substantial intra and inter-tree isotopic variability, resulting in greater than normal sample numbers being required to isolate the common variance in composite time-series. Despite sampling 7 trees (18 cores) at one site and 8 trees (21 cores) at another, only oxygen isotope time-series reach an Expressed Population Signal score of 0.85, a common benchmark of chronology quality. Further investigations using high-resolution sequential sampling of single rings show that this variability extends to a sub-annual scale. Within single rings there are large ranges in δ13C and δ18O, generally corresponding with regular annual cycles of up to 4.6‰ for δ13C and 8.1‰ for δ18O. These data show high frequency (sub weekly) changes in δ18O, demonstrating sufficiently fine resolution for event-to-seasonal scale climate/weather reconstruction. However, that potential is complicated by the lack of strong climatic correlations with isotopic cycles. Due to their stronger common signal, δ18O time series are investigated for inter-annual stable isotope dendroclimatic reconstruction from kauri and cedar. Bootstrapped correlation and multiple regression models show strong relationships between kauri and cedar δ18O and relative humidity, accumulated rainfall and soil moisture deficit. The correlations are strongest for all variables during the period from Autumn prior to growth to the current growth summer. Tree-ring δ18O in kauri and cedar is identified as an effective recorder of regional hydroclimate leading up to and during the Austral growth season. While it is demonstrated that tree-ring δ18O holds significant promise for inter-annual palaeoclimate reconstruction, it is equally apparent from this research that stable isotope dendroclimatology in New Zealand faces significant challenges. Foremost is gaining an improved understanding of seasonal dendrochemical cycles and their relationship with tree-physiology. Increasing the spatial and temporal coverage of tree-ring isotope records is vital to realising New Zealand’s vast potential for stable isotope dendroclimatic reconstruction.