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Coast redwood (Sequoia sempervirens) ecosystems are strongly influenced by the presence of summer marine fog, and variation in fog frequency is closely linked to climate variation in the NE Pacific region. Because oxygen isotope composition (δ18O) of organic matter records distinct water sources (e.g. summertime fog vs. winter precipitation) and carbon isotopes (δ13C) are typically sensitive to humidity and water status, it then follows that inter-annual variation in tree-ring isotope ratios, which are coherent across multiple sites, should preserve a potentially powerful proxy for climate reconstruction. Here we present an analysis of a 50-year time series for both δ18O and δ13C values from subdivided tree rings obtained from multiple redwood trees at multiple sites. Within-site and between-site correlations were highly significant (p < 0.01) for the δ18O time series indicating a regionally coherent common forcing of δ18O fractionation. Within-site and between-site correlation coefficients were lower for the δ13C than for the δ18O time series although most were still significant (at least to p < 0.05). The hypothesized reason for the differences in the correlation is that carbon isotope discrimination is more sensitive to microenvironmental and tree-level physiological variation than is δ18O fractionation. Stable-isotope variation in tree-ring cellulose was similar between slope, gully and riparian micro-habitats within a single watershed, implying that minor topographic variation when sampling should not be a major concern. These results indicate that stable-isotope time series from redwood tree rings are strongly influenced by regional climate drivers and potentially valuable proxies for Pacific coastal climate variability.
Tree-ring studies have demonstrated that conifer latewood measurements contain information on long-term North American monsoon (NAM) variability, a hydroclimatic feature of great importance to plants, animals, and human society in the US Southwest. This paper explores data-treatment options for developing latewood chronologies aimed at NAM reconstruction. Archived wood samples for five Douglas-fir (Pseudotsuga menziesii, Mirb. Franco) sites in southeastern Arizona are augmented with new collections. The combined dataset is analyzed along with time series of regionally averaged observed precipitation to quantify the strength of regional precipitation signal in latewood time series and to identify ways of increasing the signal strength. Analysis addresses the signal strength influences of including or excluding “false” latewood bands in the nominal “latewood” portion of the ring, the necessary adjustment of latewood width for statistical dependence on antecedent earlywood width, and tree age. Results suggest that adjusted latewood width chronologies from individual sites can explain around 30% of the variance of regional summer (July–August) precipitation—increasing to more than 50% with use of multiple chronologies. This assessment is fairly insensitive to the treatment of false latewood bands (in intra-annual width and δ13C variables), and to whether latewood-width is adjusted for dependence on earlywood-width at the core or site level. Considerations for operational chronology development in future studies are (1) large tree-to-tree differences in moisture signal, (2) occasional nonlinearity in EW-LW dependence, and (3) extremely narrow and invariant latewood width in outer portions of some cores. A protocol for chronology development addressing these considerations is suggested.
Dendrochronological collections include continuously expanding multi-taxon records of tree growth that encompass millennia and often offer irreplaceable sources of biological, environmental, and cultural information. Nevertheless, each departure of a scholar from the field—whether because of death, retirement, career change, shift in research priorities, or even move to a new institution—places collections in increased danger of being lost as viable resources. Without an organized and concerted effort to address outstanding and future issues of specimen curation, dendrochronology as a whole may become mired in the same trap that befalls many other scientific fields: collections apathy. Dendrochronological collections exist as a result of decades of effort and should function to support current and future scientific endeavors, education, and outreach, but cannot do so without adequate attention to their future. Intended as a “call to arms” this paper, focused on dendrochronology in the academic and public sector, aims to encourage discussion and, more importantly, to provide a foundation for and to instill a sense of urgency regarding long-term preservation of dendrochronological specimens.
The Lund-Spathelf House is located at 1526 Pontiac Trail in Ann Arbor, Michigan. During a recent renovation, the owner sought information regarding the construction of the house by searching through numerous written records. Despite an extensive history of the land on which the house currently sits, neither a construction year nor general period of construction could be obtained. Therefore, four samples of oak (Quercus spp.) were extracted from floor boards throughout the house for dendrochronological dating. The four samples crossdated conclusively with each other both visually and statistically and were used to build a floating 126-year tree-ring chronology. We used COFECHA to statistically evaluate the absolute temporal placement of this chronology against a nearby regional chronology (MI005.CRN) from the Cranbrook Institute, Michigan. The Lund-Spathelf House chronology was anchored in time with the regional chronology from A.D. 1720 to 1845 with a correlation coefficient of 0.62 (p < 0.0001, t < 8.76, n = 126). All four oak samples provided conclusive cutting dates of A.D. 1845, indicating the year the Lund-Spathelf House was constructed.
When coring thick-barked trees, increment cores often become compressed and jammed inside the narrow region of the borer shaft. These jams can be problematic for two reasons: first, it often leaves the core unusable; second, the jam may be so tightly compressed in the borer that removal is difficult, especially in the field. Although procedures to evacuate these jams are documented in the literature, methods of prevention are not. Here, a modified manual method of increment boring that can reduce the likelihood of jams and, in addition, decrease the number of deformed core samples is described. Traditional and modified boring methods were randomly assigned to 40 Douglas-fir trees (80 cores) at a research site along the Oregon coast. Results show that jams were associated with traditional boring over six times more than with the proposed modified technique.
Minimum blue intensity is a reflected light imaging technique that provides an inexpensive, robust and reliable surrogate for maximum latewood density. In this application it was found that temperature reconstructions from resin-extracted samples of Pinus sylvestris (L.) from Fennoscandia provide results equivalent to conventional x-ray densitometry. This paper describes the implementation of the blue intensity method using commercially available software and a flat-bed scanner. A calibration procedure is presented that permits results obtained by different laboratories, or using different scanners, to be compared. In addition, the use of carefully prepared and chemically treated 10-mm-diameter cores are explored; suggesting that it may not be necessary to produce thin laths with the rings aligned exactly perpendicular to the measurement surface.
There are at least 21 dendro-data formats used in dendrochronology laboratories around the world. Many of these formats are read by a limited number of programs, thereby inhibiting collaboration, limiting critical review of analyses, and risking the long-term accessibility of datasets. Some of the older formats are supported by a single program and are falling into disuse, opening the risk for data to become obsolete and unreadable. These formats also have a variety of flaws, including but not limited to no accurate method for denoting measuring units, little or no metadata support, lack of support for variables other than whole ring widths (e.g. earlywood/latewood widths, ratios and density). The proposed long-term solution is the adoption of a universal data standard such as the Tree-Ring Data Standard (TRiDaS). In the short and medium term, however, a tool is required that is capable of converting not only back and forth to this standard, but between any of the existing formats in use today. Such a tool is also required to provide continued access to data archived in obscure formats. This paper describes TRiCYCLE, a new application that does just this. TRiCYCLE is an open-source, cross-platform, desktop application for the conversion of the most commonly used data formats. Two open source Java libraries upon which TRiCYCLE depends are also described. These libraries can be used by developers to implement support for all data formats within their own applications.