Seasonal Contributions to the Climatic Variations Recorded in Tree Ring Deuterium/Hydrogen Data

Tree ring δD records do not always reflect variations in the average annual δD values of local precipitation, but may instead record changes in the δD values of seasonal components of precipitation. The δD values measured for tree ring sequences from the three trees in this study are correlated with variations in summer climatic conditions at each of the sites. The D/H ratios in an aspen from Fairbanks, Alaska, correlate with summer temperatures in Fairbanks. An aspen which grew near Anchorage, Alaska, and a pine located near Seeley Lake, British Columbia, contain δD records which correlate with the amount of summer precipitation at their respective sites. The δD variations of the two Alaskan aspens are correlated for the five 5-year sample intervals which they have in common. It is emphasized that a correlation between tree ring δD variations and a local seasonal climatic parameter for a given tree does not imply that all trees in that area will exhibit similar correlations. The site and growth conditions of individual trees will probably determine what climatic signal is contained in the D/H records of each

Multiple-proxy lacustrine record of moisture transport over western North America from 24,000 to 12,000 YBP, Lake Estancia, New Mexico [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Pluvial Lake Estancia in central New Mexico experienced large and rapid fluctuations in surface area and elevation during the build-up to and termination of the last glacial maximum (LGM). Due to continuous groundwater discharge, a minimum pool covering about 400 square kilometers was maintained in the central basin until about 12,000 years ago, ensuring a continuous depositional sequence even during low stands of the lake. ... The sensitive response to fluctuations in climate by several independent proxies at Estancia show that transport of Pacific moisture over western North America changed dramatically during the last Ice Age, perhaps comparable to the large and rapid changes in climate documented from high-latitude ice and North Atlantic marine sediments for the LCM and its transitions

Climatic implications of the D/H ratio of hydrogen in C-H groups in tree cellulose

Isotopic climate records in tree rings were obtained by the δD analyses of the hydrogen in cellulose nitrate extracted from tree rings in a Scots pine from Loch Affric, Scotland, and from a bristlecone pine from the White Mountains, California. This method of analysis measures δD values of only the isotopically non-exchangeable hydrogen of the cellulose in wood and thus eliminates serious complications in the δD record caused by the chemical heterogeneity of wood and by the isotopic exchangeability of some of its hydrogen. The average δD values of the two pines are markedly different, reflecting the contrasting climates of the two areas. The bristlecone δD record contains a 22-year periodicity perhaps recording a possible 20- to 22-year periodicity of drought conditions in the Great Plains of North America. There is no such significant periodicity in the δD record of the Scots pine. The long-term δD trends in the two pines, as represented by 40-year running averages of the δD data, correlate linearly over the time period 1841–1970 A.D., which is the total growth period of the Scots pine. The long-term δD trend of the Scots pine correlates well with the 1841–1970 winter temperatures of Edinburgh, Scotland. The long-term δD trend of the bristlecone pine, which extends over the time period 970–1970 A.D., correlates qualitatively with long-term climatic trends estimated by LaMarche from tree ring width data and by Lamb from many sources of climatic data. δD analyses were also made on early and late woods from the same annual ring. The δD values of these woods differ to various degrees and the sign of the difference can also vary

A reexamination of cellulose carbon-bound hydrogen δD measurements and some factors affecting plant-water D/H relationships

The method of Epstein et al. (1976) for analysis of D/H ratios of cellulose carbon-bound hydrogen has been modified. This modified “renitration” method yields δD values which are in agreement with those obtained by the sodium chlorite delignification method. Comparison of results obtained by the renitration method with the published results of Epstein et al. (1976) indicate some differences in the δD values of individual samples. However, the overall plant-water δD relationship determined by Epstein et al., is not greatly changed upon redetermination by the renitration method. Additional data from a variety of plants representing a wide geographical range reveal that relative humidity is an important variable in determining the δD value of cellulose C-H hydrogen on this inter-regional scale. The role of relative humidity can be reasonably explained by a leaf water model that assumes an isotopic steady-state during transpiration. These results reaffirm the conclusion of Epstein et al., that the δD variations of the source water are the dominant control of the δD variations of cellulose C-H hydrogen from naturally grown plants. Thus, there is an expectation that these cellulose δD variations can have climate significance

Climatic significance of the hydrogen isotope ratios in tree cellulose

A distinct relationship exists between the δD values of cellulose carbon bound hydrogen in trees and average annual temperature for a variety of trees from a wide range over North America. The slope of the δD/T relationship is 5.8‰°C^(−1). Samples of annual precipitation covering much the same geographical range as the trees exhibit a comparable temperature coefficient of 5.6‰°C^(−1). Such growth-site conditions as poor drainage and/or low relative humidity seem to perturb the spatial δD/T relationship. However, our data indicate that suitable tree growth sites are more the rule than the exception

Oxygen and Hydrogen Isotopic Ratios in Plant Cellulose

The variations of the D/H and ^(18)O/^(16)O ratios of nonexchangeable hydrogen and oxygen in plant cellulose reveal systematic differences between terrestrial plant groups. The slope of δD versus δ^(18)O of cellulose from a variety of aquatic plants is close to 8 (the meteoric water value), while the slope for a number of terrestrial species is greater than or equal to about 24. Two models involving incorporation of CO_2 and H_2O into cellulose precursors are proposed to account for these differences. Effects of evaporative transpiration on the isotopic composition of water in leaves are measured and discussed in the context of these models

The determination of the D/H ratio of non-exchangeable hydrogen in cellulose extracted from aquatic and land plants

A method has been developed for the analysis of D/H ratios of non-exchangeable hydrogen in plant cellulose. Plant samples are nitrated at low temperature and pure cellulose nitrate is extracted by acetone dissolution. Tests of this nitrated product have demonstrated that the nitration-extraction procedure eliminates the OH hydrogen and does not alter the D/H ratio of the cellulose carbon-bound hydrogen. Significant differences exist between δD values of plant total hydrogen and δD values of cellulose nitrate hydrogen. This difference is due to the effect of chemical heterogeneity of the δD value of plant material. Plant-extracted cellulose nitrate D/H ratios are systematically related to the D/H ratios of the associated environmental water. The overall relationship is linear with slope of one and intercept of −22%. Five aquatic plants which grew at 16–17°C are related isotopically to the water by a linear curve with a slope of 1 and intercept of −36%. Three plants which grew at 28–29°C have an intercept of −11%. The general dependence of plant cellulose non-exchangeable hydrogen D/H ratios on the D/H ratios of the associated environmental water suggests that variations of the extracted cellulose nitrate δD values of plants can be used as indicators of climatic change