Seasonal Isotope Patterns in Tree Rings
first papers to suggest and demonstrate that isotopic analysis of sequential
intra-annual subdivisions within tree rings could reveal important environmental
information were Wilson and Grinsted (1975) for hydrogen isotopes, Wilson and
Grinsted (1977) for carbon isotopes, and
Resolution and quantification of the patterns of seasonal carbon isotope variability in tree rings have constituted a longstanding interest and research thread. Initial comparisons were made between patterns of seasonal isotopic variations in rings and leaves (Leavitt and Long, 1982a, 1985) for Juniper and Acer. The patterns were also seen in pinyon (Pinus edulis) tree rings (Leavitt and Long, 1986), and their value as a dating tool and the possible environmental influences contained in the seasonal patterns were discussed in Leavitt and Long (1982b). These findings became the driving force for a 1983 proposal (unfunded) by Leavitt and Long intended to use the carbon isotope seasonal patterns to date tropical tree rings (the figures above are Figs. 8, 7, 5, 6 and 9, respectively, from the proposal, which show isotope results for holocellulose [upper curves] and whole wood [lower curves]), and eventually a compendium of seasonal isotope patterns in a large number of species (14) and locations with the isotope patterns largely measured on one radius from one tree (Leavitt and Long, 1991). The major exception was separate analysis of four radii from a Pinus ponderosa tree whose growth was closely monitored by Prof. Hal Fritts from 1963-67 (Fritts, 1966), for which the mean seasonal isotope patterns of the five years were compared with the environmental data monitored at the site.
This was followed up with field studies to better quantify relationships with environment by comparing responses of different species (Pinus and Acer) in different microenvironments (open and closed canopy) for trees growing under the same climate regime and analyzing the patterns in several trees (and several radii from each tree) from each species and microenvironment (Leavitt, 1993). One of the difficulties in interpreting the patterns involves uncertain temporal resolution of each segment being analyzed, so another field study monitored the growth of a number of trees through the growing season before eventually sampling and analyzing the seasonal subdivisions (of Juniperus, Populus, Quercus, Pinus, Picea, Acer) and comparing them with environment using nearby climate stations (Leavitt, 2002). The previous two studies were for the US Midwest, but seasonal subdivisions of Pinus ponderosa in Arizona-New Mexico using false latewood bands as a time marker also helped identify environmental linkages (Leavitt et al., 2002). Most recently, a US Midwest seasonal isotope study was published investigating conditions associated with the 1988 drought involving isotopic analysis for tree-ring subdivisions of 3 species (Pinus resinosa, Pinus strobus, Picea glauca) and nine sites (Leavitt, 2007).
Growth chamber studies were additionally conducted to try to better quantify the environmental influences on seasonal isotope patterns (Danzer et al., 2001; Leavitt 2001). These experiments were conducted with Pinus resinosa (and Populus- unpublished) seedlings under controlled growth conditions using temporal control provided by regular measurements of stem diameter. Again, drought (moisture condition) seemed to be the dominant effect on the isotope patterns.
Danzer, S.R., Leavitt, S.W.,
Epstein, S. and Yapp, C.J. 1976. Climatic implications of the D/H ratio of hydrogen in C-H groups in tree cellulose. Earth and Planetary Science Letters 30: 252-261.
Fritts, H.C., 1966. Growth rings of trees: Their correlation with climate. Science 154(3752): 973-979.
Leavitt, S.W., 1993. Seasonal 13C/12C
changes in tree rings: Species and
site coherence, and a possible drought influence. Canadian Journal of
Leavitt, S.W., 2001. Seasonal response of d13C in Pinus resinosa Ait. seedling growth rings to changing environment in controlled growth experiments. Dendrochronologia 19(1): 9-22.
Leavitt, S.W., 2002. Prospects for
reconstruction of seasonal environment from tree-ring d13C: Baseline findings from the Great Lakes area,
Leavitt, S.W., 2007. Regional expression of the 1988 U.S. Midwest drought in seasonal d13C of tree rings. Journal of Geophysical Research- Atmospheres 112, D06107, doi:10.1029/2006JD007081.
Leavitt, S.W. and Long, A., 1982a. Evidence for 13C/12C fractionation between tree leaves and wood. Nature 298:742-744.
Leavitt, S.W. and Long, A., 1982b. Stable carbon isotopes as a potential supplemental tool in dendrochronology. Tree-Ring Bulletin 42:49-55. (PDF)
Leavitt, S.W. and Long A., 1985. Stable-carbon isotopic composition of maple sap and foliage. Plant Physiology 78:427-429.
Leavitt, S.W. and Long, A., 1986. Stable-carbon isotope variability in tree foliage and wood. Ecology 67:1002-1010.
Leavitt, S.W. and Long, A., 1991. Seasonal stable-carbon isotope variability in tree rings: possible paleoenvironmental signals. Chemical Geology (Isotope Geoscience Section) 87:59-70.
Leavitt, S.W., Wright, W.E., Long,
A., 2002. Spatial expression of ENSO,
drought and summer monsoon in seasonal d13C of ponderosa pine tree rings in southern
Li, Z.-H., Leavitt, S.W., Mora, C.I., Liu, R.-M., 2005. Influence of earlywood-latewood size and isotope differences on long-term tree-ring d13C trends. Chemical Geology 216: 191-201.
Leavitt, S.W., 2004. Tree-Ring Isotope
Rhythms: Climate and Dating from the Bands. AAAS Pacific Division,
85th Annual Meeting,
Leavitt, S.W., 2005. Regional Expression of the 1988 U.S. Midwest Drought in Seasonal Stable-Carbon Isotope Patterns of Tree Rings, Eos Trans. AGU, AGU Fall Meeting (5-9 Dec.), 86(52), Fall Meet. Suppl., Abstract H33B-1385