The δ¹³C of tree rings in full‐bark and strip‐bark bristlecone pine trees in the White Mountains of California

Abstract

Dendrochronological work at Sheep Mountain in the White Mountains, CA has demonstrated that bristlecone pine trees in two forms, full‐bark and strip‐bark, have experienced different cambial growth rates over the past century or longer. The strip‐bark trees showed a greater growth increase than the full‐bark ones. A calculation of the plant water‐use efficiency (W) in response to anthropogenic CO2 released into the atmosphere shows that W of trees in both forms has increased for the past 200 years. However, there is no significant difference between the two tree forms in the rate of increase in W. This implies at least two possibilities with respect to the CO2 fertilization effect. First, the biomass in both tree forms might have increased, but carbon distribution among different parts of a tree was different. Second, the biomass may increase without causing any corresponding change in the plant water‐use efficiency.

Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes

“…in available CO 2 and intrinsic WUE or from increased nitrogen deposition alone, which should affect most of these sites similarly (14,28,29). The high-elevation pattern of rapid growth in recent decades at PRL (Fig.…”

“…LaMarche et al (17) proposed a hypothesis of fertilization at high elevation by increased atmospheric CO 2 concentrations through increased water-use efficiency (WUE) to explain the positive growth trend. Tang et al (14) found increased WUE in both strip-bark and whole-bark bristlecone pines, whereas Graumlich (18) did not find evidence for a CO 2 fertilization effect as a cause for enhanced growth among subalpine conifers in the Sierra Nevada. It also should be noted that nitrogen inputs from human activity are enriching some western ecosystems (19), and long-term fertilization experiments suggest these inputs may be contributing to increases in tree growth (20).…”

“…Radial growth that does not extend around the entire circumference of a tree may proceed over less surface area and therefore produce wider rings than those produced in the circular morphology of whole-bark trees. Growth differences between strip-bark and whole-bark trees have been noted in Great Basin bristlecone pine (13,14) and in whitebark pine (Pinus albicaulis) from Montana (15). In bristlecone pine, Graybill and Idso (13) concluded that the modern increase in growth was greatest in trees with an irregular strip-bark growth form.…”

Carbon isotope discrimination in photosynthetic bark

“…If this were the case, the change in δ 13 C of wood following light exclusion would be expected to approach the magnitude of the change in δ D within 2 or 3 years. This change in δ 13 C with light exclusion may have important implications for studies which attempt to reconstruct long-term trends in the physiology of leaf photosynthesis from the δ 13 C of tree-ring chronologies (e.g., Marshall and Monserud 1996;Bert et al 1997;Duquesnay et al 1998;Feng 1998Feng , 1999Tang et al 1999). …”

Surface Temperature Reconstructions for the Last 2,000 Years

“…In old age these trees can assume a "strip-bark" form, characterized by a band of trunk that remains alive and continues to grow after the rest of the stem has died. Such trees are sensitive to higher atmospheric CO 2 concentrations (Graybill and Idso 1993), possibly because of greater water-use efficiency (Knapp et al 2001, Bunn et al 2003 or different carbon partitioning among tree parts (Tang et al 1999). Support for a direct CO 2 influence on tree ring records extracted from "full-bark" trees is less conclusive.…”