Topographically modified tree-ring chronologies as a potential means to improve paleoclimate inference

Paleoclimate records from tree rings are important for understanding climate variability during the late Holocene. Some of the tree-ring chronologies of greatest interest are collected on high mountains dominated by complex terrain. Often individual trees growing at the same site will occupy discrete microenvironments particular to their own location due to the topographical differences of the landscape. These topographical differences influence how the tree records climate in its particular setting. Thus, a mean ring-width chronology from a particular site may be composed of trees from highly varied topographic positions. Such a “topographically-mixed” chronology can be confounded in terms of its climate signal. For example, ring widths of trees that are primarily recording summer temperature might be averaged with ring widths of trees that are primarily precipitation recorders. Here, we describe how dendrochronologists can use the topographic setting of individual trees within a single area to extract different growth signals and potentially improve the inference of past climates. As an example, we show how topography modifies the growth and climate associations of 69 high elevation bristlecone pine trees from the White Mountains of California and how sampling according to explicit topographic parameters might permit better understanding of complex climate-growth associations. Climate sensitive tree-ring records extending back in time more than a thousand years are relatively rare. The dry interior of the western United States has an uncommonly high density of millennial or multi-millennial tree-ring records, mainly from five-needle pines (Pinus spp.). Perhaps most noteworthy of these records are the Great Basin bristlecone pines (P. longaeva D.K. Bailey) from the White