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Category: Ecological Research

Title: Drought responses of conifers in ecotone forests of northern Arizona: tree ring growth and leaf ?13C

Author: Adams, H.D., Kolb, T.E.

Subject: Climate change, Elevation, Pinon pine (Pinus edulis), Limber pine (Pinus flexilis), Ponderosa pine (Pinus ponderosa)

Abstract: We sought to understand differences in tree response to meteorological drought among species and soil types at two ecotone forests in northern Arizona, the pinyon-juniper woodland/ponderosa pine ecotone, and the higher elevation, wetter, ponderosa pine/mixed conifer ecotone. We used two approaches that provide different information about drought response: the ratio of standardized radial growth in wet years to dry years (W:D) for the period between years 1950 and 2000 as a measure of growth response to drought, and d13C in leaves formed in non-drought (2001) and drought (2002) years as a measure of change in water use efficiency (WUE) in response to drought. W:D and leaf d13C response to drought for Pinus edulis and P. ponderosa did not differ for trees growing on coarse-texture soils derived from cinders compared with finer textured soils derived from flow basalts or sedimentary rocks. P. ponderosa growing near its low elevation range limit at the pinyon-juniper woodland/ponderosa pine ecotone had a greater growth response to drought (higher W:D) and a larger increase in WUE in response to drought than co-occurring P. edulis growing near its high elevation range limit. P. flexilis and Pseudotsuga menziesii growing near their low elevation range limit at the ponderosa pine/ mixed conifer ecotone had a larger growth response to drought than co-occurring P. ponderosa growing near its high elevation range limit. Increases in WUE in response to drought were similar for all species at the ponderosa pine/mixed conifer ecotone. Low elevation populations of P. ponderosa had greater growth response to drought than high-elevation populations, whereas populations had a similar increase in WUE in response to drought. Our findings of different responses to drought among cooccurring tree species and between low- and highelevation populations are interpreted in the context of drought impacts on montane coniferous forests of the southwestern USA.

Date: 2004

Type: Journal

Source: Oecologia

Identifier: 140:217-225

Publisher: Springer-Verlag

Format: PDF

Language: English