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Larches (Larix spp.), deciduous conifers, oc- cur in the northern hemisphere in cold-temperate and boreal climates - an environment normally thought to favor evergreen tree species. We compare foliar carbon isotope discrimination (D), instantaneous water use ef- ficiency, total foliar nitrogen concentration, and specific leaf area (for a subset of sites) between Larix spp. and co-occurring evergreen conifers at 20 sites throughout the natural range of larches. Except for Larix occiden- talis in the xeric Intermountain West, USA, D is signif- icantly (P < 0.05) greater for larches than co-occurring evergreen conifers at 77% of the sites, suggesting that larches use water less eAciently. At elevations greater than 3000 m, the D of Larix spp. and co-occurring co- nifers converge, suggesting that water is not the limiting resource. Foliar nitrogen concentration and specific leaf area are two ecophysiological characteristics that are positively correlated with high photosynthetic capacity. Foliar nitrogen concentration is significantly greater for larches than evergreen conifers at 88% of the sites and specific leaf area is approximately three times greater for larches than co-occurring conifers. Future studies should examine the potential eAect that global warming may have on the distribution of larch forests because the water use eAciency of larches is commonly less than co- occurring evergreen conifers and the boreal and high- latitude environments are likely to experience the greatest climate warming. |
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