| Summary: | The carbon sequestration potential of exotics might be considered as one of the several alternatives for forest adaptation to climate change. The results presented here demonstrate that exotic larches’ (<i>Larix</i> spp.) growth rates for both carbon accumulation and traditional forest products exceed those of both natural regeneration and other planted species when planted on a good site in Maine. Recent re-measurement of a species-site trial established in 1988 represents the 34th growing season. Species included Black Spruce (BS) (<i>Picea mariana</i> Mill.), European larch (EL) (<i>Larix decidua</i> Mill.), hybrid larch (HL) (<i>L. x marschelensi</i>), Japanese larch (JL) (<i>L. kaempferi</i> (Lam.) Carrière), Jack pine (JP) (<i>Pinus banksiana</i> Lamb.), Red pine (RP) (<i>Pinus resinosa</i> Ait.), Tamarack (TL) (<i>L. larcinia</i> (Du Roi) K. Koch), and White spruce (WS)(<i>Picea glauca</i> (Moench) Voss). All three of the exotic larches outgrew the other species. Hybrid larch had over nearly twice the merchantable volume (m<sup>3</sup> ha<sup>−1</sup>) and over three times the sawlog volume (green tonnes ha<sup>−1</sup>) than Red pine. Hybrid larch had the highest growth rate at age 34, over 20 m<sup>3</sup> per hectare per year (nearly 3.3 cords ac<sup>−1</sup> year<sup>−1</sup> or 6.8 tons<sup>−1</sup> acre<sup>−1</sup> year<sup>−1</sup>). The other two exotic larches are growing at over 19 m<sup>3</sup> ha<sup>−1</sup> year<sup>−1</sup> (3 cords acre<sup>−1</sup> year<sup>−1</sup> or 6.4 tons acre<sup>−1</sup> year<sup>−1</sup>). Converting these growth rates to accumulation of CO<sub>2</sub>eq over the 34-year period produces stunning contrasts compared to native species. Over the 34-year period, larch hybrids sequestered 2.4 times as much CO<sub>2</sub>eq as the untreated plots (444 vs. 186 tonnes<sup>−1</sup> ha<sup>−1</sup>). We discuss practical implications for forest management and carbon policies.
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