Rising concentrations of atmospheric CO₂ have increased growth in natural stands of quaking aspen (Populus tremuloides)

Abstract

As atmospheric CO 2 levels rise, temperate and boreal forests in the Northern Hemisphere are gaining importance as carbon sinks. Quantification of that role, however, has been difficult due to the confounding effects of climate change. Recent large-scale experiments with quaking aspen (Populus tremuloides), a dominant species in many northern forest ecosystems, indicate that elevated CO 2 levels can enhance net primary production. Field studies also reveal that droughts contribute to extensive aspen mortality. To complement this work, we analyzed how the growth of wild aspen clones in Wisconsin has responded to historical shifts in CO 2 and climate, accounting for age, genotype (microsatellite heterozygosity), and other factors. Aspen growth has increased an average of 53% over the past five decades, primarily in response to the 19.2% rise in ambient CO 2 levels. CO 2 -induced growth is particularly enhanced during periods of high moisture availability. The analysis accounts for the highly nonlinear changes in growth rate with age, and is unaffected by sex or location sampled. Growth also increases with individual heterozygosity, but this heterozygote advantage has not changed with rising levels of CO 2 or moisture. Thus, increases in future growth predicted from previous large-scale, common-garden work are already evident in this abundant and ecologically important tree species. Owing to aspen's role as a foundation species in many North American forest ecosystems, CO 2 -stimulated growth is likely to have repercussions for numerous associated species and ecosystem processes.

Dendroecology in the tropics: a review

“…In temperate forest, tree-ring analysis has been widely applied to show the response of trees to, most likely, increasing atmospheric CO 2 (e.g. Voelker et al 2006;Wang et al 2006;Cole et al 2010). In tropical regions, similar approaches can be applied.…”

Spring and autumn phenology of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) genotypes of different geographic origin in hemiboreal Estonia§

“…In the higher latitudes of the northern hemisphere, it is predicted that, besides the positive impact of increasing CO 2 and temperature on the productivity of forests (Cole et al 2010;Lindner et al 2010), climate change will also extend the growth period for plants (Keenan et al 2014), primarily through the earlier onset of springs (Jaagus 2006;Menzel et al 2006;Schwartz et al 2006), i.e. the date when daily mean air temperature rises above +5°C (Jaagus and Ahas 2000;Jaagus 2006).…”

Forest ecosystem vulnerability assessment and synthesis for northern Wisconsin and western Upper Michigan: a report from the Northwoods Climate Change Response Framework project

“…Elevated CO 2 reduces the rate of water loss from trees, which may enhance growth in some species and potentially offset some of the effects of drier growing seasons (Ainsworth and Rogers 200, Franks et al 2013, Norby and Zak 2011, Wang et al 2006. There is already some evidence for increased forest growth in the eastern United States (Cole et al 2010, McMahon et al 2010), but it remains unclear if enhanced growth can be sustained (Bonan 200, Foster et al 2010). …”