Elevated CO2differentially alters the responses of coocurring birch and maple seedlings to a moisture gradient.
To determine the effects of elevated CO2and soil moisture status on growth and niche characteristics of birch and maple seedlings, gray birch (Betula populifolia) and red maple (Acer rubrum) were experimentally raised along a soil moisture gradient ranging from extreme drought to flooded conditions at both ambient and elevated atmospheric CO2levels. The magnitude of growth enhancement due to CO2was largely contingent on soil moisture conditions, but differently so for maple than for birch seedlings. Red maple showed greatest CO2enhancements under moderately moist soil conditions, whereas gray birch showed greatest enhancements under moderately dry soil conditions. Additionally, CO2had a relatively greater ameliorating effect in flooded conditions for red maple than for gray birch, whereas the reverse pattern was true for these species under extreme drought conditions. For both species, elevated CO2resulted in a reduction in niche breadths on the moisture gradient; 5% for gray birch and 23% for red maple. Species niche overlap (proportional overall) was also lower at elevated CO2(0.98 to: 0.88: 11%). This study highlights the utility of of experiments crossing CO2levels with gradients of other resources as effective tools for elucidating the potential consequences of elevated CO2on species distributions and potential interactions in natural communities.
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, 02138, Cambridge, MA, USA.
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Miao
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, 02138, Cambridge, MA, USA.
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Wayne
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, 02138, Cambridge, MA, USA.
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FA
Bazzaz
Biomass; Elevated CO2; Gray birch; Moisture gradient; Niche breadth