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Belowground competition and the response of developing forest communities to atmospheric CO 2 and O 3
Author(s) -
ZAK DONALD R.,
HOLMES WILLIAM E.,
PREGITZER KURT S.,
KING JOHN S.,
ELLSWORTH DAVID S.,
KUBISKE MARK E.
Publication year - 2007
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2007.01436.x
Subject(s) - canopy , competition (biology) , limiting , nitrogen , nutrient , agronomy , environmental science , environmental chemistry , ecology , biology , chemistry , organic chemistry , mechanical engineering , engineering
As human activity continues to increase CO 2 and O 3 , broad expanses of north temperate forests will be simultaneously exposed to elevated concentrations of these trace gases. Although both CO 2 and O 3 are potent modifiers of plant growth, we do not understand the extent to which they alter competition for limiting soil nutrients, like nitrogen (N). We quantified the acquisition of soil N in two 8‐year‐old communities composed of trembling aspen genotypes ( n = 5) and trembling aspen–paper birch which were exposed to factorial combinations of CO 2 (ambient and 560 μL L −1 ) and O 3 (ambient = 30–40 vs. 50–60 nL L −1 ). Tracer amount of 15 NH 4 + were applied to soil to determine how these trace gases altered the competitive ability of genotypes and species to acquire soil N. One year after isotope addition, we assessed N acquisition by measuring the amount of 15 N tracer contained in the plant canopy (i.e. recent N acquisition), as well as the total amount of canopy N (i.e. cumulative N acquisition). Exposure to elevated CO 2 differentially altered recent and cumulative N acquisition among aspen genotypes, changing the rank order in which they obtained soil N. Elevated O 3 also altered the rank order in which aspen genotypes obtained soil N by eliciting increases, decreases and no response among genotypes. If aspen genotypes respond similarly under field conditions, then rising concentrations of CO 2 and O 3 could alter the structure of aspen populations. In the aspen–birch community, elevated CO 2 increased recent N (i.e. 15 N) acquisition in birch (68%) to a greater extent than aspen (19%), suggesting that, over the course of this experiment, birch had gained a competitive advantage over aspen. The response of genotypes and species to rising CO 2 and O 3 concentrations, and how these responses are modified by competitive interactions, has the potential to change the future composition and productivity of northern temperate forests.