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The impact of recent increases in atmospheric CO 2 on biomass production and vegetative retention of Cheatgrass ( Bromus tectorum ): implications for fire disturbance
Author(s) -
Ziska L. H.,
Reeves J. B.,
Blank B.
Publication year - 2005
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.1365-2486.2005.00992.x
Subject(s) - bromus tectorum , biomass (ecology) , agronomy , population , productivity , environmental science , carbon dioxide , zoology , ecology , biology , perennial plant , demography , macroeconomics , sociology , economics
Cheatgrass ( Bromus tectorum ) is a recognized, invasive annual weed of the western United States that reduces fire return times from decades to less than 5 years. To determine the interaction between rising carbon dioxide concentration ([CO 2 ]) and fuel load, we characterized potential changes in biomass accumulation, C : N ratio and digestibility of three cheatgrass populations from different elevations to recent and near‐term projections in atmospheric [CO 2 ]. The experimental CO 2 values (270, 320, 370, 420 μmol mol −1 ) corresponded roughly to the CO 2 concentrations that existed at the beginning of the 19th century, that during the 1960s, the current [CO 2 ], and the near‐term [CO 2 ] projection for 2020, respectively. From 25 until 87 days after sowing (DAS), aboveground biomass for these different populations increased 1.5–2.7 g per plant for every 10 μmol mol −1 increase above the 270 μmol mol −1 preindustrial baseline. CO 2 sensitivity among populations varied with elevational origin with populations from the lowest elevation showing the greatest productivity. Among all populations, the undigestible portion of aboveground plant material (acid detergent fiber ADF, mostly cellulose and lignin) increased with increasing [CO 2 ]. In addition, the ratio of C : N increased with leaf age, with [CO 2 ] and was highest for the lower elevational population. These CO 2 ‐induced qualitative changes could, in turn, result in potential decreases in herbivory and decomposition with subsequent effects on the aboveground retention of cheatgrass biomass. Overall, these data suggest that increasing atmospheric [CO 2 ] above preambient levels may have contributed significantly to cheatgrass productivity and fuel load with subsequent effects on fire frequency and intensity.