Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/8/2005
Publication Date: 2/8/2005
Citation: Runion, G.B., Prior, S.A., Torbert III, H.A., Rogers Jr, H.H. 2005. Effects of elevated atmospheric co2 on a southeastern pasture [abstract]. Special Symposium on ARS Global Change Research, Society for Range Management.
Technical Abstract: The Southeastern rural landscape is dominated by three types of ecosystems: forests; row crops; and pastures. Pastures currently occupy 80 million acres in the southeastern U.S. and account for 75% of the total pasture acreage in the eastern U.S. Research addressing the response of crop and forest species to elevated atmospheric CO2 has been conducted for the past 20-25 years and has demonstrated increased growth of most plant species due to increased rates of photosynthesis, altered C partitioning, and/or increased water and nutrient use efficiencies; variability in plant growth is due to differences between plants with a C3 (33 - 40 % increase) vs. a C4 (10 - 15 % increase) photosynthetic pathway. Similar differences between C3 and C4 plants in response to elevated CO2 have frequently been observed on natural grazing lands. The impacts of rising atmospheric CO2 has important implications within rangeland and pasture ecosystems, not only for production of forage for animal production, but also due to the ability of these ecosystems to sequester atmospheric CO2 as soil C, helping to mitigate the global rise in atmospheric CO2 concentration. However, managed pastures - such as those prevalent in the southeastern U.S. - have received extremely limited attention to date with respect to aspects of global change. The NSDL Global Change Research group has recently established a Southeastern pasture system, using bahiagrass (Paspalum notatum), along the length of an outdoor soil bin filled with a Blanton loamy sand. Plots will be exposed to either ambient (365 ppm) or elevated (725 ppm) levels of atmospheric CO2 within open top field chambers; ambient, chamberless plots are included as a check on chamber effects. The study will be conducted as a randomized complete block design with six blocks during the first two years and will be managed according to pasture establishment recommendations. After the establishment period, the study will be split into three blocks; one-half will be managed using a low N fertility regime (no N added) and the other half as a high N regime (200 kg N ha-1 yr-1). Measurements to be taken include: biomass production; root structure and function; community structure and activity of soil microbial populations; soil C and N dynamics; and soil efflux of CO2 and other trace gases (i.e., N2O and CH4).