PARENT SESSION
Poster Session #2: Carbon Storage.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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The potential of short-rotation cropping systems to sequester C.
Verburg, Paul*,1, Arnone, John1, Evans, David2, LeRoux-Swarthout, Debbie2, Obrist, Daniel1, Johnson, Dale3, Luo, Yiqi4, Coleman, James1, 1 Desert Research Institute, Reno, NV2 University of Arkansas, Fayetteville, AR3 University of Nevada, Reno, Reno, NV4 University of Oklahoma, Norman, OK
ABSTRACT- The objective of this study was to determine if short-rotation cropping systems could be used to enhance terrestrial C sequestration. Net ecosystem C exchange was measured continuously in two large model grasslands (Bromus tectorum planted in Konza prairie soils) during two cropping cycles using the Desert Research Institute's Ecologically Controlled Enclosed Lysimeter Laboratories. After the first planting period, soils were left fallow for six months. During the second cropping period, both grassland ecosystems received an N fertilizer application equivalent to 88 kg ha-1, either as a single application or as 15 applications of 5.87 kg ha-1. At the end of the experiment, net ecosystem C losses exceeded 300 g C m-2. Fertilization doubled net ecosystem productivity but that did not compensate for soil C losses occurred during the fallow period. While both fertilizer treatments caused a similar increase in harvested phytomass the one-time fertilizer application caused a faster initial increase in leaf area index. Carbon isotope data showed that all root-derived organic matter decomposed during the fallow period and that fertilization stimulated rhizosphere respiration by 60% and soil organic matter decomposition by 28%. Fertilization did not result in increased N leaching but the one-time fertilizer application caused increased N2O and NH3 emissions. While short-rotation cropping systems are important sources for food or fossil fuel alternatives, this study clearly questions the potential of these ecosystems to sequester C.
KEY WORDS: carbon storage, net ecosystem productivity, grassland, short-rotation cropping systems