|Rogers Jr, Hugo|
|Gjerstad, Dean - AUBURN UNIVERSITY|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 2007
Publication Date: March 1, 2008
Citation: Rogers Jr, H.H., Runion, G.B., Prior, S.A., Price, A.J., Torbert III, H.A., Gjerstad, D.H. 2008. Effects of elevated atmospheric CO2 on invasive plants: Comparison of purple and yellow nutsedge (Cyperus rotundus L. and C. esculentus L.). Journal of Environmental Quality. 37:395-400. Interpretive Summary: Invasive plants are a major problem in crops and natural ecosystems worldwide and their control is very expensive. How the well documented rise in atmospheric CO2 will affect invasive species is important since the growth of many plants is enhanced by CO2 enrichment. Two of the world’s most troublesome invasive weeds are purple and yellow nutsedge. We tested their growth under CO2 enrichment. Both responded positively, purple more than yellow nutsedge. These findings suggest that both nutsedge species, purple more than yellow, may be even more invasive in a future high CO2 world.
Technical Abstract: The unprecedented rise in atmospheric CO2 concentration coupled with its direct, often positive, effect on the growth of plants raises the question of the response of invasive plants to elevated CO2 levels. Here we test the response to two of the world's worst invasive weeds: purple nutsedge (Cyperus rotundus L.) and yellow nutsedge (Cyperus esculentus L.). Plants were exposed to two concentrations of CO2 [ambient (375 µmol mol-1) and elevated (ambient + 200 µmol mol-1)] for 71 days in open top chambers. Photosynthetic rate did not differ between CO2 treatments for purple or yellow nutsedge. Lower conductance was observed with purple nutsedge and it tended to be lower with yellow. Transpiration rates tended to be lower when exposed to elevated CO2. Purple nutsedge showed a higher instantaneous water use efficiency and a trend to be higher was noted for yellow nutsedge. Morphology of purple nutsedge plants differed greatly from yellow; the purple showed greater leaf area, root length, numbers of tubers, and tended to have more tillers under high CO2. However, in the case of yellow nutsedge, only tuber number went up under CO2 enrichment. Leaf dry weight was greater for both purple and yellow nutsedge when grown under elevated CO2. Only the purple nutsedge made seed heads during the experiment; CO2 level did not change seed head dry weight. Dry weight of roots was higher under the CO2 treatment only for purple nutsedge, but tuber dry weight increased for both. Belowground dry weight was higher for both species. Both species also exhibited increased total plant dry weight when exposed to elevated CO2. Purple nutsedge growth in elevated CO2 tended to increase allocation to belowground plant parts, leading to a greater root to shoot ratio. Even though an increase in allocation to yellow nutsedge tubers was observed, root to shoot ratio of this species was not affected by CO2 enrichment since there was a slight decrease in allocation to roots. These findings suggest that both species, purple more than yellow nutsedge, may be even more invasive in a future high CO2 world.