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item Tischler, Charles
item Polley, Herbert
item Johnson, Hyrum
item Mayeux Jr, Herman

Submitted to: Proceedings Symposium Shrubland Ecosystem Dynamics Changing Climate
Publication Type: Proceedings
Publication Acceptance Date: 8/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mesquite and huisache are two woody shrubs which invade pastures and rangelands and reduce forage production. We grew seedlings of both of these plants at normal, twice normal, and three times the normal atmospheric concentration of carbon dioxide to see if this positive response to carbon dioxide was also observed in the early seedling stage. Seedlings of both plants had highest shoot weights in the atmospheres enriched in carbon dioxide. Mesquite also had significantly longer roots when grown in elevated carbon dioxide. Positive effects of elevated carbon dioxide were evident as soon as one week after seedling emergence. These results indicate that the increases in atmospheric carbon dioxide concentration which are predicted for the future should allow both mesquite and huisache to grow faster in the seedling stage and be more competitive with grasses. They may become established faster, and these weedy plants may be more difficult to control in the future.

Technical Abstract: Plants such as mesquite (Prosopis glandulosa) and huisache (Acacia smallii) generally show positive growth responses to higher CO2 concentrations. Growth of the two legumes was measured at five-day intervals over 30 days from seedling emergence at 380, 700 and 1000 ppm CO2. Mesquite root elongation increased with CO2 concentration. Shoot mass of both species responded positively to elevated CO2. Positive responses to CO2 enrichment were evident within one week after emergence. Predicted increases in atmospheric CO2 could decrease time required for seedling establishment and increased seedling survival of these invasive shrubs and ultimately contribute to a further change in the species composition of Southwestern rangelands.