Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/8/2004
Publication Date: 2/2/2005
Citation: Polley, H.W., Tischler, C.R. 2005. Carbon dioxide enrichment influences the expression of genetic variation for seedling growth in honey mesquite. In: Society for Range Management 58th Annual Meeting and Trade Show, February 5-11, 2005, Fort Worth, Texas. 2005 CDROM.
Technical Abstract: The shrub honey mesquite (Prosopis glandulosa Torr.) is an aggressive invader of rangelands in the southwestern U.S. that vary in annual rainfall from less than 200 to about 1000 mm. Traits that promote rapid growth of mesquite seedlings in mesic rangelands may be a liability in drier environments, implying that mesquite from extremes of the rainfall gradient may exhibit genetic differences in growth rate. Progeny from adult trees of mesquite (open-pollinated families) located at mesic (7 trees) and arid sites (7 trees) were grown in a glasshouse at ambient and elevated carbon dioxide (CO2) concentrations. Well-watered seedlings were harvested over days 10 to 30 after emergence to test the hypothesis that CO2 enrichment reinforces any genetic differences in growth among mesquite families from extremes of the rainfall gradient. Biomass on day 30 was greatest in families from mesic grasslands and smallest in families from arid environments at both CO2 levels. The ratio of biomass at elevated CO2 to biomass at ambient CO2 varied among families from 1.03 to 1.74, and was highly correlated with the stimulation of relative growth rate (RGR) at elevated CO2. Enriching CO2 did not significantly affect RGR, but RGR was greater for families from mesic than arid systems. Biomass increased proportionally more at elevated CO2 among families that originated from mesic than arid rangelands, but the increase was significant for only three families from mesic sites. Our results indicate that CO2 enrichment may exaggerate genetic differences in the growth of honey mesquite.