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Abstract Detail


Constable, John [1], Braganza , Conrad Fredrick [2].

Comparative Ecophysiology of Invasive and Native Annuals of the San Joaquin Valley, California.

Retired farmland in the western San Joaquin Valley (SJV) of California is frequently colonized by invasive plants that may limit the establishment of native flora; however, the physiology of native seedlings may also play a role. Limited baseline data on ecophysiological characteristics of native SJV plant species constrains science-based native flora restoration efforts. In this greenhouse evaluation, we compared photosynthetic rates, in vivo nitrate reductase activity (NRA), and biomass accumulation of two invasive (Brassica nigra and Bromus madritensis) and three native (Phacelia ciliata, Hordeum depressum, and Vulpia microstachys) annuals. Two cohorts of each species were grown from seed and harvested at 35d (15 individuals) and 75d (15 individuals) to determine total plant biomass accumulation. Prior to each harvest photosynthesis was measured (Li-Cor Li-6400) and prior to the second harvest NRA was measured in roots (rNRA) and leaves (lNRA). At harvest 1, the average photosynthetic rate of the two invasive species (15.5±0.56 umoles CO2m-2s-1) was greater (p<0.05) than the three native species (10.6±0.43 umoles CO2m-2s-1), but no significant difference was observed at harvest 2. The water use efficiency (WUE) of the invasive monocot (Bromus) was 20% less than the native monocots (Hordeum and Vulpia); all monocots had 70% greater WUE than the invasive dicot (Brassica) and the native dicot (Phacelia) which had similar WUE values. In all species, lNRA exceeded rNRA (p<0.001) and dicot species had greater lNRA than all monocot species (p<0.05), but no significant differences existed between native and invasive species. At harvest 2, the total biomass of invasive monocots (0.38±0.024 g) exceeded native monocots (0.225±0.03 g, p<0.05), a similar relationship occurred between invasive dicots (0.46±0.02 g) and native dicots (0.071±0.05 g, p<0.001). Root biomass of invasive monocot and dicot species exceeded that of native monocot and dicot species by 54% (p<0.05) and 98% (p<0.001), respectively. The average RGR of the invasive species (0.084±0.05 gg-1d-1) exceeded that of native species (0.023±0.08 gg-1d-1) at harvest 1 (p<0.001). However, at harvest 2 the reverse was true, and native species RGR (0.069±0.03 gg-1d-1) exceeded invasive species RGR (0.043±0.07 gg-1d-1, p<0.05). Greater early season photosynthesis and RGR of invasive species likely provides a preemptive competitive advantage over natives and may contribute to low rates of native species establishment on retired farmland.

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1 - California State University, Department Of Biology, 2555 E. SAN RAMON AVE M/S SB73, FRESNO, CA, 93740-8034, USA
2 - California State University, Fresno, Biology, 2555 E. San Ramon Avenue, Fresno, CA, 93740, USA


Presentation Type: Poster:Posters for Topics
Session: P
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM
Number: PEP005
Abstract ID:863

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