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United States Department of Agriculture

Agricultural Research Service

Title: Are Mojave Desert Annual Species Equal? Resource Acquisition and Allocation for the Invasive Grass Bromus Madritensis Ssp. Rubens (Poaceae) and Two Native Species.

Authors
item Defalco, Lesley - UNIV OF NEVADA, RENO
item Bryla, David
item Smith-Longozo, Vickie - UNIV OF NEVADA, RENO
item Nowak, Robert - UNIV OF NEVADA, RENO

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2003
Publication Date: July 1, 2003
Citation: DEFALCO, L.A., BRYLA, D.R., SMITH-LONGOZO, V., NOWAK, R.S. ARE MOJAVE DESERT ANNUAL SPECIES EQUAL? RESOURCE ACQUISITION AND ALLOCATION FOR THE INVASIVE GRASS BROMUS MADRITENSIS SSP. RUBENS (POACEAE) AND TWO NATIVE SPECIES.. AMERICAN JOURNAL OF BOTANY. 2003.

Interpretive Summary: The abundance of invasive annual grasses and forbs in the Mojave Desert is often attributed to greater competitiveness of these species compared to natives. We compared resource acquisition and allocation between the invasive grass Bromus madritensis and two native co-occurring Mojave Desert annuals Vulpia octoflora and Descurainia pinnata. Each species was planted at two densities (80 and 800 plants m-2 soil) and two levels of nitrogen availability (1.5 and 12.0 g N m-2 soil) in a glasshouse experiment. After more than 4 months of growth, B. madritensis developed a larger root system and had greater water and nitrogen uptake than both native species, which enabled it to acquire more water and nitrogen from the soil profile and produce significantly more biomass than the natives. Bromus madritensis also produced relatively large (although fewer) seeds that readily germinated, while seeds produced by the native species were significantly smaller and tended to remain dormant. These traits give B. madritensis more potential to establish in varied habitats of the Mojave Desert, and to have a competitive advantage over cohabiting native annuals.

Technical Abstract: The abundance of invasive annual grasses and forbs in the Mojave Desert is often attributed to greater competitiveness of these species compared to natives. We compared resource acquisition and allocation between the invasive grass Bromus madritensis ssp. rubens and two native co-occurring Mojave Desert annuals Vulpia octoflora and Descurainia pinnata. Each species was planted in monoculture at two densities (80 and 800 plants m-2 soil) and two levels of N availability (1.5 and 12.0 g N m-2 soil) in a glasshouse experiment. After more than 4 months of growth, B. madritensis developed a larger root system with higher water and N uptake rates than both native species (regardless of soil N availability or planting density), which enabled it to acquire more water and N from the soil profile and produce significantly more biomass than the natives. It also produced more leaf area and had higher rates of photosynthesis and stomatal conductance than V. octoflora. Furthermore, B. madritensis produced relatively large (although fewer) seeds that readily germinated during a 15-d germination study, while seeds produced by the native species were significantly smaller and tended to remain dormant. These traits give B. madritensis more potential to establish in varied habitats of the Mojave Desert, and to have a competitive advantage over cohabiting native annuals.

Last Modified: 12/20/2014
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