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Abstract Detail


Ecophysiology

Walker, Jeffrey T. [1], James, Jeremy [2], Drenovsky, Rebecca [3].

The effects of competition and nitrogen availability on acquisition, use, and storage in the first year of growth of two perennial bunchgrass species.

Competition and nitrogen (N) availability can be important determinants of plant community structure. Subsequently, these factors may influence restoration outcomes. We conducted an experiment at the Eastern Oregon Agricultural Research Station in Burns, OR, to determine the effects of competition and N availability on N acquisition, use, and storage for the first year of growth in two perennial bunchgrass species: Psuedoroegnaria spicata (Bluebunch Wheatgrass, a low nutrient adapted species native to the Northern Great Basin) and Agropyron desertorum (Desert Wheatgrass, a non-native species, commonly used in restoration of grazed regions of the Great Basin). It was hypothesized that: 1) plants experiencing competition would produce less biomass and that increased N availability would have a greater effect on biomass production for A.desertorum than it would for P. spicata, a low nutrient adapted species; And 2) competition plants would have a higher rate of acquisition, a longer mean retention time, and would exhibit more complete resorption; additionally, P. spicata, as a low nutrient adapted species, was predicted to exhibit these same attributes. Ninety-six plants of each species were grown inpots, either in monoculture, or with Bromus tectorum neighbors. As seedlings, plants were labeled with 15N in order to help track N losses over the growing season. Throughout the experiment (April - December), plants were harvested in four groups (an initial, early, mid, and late season harvest); all senescing leaves were collected throughout the experiment. Monoculture plants grew significantly larger than plants experiencing competition and A. desertorum consistently built significantly more biomass than P. spicata. Nitrogen had no significant impact on the overall size of the plants or on carbon allocation; however, those plants that received more N senesced significantly more leaf tissue. All tissues from harvests are to be analyzed for N concentrations to determine N acquisition rates, N use efficiency (the product of mean retention time, estimated with 15N techniques, and N productivity), and resorption proficiency and efficiency. We expect that the various aspects of N cycling are closely linked to carbon allocation (i.e. low nitrogen will resultin greater allocation to storage organs); plasticity of carbon allocation may determine the fitness of an individual plant. Understanding this relationship will help us to gauge how external factors, such as competition and N availability, will alter the potential restoration success of P. spicata.

Broader Impacts:


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1 - John Carroll University, Biology Department, 20700 North Park Blvd, University Heights, OH, 44118, USA
2 - USDA-ARS, 67826A Hwy 205, Burns, OR, 97720, USA
3 - John Carroll University, Biology, 20700 North Park Blvd, University Heights, OH, 44118, USA

Keywords:
resorption
nitrogen use efficiency
15N
Psuedoroegnaria spicata
Agropyron desertorum.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM
Number: PEP004
Abstract ID:882


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