U.S. Department of Energy, Office of Science

Program for Ecosystem Research

Research Project   Hierarchical Experimental Responses at Macromolecular to Ecosystem Scales (HERMES)

Principal investigators:   Stan D. Wullschleger, Cheryl R. Kuske, and Alistair Rogers

Arabidopsis in mesocosm

An Arabidopsis thaliana-based mesocosm.

Project goal

Determine how a highly defined alteration in nitrate reductase activity can alter plant responses to atmospheric carbon dioxide enrichment, and how that alteration may translate across multiple levels of biological organization to produce detectable and predictable effects at the level of macromolecules, organisms, populations, communities, and ecosystems.

Ecosystem being studied

A model plant species, Arabidopsis thaliana, growing in an agricultural soil in well-replicated controlled-environment chambers. This model ecosystem allows effective assessment of translation of information across levels of biological and ecological organization.

Results

Efforts to date have been directed primarily at construction of the mesocosms and hydroponic systems, production of plants, selection of soils, and development of assay techniques. Initial experiments in the hydroponic systems will assess responses of nitrate reductase-deficiet and control (unaltered nitrate reductase) plants to varying levels of nitrate, ammonium, and atmospheric carbon dioxide in hydroponic and soil-based systems. This will lead to identification of growing conditions and plant genotypes that will allow discrimination of the effects of nitrate reductase on plant performance, population composition, and interactions with the microbial rhizosphere community.

Why this is important

By enhancing understanding of linkages among levels of biological organization, this project contributes to a mechanistic understanding of how environmental change associated with energy production can influence the structure and functioning of terrestrial ecosystems. Findings from this project will be informative for extending macromolecular methods of inquiry to more complex ecosystems, including those in nature. This will in turn aid in assessing and predicting responses of many ecosystems to climatic change.

more infrastructure

Mescosom/glasshouse infrastructure.

Methods

Hydroponic systems are used to closely control the source and concentration of nitrogen. A parallel soil-based system is used to address how mechanistic relationships at cellular and organismal levels influence population, community, and ecosystem-scale processes, including the response and functioning of soil microbes, via perturbations of the nitrogen cycle.

The factorial study involves wild type and transformed Arabidopsis thaliana, and mixtures of the two, exposed to ambient and elevated atmospheric carbon dioxide concentration. Elevated carbon dioxide treatments will help identify causal associations among levels of biological organization by accentuating interactions between the carbon and nitrogen cycles. Further details are given at the project website.

Personnel

Stan D. Wullschleger, Oak Ridge National Laboratory

Cheryl R. Kuske, Los Alamos National Laboratory

Alistair Rogers, Brookhaven National Laboratory

Lee E. Gunter, Oak Ridge National Laboratory

Christopher W. Schadt, Oak Ridge National Laboratory

Timothy J. Tschaplinski, Oak Ridge National Laboratory

Ramie V. Wilkerson, Oak Ridge National Laboratory

Funding period:   March 2005 to present