U. S. Environmental Protection Agency, Contracts Management Division (MD-33), Attn: ORDSC, Research Triangle Park, NC 27711

A -- ENHANCEMENT OF THE GENERAL ECOSYSTEM MODEL FOR SIMULATING CARBON AND NITROGEN ISOTOPE SOL XMT062 POC Ramona G. Evans, Contract Specialist (919/541-4749) E-MAIL: Click here to contact the Contract Specialist via, evans.ramona@epa.gov. The U.S. Environmental Protection Agency (EPA) intends to negotiate on a sole source basis with Dr. Edward Rastetter, The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, for expanded software development. An objective of EPA's Nitrogen Project is to use the General Ecosystem Model (GEM) (Rastetter et al, 1991) to assess how forested watersheds will respond to existing or projected stressor scenarios. GEM is a process-based model of ecosystem carbon, nitrogen and soil water dynamics that simulates the responses of vegetation and soils to changes in atmospheric CO2, temperature, precipitation, irradiance, nitrogen deposition and disturbances such as forest management. This model can play an important role in EPA's risk assessment activities by providing a means for relating stressors to probable effects, integrating diverse measures into a self-consistent framework, and making meaningful extrapolations across scales of time, space, and biological organization. A major objective of this particular modeling work is to provide EPA the predictive capabilities for determining the impact of anthropogenic nitrogen deposition to terrestrial watersheds and the loss of nitrogen to surface waters and estuaries. Isotopes have proven to be a very valuable tool for tracking element cycles in ecosystems, particularly in the context of element retention and loss. A limitation of the current version of GEM is that isotopes of carbon and nitrogen are not included in the model. Enabling GEM to simulate cycling of carbon and nitrogen isotopes would substantially improve analyses of the uptake, internal recycling, and loss of these elements in forested watersheds. For example, EPA is currently conducting 15N-tracer studies to assess the fate of anthropogenic nitrogen additions to forest ecosystems in the Pacific Northwest. While the experimental results will provide insights into short-term (1-3 years) nitrogen dynamics, an isotopic version of GEM is needed to extrapolate those results across scales of space and time. One objective of this sole source procurement will be to develop software that works in conjunction with previous software developed by Dr. Rastetter to enhance the General Ecosystem Model (GEM) for simulating carbon and nitrogen isotope dynamics. The software developed through this procurement must work in conjunction with the GEM to simulate the uptake, internal recycling and loss of isotopes of carbon (12C, 13C) and nitrogen (14N, 15N) in terrestrial ecosystems, including plants and soils. The enhancements for simulating isotopes will build on other changes to the model that the original developer of the GEM is making or has made. Because of the complexity of the GEM and the difficulty of linking the new model changes to the changes currently being made or which have already been made, which are both unavailable to other contractors and too costly to reproduce, EPA believes only the above named vendor is capable of satisfying these requirements. The isotope simulation software shall be designed to work directly on the output of GEM, which will provide both the magnitude of all carbon and nitrogen pools and the rates of all fluxes. The software shall allow specification of the initial isotopic signature for all pools and the isotopic discrimination for all fluxes. Because the changes in isotopic signature of interacting pools will depend on both forward and backward fluxes of material, the isotopic signature cannot be simulated by applying a simple mass balance for each isotope to the net flux. Therefore, GEM may need to be changed to simulate only gross fluxes, or some other means will need to be devised to infer these gross fluxes from the model. The isotope simulation software shall also include an algorithm that (1) calculates daily changes in isotope discrimination associated with changes in daily water stress, and (2) temporally aggregates the daily changes to annual changes in isotope discrimination. This temporal aggregation shall be designed to work in coordination with the algorithms in GEM that link the daily water budget to the annual carbon and nitrogen budgets. The daily water budget in GEM is currently under development but will be available no later than March 15, 2001. This will provide ample time to meet the deliverable dates for this effort. The anticipated period of performance for this effort is from date of award through March 15, 2002. The recipient of this work must have extensive experience in four areas: (1) at least 3 years of experience in writing and debugging GEM program code (publically available since the model was first published in 1991 -- see web site: http://ecosystems.mbl.edu/research/models/gem/welcome.html ); (2) at least 1 year of experience in applying GEM to analyze terrestrial ecosystem carbon and nitrogen dynamics, as demonstrated by at least one co-authored publication in a peer-reviewed scientific journal; (3) at least 2 years experience in Delphi programming, including writing and debugging code; and (4) proficiency in mathematics as demonstrated by a Bachelor's degree or higher in a mathematics-related field (mathematics, physics, quantitative ecology, etc.). EPA believes that the original developer of the General Ecosystem Model (GEM) is the only vendor capable of satisfying the complex technical requirements stated above on a quick-response basis within the time frame required by EPA without the costly duplication of prior efforts. No solicitation is available. This notice of intent is not a request for competitive proposals. All interested parties must identify their interest and capability to respond to the requirement as evidenced by response to the four criteria identified above or submit proposals within 15 days of the date of this announcement. A determination by the Government not to compete this procurement based upon responses to this notice is solely within the discretion of the Government. Information received will be considered solely for the purpose of determining whether to conduct a competitive procurement. Interested vendors shall: (1) include information on the proposed services which clearly supports all the requirements outlined above and; (2) provide itemized pricing that is sufficient to make a determination that competition is feasible. Submit responses to the U.S. EPA, Attn: Ramona G. Evans, ORD Service Center/NHEERL, Contracts Management Division (MD-33), Research Triangle Park, N.C. 27711. No telephone requests will be honored. See also numbered Note 26. Posted 08/17/00 (W-SN487363). (0230)

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