Response of a Tundra Ecosystem to Elevated Atmospheric Carbon Dioxide and CO₂-Induced Climate Change: A Renewal Research Proposal

Technical Report · Wed Apr 01 00:00:00 EST 1992

DOI:https://doi.org/10.2172/230262· OSTI ID:230262

Oechel, Walter C. ^[1]

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1. San Diego State Univ., CA (United States)

Northern ecosystems contain up to 455 Gt of C in the soil active layer and upper permafrost. The soil carbon in these layers is equivalent to approximately 60% of the carbon currently in the atmosphere as CO₂. Much of this carbon is stored in the soil as dead organic matter. Its fate is subject to the net effects of global change on the plant and soil systems of northern ecosystems. The arctic alone contains about 60 Gt C, 90% of which is present in the soil active layer and upper permafrost. The arctic is assumed to have been a sink for CO₂ during the historic and recent geologic past. The arctic has the potential to be a very large, long-term source or sink of CO₂ with respect to the atmosphere. In situ experimental manipulations of atmospheric CO₂, indicated that there is little effect of elevated atmospheric CO₂ on leaf level photosynthesis or whole-ecosystem CO₂ flux over the course of weeks to years, respectively. However, there may be longer-term ecosystem responses to elevated CO₂ that could ultimately affect ecosystem CO₂ balance. In addition to atmospheric CO₂, climate may affect net ecosystem carbon balance. Recent results indicate that the arctic has become a source of CO₂ to the atmosphere. This change coincides with recent climatic variation in the arctic, and suggests a positive feedback of arctic ecosystems on atmospheric CO₂ and global change. Measurements along a latitudinal gradient across the north slope of Alaska indicate a loss of carbon from tussock tundra of 156 g m^-2 y^-1, and from the wet tundra of 34 g m^-2 y^-1. If these rates are representative of the circumpolar tundra, then they equate to a net annual global loss of carbon as CO₂ to the atmosphere of 0.17 Gt C, 0.14 Gt from tussock tundra, and 0.03 Gt from wet coastal tundra. Depending on the nature, rate, and magnitude of global environmental change, the arctic may have a positive or negative feedback on global change. At present, the initial response of the arctic indicates a net loss of carbon to the atmosphere which could result in a positive feedback on atmospheric C0₂ concentration and greenhouse warming. There are obvious potential errors in scaling plot level measurements to landscape, mesoscale, and global spatial scales. The research proposed in this application has four principal aspects: (A) Long-term response of arctic plants and ecosystems to elevated atmospheric CO₂; (B) Circumpolar patterns of net ecosystem CO₂ flux; (C) In situ controls by temperature and moisture on net ecosystem CO₂ flux; (D) Scaling of CO₂ flux from plot, to landscape, to regional scales (In conjunction with research proposed for NSF support). In Iceland, we will evaluate the long-term (hundreds to thousands of years) effect of atmospheric CO₂ enrichment from cold, CO₂-rich springs on plant photosynthesis, ecosystem CO₂ flux, and community composition and structure. CO₂ flux estimates at a circumpolar scale will be initiated with research in the Russian arctic and Iceland (measurements in Iceland will be obtained in the process of determining the long-term effect of elevated CO₂ on arctic ecosystems). Temperature and moisture will be manipulated in the field to determine their effects on net ecosystem CO₂ flux. In cooperation with a project proposed for funding from NSF's ARCSS LAII program, measurements of CO₂ and other trace gas flux at three spatial scales (plot, landscape, and mesoscale) using chamber, tower-based eddy correlation techniques and aircraft-based eddy correlation techniques will be made. The information obtained from each of these techniques will be analyzed and compared, especially in light of defining the most efficient approaches for estimating large spatial scale CO₂ in the arctic. Remotely-sensed spectral indices, GIS, process models, and phenomenological models will be used to develop a methodology for efficiently estimating ecosystem CO₂ flux over meso- and global scales. Initial testing of the applicability of these methods will be undertaken. Support from the Department of Energy is requested for plat level measurements. support from NSF is also requested for other aspects of scaling.

• Research Organization: San Diego State Univ., CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: FG03-86ER60479
• OSTI ID: 230262
• Report Number(s): DOE/ER/60479-T6; ON: DE96009525
• Resource Relation: Other Information: PBD: Apr 1992
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
carbon dioxide
environmental effects
tundra
arctic regions
terrestrial ecosystems
progress report
seasonal variations
climatic change
climate models
photosynthesis
plants
air pollution abatement