Author
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Reeder, S |
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Submitted to: OECD Expert Meeting on Soil Organic Indicators for Agricultural Lands
Publication Type: Proceedings Publication Acceptance Date: 5/2/2003 Publication Date: 6/2/2003 Citation: REEDER, S.J. OVERCOMING SPATIAL VARIATION IN MEASURING CARBON STOCKS AND SEQUESTRATION POTENTIAL OF NATIVE RANGELANDS IN THE WESTERN U.S.. OECD Expert Meeting on Soil Organic Indicators for Agricultural Lands. 2003. Interpretive Summary: Native rangelands of the western U.S. occupy over 300 Mha (700 million acres), which is more than twice the land area that is occupied by annual and perennial crops in the U.S. This large land area makes these native rangelands an important component terrestrial carbon (C) sequestration and emissions. However, currently very little is known about the amount of carbon stored in these dry native ecosystems, nor do we understand the effects of management on the rates at which C is lost or gained from these systems. It is particularly hard to accurately measure C stocks and changes in C stocks in these ecosystems because C is distributed very unevenly in these dry native ecosystems, both across the landscape and within the soil profile. This paper discusses procedures for sampling the landscape and for processing collected soil samples that reduce the variability in measured C to the extent that small but statistically significant management-induced changes in rangeland C can be detected. Technical Abstract: Grazing lands represent the largest and most diverse single land resource in the world, and as such, are an important terrestrial sink for carbon (C). Native grazing lands of the western U.S. (including Alaska and Hawaii) occupy over 300 Mha, more than twice the land area that is occupied by annual and perennial crops in the U.S. However, few data exist quantifying C emissions and storage in these native ecosystems. Accurate long-term field measurements of both organic and inorganic forms of rangeland soil C are needed to develop and validate empirical model estimates of C stocks and management-induced changes in C sequestered. Measurement accuracy is particularly important in semi-arid and arid ecosystems where annual changes in soil C, as the result of changes in management, frequently are very small relative to the spatial heterogeneity of C stocks. Critical factors influencing the magnitude of variance in soil C estimates include horizontal and vertical C distribution patterns, and consistent sample collection and processing protocols. By careful stratification of soil sampling both across landscape and within the soil profile, significant management-induced differences in soil C pools have been detected in northern mixed-grass prairie, short-grass steppe and sagebrush steppe. |
