A Broad- Scale Perspective on the Extent, Distribution, and Characteristics of U. S. Grazing Lands

Sobecki, Terry; Moffitt, D; Stone, Joseph E.; Franks, C. I.; Mendenhall, Amy N.

doi:10.1201/9781420032468.ch2

Cited by 16 publications

(11 citation statements)

References 12 publications

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“…If N availability increases, for instance due to increased grazing, belowground C inputs could be reduced even further despite an increase in biomass as heterotrophic organisms will favor root‐derived organic matter over native SOM as their primary energy source. Our results support modeling studies showing that conversions of native rangeland communities including pinyon‐juniper woodlands, sagebrush scrublands, and bunchgrasslands to cheatgrass as occurs in the western United States will result in C losses (Sobecki et al , 2001) since large C stocks accumulated over long time periods are replaced by a small pool of regrowth, while C inputs into stable SOM pools are reduced (Schulze et al , 2000).…”

Section: Discussionsupporting

confidence: 85%

Net ecosystem carbon exchange in two experimental grassland ecosystems

Verburg¹,

Arnone²,

Obrist³

et al. 2004

Global Change Biology

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Increases in net primary production (NPP) may not necessarily result in increased C sequestration since an increase in uptake can be negated by concurrent increases in ecosystem C losses via respiratory processes. Continuous measurements of net ecosystem C exchange between the atmosphere and two experimental cheatgrass (Bromus tectorum L.) ecosystems in large dynamic flux chambers (EcoCELLs) showed net ecosystem C losses to the atmosphere in excess of 300 g C m À2 over two growing cycles. Even a doubling of net ecosystem production (NEP) after N fertilization in the second growing season did not compensate for soil C losses incurred during the fallow period. Fertilization not only increased C uptake in biomass but also enhanced C losses through soil respiration from 287 to 469 g C m À2 , mainly through an increase in rhizosphere respiration. Fertilization decreased dissolved inorganic C losses through leaching of from 45 to 10 g C m À2 .Unfertilized cheatgrass added 215 g C m À2 as root-derived organic matter but the contribution of these inputs to long-term C sequestration was limited as these deposits rapidly decomposed. Fertilization increased NEP but did not increase belowground C inputs most likely due to a concurrent increase in the production and decomposition of rhizodeposits. Decomposition of soil organic matter (SOM) was reduced by fertilizer additions. The results from our study show that, although annual grassland ecosystems can add considerable amounts of C to soils during the growing season, it is unlikely that they sequester large amounts of C because of high respiratory losses during dormancy periods. Although fertilization could increase NEP, fertilization might reduce soil C inputs as heterotrophic organisms favor root-derived organic matter over native SOM.

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Section: Discussionsupporting

confidence: 85%

Net ecosystem carbon exchange in two experimental grassland ecosystems

Verburg¹,

Arnone²,

Obrist³

et al. 2004

Global Change Biology

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“…Though substantial areas of the Northern Great Plains are used for crop production, significant parts of this province remain unploughed and are used as rangelands. Quantification of the parameters for carbon cycle in Northern Plains grasslands is an essential part of the general task to evaluate the carbon budget of North America (Sobecki et al ., 2001; Wofsy & Harriss, 2002). Many of the early methods for studying carbon budgets of grazing lands can be traced back to the International Biological Program (Coupland, 1979; Breymeyer & Van Dyne, 1981) with its emphasis on both net primary production and field photosynthesis based on measurements from towers and chambers.…”

Section: Introductionmentioning

confidence: 99%

Integration of CO₂ flux and remotely‐sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation

Gilmanov

Tieszen

Wylie

et al. 2005

Global Ecology and Biogeography

144

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Aim Extrapolation of tower CO 2 fluxes will be greatly facilitated if robust relationships between flux components and remotely sensed factors are established. Long-term measurements at five Northern Great Plains locations were used to obtain relationships between CO 2 fluxes and photosynthetically active radiation ( Q ), other on-site factors, and Normalized Difference Vegetation Index ( NDVI ) from the SPOT VEGETATION data set.Location CO 2 flux data from the following stations and years were analysed: Lethbridge, Alberta 1998 Fort Peck, MT 2000 Miles City, MT 2000 -01; Mandan, ND 1999 and Cheyenne, WY 1997-98.Results Analyses based on light-response functions allowed partitioning net CO 2 flux ( F ) into gross primary productivity ( P g ) and ecosystem respiration ( R e ). Weekly averages of daytime respiration, γ day , estimated from light responses were closely correlated with weekly averages of measured night-time respiration, γ night ( R 2 0.64 to 0.95). Daytime respiration tended to be higher than night-time respiration, and regressions of γ day on γ night for all sites were different from 1 : 1 relationships. Over 13 site-years, gross primary production varied from 459 to 2491 g CO 2 m − 2 year , and net ecosystem exchange from − 537 (source) to +610 g CO 2 m − 2 year − 1 (sink). Maximum daily ecological light-use efficiencies, ε d , max = P g /Q , were in the range 0.014 to 0.032 mol CO 2 (mol incident quanta)Main conclusions Ten-day average P g was significantly more highly correlated with NDVI than 10-day average daytime flux, P d ( R 2 = 0.46 to 0.77 for P g -NDVI and 0.05 to 0.58 for P d -NDVI relationships). Ten-day average R e was also positively correlated with NDVI , with R 2 values from 0.57 to 0.77. Patterns of the relationships of P g and R e with NDVI and other factors indicate possibilities for establishing multivariate functions allowing scaling-up local fluxes to larger areas using GIS data, temporal NDVI, and other factors.

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“…7 This lack of attention stems, no doubt, from the relatively low carbon storage capacity per unit area, the extreme heterogeneity of rangeland soils and the fact that signifi cant gains in carbon storage capacity would likely require major changes in existing rangeland management. 8 Estimating the potential gains in carbon storage on rangeland soils is complicated and the synthesis of multiple studies rarely provides unambiguous fi ndings with respect to land management impacts on carbon storage. However, with respect to two common range management activities, grazing generally causes total biomass and carbon to decline on rangelands, while vegetation burning over the long-term results in little change in carbon although the above-vs. below-ground allocations may be altered.…”

Section: Carbon Offsetsmentioning

confidence: 99%

Semi-Arid Rangelands and Carbon Offset Markets: A Look at the Economic Prospects

Steiguer¹

2008

Rangelands

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A Broad- Scale Perspective on the Extent, Distribution, and Characteristics of U. S. Grazing Lands

Cited by 16 publications

References 12 publications

Net ecosystem carbon exchange in two experimental grassland ecosystems

Net ecosystem carbon exchange in two experimental grassland ecosystems

Integration of CO₂ flux and remotely‐sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation

Semi-Arid Rangelands and Carbon Offset Markets: A Look at the Economic Prospects

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A Broad- Scale Perspective on the Extent, Distribution, and Characteristics of U. S. Grazing Lands

Cited by 16 publications

References 12 publications

Net ecosystem carbon exchange in two experimental grassland ecosystems

Net ecosystem carbon exchange in two experimental grassland ecosystems

Integration of CO2 flux and remotely‐sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation

Semi-Arid Rangelands and Carbon Offset Markets: A Look at the Economic Prospects

Contact Info

Product

Resources

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Integration of CO₂ flux and remotely‐sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation