Grazing and ecosystem carbon storage in the North American Great Plains

• Published in: Plant and soil Vol. 280; no. 1-2; pp. 77 - 90
• Main Authors: Derner, J.D, Boutton, T.W, Briske, D.D
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01-02-2006; Springer Nature B.V
• Subjects: Aboveground biomass; Agronomy. Soil science and plant productions; Animal and plant ecology; Animal, plant and microbial ecology; Biogeochemistry; Biological and medical sciences; biomass; Bouteloua gracilis; C3 plants; C4 plants; Carbon; Carbon sequestration; Chemical, physicochemical, biochemical and biological properties; Community composition; Ecosystems; Environmental gradient; forage grasses; Functional groups; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Grasses; Grasslands; Grazing; Livestock; Organic carbon; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant communities; Plants; Prairie soils; rangeland soils; Root biomass; Soil depth; Soil ecology; soil organic carbon; Soil profiles; Soil science; soil-plant interactions; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Soils; species diversity; Synecology; Terrestrial ecosystems; Great Plains region; Great Plains of America; Kansas; United States; North America; America; Organic carbon; Organic matter; Monocotyledones; δ13C; Carbon isotope discrimination; Carbon Isotopes; Prairies; C4-Type; soil organic carbon; Isotopic composition; Bouteloua gracilis; Temperate zone; Animal effect; Signing; Gramineae; C isotope signatures; Ecosystem; Angiospermae; C3-Type; Terrestrial environment; carbon storage; Plant community; Great Plains; Grazing; Carbon cycle; Soils; Biogeochemistry; Storage; Vegetation type; Herbaceous plant; Spermatophyta; Soil plant relation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-005-2554-3

Isotopic signatures of 13C were used to quantify the relative contributions of C3 and C4 plants to whole-ecosystem C storage (soil+plant) in grazed and ungrazed sites at three distinct locations (short-, mid- and tallgrass communities) along an east-west environmental gradient in the North American Great Plains. Functional group composition of plant communities, the source and magnitude of carbon inputs, and total ecosystem carbon storage displayed inconsistent responses to long-term livestock grazing along this gradient. C4 plants [primarily Bouteloua gracilis (H.B.K.) Lag ex Steud.] dominated the long-term grazed site in the shortgrass community, whereas the ungrazed site was co-dominated by C3 and C4 species; functional group composition did not differ between grazed and ungrazed sites in the mid- and tallgrass communities. Above-ground biomass was lower, but the relative proportion of fine root biomass was greater, in grazed compared to ungrazed sites at all three locations. The grazed site of the shortgrass community had 24% more whole-ecosystem carbon storage compared to the ungrazed site (4022 vs. 3236 g C m-2). In contrast, grazed sites at the mid- and tallgrass communities had slightly lower (8%) whole-ecosystem carbon storage compared to ungrazed sites (midgrass: 7970 vs. 8683 g C m-2; tallgrass: 8273 vs. 8997 g C m-2). Differential responses between the shortgrass and the mid- and tallgrass communities with respect to grazing and whole-ecosystem carbon storage are likely a result of: (1) maintenance of larger soil organic carbon (SOC) pools in the mid- and tallgrass communities (7476-8280 g C m-2) than the shortgrass community (2517-3307 g C m-2) that could potentially buffer ecosystem carbon fluxes, (2) lower root carbon/soil carbon ratios in the mid- and tallgrass communities (0.06-0.10) compared to the shortgrass community (0.20-0.27) suggesting that variation in root organic matter inputs would have relatively smaller effects on the size of the SOC pool, and (3) the absence of grazing-induced variation in the relative proportion of C3 and C4 functional groups in the mid- and tallgrass communities. We hypothesize that the magnitude and proportion of fine root mass within the upper soil profile is a principal driver mediating the effect of community composition on the biogeochemistry of these grassland ecosystems.