Scale and the isotopic reocrd of C<sub>4</sub> plants in pedogenic carbonate: from the biome to the rhizosphere

TitleScale and the isotopic reocrd of C4 plants in pedogenic carbonate: from the biome to the rhizosphere
Publication TypeJournal Article
Year of Publication2009
AuthorsH. Monger C, Cole DR, Buck BJ, Gallegos RA
Date Published2009
Call Number00964
Keywordsarticle, C3 vs C4 vegetation, carbon isotopes, Chihuahuan Desert, climate change, desertification, Jornada Experimental Range, journal, landscape ecology, pedogenic carbonate, peleoclimate, peleoecology, soil-geomorphic-clmatic interaction, southern New Mexico, USA
AbstractThe 13C/12C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaningof d13C values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that reveal four scales important for paleoecologic interpretations. (1) At the broadest scale, the biome scale (hundreds to millions of km2), an isotopic record interpreted as C3 vegetation replacing C4 grasslands may indicate invading C3 woody shrubs instead of expanding C3 forests (a common interpretation). (2) At the landscape scale (several tens of m2 to hundreds of km2), the accuracy of scaling up paleoclimatic interpretations to a regional level is affected by the landform containing the isotopic record. (3) At the soil-profile scale (cm2 to m2), soil profiles with multiple generations of carbonate mixed together have a lower-resolution paleoecologic record than soil profiles repeatedly buried. (4) At the rhizosphere scale (lm2 to cm2), carbonate formed on roots lack the 14–17ø enrichment observed at broader scales, revealing different fractionation processes at different scales. A multi-scale approach in dealing with d13C in pedogenic carbonate will increase the accuracy of paleoecologic interpretations and understanding of soil–geomorphic–climatic interactions that affect boundaries between C4 and C3 vegetation.
Reprint EditionIn File (07/13/2009)