Carbon Dioxide Emissions from Exhumed Petrocalcic Horizons

Abstract

The second largest pool of terrestrial carbon is soil CaCO 3. In addition to being an important sink of atmospheric CO 2 , soil carbonate is potentially an important source of atmospheric CO 2. The cemented form of soil carbonate-the petrocalcic horizon-develops in geomorphically stable soil in arid, semiarid, and some subhumid climates. In many of these dryland areas, such as the Chihuahuan Desert of North America, erosion has stripped away overlying soil and exhumed the petrocalcic horizon, thereby exposing it to a weathering zone above the calcification zone where it normally forms. This research tested the hypothesis that soil type 1 (eroded Aridisols with exhumed petrocalcic horizons) will emit more CO 2 than soil type 2 (noneroded Aridisols with petrocalcic horizons) or soil type 3 (Entisols formed in sandy, noncalcareous sediments). We tested this hypothesis by comparing the amount of CO 2 and the d 13 C of CO 2 released from the three soil types. Using a randomized complete block design, CO 2 emissions were measured using NaOH and soda lime traps from June 2002 to October 2003. Neither the NaOH traps nor soda lime traps detected any statistical difference in cumulative CO 2 emissions from the three soil types at the a 5 0.05 level. Moreover, the isotopic analysis of CO 2 did not match the isotopic values of pedogenic carbonate, nor were there any statistical differences (a 5 0.05) in d 13 C of CO 2 among the three soil types. We conclude, therefore, that exhumed petrocalcic horizons are not actively emitting CO 2 at a rate significantly greater than adjacent soils, and thus carbon stored in petrocalcic horizons can be considered a recalcitrant reservoir within the decadal timeframe pertinent to carbon sequestration policies.

Rain pulse response of soil CO2exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States

“…The soils at Corral Pocket are high in inorganic carbon [ Bowling et al , 2010; Goldstein et al , 2005], and soil carbonates may play a role in short‐term CO 2 dynamics in arid soils [ Serrano‐Ortiz et al , 2010]. However, the δ 13 C of CO 2 evolved from calcite precipitation would be more enriched (less negative) than the C 4 range [ Serna‐Perez et al , 2006; Stevenson and Verburg , 2006].…”

Modeling salt movement through a Mojave Desert soil

“…Only a process, such as soil acidification, causing CaCO 3 dissolution could cause carbonates to become a source of global carbon. Recently, Serna-Perez et al (2006) concluded that exhumed petrocalcic horizons are not emitting significantly more CO 2 than adjacent soils. Therefore, soil CaCO 3 can be considered a recalcitrant reservoir for carbon sequestration, which is consistent with our modeling simulations.…”

“…Despite the fact that N is often the most limiting plant nutrient in terrestrial ecosystems, NO À 3 in desert soils often accumulates to highest concentrations at depth (1-5 m) (Hartsough et al, 2001;Marion et al, in press;Stokstad, 2003;Wallace et al, 1978;Walvoord et al, 2003), rather than near the surface (Jobbagy and Jackson, 2001). Another example is the potential role that CaCO 3 deposition may play in desert soils as a sink for and possibly as a source of atmospheric CO 2 (Capo and Chadwick, 1999;Monger and Gallegos, 2000;Schlesinger, 1982;Serna-Perez et al, 2006).…”

Carbon Budgets of Biological Soil Crusts at Micro-, Meso-, and Global Scales

“…These are potentially a major problem in modeling biocrust-derived C fluxes. The large differences between modeled respiration (see Castillo-Monroy et al 2011) and NPP for desert biocrusts shows that the calculated NPP will be very sensitive to non-biocrust-derived C. However, the literature indicates that abiotic fluxes from soil carbonates, the obvious potential source of C flux from soils, can be very low (Serna-Perez et al 2006; although see Rey 2015). A combination of the datasets accumulated in the SCIN project ) with the current knowledge regarding CO 2 fluxes in biocrusts from arid and semiarid environments will allow modeling the behavior of these communities in a global change scenario ( Fig.…”