Stable carbon isotope analysis of soil organic matter illustrates vegetation change at the grassland/woodland boundary in southeastern Arizona, USA

McPherson, Guy R.; Boutton, Thomas W.; Midwood, Andrew J.

doi:10.1007/bf00321197

Cited by 106 publications

(53 citation statements)

References 46 publications

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“…SOC pools with slow turnover rates can carry the imprint of previous vegetation for centuries to millennia, as revealed by carbon isotopes (Dzurec et al 1985, McPherson et al 1993, Connin et al 1997, Ehleringer et al 2000. A high proportion of these pools may dilute the association between SOC profiles and vegetation types if the vegetation had changed previously at some of the sites analyzed here.…”

Section: Discussionmentioning

confidence: 84%

The Vertical Distribution of Soil Organic Carbon and Its Relation to Climate and Vegetation

Jobbágy

Jackson

2000

Ecological Applications

1,417

130

1,790

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Abstract. As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on Ͼ2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers.Plant functional types significantly affected the vertical distribution of SOC. The percentage of SOC in the top 20 cm (relative to the first meter) averaged 33%, 42%, and 50% for shrublands, grasslands, and forests, respectively. In shrublands, the amount of SOC in the second and third meters was 77% of that in the first meter; in forests and grasslands, the totals were 56% and 43%, respectively. Globally, the relative distribution of SOC with depth had a slightly stronger association with vegetation than with climate, but the opposite was true for the absolute amount of SOC. Total SOC content increased with precipitation and clay content and decreased with temperature. The importance of these controls switched with depth, climate dominating in shallow layers and clay content dominating in deeper layers, possibly due to increasing percentages of slowly cycling SOC fractions at depth. To control for the effects of climate on vegetation, we grouped soils within climatic ranges and compared distributions for vegetation types within each range. The percentage of SOC in the top 20 cm relative to the first meter varied from 29% in cold arid shrublands to 57% in cold humid forests and, for a given climate, was always deepest in shrublands, intermediate in grasslands, and shallowest in forests (P Ͻ 0.05 in all cases). The effect of vegetation type was more important than the direct effect of precipitation in this analysis. These data suggest that shoot/root allocations combined with vertical root distributions, affect the distribution of SOC with depth.Global SOC storage in the top 3 m of soil was 2344 Pg C, or 56% more than the 1502 Pg estimated for the first meter (which is similar to the total SOC estimates of 1500-1600 Pg made by other researchers). Global totals for the second and third meters were 491 and 351 Pg C, and the biomes with the most SOC at 1-3 m depth were tropical evergreen forests (158 Pg C) and tropical grasslands/savannas (146 Pg C).Our work suggests that plant functional types, through differences in allocation, help to control SOC distri...

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Section: Discussionmentioning

confidence: 84%

The Vertical Distribution of Soil Organic Carbon and Its Relation to Climate and Vegetation

Jobbágy

Jackson

2000

Ecological Applications

1,417

130

1,790

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“…In such cases the most likely cause for this large J3C enrichment with depth is the existence of prior C4 vegetation (Dzurec et al 1985;Mondenesi et al 1986;Schwartz et al 1987;Volkoff and Cerri 1987;Martin et al 1990;Desjardins et al 1991;McPherson et al 1993;Wang et al 1993;Mariotti and Peterschmitt 1994;Victoria et al 1995). Both profiles of Salitre, NhecoJandia, and Tunas had intermediate 613C values varying approximately from 4 .0 to 6.0%0 (Fig.…”

Section: Resultsmentioning

confidence: 93%

“…In addition, seven other profiles collected in several areas of the Amazon region down to 4 m depth show no significant variation in carbon stable isotopic composition (Sanaiotti, unpublished work). As modern savannah soils clearly show the presence of C4 grasses in their SOM (Dzurec et al 1985;Mondenesi et al 1982;Schwartz et al 1987;Volkoff and Cerri 1987;Martin et al 1990;Desjardins et al 1991;McPherson et al 1993;Wang et al 1993;Mariotti and Peterschmitt 1994), the apparent absence of C4 signal in majority of the profiles is intriguing.…”

Section: Resultsmentioning

confidence: 98%

Carbon-13 variation with depth in soils of Brazil and climate change during the Quaternary

et al. 1996

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Paleoecological and geomorphological studies indicate that, during the middle Holocene, there was a predominance of drier conditions with grassy savannahs replacing forests across the South American continent. Modern savannahs are composed mainly of C4 plants and soils developed under this type of vegetation show enrichment in 13C compared to soils under C3 vegetation cover. If soils contain stabilized organic mauer formed in the middle Holocene, we hypothesize that former C4 vegetation would be evidenced by a large enrichment of nc in soil organic matter (SOM). We investigate this possibility examining the depth variation of carbon isotopic composition in 21 soil profiles collected by different researchers at 14 different sites in Brazi I. Of these, profiles from only three sites showed a marked increase of nc with depth (9-10%0 enrichment in one difference between the surface soil and deepest depth); two sites showed intermediate enrichment (4-5%0), and nine sites showed a small enrichment of approximatelly 2.5%0. The majority of sites showing all-C3 derived SOM were in the Amazon region. Possible causes for the absence of a large I 3C enrichment with depth are: ( I) dominance of C3 rather than C4 grasses in mid-Holocene savannahas, (2) soil profiles did not preserve organic matter derived from mid-Holocene plants, (3) the retreat of forest areas did not occur on a regional scale, but was a much more localized phenomenon.

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“…The average value of 8^-^C found in the literature for samples collected from surface soils covered with C4 grasses was -16.1 ±2.2 %o (Dzurec et al 1985;Mondenesi et al 1986;Schwartz et al 1986;Volkoff & Cerri 1987;Martin et al 1990;Desjardins et al 1991;McPherson et al 1993;Wang et al 1993;Mariotti & Peterschmitt 1994;Trouve et al 1994).…”

Section: Carbon Isotopic Composition Of Soil Organic Matter Along Thementioning

confidence: 89%

Past vegetation changes in the Brazilian Pantanal arboreal–grassy savanna ecotone by using carbon isotopes in the soil organic matter

Victória¹,

Fernandes

Martinelli³

et al. 1995

Global Change Biology

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Measurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in the Brazilian Pantanal. The Pantanal is a large floodplain area with grass-dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in ^^C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM "C values reflect the change from C3 to C4 plants between the sites, as confirmed by measurements of '^C of vegetation and the soil surface along a transect between the upland closed-canopy forest and lowland grassy savanna. Changes of ^^C in SOM with depth at both sites are larger than the 3-4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C3 and C4 plants at these sites. Mass balances with ^'*C and "C suggest that past vegetational changes from C3 to C4 plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11 400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C4 to C3, observed only in the upper part of the arboreal savanna, was much more recent (1400 BP), and was probably caused by a local change in the flooding regime.

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Stable carbon isotope analysis of soil organic matter illustrates vegetation change at the grassland/woodland boundary in southeastern Arizona, USA

Cited by 106 publications

References 46 publications

The Vertical Distribution of Soil Organic Carbon and Its Relation to Climate and Vegetation

The Vertical Distribution of Soil Organic Carbon and Its Relation to Climate and Vegetation

Carbon-13 variation with depth in soils of Brazil and climate change during the Quaternary

Past vegetation changes in the Brazilian Pantanal arboreal–grassy savanna ecotone by using carbon isotopes in the soil organic matter

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