Stable Carbon Isotope Record of Holocene Environmental Change in the Central Great Plains

2004 ◽  
Vol 25 (2) ◽  
pp. 170-190 ◽  
Author(s):  
Aaron J. Feggestad ◽  
Peter M. Jacobs ◽  
Xiaodong Miao ◽  
Joseph A. Mason
1999 ◽  
Vol 52 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Edmund C. February ◽  
William D. Stock

Stable carbon isotope chronologies using tree ring wood cellulose have proved useful for developing hypotheses on climate and environment change. However, within both the Southern Hemisphere and Africa there has been very little tree-ring-based isotope research. Here we report the first high-resolution (annual) 13C/12C chronology for both Africa and the Southern Hemisphere. The 77-yr stable carbon isotope chronology was developed from six Widdringtonia cedarbergensis trees from a site in the Cedarberg Mountains, Western Cape Province, South Africa. The results indicate that 13C/12C ratios are not different from 1900 to 1949. After 1949, however, values become significantly more negative to 1977. The isotopic record from the pooled trees at the Die Bos site does not correlate with rainfall. This correlation is not significant even when the Widdringtonia stable carbon isotope record is de-trended for the anthropogenic CO2 contribution. The Widdringtonia record does, however, correlate significantly with atmospheric 13C/12C CO2 values derived from ice core data, tree ring 13C/12C chronologies from the Northern Hemisphere, and recent Southern Hemisphere records.


2011 ◽  
Vol 8 (7) ◽  
pp. 1769-1778 ◽  
Author(s):  
C. Alewell ◽  
R. Giesler ◽  
J. Klaminder ◽  
J. Leifeld ◽  
M. Rollog

Abstract. Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by a high biodiversity and sensitive ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and induce a degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Soils dominated by aerobic degradation can be expected to have a clear increase of carbon isotopes (δ13C) with depth, due to preferential release of 12C during aerobic mineralization. In soils with suppressed degradation due to anoxic conditions, stable carbon isotope depth profiles are either more or less uniform indicating no or very low degradation or depth profiles turn to lighter values due to an enrichment of recalcitrant organic substances during anaerobic mineralisation which are depleted in 13C. The isotope depth profile of the peat in the water saturated depressions (hollows) at the yet undisturbed mire Storflaket indicated very low to no degradation but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent breaking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 and 25 cm. The age of these turning points was 14C dated between 150 and 670 yr and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.


2002 ◽  
Vol 50 (4) ◽  
pp. 441 ◽  
Author(s):  
Bradd Witt

The field of 'historical ecology' is coming to maturity at a time when we, in Australia, are reflecting on our relationship with, and place in, the land. After an essentially ahistorical approach to land use we are now attempting to place land management into the context of environmental change since and immediately preceding Western European settlement. This volume reflects an emerging concern that, collectively, non-indigenous Australians have no 'environmental history'. One component of 'living in' rather than 'battling against' the land is developing a sense of our history. Without an oral narrative that is commonly shared, attempts to develop the story of environmental change have to be based on retrospective and reconstructive research. This volume captures part of this movement to develop an environmental narrative and context for our future relationship with the land. There are many methodological approaches to reconstructing a story of the past, from local knowledge and oral history to the 'high-tech' and hard sciences. This paper reviews methods that apply stable carbon isotope techniques to reconstruct environmental change. Although well suited to environmental history, carbon isotope techniques remain under-utilised in the Australian context. Here I review applications to highlight the strengths and limitations of carbon isotope techniques in the reconstruction of century-scale vegetation change. There have been two dominant applications of carbon isotope techniques to environmental reconstruction. These applications fall broadly into either stable carbon isotope analysis of organic matter in soils and sediments, or inferences of environmental states have been drawn from carbon isotope analysis of animal tissues and residues. The main strength of stable carbon isotope techniques is that they can be spatially precise while integrating a range of environmental information into one isotopic signal. This integrative strength is at the same time one of the major limitations of carbon isotope techniques because floristic (taxonomic) resolution is low.


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