Publication Date:
2013-03-07
Description:
Global soil carbon (C) stocks account for approximately three times that found in the atmosphere. In the Aso mountain region of southern Japan, semi-natural grasslands have been maintained by annual harvests and/or burning for more than 1,000 years. Quantification of soil C stocks and C sequestration rates in Aso mountain ecosystem is needed to make well-informed, land-use decisions to maximize C sinks while minimizing C emissions. Soil cores were collected from six sites within 200 km 2 (767-937 m asl.) from the surface down to the k-Ah layer established 7,300 years ago by a volcanic eruption. The biological sources of the C stored in the Aso mountain ecosystem was investigated by combining C content at a number of sampling depths with age (using 14 C dating) and δ 13 C isotopic fractionation. Quantification of plant phytoliths at several depths was used to make basic reconstructions of past vegetation and was linked with C-sequestration rates. The mean total C stock of all six sites was 232 Mg C ha -1 (28-417 Mg C ha -1 ), which equates to a soil C sequestration rate of 32 kg C ha -1 yr -1 over 7,300 years. Mean soil C sequestration rates over 34, 50 and 100 years were estimated by an equation regressing soil C sequestration rate against soil C accumulation interval, which was modeled to be 618, 483 and 332 kg C ha -1 yr -1 , respectively. Such data allows for a deeper understanding in how much C could be sequestered in Miscanthus grasslands at different time scales. In Aso, tribe Andropogoneae (especially Miscanthus and Schizoachyrium genera) and tribe Paniceae contributed between 64 and 100% of soil C based on δ 13 C abundance. We conclude that the semi-natural, C 4 -dominated grassland system serves as an important C sink, and worthy of future conservation. © 2013 Blackwell Publishing Ltd
Print ISSN:
1354-1013
Electronic ISSN:
1365-2486
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Geography
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