Assessing carbon lability of particulate organic matter from delta C-13 changes following land-use change from C-3 native vegetation to C-4 pasture

作者：Dalal R C^*; Cowie B A; Allen D E; Yo S A

来源：Soil Research, 2011, 49(1): 98-103.

DOI：10.1071/SR10083

• C-3
• C-4
• delta C-13
• labile C
• particulate organic matter C
• soil organic C

Land-use change from C-3 vegetation (delta C-13 values, -30% to -24%) to C-4 vegetation (delta C-13 values, -14% to -11%) provides a useful quantitative technique for estimating organic C turnover in soil, even when total organic C changes are negligible. We utilised this technique to estimate C turnover in physically fractionated soil organic matter, particulate organic matter C (POM C >250 mu m fraction and POM C 250-53 mu m fraction), and the <53 mu m fraction. There were small changes in total soil organic C (SOC) after 23 years of land-use change from native vegetation (mixed vegetation of Acacia harpophylla and Casuarina cristata) to buffel grass (Cenchrus ciliaris L. cv. Biloela) pasture grown on Vertosol-Dermosol-Sodosol soil types. The SOC values (t/ha) under native vegetation were: 31 +/- 3 for the 0-0.1m depth, 21 +/- 1 for the 0.1-0.2m depth, 15 +/- 3 for the 0.2-0.3m depth, and 16 +/- 2 for the 0.3-0.4m depth; the corresponding SOC values under pasture were 25 +/- 2, 19 +/- 2, 14 +/- 2, and 13 +/- 1 t/ha. The respective delta C-13 values in 0-0.1m depths of the whole SOC and POM C >250 mm fraction changed from -25.5 +/- 0.1% and -25.5 +/- 0.3% under native vegetation to -20.1 +/- 0.5% and -19.4 +/- 0.2% under pasture. Similar, although smaller, differences were observed for other depths and SOC fractions. The SOC turnover periods (years) were 31 +/- 6 for the 0-0.1m depth, 60 +/- 5 for the 0.1-0.2m depth, 55 +/- 15 for the 0.2-0.3m depth, and 63 +/- 20 for the 0.3-0.4m depth; the corresponding turnover periods for the POM C >250 mu m fraction were 13 +/- 2, 19 +/- 5, 14 +/- 4, and 12 +/- 5 years. The turnover periods of SOC in the POM C 250-53 mu m and <53 mu m fractions were similar to, or longer than, for the whole SOC at all depths studied. Thus, the lability of the SOC and SOC pools was in the order: POM C >250 mu m fraction > POM C 53-250 mu m fraction = POM C <53 mu m fraction = whole SOC.

• 出版日期2011