Carbon Isotope Dynamics in Some Tropical Soils

Fixed ammonium and carbon-nitrogen ratios of some semi-arid tropical Indian soils

Relatively little is known about the fixed NH4-N status of soils in the semi-arid tropics (SAT) but information is needed in view of its role in N cycling and the N economy of the soils. The distribution of fixed NI-L-N and C/N ratios of soil profiles from two benchmark Vertisols and one Alfisol in the Indian SAT were studied. From 15.9 to 58.6% of the total soil N was present as fixed NHa-N in...

Carbon sequestration in soils: some cautions amidst optimism

A sink for atmospheric carbon (i.e., CO2) in soils may derive from the application of conservation tillage and the regrowth of native vegetation on abandoned agricultural land. Accumulations of soil organic matter on these lands could offset emissions of CO2 from fossil fuel combustion, in the context of the Kyoto protocol. The rate of accumulation of soil organic matter is often higher on fert...

Carbon Leaching from Tropical Peat Soils and Consequences for Carbon Balances

Drainage and deforestation turned Southeast (SE) Asian peat soils into a globally important CO2 source, because both processes accelerate peat decomposition. Carbon losses through soil leaching have so far not been quantified and the underlying processes have hardly been studied. In this study, we use results derived from nine expeditions to six Sumatran rivers and a mixing model to determine l...

Climate-Mediated Nitrogen and Carbon Dynamics in a Tropical Watershed

Stable carbon isotope evidence for the microbial origin of C14-C18 n-alkanoic acids in soils

In order to delineate the origin of soil fatty acids, crop soil samples have been incubated for 21 days in vitro either with unlabelled or 13C-labelled glucose. Analyses of C14-C32 n-alkanoic acids from monocarboxylic acid fractions, as methyl esters, by gas chromatography-combustion-isotope ratio monitoring mass spectrometry (GC-C-IRMS) show that C14, C16 and C18 n-alkanoic acids are 13C-label...