On the basis of different photosynthetic pathway,there's obvious difference in
δ 13 C values between C\-3 plants and C\-4 plants.Use this characteristic,the δ 13 C values in different size and
density fractions of two profile soil samples either in farm land and forest lands near Maolan Karst virgin forest was analyzed,there plant C\-3 plants previously and plant C\-4 plants now.Results showed that the δ 13 C values of different
size fractions in forest soil aere δ 13 C
coarse sand < δ 13 C fine sand < δ 13 C coarse
silt < δ 13 C clay < δ 13 C fine silt ,and the δ 13 C values of different size
Fractions in farmland soil were δ 13 C coarse sand > δ 13 C fine sand > δ 13 C coarse silt > δ 13 C clay > δ 13 C fine silt ,it indicated that the
soil organic matter was fresh in coarse sand and oldest in fine silt.The δ 13 C values of different density fractions in forest soil ware δ 13 C light < δ 13 C heavy ,and the δ 13 C values of different density fractions in farmland soil were δ 13 C light > δ 13 C heavy ,it also indicated that the soil organic matter was fresh in light fractions and old in heavy fractions.
More abstracts about the The Dynamics Rules of Soil Organic Matter of Turnover Ecosystems Traced by Stable Carbon Isotopes