Document: AAR-3-59-29

The effect of cultivation on soil organic C and N storage in India: A reanalysis of Jenny's 1960 data set .

MILLER, A.J* and R.AMUNDSON

University of California, Berkeley, Ca, 94720-3110, USA ¹

Abstract:
Recent studies have shown that land use continues to be responsible for converting soil organic carbon (SOC) to atmospheric CO₂. Here, we investigate the response of SOC to cultivation by reexamining a large data set of over 500 soils collected from India in the late 1950's. A paired-site analysis between cultivated and natural soils showed that following cultivation, SOC and soil organic nitrogen (SON) pools decreased an average of 28% and 22%, respectively, while C/N decreased in soils with an initial ratio greater than about 11, and increased in soils with initial ratios below this value. 3-D plots of SOC and SON vs. climate were used to show that the greatest concentrations of SOC and SON, as well as the highest C/N ratios, occur in regions with both low temperatures and high precipitation. These results were supported by a generalized global data set organized by Holdridge life zones that, when modeled in the same method as the India data, illustrate similar trends to those of India. Following cultivation, absolute losses of both SOC and SON were greatest under low temperatures and high precipitation. Using a paired plot analysis, we were unable to demonstrate any relationship between the fraction of SOC or SON lost to cultivation as a function of the initial soil content. However, a broader examination of fractional loss as a function of climatic factors demonstrates increasing losses of SOC with decreasing temperatures, whereas the fractional losses of SON increased with decreasing temperature and precipitation.

Keywords: land use-change, organic carbon, organic nitrogen, global carbon cycling

This abstract is being presented at: 10:30 AM in session:
CARBON STORAGE