COMPARISON OF SOIL CARBON IN SCRUBLAND, CROPPING LAND, PASTURELAND AND SPOTTED GUM LAND IN LOW RAINFALL AREA OF SOUTHEAST QUEENSLAND

摘要

Forest to non-forest land use change is one of the major causes of environmental degradation. Queensland government is encouraging people for hardwood plantation in inland (low rainfall) area of Southeast Queensland (SEQ). However, the economic viability of the plantation is suspicious. Since the carbon sequestration is payable in the Kyoto context, this study has compared the total soil carbon and its long-term in-/decreasing rate in scrubland, pastureland, cropping land and spotted gum land in Krasnozem soil of Kingaroy, an inland SEQ. We have demonstrated how the timeline of land use transformation could be useful to triangulate the soil carbon trends efficiently and effectively. Isoprime isotope ratio mass spectrometer coupled to a Eurovector elemental analyser was used for soil analysis. The lowest amount of soil carbon was found in cropping land (77.39 t/ha up to 110 cm), which was even bit lower than the global average of similar land use types (80 t/ha up to 100 cm). The soil carbon under the mature spotted gum (306 tC/ha) was found much higher than the world average soil carbon amount of similar region's forest and was closer to the world richest soil carbon boreal forest. The annual decreasing rate of soil carbon in cropping land was found 2.6811166 percent which was almost similar to the ROTHC modelled value. The annual increasing rate of soil carbon under the pasture and spotted gum plantation was 0.575841948 and 0.926507307 percent respectively. Thus, the current cropping practices of Kingaroy are not favourable for carbon sequestration but the spotted gum plantation has considerable potential of sequestrating soil carbon.