Soil microbial diversity shift as affected by conversion of shallow and rocky wastelands to Jatropha curcas L. plantation

摘要

The cultivation in wastelands of Jatropha curcas as a biofuel crop avoids the alleged food vs. fuel dilemma. Converting wastelands into Jatropha plantation will produce changes in microbial composition which in turn may have a profound effect on biochemical activities and physico-chemical properties of soil. These changes may be permanent and the soil may attain a different equilibrium through this land use change. The objective of this study was to compare the microbial diversity of native undisturbed soil of barren rocky wasteland and soil drawn from 24 months old J. curcas plantation. Cultivation of Jatropha employing suitable agronomic practices improved soil organic carbon, available P and K. Total soil DNA extracts were used as template DNA to amplify 16S and 18S rDNA gene fragments that were further sequenced and taxonomically assigned by comparisons with gene bank resources. Diversity indices showed that the microbial diversity was higher and more evenly distributed in native soil than in Jatropha planted soil. A prominent diversity shift from Ascomycota in the native soil to Basidiomycota and Chytridiomycota in the Jatropha bulk soils was observed. Interestingly, the conversion from barren land to Jatropha cultivation with recommended agricultural practices also brought about a marked decrease in population of several fungal pathogens. There was a striking increase in members of Proteobacteria (1.7-fold) as well as of Bacteroidetes in Jatropha planted soil as compared to native soil. In contrast, there was a decrease in the Acidobacteria and Chloroflexi community in Jatropha planted soil. It would be useful to follow the microbial pattern over the long term and to study the evolution of the Jatropha soil ecosystem on wastelands.