Impact of Land-Use Change on Soil Microbial Community Composition and Organic Carbon Content in the Dry Tropics

Restoration of forests poses a major challenge globally, particularly in the tropics, as the forests in these regions are more vulnerable to land-use change. We studied land-use change from natural forest (NF) to degraded forest (DF), and subsequently to either Jatropha curcas plantation (JP) or agroecosystem (AG), in the dry tropics of Uttar Pradesh, India, with respect to its impacts on soil microbial community composition as indicated by phospholipid fatty acid (PLFA) biomarkers and soil organic carbon (SOC) content. The trend of bacterial PLFAs across all land-use types was in the order: NF > JP > DF> AG. In NF, there was dominance of gram-negative bacterial (G(-)) PLFAs over the corresponding gram-positive bacterial (G(+)) PLFAs. The levels of G(-) PLFAs in AG and JP differed significantly from those in DF, whereas those of G(+) PLFAs were relatively similar in these three land-use types. Fungal PLFAs, however, followed a different trend: NF > JP > DF = AG. Total PLFAs, fungal/bacterial (F/B) PLFA ratio, and SOC content followed trends similar to that of bacterial PLFAs. Across all land-use types, there were strong positive relationships between SOC content and G(-), bacterial, fungal, and total microbial PLFAs and F/B PLFA ratio. Compared with bacterial PLFAs, fungal PLFAs appeared to be more responsive to land-use change. The F/B PLFA ratio, fungal PLFAs, and bacterial PLFAs explained 91%, 94%, and 73% of the variability in SOC content, respectively. The higher F/B PLFA ratio in JP favored more soil C storage, leading to faster ecosystem recovery compared to either AG or DF. The F/B PLFA ratio could be used as an early indicator of ecosystem recovery in response to disturbance, particularly in relation to land-use change.