Structure of the microbial community in a soil under shrub after an experimental fire and application of different treatments for soil erosion control

In this study the microbial community structure of a shrubland soil after an experimental fire and application of different post-fire stabilization treatments (seeding and mulching) was analyzed by means of the analysis of phospholipid fatty acid (PLFA) and compared with the respective unburnt control. Measurements were made immediately and 3, 6 and 12 months after the fire and application of treatments. The principal component analysis performed with the PLFA data separated clearly soil samples according the sampling time, indicating that marked seasonal variations rather than soil treatment (experimental fire, post-fire stabilization treatments) were responsible for determining the composition of soil microbial communities. It should be noticed, however, that when samples of same sampling time were analyzed separately, PLFA analysis clearly allow us to separate burnt samples (burnt, burnt + mulching, burnt +seeding) from the corresponding unburnt control but did not differentiate among the burnt treatments. The unburnt samples were characterized by high concentrations of fatty acids characteristic of fungi and Gram-negative bacteria while the burnt samples were characterized by high concentration of fatty acids characteristic of bacteria and actinobacteria. These microbial changes induced by experimental burning persisted even after one year.