Impact of burning and fertilization on dry Mediterranean grassland productivity and diversity

Fire alters plant community structure by changing dominant plant species and shifting resource mobilization, while fertilizer application alters plant community structure through its impact on productivity. Here we studied prescribed burning and fertilizer treatments on the productivity and diversity of a semi-arid Mediterranean grassland ecosystem. Variables measured were aboveground plant productivity, vegetation, litter and soil cover, species richness and plant density of an Avena/Hordeum (A-H) dominated plant community using a split-plot experimental design over a three-year period. Burning increased vegetative cover by 21.2% and reduced litter cover by 22.6%, while fertilization increased vegetative cover by 31.6%. The combined effect of burning and fertilization increased vegetative cover by 35.5% and reduced litter cover by 13.9%. Aboveground biomass was also higher in burned treatments (52.41 g 0.25 m−2) by 39.5% over unburned treatments. Burning reduced the proportion of the dominant Avena/Hordeum complex by 43.1%, thus significantly enhancing overall species richness by 52.5% over the unburned plots. On the other hand, fertilizer application increased biomass production and species richness by 37.4% and 13.5%, respectively, over the unfertilized plots. The combined effect of burning and fertilization enhanced biomass production and species richness by 90.8% and 69.8%, respectively, and reduced the dominant A-H by 45.5%. Burning generally resulted in lowering the dominance of the A-H complex compared to the control while fertilizer application had variable effect, reducing the proportion of A-H with burning but increasing it without burning. Reduction in the A-H complex increased the presence of other species, therefore enhancing diversity. Our findings showed that burning and fertilization treatments have a synergistic effect on both productivity and diversity of an arid grassland.

► Burning reduced litter cover thus enhancing light penetration. ► Burning reduced the proportion of Avena/Hordeum complex and enhanced biodiversity. ► Burning significantly enhanced species richness by 52.5%. ► Combined effect of burning and fertilizer enhanced biomass production by 90.8%. ► Combined effect of burning and fertilizer enhanced species richness by 69.8%.