The role of management on the rate of secondary succession in Mediterranean shrubland after fire

Abstract

Ephemeral grasslands follow fire in Mediterranean batha communities on phosphorus-deficient terra-rossa soils, but successional processes rapidly restore shrub dominance. In an experiment aimed at reducing the rate of successional change and extending the period of grassland dominance, phosphorus was applied to a shrub community dominated by Sarcopoterium spinosum. This was done once in 1988, immediately after a fire. Two years later, the regenerating shrubs were treated with herbicide. Subsequently, the vegetation in the treatments was monitored for 20 consecutive years. The vegetation was undisturbed during the winter/spring growing season but was grazed during the dry summer of each year by beef cattle, which were given ad libitum access to poultry litter to supplement the nitrogen deficiency of the dry herbaceous vegetation. In control plots, the shrubs returned to pre-fire dominance within 5 years. With phosphorus and herbicide, shrub dominance was delayed by the vigorous herbaceous vegetation for more than 20 years. The practical feasibility of this management option depends on the relation between costs and benefits. A preliminary economic analysis based on the long-term experiment and a case study allowed us to define the conditions under which control of successional shrub encroachment can be economically feasible.