Post-fire dynamics of soil surface compaction in relation to the previous stage of land abandonment

Abstract

The abandonment of agricultural landscapes has been a widespread phenomenon in European Mediterranean areas since the second half of the past century. Land abandonment promotes soil structuration and increases soil organic matter content, even though the abandoned lands are still affected by old degradation processes from cropping. In addition, old fields are often colonised by opportunistic plant species, giving way to fire-prone formations. This work presents a nine-year monitoring of soil surface compaction which includes unburned and burned areas and two stages of abandonment: (1) lands abandoned 8-15 years prior to fire and occupied by dry grassland with young Pinus halepensis, and (2) old fields (>35 years of abandonment) colonised by mature pine forest. The study area is located near the Guadalest reservoir (Alacant province, East of Spain). Soil surface compaction (0-1 cm mineral soil depth) was assessed by means of a cone penetrometer. Analysis of unburned areas showed that the pine forest always of abandonment showed increased compaction during the first year, although their subsequent dynamics were quite different. In the recently abandoned fields, soil surface compaction values returned to those found on unburned plots in the short term. In contrast, burned pine forest showed higher values than unburned pine forest until the sixth year after the fire. These results indicate that old fields colonised by pine forest are more vulnerable to fire than recently abandoned fields in terms of soil compaction.