The Colmeal catchment – A brief history of a recently burned Mediterranean forest catchment.

Abstract:

The Colmeal catchment concerns a small (10ha) forest area located in Central Portugal that was impacted by a wildfire on 28 August 2008. Following the fire, this catchment was highly instrumented for an intense field monitoring on the post-fire hydrological and erosive response at various scales (plot-to-catchment) that lasted for four years. Despite 12 years have passed since the beginning of this monitoring, and many data is yet to be published, the story behind the research findings of this catchment can provide a snapshot of the Portuguese forest management, and explain why ecosystems such as these are leading towards desertification.

The experimental design of this study involved a nested approach with runoff plots at micro-plot scale (0.25-0.5 m²), open plots at hillslope scale (30-45 m²), and streamflow measurements at catchment scale (10ha). Part of this data was also used for hydrological model calibration and validation for runoff and erosion with RUSLE, MMF and PESERA models at hillslope scale, and with the event-based LISEM model at catchment scale.

By the end of the four years of monitoring, few signs of vegetation recovery were observed as the window of disturbance appeared to be enlarged by pre-fire disturbances, such as recurrent wildfires and soil mobilization operations. During this period, post-fire runoff generation was largely explained by rainfall amounts and soil water repellency, while erosion processes were better explained by rainfall intensity and ground cover. An important finding of this work is that the history of a study site affects present post-fire hydrological responses, whether we are referring to disturbances that occurred many years ago, or to soil moisture conditions just before a rainfall event.