Ground‐level changes after wildfire and ploughing in eucalyptus and pine forests, Portugal: implications for soil microtopographical development and soil longevity

Abstract

AbstractSoil level changes over four years at 50 sites in three types of post‐fire eucalyptus and pine forest management practices (natural pine seedling regeneration; eucalyptus regrowth from coppiced stumps; and deep‐(rip‐) ploughed areas planted with eucalyptus seedlings) in the Águeda Basin, Portugal are reported. Average ground lowering at regrowth sites was high during the first year after fire (up to an estimated 18 mm), declining sharply by the third year with vegetation growth and litter cover development. In the first year after rip‐ploughing, there was greater surface lowering (up to 27 mm recorded), with recovery within three–four years. This sharp post‐ploughing reduction in soil loss is attributed to stone lag development through erosion of fines. Soil erosion resulting from a wildfire—rip‐ploughing cycle is estimated to be up to 174 t ha−1, which would lead to ultimate physical degradation for typically thin soils within 50–100 years. Soil surface roughness decreased slightly or remained virtually stable for the moist Águeda Basin stony soil compared with a model of increased roughness for dry Mediterranean stony soils. This difference is attributed to moist conditions encouraging vegetation growth and rapid fermentation of organic matter together with transported sediment infilling surface indentations. The value of a ground‐level change approach, and of the soil erosion bridge in particular, in soil erosion studies is discussed. Copyright © 2002 John Wiley & Sons, Ltd.