| Fires often occur on shallow or stony soils. In Portugal for instance, one of the most
fire-prone countries in Europe, 51% of the fires between 1990 and 2008 occurred on
shallow soils ( 2300 topsoil samples collected at
13 sites in the Portuguese schist region in north-central Portugal. Soil physical
properties assessed include soil water retention, saturated hydraulic conductivity, soil
water repellency, bulk density and soil organic matter content. I will additionally
show how surface rock fragments, and rock fragments incorporated into the soil,
affect soil temperatures during fire. The particle density of these rock fragments
was determined at 2.36 g cm-3 (for particles 2–20 mm), indicating that use of
the common value of 2.65 g cm-3 to calculate rock fragment volume from their
weight may lead to underestimation of the volume of rock fragments in the soil, and
an associated underestimation of the bulk density of the fine earth fraction. The
differences and commonalities between sites will be highlighted, and the impacts of rock
fragments on fire impact and soil hydrology in fire-prone environments discussed. |