Temperature-time curves at the soil surface in maquis summer fires

Many summer fires in Valencia are enhanced by the abundance of maquis. Neve rtheless, fire field studies on the soil temperature-time curves under summ er conditions with controlled amount and structure of fuel are scarce. Expe rimental summer fires were conducted to analyse the influence of the fuel l oad and the fuel structure on the soil temperature-time profiles. The increase of fuel load from 2 to 4 kg m(-2) increased the net radiant he at per unit area (5691 to 11263 kJ m(-2)), the total duration of heat (190 to 396 min) and the duration of temperatures greater than 100 degreesC (19. 8 to 35.9 min) whereas the peak temperature increased 100 degreesC (from 41 6 degreesC to 516 degreesC). Variations of fuel height from 1.5 to 0.75 m and bulk density from 2 to 4 k g m(-3) respectively, increased net radiant heat per unit area, H-p/a (6510 to 10 444 kJ m(-2)), t(total) (219 to 375 min), and t(>100 degreesC) (9.7 to 36.1 min) wheras T-max increased 40 degreesC (446 to 486 degreesC). At plot scale, fire intensity and severity will increase with the fuel load . At plant scale, more degradation will occur in the soil patches with high er bulk density, mainly because an increased duration of high temperatures in soil. Fuel amount and structure are then key factors in maquis fires sin ce they will determine the post-fire patchiness of soil conditions and plan t recovery.