Reduction of Nutrient Losses with Eroded Sediments by Post-Fire Soil Stabilisation Techniques

Resumen

After an experimental fire in steep shrub land in a temperate–humid region (north-west Spain), the effects of
two post-fire stabilisation treatments (grass seeding and straw mulching) on the chemical properties of eroded sediments,and the amount of nutrients lost with them, we reevaluated relative to control burnt soil, over a period of 13 months. Total C
and N concentrations, and
d
13
C, indicated that sediments were mainly contributed by charred plant and litter material. The
highest concentrations of extractable base cations in the sediments occurred during the first 3 months following fire,
especially for Na and K. As treatments had little or no effect on nutrient concentration in sediments, differences in nutrient
losses were due to the 10-fold lower sediment production in mulching compared with other treatments. In control and
seeding treatments, the accumulated amounts of nutrients lost with sediments were 989–1028kgha
1
(C), 77kgha
1
(N),
1.9–2.4kgha
1
(Ca), 0.9–1.1kgha
1
(Mg), 0.48–0.55kgha
1
(NH
4
þ
–N), 0.39–0.56kgha
1
(K), 0.19–0.34kgha
1
(Na)
and
,
0.1kgha
1
(P and NO
3
–N)
.
These values accounted for 22–25% (total C and N) and 5–12% (NH
4
þ
–N, Ca, P and
Mg) of available nutrients in ash, and 1.0–2.4% of those in ash
þ
topsoil. As nutrient and sediment losses were strongly
correlated, the reduction of the latter by mulching application leads to an effective decrease of post-fire nutrient losses.