Agriculture Reference
In-Depth Information
Fig. 5.3
Seral stage chaparral 5 years after fire dominated by resprouting
Adenostoma
fasciculatum
and a dense layer of ephemeral subshrubs arising from dormant seedbanks
(primarily
Lotus scoparius
) illustrating the high potential flammability of postfire chaparral
during the first decade. This scene is the site of the 2002 Bouquet Canyon in northern Los
Angeles County and 2700 ha reburned in the 2007 Buckweed Fire. (Photo by Jon Keeley.)
1-hr fuel moisture
3%
90
75
7%
60
45
30
15
0
0
10
20
30
40
50
60
Wind speed at midflame (km/h)
Fig. 5.4
Behave model results for rate of fire spread for the young chaparral illustrated in
Fig. 5.3
demonstrating that, contrary to some assertions, young fuels in postfire chaparral can
carry fire (from Keeley & Zedler
2009
). Such reburns are a major contributor to type
conversion of native shrubland to alien annual herbaceous associations (see Chapter 12).
As a consequence of these different successional stages, these communities go
through a change from being highly vulnerable to fires during the first 5 yrs or so,
then less susceptible for a decade or more (Schoenberg
et al.
2003
) until dead fuels
accumulate in the shrub canopies (
Fig. 5.5
). In general, there is about a 30%
live/dead ratio for mature stands that varies according to shrub species compos-
