Agriculture Reference
In-Depth Information
Box 12.2 (
cont.
)
(a)
40
Starthistle cover
30
20
10
0
(b)
12 000
10 000
8000
6000
Starthistle seeds
4000
2000
0
(c)
500
Starthistle seedlings
400
300
200
100
1993 94 95
Fire Fire
96
97
98
99
2000
Fire
Fig. B12.2.2
Yellow starthistle
(Centaurea solstitialis)
cover and seed and seedling production
following three consecutive annual burns applied to extremely dense populations of this
noxious alien weed. Immediate postfire results were very promising (DiTomaso
et al.
1999
),
but follow-up studies indicate that burning destabilized these grasslands and allowed
subsequent reinvasion once burning was stopped (Kyser & DiTomaso
2002
).
competitors in the community. The temporary disequilibrium creates oppor-
tunities for the most aggressive colonizing species and often this will include the
target species. In most cases there are better methods than fire for specifically
targeting a species of concern. Sustainable control of most aggressive weeds is
likely going to occur only when natural, intact ecosystems are restored. When
restoration of natural ecosystems is desired, more often than not there will be
the need for active restoration of native species along with targeted eradication
of specific alien species.
