Agriculture Reference
In-Depth Information
Table 3.3 Example of recruitment patterns for different life histories taken from a five-year study of postfire seedling
recruitment patterns for representative woody species in California chaparral
Precipitation was below average in years 1, 3, and 4 and substantially above average in years 2 and 5.
Total seedling recruitment (ha
1
)
Percentage by year
Growth
form
a
No.of
sites
Species
X
S.E.
1
2
3
4
5
Obligate seeders
Ceanothus crassifolius
s
10
62 100
17 800
99
1
0
0
0
C. greggii
s
8
18 500
18 500
100
0
0
0
0
C. oliganthus
s
6
103 900
95 500
100
0
0
0
0
Helianthemum
scoparium
ss
12
33 500
17 500
73
13
7
0
7
Lotus scoparius
ss
39
46 100
8400
72
9
2
1
16
Facultative seeders
Adenostoma
fasciculatum
s
31
104 500
22 800
94
3
0
0
3
Ceanothus spinosus
s
9
36 600
25 100
92
3
0
0
5
Artemisia californica
ss
12
11 600
4800
41
42
13
1
4
Eriogonum
fasciculatum
ss
24
8600
2900
71
21
5
0
3
Salvia mellifera
ss
27
41 900
16 100
73
12
3
3
9
Obligate resprouters
Cercocarpus betuloides
s
8
200
รพ
100
0
33
0
33
34
Rhamnus crocea
s
21
400
100
4
0
15
4
77
Encelia californica
ss
2
497 300
487 800
0
67
15
0
18
Hazardia squarrosa
ss
13
37 700
17 300
0
54
34
6
6
a
s, shrub, large stature, typically
>
2 m, hard wood and long lived; ss, subshrub or suffrutescent growth
forms that are smaller stature with light wood and short lived.
Source:
From Keeley
et al.
(
2006b
).
suffrutescents or subshrubs that grow rapidly and set seed before the canopy
closes in (Table
3.3
).
In more open shrub communities where canopies do not close in, seedling
recruitment may occur both after fire and continuously between fires in gaps
between shrubs (e.g. Lloret
1998
; Carrington & Keeley
1999
; DeSimone & Zedler
1999
; Holmes & Newton
2004
). Some of these species have long-lived seedbanks
and others more transient seedbanks that require continuous replenishing in order
to maintain a seedbank for postfire recruitment.
Although seeds of some species may colonize burned sites (see below), most
recruitment derives from
in situ
dormant seedbanks that accumulate between fires.
This conclusion is based on seedbank studies that show that most species recruit-
ing after fire are present in the soil prior to fire (Zammit & Zedler
1988
; Parker &
Kelly
1989
; Auld
1994
; Enright
et al.
2004
) and on inferences based on the timing
of dispersal, fire and recruitment. Most taxa disperse seeds in spring or summer
and most fires occur after dispersal is completed, thus making it unlikely that
