Biogeography of San Diego County Oak Mortality Tom Scott UC INTEGRATED HARDWOOD RANGE MANAGEMENT PROGRAM and Department of Environmental Science, Policy, and Management, University of California, Berkeley CENTER FOR CONSERVATION BIOLOGY and Department of Earth Sciences, University of California, Riverside
Distribution of California Oaks TAXA
COMMON NAME
Quercus kelloggii Newb. Quercus agrifolia agrifolia Nee Quercus agrifolia oxyadenia Quercus wislizeni A. DC. var. wislizeni Quercus wislizeni var. frutescens Engelm. Quercus peninsularis Quercus parvula Greene var. parvula Quercus parvula var. shrevei (Muller) Nixon & Muller Quercus chrysolepis Liebm. Quercus vaccinifolia Kellogg Quercus tomentella Engelm. Quercus palmeri (Quercus dunnii). Quercus cedrosensis Quercus sadleriana R. Brown, Campst. Quercus engelmannii Greene Quercus lobata Nee Quercus douglasii H. & A. Quercus garryana Dougl. var. garryana Quercus garryana var. breweri Jeps. Quercus garryana var. semota Quercus dumosa Nutt. sensus stricto Quercus berberidifolia Liebm Quercus john-tuckeri Nixon & Muller Quercus pacifica Nixon & Muller Quercus cornelius-mulleri Nixon & Steele Quercus durata Jeps. var. Durata Quercus durata var. gabrielensis Nixon & Muller Quercus turbinella Greene
BLACK OAK COAST LIVE OAK INTERIOR LIVE OAK PENINSULAR OAK SHREVE OAK CANYON LIVE OAK HUCKLEBERRY OAK ISLAND OAK PALMERS OAK CEDROS ISLAND OAK SADLER OAK ENGELMANN OAK VALLEY OAK BLUE OAK OREGON WHITE OAK
COASTAL SCRUB OAK SCRUB OAK TUCKER’S SCRUB OAK PACIFIC OAK MULLER OAK
ARIZONA SCRUB OAK
NARROW DISTRIBTUION NO YES YES NO NO YES YES YES NO YES YES NO YES YES YES NO YES NO
YES NO YES YES NO YES YES NO
A large number of oak species and subspecies have a geographically limited distribution Wide Distribution
Limited Distribution
Geographic Artifacts
3
3
2
Protobalanus
2
2
2
Section Quercus Tree Group
2
2
0
Section Quercus Scrub Group
3
4
1
10
11
5
Section Lobatae Section
total
Tree oak Species with narrow distributions in San Diego County
TAXA
COMMON NAME
DISTRIBTUION
Quercus engelmannii Greene Quercus agrifolia agrifolia Nee Quercus agrifolia oxyadenia Nee
ENGELMANN OAK COAST LIVE OAK COAST LIVE OAK
Southern Counties Coastal Ranges Southern California
Quercus kelloggii
BLACK OAK
Quercus wislizeni Quercus chrysolepis Liebm.
Baja California to Eastern Sierra, Oregon INTERIOR LIVE OAK California, Baja California, Main Mexico CANYON LIVE OAK California, Arizona, Baja California, Main Mexico
All these species/subspecies or similar taxa have been present in California since the Miocene (25 to 5 Ma)
SIZE OF TREE CANOPY
Restricted distributions but oak trees have exceptional plasticity in growth and life history of oaks
AS
RG
CS
CD
D
TIME AS = Acorn/Seedling stasis RG = Rapid growth
CS = Canopy Stasis CD = Canopy decline
D
= Death
2003
1990
Historical photos provide a counter-intuitive result: sequential aerial photographs show an increase in oak woodlands between 1928 and 1990
Quercus engelmannii
Quercus agrifolia 1928
1990
Strong indication that overuse and drought(s) occurred in San Diego County the late 1800’s and early 1900’s, as well as a strong recovery of woodlands since that time
ORCHARD
OVERUSE
DRY FARMING
1928
1998
Stasis in oak seedlings: Rates of growth in slowest growing trees in Engelmann Oak (Q. engelmannii) plots at South Coast Field Station 700
600
1-4b 2-14a 3-13a
500
5-12b
HEIGHT (cm)
6-4b 7-11b
400
9-1bn 9-5bs 9-7an
300
12-14b 15-8a 16-1as
200
16-4bs 16-13b 16-14b
100
averg top
0 0
1
2
3
4
5
YEARS OF GROWTH
6
7
8
9
Minimum oak generation time: Mast can occur after 3 to 5 years of growth (4 to 6 years after emergence, 5 to 7 after acorn production) (Engelmann Oak (Q. engelmannii) 2000
1800 ACORNS REPROD 1600
M AST
1400
AVERAGE
1200
1000
800
600
400
200
0 0
1
2
3
4
5
6
Y EA R S OF GR OW T H
7
8
9
10
Engelmann oaks live about 70 years then start a slow decline We can create a general model of the life-history of Q. engelmannii but individual sites often lack young age classes.
25
20
15
10
5
YEARS AT DAH Years of age based on annual rings
125
121
117
113
109
105
101
97
93
89
85
81
77
73
69
65
61
57
53
49
45
41
37
33
29
25
21
17
13
9
5
0 1
Frequency distribution FREQUENCY (n) in population
30
What governs oak distribution? Monthly precipitation is concentrated in February and March (Palomar Mountain data) 20 0 1
18
2 3 16
4 5 6
14
7 98 12
99
10
8
6
4
2
0 1
2
3
4
5
6
7
8
9
10
11
12
Evapotransporation (ET) depicted as a U-shaped curve of daily rates, and as cumulative water-loss in summer droughts. 0 6
3
0 29 7 30 4 31 1 31 8 32 5
29
28
2
5
8
9
27
26
26
25
4
7
1
24
24
23
3
6
9
0
22
22
21
20
5
8
2
19
19
18
17
7
4
0
6
3
9
1
17
16
15
15
14
13
12
8
2 12
1
5
11
10
10
80
87 94
1
0
-5 -0.05
-10
-15
-0.1
-20 2001 2002 2003 2004
-0.15
-25
-26
2005 -0.2
-0.25
-30
2002 2003 2004 2005
-35
-38 -40
-41
-0.3
-45
-0.35
-44
-50
Estimated daily rates of water loss (ETo, inches/day) at the UC Riverside CIMIS station. Figure 2A shows a traditional representation of daily variation in ETo but fails to show the cumulative effect of long-term dry-downs on Mediterranean ecosystems. Figure 2B shows the cumulative water loss (inches) occurring in summer droughts, which can last as long as 260 days. These annual droughts can extract 3 to 7 times the amount of water entering ecosystems as winter rain.
Variation in precipitation among last by 9 water years at seven southern California locations 70
60 JULIAN PALOMAR IDYLLWILD
50
RAMONA BOREGO BIGBEAR 40
RAMONA BOREGO PALM SPRNG
30
20
10
0 98-99
99-00
00-01
"01-02
"02-03
"03-04
"04-05
"05-06
"06-07
Weekly Rain Fall Vs Soil Water Content 120
0.30
MAR
FEB
100
0.25
0.20
Rain Fall (mm)
APR 0.15
60
AUG 40
0.10
20
0.05
JUL
JUN
0 30
40
50
60
70
80
90
100
Weeks from 1/2/2005
110
120
130
140
0.00 150
Water Content (-)
80
Rain (mm) WC_2 WC_8 WC_16
80% loss In 8 weeks
About 46% of the distribution of Coast Live Oak (Quercus agrifolia) burned Between 2003 and 2007
Concern over oak persistence: >60% of Engelmann oak (Quercus engelmannii) woodlands burned in 2003 and 2007
Mortality and survivorship of Engelman oaks in burned plots by size classes (cm) 100%
Combination of responses Crown refoliation
80%
60% Stem epicormic sprouting Basal sprouting
40%
Dead 20%
0% <10
10-29.9
30-59.9
>60
Large stems tend to survive better, but do not sprout as easily from root crowns
Coast Live Oak (Quercus agrifolia) Trees decline in San Diego County (percent of healthy trees in 1996 by condition in 2006) Declining
Unknown
Okay 06
Descanso_C
0.85
0.07
0.07
McCain_Valley_B
0.70
0.19
0.11
Campo_And_West
0.66
0.16
0.18
Rincon_Indian_Reservation
0.58
0.17
0.25
Cibbets_Flat_A Total
0.56
0.25
0.20
McCain_Valley_A
0.47
0.29
0.24
Morena_Village
0.46
0.22
0.32
Mesa_Grande_Indian_Reserv
0.33
0.21
0.45
Valley_Center
0.29
0.30
0.41
Pala_Indian_Reservation
0.28
0.23
0.50
Alpine
0.21
0.28
0.51
Chihuahua_Valley
0.15
0.19
0.65
Oak tree declines in northern and southern parts of San Diego County
Southern
Northern
Red circles = declining Green circles = healthy
