Biogeography of San Diego County Oak Mortality

Biogeography of San Diego County Oak Mortality Tom Scott UC INTEGRATED HARDWOOD RANGE MANAGEMENT PROGRAM and Department of Environmental Science, Poli...

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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