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Forest tree species restoration – where and why. The importance of integrating ecological and genetic approaches in forest ecosystem science

Patricia Maloney1, Detlev Vogler2, Camille Jensen1, Annette Delfino Mix2, Andrew Eckert3, David Neale4

1University of California – Davis, Department of Plant Pathology & Tahoe

Environmental Research Center

2USDA Forest Service, PSW Research Station, Institute of Forest Genetics 3Department of Biology, Virginia Commonwealth University 4Department of Plant Sciences, University of California – Davis

Forest restoration versus Species restoration

• Prescription burning,

thinning

• Structural shifts (mixed

size structure)

• Compositional shifts
• Restore population numbers –

facilitate recruitment

• Enhance genetic diversity
• Deploy disease resistance (if

warranted)

• Deploy drought tolerant

phenotypes

Sugar pine restoration

• Extensive logging and fire suppression policies have changed the

structure & composition in lower montane forests (Lindstrom et al. 2000;

Manley et al.2000).

• Historical composition: 20–25%, in some locations (Lindstrom et al.

2000).

• Present–day composition: 1–6% (Barbour et al. 2002; Lindstrom et al. 2000).
• Population & genetic consequences: Effects on population structure

and dynamics, but also genetic structure and diversity. Population and genetic losses.

• Non-native pathogen introduction: Cronartium ribicola, cause of

white pine blister rust (WPBR)

• Such losses could affect sugar pine’s resilience to disturbances and

environmental change (e.g., WPBR, MPB, climate).

Sugar pine restoration – Where?

• Sugar Pine Point State Park
• Tunnel Creek – Sand Harbor
• Granlibakken – 3rd candidate

site

Sugar pine restoration – Why?

• Reduced population sizes
• Low lambda () – low

survival of small– and intermediate–sized individuals

• Low recruitment
• High levels of WPBR
• Low frequency of Cr1

Tunnel Creek

5 10 15 20 25 30 35 40 45 50 0.1-5.0 5.1-10.0 10.1-20.0 20.1-40.0 ³40.1 Diameter size class (cm dbh) Bliss State Park 5 10 15 20 25 30 35 40 45 50 0.1-5.0 5.1-10.0 10.1-20.0 20.1-40.0 ³40.1 Diameter size class (cm dbh)

Sugar Pine State Park

5 10 15 20 25 30 35 40 45 50 0.1-5.0 5.1-10.0 10.1-20.0 20.1-40.0 ³40.1 Diameter size class (cm dbh)

= 0.993 Density = 14 inds. ha-1 Recruitment = 128 (inds. ha-1) WPBR = 41% (Cr1 = 0.12)

Granlibakken

5 10 15 20 25 30 35 40 45 50 0.1-5.0 5.1-10.0 10.1-20.0 20.1-40.0 ³40.1 Diameter size class (cm dbh)

= 1.048 Density = 95 inds. ha-1 Recruitment = 262 (inds. ha-1) WPBR = 5% (Cr1 = 0.07) = 0.997 Density = 37 inds. ha-1 (inds. ha-1) Recruitment = 25 WPBR = 48% (Cr1 = 0.00) = 0.994 Density = 16 inds. ha-1 Recruitment = 10 (inds. ha-1) WPBR = 11% (Cr1 = 0.00)

Sugar pine restoration, cont.

Consequences of historical logging

• High genetic drift in some

populations

• Effects of genetic drift are greater

in small populations

• In small populations drift can act

faster to reduce genetic variation

Sugar pine restoration strategies

Tunnel Creek/Sand Harbor

• Facilitate recruitment
• Increase sugar pine

numbers – population size

• Enhance genetic diversity

Sugar Pine Point SP

• Increase population size
• Deploy WPBR resistance

(≤ 0.20)

• Enhance genetic diversity

Western white pine restoration – Where?

• Blackwood Canyon

Western white pine restoration – Why?

• Highest disease pressure by WPBR in

upper montane forests – 44%

• Moderate levels of MPB – 15%
• Relatively low mean survivorship

across diameter classes (0.833), with the lowest for trees 5.1–10.0 cm dbh (0.700)

• Most mesic upper montane location in

study – Average annual ppt = 1472 mm 1.Mesic adapted?

• 2. Favorable conditions for WPBR

infection

Western white pine restoration, cont.

0.800 0.820 0.840 0.860 0.880 0.900 0.920 0.940 0.960 0.980 1.000 10 20 30 40 50 Incidence of WPBR (%) 0.800 0.820 0.840 0.860 0.880 0.900 0.920 0.940 0.960 0.980 1.000 5 10 15 20 25 30 Incidence of Mountain Pine Beetle (%)

Western White Pine Size Structure at Blackwood Canyon 20 40 60 80 100 120 140 160 180 seedlings 0.1-5.0 5.1-10.0 10.1-20.0 20.1-40.0 ³40.1 Size class WPBR = 44%

WPBR is known to be a predisposing agent to MPB attack

Western white pine restoration strategies at Blackwood Canyon

• A diversity of seedling material will be planted as well as WPBR –

resistant genotypes – to increase small tree survival (Cr2 is found in WWP

at 2 locations in the Lake Tahoe Basin – Armstrong Pass and Meiss Meadow).

• Given the local environmental conditions at Blackwood Canyon the

tree species here may be more mesic-adapted and less drought tolerant than species growing in more xeric conditions (i.e., east side locations, granitic soil types).

• Next year common garden studies will be completed for WWP and

drought tolerant families & populations will be identified. Out–planted seedlings will include drought tolerant phenotypes.

Whitebark pine restoration – Where?

• Rifle Peak area – Ridge from

Mt Baldy, Rifle Peak to east of Rose Knob Peak

Whitebark pine restoration – Why?

• Very high disease pressure

by WPBR – 65%

• Most critical effect of WPBR

is infection and mortality of cone-bearing branches.

• Low cone production and

recruitment

Photo: Cheryl Beyer

Whitebark pine restoration, cont.

• Negative relationships between cone production and

WPBR incidence and severity.

• Percent of individuals infected (incidence), average

number of infected branches per population, and severity

• f stem girdling are all negatively related with cone

production.

• Whitebark pine at Rifle Peak has the lowest female cone

numbers [960 cones ha-1 (mean across sites = 2,456)], lowest recruitment numbers [44 seedlings/saplings ha-1 (mean across sites = 139)], and the highest incidence of WPBR (65%) of all whitebark pine populations surveyed in the Lake Tahoe Basin.

• A threshold number of ≥ 1,000 cones ha-1 has been

estimated to maintain seed dispersal within a forest stand by Clark’s nutcracker (McKinney et al., 2009). Whitebark pine cone production at Rifle Peak falls below this threshold.

1000 2000 3000 4000 5000 10 20 30 40 50 60 70 WPBR incidence (%) 1000 2000 3000 4000 5000 1 2 3 4 5 6 Average number of branch cankers per tree

1000 2000 3000 4000 5000 0.00 0.25 0.50 0.75 1.00 1.25 1.50 Average stem girdle category population-

R2 = 0.78, P = 0.003 R2 = 0.72, P = 0.008 R2 = 0.76, P = 0.005

Whitebark pine restoration strategies

• Facilitate whitebark pine recruitment to maintain adequate species

numbers

• Deploy WPBR resistant and/or tolerant phenotypes
• Diverse seedling material

Photo: Martin Frye

Testing white pine restoration protocols

• Will use 2-year old seedlings
• Planting season (spring vs fall)
• Microhabitat (closed canopy,
• pen canopy, log/litter debris,

rock shelter)

• Protective enclosures (above

and belowground herbivore pressure)

Acknowledgements

• Tom Burt, Martin Frye
• CA State Parks: Tamara Sasaki, Rich

Adams

• LTBMU: David Fournier, Cheryl Beyer,

Joey Keeley

• NDF & NV State Parks: Roland Shaw, Bill

Champion

• Funding sources:
• Southern Nevada Public Lands Management

Act – Sponsored by the USDA FS Pacific Southwest Research Station

• NVDSL Lake Tahoe License Plate Program