1. (Part 3)
Climate change, forests and fire in the Sierra Nevada, California: implications for current and future resource management
Hugh Safford
Regional Ecologist
USDA Forest Service
Pacific Southwest Region
1323 Club Drive
Vallejo, CA 94592
Department of Environmental Science
and Policy
University of California
Davis, CA 95616

2. V E G E T A T I O N Sierra Nevada Ecoregion
Same ppt.
& warmer
Much drier
& much
warmer
Slightly drier
& warmer
V E G E T A T I O N
Lenihan et al. 2008
Future projections: Increase in hardwood types, loss in conifer forest; increase in grassland; major loss of subalpine forest

3. Projected changes in vegetation are already underway
1934
2000
Grassland
Blue oak
Loss of yellow pine dominated forest (logging X fire suppression X climate)
(2) Increase in hardwood density and forest cover (climate X disturbance)
(3) Loss of subalpine forest (climate)
plus
(4) Loss of blue oak woodland (urban & ag expansion)
Hardwoods
Ponderosa
Fir/Mixed conifer
Red fir/Lodgepole
Subalpine
Jeffrey
Thorne 2008

4. Forestland to shrubland and grassland
Interactions among fire, insects, disease, drought, pollution, and other stressors are provoking vegetation changes across California
Forestland to shrubland and grassland
Jeffrey pine killed by fire near San Diego, 6 yrs post-fire with no regeneration: fire X temperature X drought X pine beetles
Loss of piñon pine near Topaz Lake, western Great Basin: invasive species X fire X pine beetles

5. Forestland to shrubland Shrubland to grassland
Repeated wildfire reducing forest to shrubland: fire X temperature X drought
Frequent anthropogenic fire reducing coastal sage scrub to grassland: fire X exotic species X drought

6. Calocedrus decurrens (incense cedar)
Ponderosa
Jeffrey
White fir
Sensitivity to air pollution (N and ozone)
Susceptibility to insect/disease
Sugar
Sensitivity to increased temperatures
Sensitivity to water stress
Sensitivity to fire (adult)
Ponder.
California forests are under major ecological stress: California forest conifer trees
Who wins?
Pollution
Fire
Insects/disease
H2O stress
Temps
White fir and ponderosa pine are the current dominants
Pinus ponderosa, P. Jeffreyi, P. lambertiana (sugar pine), Abies concolor (white fir),
Calocedrus decurrens (incense cedar)

7. Mean distance to nearest living seed tree, Angora Fire
Trends in high severity patch size
R2 = 0.325, P = 0.011
Sierra Nevada: mean high severity patch size
In conifer vegetation, the size of high severity patches in Sierra Nevada fires has increased over the last two decades
Mean patch radius = 130 m
Mean distance to nearest living seed tree, Angora Fire
Miller and Safford 2008
These patterns have important implications for forest fragmentation, postfire regeneration, vegetation succession, soil erosion, etc.
Safford et al., in prep.

8. Postfire regeneration data from recent wildfires
8750
7500
6250
5000
3750
2500
1250
Welch, Safford & Young , in prep. 60 54 48 42 36 30 24 18 12 6
Some evidence of low yellow pine seedling success at lower elevations: interactions between fire and climate (and…)?

9. The postfire environment for tree seedlings
Data from 14 large wildfires,

10. Pendola Fire 1999, sampled in 2009-2010.
Higher fire severity leads to stronger regeneration of hardwood resprouts and shrubs
Light competition and for water resources, so it would be interesting to see through time.
Pendola Fire 1999, sampled in

11. Increasing shrub cover is negatively related to conifer seedling density
P <0.001
V E G E T A T I O N
Redo this graphic for all fires
Plus: Statistically stronger effect of shrub cover on shade intolerant spp (Pinus) than shade tolerant species (Abies)

12. Pine forest to fir forest
Fire suppression: in much of the Sierra Nevada, lack of fire is just as serious an ecosystem disturbance as uncharacteristically severe fire
Pine forest to fir forest
Meadow to forestland
Loss of large pine dominance in many montane forests: lack of fire X water stress
Meadows being invaded by conifers: lack of fire X decreasing snowpack X grazing

13. Fire severity comparison, Baja California ref conds vs Sierra Nevada, 1984-2010
Data from Safford & Rivera, in prep.
Sierra Nevada data from Miller et al. 2009, Miller and Safford 2012; YP = average of eastside pine and ponderosa

14. V E G E T A T I O N Vegetation summary
Fire will interact with climate and other factors to provoke major changes in vegetation; projected changes are already occurring
As high severity area and patch size increase, and as summer droughts deepen, regeneration of some conifer species will become progressively more difficult
Given sufficient precip., hardwood species will replace many lower elevation conifer forests after disturbance
Many areas of persistent shrubland that succeeded to conifers under fire suppression may return to shrubs
Major expansion of grassland is projected for much of California due to frequent fires in forests and shrublands
Densification of subalpine forests and expansion of subalpine trees into previously “permanent” snowfields may increase continuity of subalpine fuels
V E G E T A T I O N