(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 hughsafford@fs.fed.us 707-562-8934

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

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

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

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

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)

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.

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…)?

The postfire environment for tree seedlings Data from 14 large wildfires, 1999-2007

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 2009-2010.

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)

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

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

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