PLS 147 Lecture 17: Lower Montane Forests, Ponderosa Pine and Mixed Conifer
Iconic example: Yosemite National Park (parts of it)
Geographic distribution
●Sierra Nevada, Southern Cascades, northern Coast range, Transverse range
Elevation range:
North: 700-2000 m, wide band
South: 1600 to 2600 m, narrow band
Climate
●elevation range based on climate
●lower limit: too dry
●upper limit: too cold
●snow: 500-5000mm (25-40% total water inputs)
●summer highs 93, winter lows 22 F
●annual precipitation 600-2000mm
Mixed conifer (white fir) and Ponderosa pine forest/woodland
Sierra Transect
Foothills: merging from chaparral or oak woodland
into lower montane (above, wetter) - trees and shrubs
●patchy forests: sunlight and shade
●multi-layer understory and tall overstory
●conifer-dominated overstory (mixed ages)
●flammable litter layer on the ground
●fire char
●tall trees (mostly secondary growth - logging)
●partial to complete canopy
●understory tree layer (st)
●shrub layer (st)
●low herbaceous cover bc fire
●woody fuels and litter layer
Lower montane species
●white fir, douglas fir, black oak, incense cedar, sugar pine, ponderosa pine
●colder and wetter: alpine
●dryer and warmer: woodland
Ponderosa pine woodland
●pinus ponderosa
Mixed conifer forest
●multiple co-dominants
●drier
●tall two-layer woodland
●frequent surface fires
●moister
●tall two-to four-layer forest
●relatively less frequent surface and
crown fires
PINUS PONDEROSA
●three-needle pine
●>200 years old
●up to 50m tall
●sparse woodland to open forest (like the sun)
○shade intolerant seedlings
●300-2000 m (1000-6000ft) in horth, higher in south
●historically frequent fires, open stand structure
other common canopy species
●sugar pine (pinus lambertiana)
○5 needle pine with BIG cones, droopy tree
○800-2300m
○less drought and less fire tolerant
○shade intolerant seedlings
○vulnerable to white pine blister rust
○still widespread and long-lived
■species of concern though
●incense cedar (calocedrus decurrens)
○700-2300m
○stripey bark
○strictly a component of mixed-conifer forest
○moister
○tolerant of air pollution and pest/pathogen
○shade tolerant species
■fire suppression allows it to dominate
●white fir (abies concolor)
○true fir (unlike douglas)
○1000-2700m
○shade tolerant
○historically minor component, increasing now
●Douglas fir (pseudotsuga menziesii)
○mesic forests, northern lower montane
Document Summary
Iconic example: yosemite national park (parts of it) Sierra nevada, southern cascades, northern coast range, transverse range. Summer highs 93, winter lows 22 f. Mixed conifer (white fir) and ponderosa pine forest/woodland. Foothills: merging from chaparral or oak woodland into lower montane (above, wetter) - trees and shrubs. Tall trees (mostly secondary growth - logging) White fir, douglas fir, black oak, incense cedar, sugar pine, ponderosa pine. Relatively less frequent surface and crown fires. Sparse woodland to open forest (like the sun) 300-2000 m (1000-6000ft) in horth, higher in south. Historically frequent fires, open stand structure other common canopy species. 5 needle pine with big cones, droopy tree. Can be its own type farther north and along coast. Increase in small diameter trees, stand density. Ponderosas looking more like mixed conifer, but even more dense. Issue bc other stressors (increased density, drought) Weakened trees much more susceptible, proximity of trees allows beetles to spread.
