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A3673 Pinus ponderosa - Calocedrus decurrens - Pseudotsuga menziesii Forest Alliance

Type Concept Sentence: This forest alliance is codominated by Pseudotsuga menziesii, Pinus ponderosa, and Calocedrus decurrens. A variety of other conifers usually co-occur, including Pinus lambertiana, Pinus jeffreyi, and/or Pinus attenuata. This alliance occurs along the western slope of the southern Oregon Cascades and throughout the Klamath Mountains in Oregon and California, south into the California Coast Ranges. It occurs at low to middle elevations (600-1200 m) with high winter rainfall (75-250 cm), warm to hot, dry summers, and extremely variable geology.


Common (Translated Scientific) Name: Ponderosa Pine - Incense-cedar - Douglas-fir Forest Alliance

Colloquial Name: Ponderosa Pine - Incense-cedar - Douglas-fir Forest

Hierarchy Level:  Alliance

Type Concept: These forests are typically codominated by Pseudotsuga menziesii, Pinus ponderosa var. benthamiana, and Calocedrus decurrens. A variety of other conifers co-occur, including Pinus lambertiana, Pinus jeffreyi, and/or Pinus attenuata. A diverse broad-leaved deciduous or evergreen tree layer may be present and may include Quercus garryana, Arbutus menziesii, Notholithocarpus densiflorus, Umbellularia californica, Acer macrophyllum, and others. Quercus kelloggii and Quercus chrysolepis may also codominant in the Sierra Nevada. A shrub layer may or may not be present and is generally best developed in comparatively moist northern or high-elevation stands. Common species in such mesic stands include Acer circinatum, Mahonia nervosa, Gaultheria shallon, and Cornus nuttallii, which can occasionally be a small tree. In southern or lower elevation stands, drought-tolerant species such as Holodiscus discolor, Toxicodendron diversilobum, Symphoricarpos mollis, Ceanothus spp., and Arctostaphylos spp. become prevalent. The herbaceous understory can be similarly variable, depending upon site moisture, canopy closure, and location. This alliance occurs along the western slope of the southern Oregon Cascades and throughout the Klamath Mountains in Oregon and California. From the Klamath region, the range extends south into the California Coast Ranges as far as the Yolla-Bolly region, and in the Sierra Nevada as far south as Yosemite National Park. These communities are usually associated with sunny aspects and droughty or infertile soils of lower mountain slopes. They occur at low to middle elevations (600-1200 m) with high winter rainfall (75-250 cm), warm to hot, dry summers, and extremely variable geology.

Diagnostic Characteristics: Upper canopy mixed dominance by two of the three nominal species.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance includes Pinus ponderosa var. benthamiana; other races of Pinus ponderosa are in other USNVC groups. This alliance lacks Abies concolor in the upper canopy or, if present, has less than 10% relative cover, or may be present only in subcanopy regenerating layers.

Similar NVC Types: No Data Available
note: No Data Available

Physiognomy and Structure: Vegetation within this alliance is typified by a closed or nearly closed canopy of needle-leaved evergreen trees approaching 50 m in height. A subcanopy of broad-leaved cold-deciduous or evergreen trees is common. The shrub layer is often structurally diverse, sometimes with several strata of cold-deciduous and evergreen species. The herbaceous layer is variable, from sparse graminoid cover in xeric stands to dense forb, graminoid, and fern cover in moist habitats.

Floristics: These forests are typically codominated by Pseudotsuga menziesii, Pinus ponderosa var. benthamiana (= var. pacifica), and Calocedrus decurrens. A variety of other conifers co-occur, including Pinus lambertiana, Pinus jeffreyi, and Pinus attenuata. A diverse broad-leaved deciduous or evergreen tree layer may be present and may include Quercus garryana, Arbutus menziesii, Notholithocarpus densiflorus (= Lithocarpus densiflorus), Umbellularia californica, Acer macrophyllum, and others. Quercus kelloggii and Quercus chrysolepis are reported to share a codominance with these mixed conifers in Yosemite and other areas in the Sierra Nevada. A shrub layer may or may not be present and is generally best developed in comparatively moist northern or high-elevation stands. Common species in such mesic stands include Acer circinatum, Mahonia nervosa, Gaultheria shallon, and Cornus nuttallii, which can occasionally be a small tree. In southern or lower elevation stands, drought-tolerant species such as Holodiscus discolor, Toxicodendron diversilobum, Symphoricarpos mollis, Ceanothus spp., and Arctostaphylos spp. become prevalent. The herbaceous understory can be similarly variable, depending upon site moisture, canopy closure, and location.

Dynamics:  These communities are usually associated with seasonal drought and historically high fire frequencies when high frequency of late summer lightning storms, at a time of low fuel moisture, created short fire-return intervals (20-30 years). With fire suppression stands have become more closed and unnaturally dense. Many of these communities are believed to be seral to Abies concolor forests in the absence of fire or other disturbance.

Environmental Description:  The associations in this alliance occur in low to middle elevations (600-1200 m) with high winter rainfall (75-250 cm), warm to hot, dry summers, and extremely variable geology. These communities are usually associated with sunny aspects and droughty or infertile soils of lower mountain slopes.

Geographic Range: This alliance is found along the western slope of the southern Oregon Cascades, throughout the Klamath Mountains, south into the California Coast Ranges as far as the Yolla-Bolly region, and in the Sierra Nevada as far south as Yosemite National Park.

Nations: MX?,US

States/Provinces:  CA, MXBCN?, OR




Confidence Level: Moderate

Confidence Level Comments: No Data Available

Grank: GNR

Greasons: No Data Available

Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.2 Cool Temperate Forest & Woodland Formation F008 1.B.2
Division 1.B.2.Nd Vancouverian Forest & Woodland Division D192 1.B.2.Nd
Macrogroup 1.B.2.Nd.2 Incense-cedar - Jeffrey Pine - Sierra White Fir Forest Macrogroup M023 1.B.2.Nd.2
Group 1.B.2.Nd.2.a Incense-cedar - Sugar Pine - Sierra White Fir Forest & Woodland Group G344 1.B.2.Nd.2.a
Alliance A3673 Ponderosa Pine - Incense-cedar - Douglas-fir Forest Alliance A3673 1.B.2.Nd.2.a
Association CEGL000061 Ponderosa Pine / Greenleaf Manzanita - Sticky Whiteleaf Manzanita Forest CEGL000061 1.B.2.Nd.2.a
Association CEGL000065 Sugar Pine - Ponderosa Pine - Douglas-fir / California Fescue Forest CEGL000065 1.B.2.Nd.2.a
Association CEGL000066 Incense-cedar - Douglas-fir / Pinemat Manzanita Forest CEGL000066 1.B.2.Nd.2.a
Association CEGL000208 Ponderosa Pine / Douglas-fir / Pinemat Manzanita Woodland CEGL000208 1.B.2.Nd.2.a
Association CEGL000209 Ponderosa Pine - Douglas-fir / Greenleaf Manzanita Woodland CEGL000209 1.B.2.Nd.2.a
Association CEGL005813 Douglas-fir - Sierra White Fir - Incense-cedar Forest CEGL005813 1.B.2.Nd.2.a
Association CEGL005814 Douglas-fir - Canyon Live Oak Forest CEGL005814 1.B.2.Nd.2.a
Association CEGL008672 Ponderosa Pine - Incense-cedar / Mountain Misery Forest CEGL008672 1.B.2.Nd.2.a
Association CEGL008673 Ponderosa Pine - Incense-cedar - California Black Oak Forest CEGL008673 1.B.2.Nd.2.a
Association CEGL008674 Ponderosa Pine - Incense-cedar - Canyon Live Oak / Mountain Misery Forest CEGL008674 1.B.2.Nd.2.a
Association CEGL008684 Douglas-fir - Ponderosa Pine - Incense-cedar Forest CEGL008684 1.B.2.Nd.2.a

Concept Lineage: A.155, A.2559

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available

Synonomy: = Pinus ponderosa - Calocedrus decurrens (Mixed conifer forest) Alliance (Sawyer et al. 2009) [87.015.00]
= Pinus ponderosa - Calocedrus decurrens Forest Alliance (Keeler-Wolf et al. 2012)

Concept Author(s): G. Kittel, in Faber-Langendoen et al. (2013)

Author of Description: G. Kittel

Acknowledgements: We have incorporated significant descriptive information previously compiled by J. Evens.

Version Date: 12-18-14

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