Species Brief
Pinus strobiformis, southwestern white pine
Written
July, 2026
Contributors
Ilana L. Abrahamson - 1st Compiler, Leila Duchac - 1st Editor
Abrahamson, Ilana L., compiler. 2026. Species Brief: Pinus strobiformis, southwestern white pine. In: Fire Effects Information System, Online. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-briefs/pinsto
DOI
10.2737/feis-species-brief-pinsto
Scientific Name
Pinus strobiformis
Common Names
southwestern white pine
Arizona white pine
Mexican white pine
border white pine
border limber pine
FEIS Lifeform Type
Tree
Kingdom
Plantae
Class
Pinopsida (Conifer)
Order
Pinales
Family
Pinaceae
Genus
Pinus
Nativity
Native
Invasiveness
Noninvasive
This Species Brief is a concise summary of the biological, ecological, and fire‑related characteristics of an individual species derived from a Fire Effects Information System (FEIS) Species Review. Table 1 is derived from a standardized template and highlights these characteristics.
| Attribute | Characteristic | Justification | Source |
|---|---|---|---|
| Biological characteristics | |||
| Life form | Tree | Southwestern white pine is a native, five-needle conifer. Mature trees have heights ranging from 15 to 30 m and trunk diameters from 0.5 to 1.0 m. | FEIS: Botanical Description [3] |
| Typical lifespan | 200+ years* | Information about the typical lifespan of southwestern white pine is lacking, but one study reported a maximum age of 295 years in mixed-conifer stands throughout Arizona and portions of New Mexico. | FEIS: [3]; Looney and Waring [2] |
| Life cycle | Perennial | Southwestern white pine is a native, five-needle conifer. | FEIS: Botanical Description [3] |
| Drought tolerance | Moderate | Southwestern white pine is moderately drought tolerant, although likely less tolerant than limber pine. It has genetic traits that confer drought tolerance and has the flexibility to adapt to hot and dry environments, enhancing its water use efficiency and chances of survival. | FEIS: Other Management Considerations; Site Characteristics [3] |
| Rooting depth | Deep* | Information about mature tree roots is lacking. However, seedlings develop a large taproot. | FEIS: Seedling Establishment and Mortality [3] |
| Bark thickness at maturity | Thick | Mature trees have deeply furrowed bark, enabling them to survive low-severity surface fire. When trees are young, the bark is gray and smooth to shallowly fissured. | FEIS: Fire Adaptations; Botanical Description; Immediate Fire Effects [3] |
| Sheds low branches | Sometimes*, Often | Lower branches are horizontal to hanging, but lowest branches may get higher over time as a fire-resistance trait [1]. Over 65 stands, mean height of lowest live branches was 4.3 m [2]. | FEIS: Botanical Description; Plant Response to Fire [3]; Leal-Saenz et al. [1] |
| Reproduction and Regeneration | |||
| Adventitious buds | None | Southwestern white pine does not reproduce or regenerate vegetatively. | FEIS: Vegetative Reproduction and Regeneration [3] |
| Time to reproductive maturity | 11-20 years | Southwestern white pine begins producing seed cones at about 15 years old. | FEIS: Seed Production and Predation [3] |
| Soil seed bank longevity | Transient (<1 year) | Evidence of soil seed banking was not found, nor is it likely to occur given its large seed size and relatively low seed production. Seeds shed in autumn germinate in spring or summer after rain. | FEIS: Seed Banking; Seasonal Development [3] |
| Serotinous cones | No | Cones have thick, reflexed scales that open when mature to release seeds. | FEIS: Botanical Description; Fire Adaptations [3] |
| Seed dispersal mechanism | Animal; Wind; Gravity | Seeds are dispersed by birds, rodents, and wind. | FEIS: Seed Dispersal [3] |
| Seed dispersal distance | Short (mostly under parent plant); Medium*; Long (>1 km)* | Seeds, being large and mostly wingless, do not typically disperse far by wind or gravity. In the northern populations, Clark's nutcracker caches seeds over considerable distances (>20 km), but nutcrackers are absent from much of the southern range. | FEIS: Seed Dispersal [3] |
| Optimal conditions for seedling establishment | Litter and/or duff; Shade | Shaded duff and litter layers significantly enhance seedling survival and growth, and regeneration is negatively associated with bare mineral soil. | FEIS: Seedling Establishment and Mortality [3] |
| Successional Status | |||
| Shade tolerance | Moderately shade tolerant | Southwestern white pine is intermediate in shade tolerance. It is more shade-tolerant than associated pines but less so than firs and spruces. Seedlings have greater growth and survival in shaded environments than associated pine species. Seedlings generally grow slowly, but grow faster and larger with more light, and slower in heavily shaded conditions. | FEIS: Successional Status; Plant Growth and Mortality; Seedling Establishment and Mortality [3] |
| Successional status | Mid; Late* | Depending on its associates, southwestern white pine can occupy lower strata, the mid-canopy, or dominate the overstory. When it is a canopy dominant in mixed stands, it is likely to be replaced by more shade-tolerant competitors. | FEIS: Successional Status; Stand Structure; Plant Response to Fire [3] |
| Fire | |||
| Primary fire response(s) or adaptation(s) | Resist | Mature trees with deeply furrowed bark survive low-severity surface fire. Regeneration dynamics, response to disturbance, and optimal conditions for seedling establishment and recruitment are not well understood for southwestern white pine. Postfire establishment varies by ecosystem type and fire severity. | FEIS: Fire Adaptations; Plant Response to Fire [3] |
| Germination is fire stimulated | Rarely/No | Seeds germinate in spring or summer after rain and require 2 weeks to 4 months stratification; no fire cue for germination is described. | FEIS: Seasonal Development; Germination [3] |
| Flowering/fruiting is fire stimulated | Rarely/No | Southwestern white pine flowers in June and produces seed crops every 3 to 4 years, with fewer seeds in drought years; no fire-stimulated seed production is described. | FEIS: Seasonal Development; Seed Production and Predation [3] |
| Season when it is most sensitive to fire | Insufficient information | The source does not provide explicit information about seasonal differences in fire sensitivity. In communities where southwestern white pine is most common, fires primarily occurred in the spring (as indicated by earlywood fire scars), suggesting that mature trees survive spring fires under historical conditions. | FEIS: Fire Regimes [3] |
| Plant flammability | Insufficient information | The source does not provide explicit information about plant flammability. | FEIS [3] |
| Early colonizer/recolonizer of burned or disturbed sites | Rarely/No* | Southwestern white pine is a secondary colonizer from off-site seed. Establishment may increase with the time between historical fires. Its large, mostly wingless seeds do not disperse far by gravity or wind, so where Clark's nutcrackers are absent, colonization into large burns is limited. | FEIS: Postfire Regeneration Strategy; Plant Response to Fire [3] |
| Effect of fire exclusion on population | Possible decrease* | With fire exclusion, southwestern white pine populations could decrease in areas where it is replaced by more shade-tolerant competitors such as Douglas-fir and white fir. However, southwestern white pine is moderately shade tolerant, so it may continue to persist with fire exclusion. | FEIS: Stand Structure [3] |
| Is this species typically managed with prescribed fire? | Rarely/No | Published literature on the use of prescribed burning in southwestern white pine stands was not found. | FEIS: Fire Management Considerations [3] |
| Predominant historical fire frequencies of ecosystem where it most commonly occurs | Frequent | Fires were historically frequent (<20-year intervals) in communities where southwestern white pine is most common, with estimated mean fire intervals from 3 to 35 years in AZ, NM, and TX. Intervals are longer on mesic higher elevation sites. | FEIS: Fire Regimes [3] |
| Predominant historical fire severity where it most commonly occurs | Low; Mixed | Fires were historically mostly low-severity with some component of mixed-severity fires and/or patches of high-severity within larger fires. | FEIS: Fire Regimes [3] |
| Predominant historical fire regime group where it most commonly occurs | 1 | The communities where southwestern white pine is most common historically had frequent fires that were mostly low-severity with some mixed-severity component, consistent with fire regime group 1. | FEIS: Fire Regimes [3] |
| Alters historical fuel characteristics of ecosystems where it occurs | Rarely/No | Altered fuels where southwestern white pine occurs are attributed to grazing and fire exclusion over more than 100 years, not to southwestern white pine. | FEIS: Fuel Characteristics [3] |
| Biophysical Setting | Mean Fire Interval (years) | Fire Severity Percent (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| Code | Fire Regime Group | Low | Mixed | Replacement | All | Low | Mixed | Replacement |
| Series 10240 - Madrean Lower Montane Pine-Oak Forest and Woodland | ||||||||
| 10240_25_27 | I-B | 11 | 30 | 60 | 7 | 65 | 23 | 12 |
| 10240_26 | I-A | 10 | 24 | 16 | 5 | 50 | 20 | 30 |
| Series 10520 - Southern Rocky Mountain Mesic Montane Mixed Conifer Forest and Woodland | ||||||||
| 10520_27 | III-A | 77 | 98 | 253 | 37 | 48 | 37 | 15 |
| 10520_28 | III-A | 153 | 144 | 202 | 54 | 35 | 38 | 27 |
| Series 10540 - Southern Rocky Mountain Ponderosa Pine Woodland | ||||||||
| 10540_26 | I-B | 11 | 105 | 76 | 9 | 79 | 9 | 12 |
| Series 10610 - Inter-Mountain Basins Aspen-Mixed Conifer Forest and Woodland | ||||||||
| 10610_15_25 | I-B | 110 | 20 | 43 | 12 | 11 | 61 | 28 |
| Series 10510 - Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest and Woodland | ||||||||
| 10510_28 | I-C | 32 | 54 | 325 | 19 | 59 | 35 | 6 |
| Summary | ||||||||
| Minimum | 10 | 20 | 16 | 5 | 11 | 9 | 6 | |
| Maximum | 153 | 144 | 325 | 54 | 79 | 61 | 30 | |
| Mean | 58 | 68 | 139 | 20 | 50 | 32 | 19 | |
| Median | 32 | 54 | 76 | 12 | 50 | 35 | 15 | |
| Percentage of fires in 3 fire severity classes, derived from LANDFIRE succession modeling. Replacement-severity fires cause >75% kill or top-kill of the upper canopy layer; mixed-severity fires cause 26%-75%; low-severity fires cause <26%. | ||||||||
| LANDFIRE. 2020. Biophysical settings models and descriptions, [Online]. Washington, DC: U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; U.S. Geological Survey; Arlington, VA: The Nature Conservancy, (Producers). Available: https://www.landfirereview.org/search.php [96496] | ||||||||
1. Leal-Saenz, Alejandro; Waring, Kristen; Menon, Mitra; Cushman, Samuel; Eckert, Andrew; Flores-Renteria, Lluvia; Hernandez-Diaz, Jose; Lopez-Sanchez, Carlos; Martinez-Guerrero, Jose; Wehenkel, Christian. 2020. Morphological differences in Pinus strobiformis across latitudinal and elevational gradients. Frontiers in Plant Science. 11: 559697. [100083]
2. Looney, Christopher E.; Waring, Kristen M. 2012. Patterns of forest structure, competition and regeneration in southwestern white pine (Pinus strobiformis) forests. Forest Ecology and Management. 286: 159-170. [86898]
3. McKinney, Shawn T. 2025. Pinus strobiformis, southwestern white pine. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/pinsto
Last updated August 20, 2026