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Fire regimes of California pinyon-juniper communities: Information from the Pacific Southwest Research Station and LANDFIRE

Citation:
U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2018. Fire regimes of California pinyon-juniper communities: Information from the Pacific Southwest Research Station and LANDFIRE. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: www.fs.usda.gov/database/feis/fire_regimes/CA_pinyon-juniper/all.html [].

• PACIFIC SOUTHWEST RESEARCH STATION
• LANDFIRE MODELING

The Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture, provides a literature review of the historical range of variability for California pinyon-juniper communities. The review includes information on climate; succession; nonnative plant species invasion; dispersal and establishment of pinyons and junipers; and disturbances (fire, insects and disease, and grazing) (USDA 2016 [9]).

Figure 1—A California juniper community in Riverside County. Image by Charles Webber, © California Academy of Sciences. Used with permission.

Historically, persistent pinyon-juniper woodlands of California had both crown fires, mixed fires, and moderate- to high-severity surface fires. Limited information suggests that low-severity fires were uncommon in the woodlands. Fire histories are lacking for pinyon-juniper savannas, so their historical fire regimes are poorly understood [2,9] listed nine relevant studies, although few occurred in California:

Northern area (western juniper, persistent woodlands):

• Estimated fire interval >250 years for Lava Beds National Monument, California (2 fires sampled, fire interval estimated from tree ages) [8].
• Mean fire interval of 30 years (time frame: 1650-1860) for woodlands on the Owyhee Plateau of southwestern Idaho ([3]). Fire scars on old-growth western junipers growing in small patches on rocky outcrops were sampled. It was not clear if the fire scars reflected a low-severity surface fire regime in the persistent woodland or the fire regime of the adjacent mountain big sagebrush community [8].
• The mean fire interval of 30 years from Burkhart and Tisdale [3] for persistent woodlands of southern Idaho may actually reflect increased fire frequency in adjacent mountain big sagebrush and low sagebrush shrublands that are now wooded western juniper woodlands (due to western juniper expansion) [4].

Southern area (singleleaf pinyon and Utah juniper, persistent woodlands):

• The fire cycle for a singleleaf pinyon-Utah juniper woodland in central Nevada was 427 years. There was large temporal variation throughout the record, with fire cycle ranging from 187-508 years (time frame: 1300-2004). Fire cycle averaged 187 years from 1300-1570 [2]. The 187-year cycle may be most applicable to current natural variation because current climate is similar; however, that cycle also had the greatest uncertainty because of the high mortality rate of the old-growth singleleaf pinyons [5].
• In the Sweetwater Mountains and Bodie Hills on the California-Nevada border, old-growth singleleaf pinyons (300-400 years old) on fire-resistant sites had one fire scar each, suggesting an open, scattered stand structure and showing evidence of at least one fire [5].
• In central Nevada, there were small, infrequent stand-replacement fires in Wyoming big sagebrush and mountain big sagebrush communities adjacent to persistent woodlands (time frame: 1445-2006). Estimated fire cycle was 427 years [2].

Distribution of pinyon-juniper communities changes with long-term climatic trends: they tend to shift upward in elevation and north in latitude during warm periods. Pinyon-juniper communities expanded during extended periods of high precipitation and in southern California, with pinyons replacing junipers on many sites (during the Neoglacial Period 3,500-2,600 years BP and the Little Ice Age 650-100 years BP). During extended drought following the Neoglacial Period, stands tended to become more open. Fires were more frequent and therefore, pinyon-juniper communities less extensive [9].

The influence of climate on pinyon-juniper fire regimes is not well studied. In northern California, probability of fire in pinyon-juniper communities was historically most likely when drought followed a year of above-average precipitation. Because pinyon-juniper communities in northern California historically contained a large component of perennial grasses, fine fuel continuity was likely enhanced in wet years. A study in southern California study found that historically, probability of fire in pinyon-juniper communities was high during drought, regardless of last year's precipitation [9].

Current fire regimes in persistent pinyon-juniper woodlands without nonnative herbaceous fuels in the ground layer may be similar to historical fire regimes. However, fires are becoming more frequent in areas with nonnative, invasive herbaceous fuels. Common invasive herbs include cheatgrass, red brome, and tall tumblemustard, with red brome replacing cheatgrass in the Mojave Desert. Invasives change the fire regime by increasing continuity of fine fuels, resulting in more frequent, and possibly larger, fires [9].

In sagebrush communities experiencing juniper expansion (nonpersistent juniper woodlands), fires are less frequent in contemporary times compared to presettlement times (before 1860). This has been attributed to a combination of fire exclusion, climate change, and grazing. Fire sizes have increased, and modeling predicts even further increases in fire sizes [9].

• western juniper communities on the Modoc Plateau and in the northwestern Great Basin, see the FEIS synthesis Fire Regimes of juniper communities in the Columbia and Great basins;
• mountain big sagebrush communities (and conifer expansion) throughout the West, see the FEIS synthesis Fire regimes of mountain big sagebrush communities.

LANDFIRE provides succession modeling of pinyon-juniper Biophysical Settings (BpS) of California. Table 1 summarizes LANDFIRE data on pinyon-juniper BpSs in California; figure 2 shows where they occur. Table A2 lists the BpSs and the results of LANDFIRE's modeling for pinyon-juniper BpSs in California.

Figure 2—Land cover distribution of California pinyon-juniper communities based on the LANDFIRE Biophysical Settings (BpS) data layer [10]. Click on the map for a larger image and zoom in to see details.

References:

1. Barrett, S.; Havlina, D.; Jones, J.; Hann, W.; Frame, C.; Hamilton, D.; Schon, K.; Demeo, T.; Hutter, L.; Menakis, J. 2010. Interagency fire regime condition class guidebook (FRCC), [Online], (Version 3.0). In: Interagency fire regime condition class website. U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; The Nature Conservancy (Producers). Available: https://www.frames.gov/files/7313/8388/1679/FRCC_Guidebook_2010_final.pdf [2017, March 1]. [85876]

2. Bauer, John M.; Weisberg, Peter J. 2009. Fire history of a central Nevada pinyon-juniper woodland. Canadian Journal of Forest Research. 39(8): 1589-1599. [83029]

3. Burkhardt, Wayne J.; Tisdale, E. W. 1976. Causes of juniper invasion in southwestern Idaho. Ecology. 57(3): 472-484. [565]

4. Gruell, George E. 1999. Historical and modern roles of fire in pinyon-juniper. In: Monsen, Stephen B.; Stevens, Richard, comps. Proceedings: Ecology and management of pinyon-juniper communities within the Interior West: Sustaining and restoring a diverse ecosystem; 1997 September 15-18; Provo, UT. Proceedings RMRS-P-9. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 24-28. [30486]

5. Gruell, George E.; Eddleman, Lee E.; Jaindl, Ray. 1994. Fire history of the pinyon-juniper woodlands of Great Basin National Park. NPS/PNROSU/NRTR-94/01. Seattle, WA: U.S. Department of the Interior, National Park Service, Pacific Northwest Region. 27 p. [40166]

6. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1). Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior. 72 p. On file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. [66741]

7. LANDFIRE. 2008. CONUS refresh (LANDFIRE 1.1.0). Biophysical settings layer, LANDFIRE data distribution site, [Online]. In: LANDFIRE. U.S. Department of the Interior, Geological Survey (Producer). Available: https://landfire.cr.usgs.gov/viewer/ [2017, January 10]. [89416]

8. Miller, Richard F.; Heyerdahl, Emily K. 2008. Fine-scale variation of historical fire regimes in sagebrush-steppe and juniper woodland: An example from California, USA. International Journal of Wildland Fire. 17: 245-254. [70528]

9. USDA. 2016. Pinyon-juniper natural range of variation, [Online]. In: Pacific Region, Ecology program documents, reports and publications, Natural range of variation of Sierra Nevada habitats. Vallejo, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Region (Producer). Available: https://www.fs.usda.gov/detail/r5/plants-animals/?cid=stelprdb5434436 [2016, November 4]. 31 p. [+ tables & figures]. [91157]

10. LANDFIRE. 2020. Biophysical settings layer, CONUS (LANDFIRE 2.2.0). In: LANDFIRE download data mosaic products, [Online]. U.S. Department of the Interior, Geological Survey; U.S. Department of Agriculture (Producer). Available: https://www.landfire.gov/version_download.php [2023, June 20]. [98050]

11. 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: http://www.landfirereview.org/search.php [2022, February 2]. [96496]