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Land Use and Fire History in the Mountains of Southern California 1

Joe R. McBride and Diana F. Jacobs2

Fire frequencies are related to periods of land use in the mountains of Southern California. Differences in fire frequencies were found for coastal sage scrub, chaparral, and yellow pine forest types between various sets of the Native American, Spanish-Mexican, American Pioneer, and Modern American land use periods. Analysis of fire maps was em­ ployed in the scrub; ring counts were used between fire scars in the forest types.

The mountains of southern California have The vegetation varies along altitudinal gradients experienced recurring wild fire for a very long with the following sequence of types moving upon time. The flora exhibits a variety adaptations the seaward side: coastal sage scrub, chaparral, indicating an evolutionary history in which fire oak woodland, yellow pine forest, fir forest. On was a major selective force. Man has been prob­ the desert side the vegetation shows the influence ably present in southern California for at least of lower precipitation with a pinyon-juniper wood­ 11,000 years. His use of fire during this period land followed by a high desert scrub community has influenced the frequency of wild fires. occurring at lower elevations in place of the Knowledge of fire frequency and its relation to coastal sage scrub. land use history is prerequisite to understanding and properly managing vegetation. The objective Fire history investigations were conducted of this paper is to investigate the relationship in the coastal sage scrub, chaparral, and yellow between land use and the frequencies of wild fires pine forest types. These types were selected occurring in four major vegetation types in the because they present major problems of fire control mountains of southern California. and management.

The coastal sage scrub occurs from sea level The Setting to about 1000 m. The type is common on sites that are climatically or edaphically dry. Rainfall is The mountains of southern California occur in 40-80 ern annually. The dominants in this type are four landform provinces: the Transverse Ranges, Artemisia californica (coast sagebrush), Salvia Peninsular Ranges, Mojave Desert, and Colorado apiana (white sage), !· mellifera (black sage), Desert. Only mountains in the Transverse and !· leucophylla (purple sage), Eriogonum fascicu­ Peninsular Ranges support coniferous forests of latum (California buckwheat), Rhus integrifolia commercial value or dense scrub-dominated vege­ (lemonade-berry), and Encelia californica (Cali­ tation which presents a significant fire hazard. fornia encelia). These soft shrubs form a gener­ This paper discusses studies made in the Transverse ally discontinuous cover .5 to 1.5 m tall. Ranges. Chaparral is found from 300 to 1500 m on the The Transverse Ranges are oriented along more rainy coastal sides of the mountains and from east-west axes from Santa Barbara to San Bernardino. 1000 to 1600 m on interior sides. Average annual rainfall ranges from 55 to 100 ern. Species compo­ 1 sition varies throughout the type. Adenostema Paper presented at the Fire History Workshop. fasciculatum (chamise), is common and often domi­ (Laboratory of Tree-Ring Research, University of nant. Co-dominants may be species of Arctosta­ Arizona, Tucson, Arizona. October 20-24, 1980). phylos (manzanitas), Ceanothus (ceanothus), 2 Joe R. McBride is Associate Professor of Forestry Heteromeles (toyon), Rhus (sumacs), and Quercus and Landscape Architecture and Diana Jacobs is (oaks). These hard shrubs form a complete crown Research Assistant in Forestry, University of canopy 1 to 3 m in height. California, Berkeley, CA. The work upon which this publication is based was performed in part The yellow pine forest dominates above the pursuant to Contract No. 68-03-0273 with the U.S. chaparral on the higher mountains between 2000 and Environmental Protection Agency. 2700 m. On north-facing slopes it may be found in

85 favorable canyons below 1300 m; on south-facing sawmills and a timber industry. Others had ranches slopes it is usually first encountered above at lower elevations and returned to the mountains 1600 m. It occupies a variety sites and may be for summer grazing of both sheep and cattle. locally replaced by chaparral on shallow soil on Coniferous zones of the San Bernardino Mountains south-facing slopes or by riparian species in were often used for summer grazing. Sheep herders areas of saturated soil. Species composition commonly set fires in mountain meadows at the end varies with altitude. Pinus ponderosa (ponderosa of each grazing season to improve forage the pine) and Quercus kelloggii (California black oak) following year. It was common practice among the dominate at lower elevations while ~ Jeffreyi early lumbermen to burn slash which interfered with (Jeffrey pine) and Abies concolor (white fir) log extraction, and sawmill fires were another dominate higher up. The yellow pine forest type common source of wild fire (Johanneck, 1975). was divided in this study into a ponderosa pine type and a Jeffrey pine type. The exploitation of resources through mining, logging, and livestock grazing was curtailed in the 1890's with the establishment of federal forest History of Land Use reserVes. The year 1905 was the beginning of a new period in which conservation practices controlled The history of land use in the Transverse land use. In 1905 the Forest Reserves were trans­ Ranges can be divided into four periods: Native ferred from the Department of the Interior to the American, Spanish-Mexican, American Pioneer, and newly formed U.S. Forest Service. In the same year, Modern American. Land use in the Native American California enacted the Forest Protection Act which period was characterized by hunting and gathering. provided for fire control on private lands. These Ethnographic information indicates that Native events resulted in the elimination of broadscale Americans used fire as a management tool to facili­ burning for range and initiated a regulation of tate both hunting and gathering of certain plant forest harvesting. Since 1905 land use has shifted materials (Lewis, 1973). Fires were set annually from logging and grazing to recreation and water­ in lower elevation grasslands and some chaparral shed protection. areas were periodically burned in the fall (Aschmann, 1959). The major concentrations of Native Americans were along the coast and in lower Fire History in Coastal Sage Scrub elevation valleys. They traveled into the mountains and Chaparral annually to collect acorns and pine seeds in the autumn, and occasionally to hunt. The Santa Monica Mountains, west of Los Angeles, were selected for studying fire history • The Spanish-Mexican period can be character­ in the coastal sage scrub and chaparral. These ized as a period of livestock grazing. It began in mountains lie near the western end of the Trans­ 1769 with the establishment of the first mission. verse Ranges and rise from sea level to an ele­ Spanish and later Mexican land grants divided up vation of 945. The vegetation is composed of the lower elevation into ranchos where large herds (1) grassland occurring along coastal terraces and of cattle were raised for hides. Conflicts arose at lower elevations at the northern base of the between the early Spanish settlers and the Native mountains, (2) coastal sage scrub extending from Americans over burning of grassland at lower ele­ sea level on mountain slopes, or at the base of vations. The Spanish were dependent upon these slopes behind the coastal terraces to elevations grasslands for winter range; the Native Americans of about 330 m on the seaward side (south) and were dependent on these same grasslands for root from elevations of 150 to 350 m on the interior and bu~b crops which they collected annually after (north) side of the mountains, and (3) chaparral burning the grass. The Spanish stopped the burning occurring at elevations above the coastal sage and the Native Americans were removed from the scrub. Minor areas of oak woodland occur along grasslands. The higher elevation coniferous forests streams. were generally not utilized by Spaniards or Mexicans for grazing. An analysis of historic fires was used to determine frequencies of fire in the coastal sage The Spanish-Mexican period ended in 1848 when scrub and chaparral of the Santa Monica Mountains. the United States took possession of California Maps of areas burned in these mountains from 1909 from Mexico. In the same year gold was discovered to 1977, compiled by the Division of Forestry of in Cal~fornia. American prospectors explored not the Los Angeles County Fire Department, were used only the Sierra Nevada, but the mountains of to determine fire frequencies. These maps recorded southern California too. Significant lodes were all fires over 0.1 ha (Class Band larger). discovered at higher elevations in the Transverse Ranges. Mining towns sprang up overnight. Fire Two hundred eighty-one sample plots, each was a constant threat to these crudely constructed with an area of 4 ha, were located at random within towns and many were hurned to the ground more than the areas dominated by coastal sage scrub and once in their brief lfespans. Many of these fires chaparral on U.S.G.S. topographic maps. The plots spread into adjacent forests. When the gold was were divided between the two vegetation types to depleted these towns were abandoned and much of the give a 3% sample of the area in each type. These mining population shifted to the lower elevation plot maps were compared with the fire history maps valleys to farm. A few stayed behind to develop and each fire which had burned at least one-half

86 of any plot was tallied as a fire event in th~t practiced by Native Americans. This suggests that plot. This procedure was adopted to minimize the a reduction has occurred in the interval between error associated with transferring fire boundaries fires in the Santa MOnica Mountains, when one from Los Angeles County Fire Department Maps contrasts the Native American period with the modern (which had been drawn at various scales) to the American period. Information on the fire history U.S.G.S. maps. The number of fires on each plot of both the Spanish-Mexican period and American was divided into the time period covered by the Pioneer periods is unfortunately limited. maps (68 years) to determine the intervals between fires. Average intervals were determined for the plots in each vegetation type. Fire History in Ponderosa and Jeffrey Pine Forests The average interval between fires was 14 years for the coastal sage scrub and 16 years for The San Bernardino MOuntains, near the eastern the chaparral. These averages are significantly end of the Transverse Ranges, were used as a location different at the .05% level. The difference in to study fire history in the ponderosa and Jeffrey fire frequencies between the two types may be due pine forest types. The San Bernardino MOuntains to differences in access, temperature, and rate range in elevation from about 400 m to 3,500 m. of recovery following fire of shrub species in the Coniferous forests found at elevations above 1500 m. two types. Access to the coastal sage scrub is Ponderosa pine dominates the somewhat lower eleva­ better than to the chaparral. There is a greater tions of southern and western portions in this zone, density of roads and houses in the coastal sage while Jeffrey pine dominates the higher elevations scrub than chaparral. Opportunities for accidental to the north and east. The ponderosa pine forest as well as arson fires are, therefore, considered is contiguous with either chaparral or oak woodland greater. Temperature gradients result in higher types at its lower edge. The lower elevations at summer and fall temperatures in the lower elevation the northern and eastern boundaries of the Jeffrey coastal sage scrub than in the chaparral. This pine forest are bordered by pinyon-juniper woodlands. difference increases the number of days during the Fire frequency was determined by counting year when fires can readily be ignited ·in the annual rings between fire scars on wood sections coastal sage scrub. Recovery of crown canopies removed from the base of living trees. Twenty-nine following burning is more rapid among the coastal ponderosa and 38 Jeffrey pines were sampled. Trees sage scrub species than in the chaparral species. were selected over the entire range of each forest (Hanes, 1971). This more rapid rate of recovery type. A minimum distance of 1.6 kilometers was on the part of the coastal sage scrub may result maintained between any two trees selected for samp­ in an earlier reestablishment of the fuel con­ ling. A tree was considered for selection only if tinuity necessary to carry fire. one or more trees within 100 m had similar fire scars. Some inaccuracy in dating by this method The fire intervals of 14 and 16 years rep­ can be expected because of the possible occurrence resent the intervals occurring in the modern of missing rings. Cross dating of rings was not American period of land use. An interval of from possible because of the distortion of ring widths 2 to 10 years has been suggested for coastal sage in the healed over portions of the small wood scrub in the San Gabriel and San Bernardino samples. Removal of larger wood sections would have Mountains for the same period by Hanes (1971). resulted tree mortality. Philpot (1973) proposed intervals of 15 to 17 years for chaparral in the San Bernardino Mountains. In Average intervals between fires were determined this modern American period man has acted both as for three periods in each forest type. These the principal agent of fire ignition and as the periods were (1) prior to 1860, (2) 1860 to 1904, control. In earlier periods of land use man was and (3) 1905 to 1974. They correspond to the Native also the primary cause of fires at lower elevations, American, American Pioneer, and Modern American but it is unlikely that man's influence was as periods of land use. Those fires prior to 1860 important in the higher elevation stands of can be used to characterize the Native Amercan chaparral in the Santa Monica MOuntains. These period because neither the Spanish nor the Mexican chaparral stands were of little value for grazing settlers used the ponderosa or Jeffrey pine forests during the American Pioneer and Spanish-Mexican of the San Bernardino MOuntains. However, the periods. Sauer (1977) reports that unlike many population of the major tribe using the pine forest Native American tribes in southern California, the of the San Bernardino Mountains was reduced about Chumash living in the Santa Monica Mountains did 50% during the Spanish/Mexican period (Bean, 1978). not burn vegetation in their management of the Use of these mountains by Native Americans was land. Fire ignition may have resulted as a result further reduced in 1852 when American pioneers con­ of carelessness with campfires, but the major cause structed a road into the mountains. By 1860 the of fire during this period was from lightning. American pioneers had essentially eliminated the Lightning is infrequent in the Santa Monica Native Americans. MOuntains but is the cause of occasional fires. Vogl (1976) has suggested a fire frequency of 20 The fire intervals for each period are shown years for lightning caused fires in chaparral during in Table 1. Analysis of these data shows signifi­ pre-historic times. A similar interval has been cant differences at the .05% level between the proposed by Aschman (1976) for pre-historic chapar­ period from 1905 to 1974 and the earlier periods ral fires in those regions where burning was not within each species. No significant differences

87 were found between the period prior to 1860 and of Forestry. These activities included the pre­ the period from 1860 to 1904 for either species. vention of burning by stockmen and the enforcement There was a significant difference between the of fire safety regulations at sawmills and lumber two species for the modern period; 1905 to 1975. camps. Advancements in fire suppression technology No significant difference occurred between the have allowed for a more rapid control of fires, two types prior to 1905. thus reducing the average extent of individual fires. As the area of forest burned has decreased Table !.--Average interval between fires in since fire records have been maintained, the number ponderosa and Jeffrey pine forests of of fires have increased (U.S.F.S., 1940-79). the San Bernardino Mountains. Lightning has accounted for about 33% of all fires during the last twenty years. Fires initiated in Interval between fires (yrs) the chaparral continue to be a source of ignition Forest Prior to 1860 to 1905 to for fires in the yellow pine forest. In the more ~ 1860 1904 1974 recent part of the Modern American period, recre­ ation has replaced grazing and lumbering as the Ponderosa principal land use in the conifer forests of the pine 10 14 32 San Bernardino Mountains. The long term impact of this land use is yet to be determined. Jeffrey pine 14 19 66 Literature Cited The fire frequencies determined in ponderosa and Jeffrey pine forests in the Native American Aschmann, H. 1959. The evolution of a wild land­ period reflects ignitions by the Cahuillas and by scape and its persistence in southern California. lightning. The Cahuilla-caused fires were usually Ann. Assoc. Amer. Geographers 49:34-57. set in meadows within the forests or in the chapar­ Aschmann, H. 1976. Man's impact on the southern ral. Some of these fires burned into adjacent California flora. Symposium Proceedings: Plant Communities of.Southern California. Special forest ~tands. Fires set in the chaparral may have played a significant role in igniting the Publ. No. 2. Calif. Nat. Plant Soc. Berkeley, lower elevation coniferous stands. The distribution CA. pp. 40-48. of chaparral, oak woodland, and coniferous forest Bean. L. J., 1978~ Cahuilla. In R. F. Heizer (ed.) species at the interface between the chaparral and Handbook of North American Indians: California. yellow pine forest in the San Bernardino Mountains Smithsonian Institution. Washington, DC. has been interpreted by Minnich (1977) as a pattern pp. 575-587. controlled by fires moving up from the lower ele­ Hanes, T. L. 1971. Succession after fire in the vations of the chaparral. Lightning was the common chaparral of southern California. Ecol. cause of fire ignition in the higher elevations of Monogr. 41:27-52. the Jeffrey pine forest. The Native Americans made Johann~ck, D. P. 1975. A history of lumbering in limited use of these higher elevation forest stands the San Bernardino Mountains. San Bernardino and a less frequent interface occurs between Jeffrey County Museum Assoc. 22:1-124. pine stands and chaparral. Kilgore, B. M. and D. Taylor. 1979. Fire history of a Sequoia-mixed conifer forest. Ecology The fire frequencies calculated for the 60:129-142. American pioneer period in both the ponderosa pine Lewis, H. T. 1973. Patterns of Indian burning in and Jeffrey pine forest types do not differ sig­ California: Ecology and Ethnohistory. Ballena nificantly from frequencies in the Native American Press Anthropological Papers 1:1-101. Ramona, period. It is assumed that the pioneer miners, CA. sheep herders, ranchers, and lumbermen replaced Minnich, R. A. 1977. The geography of fire and the Native American as causal agents for wildfires. big cone-Douglas fir, Coulter pine, and western The elimination of the Native Americans from the conifer forests in the east Transverse Ranges, mountains did not result in a significant increase Southern California. In Proc. Symp. on the in the interval between fires as has been reported environmental consequences of fire and fuel for the Sequoia-Kings Canyon region of the Sierra management in Mediterranean ecosystems. August Nevada by Kilgore and Taylor (1979). 1-5, 1977, Palo Alto, CA. USDA Forest Serv. Gen. Tech. Rep. W0-3. pp. 443-450. The activities of the American pioneers may Philpot, C. W. 1973. The changing role of fire have resulted in more fires actually having been on chaparral lands. In Proc. Symp. on living set, purposefully or by accident, in the forests with the chaparral. Univ. Calif., Riverside, themselves. The use of fire by stockmen, which CA. March 30-31, 1973. pp. 131-150. was considered a serious threat to the fot;est·s, Sauer, J. D. 1977. Fire history, environmental was a major impetus for the establishment'of a patterns, and species patterns in Santa Monica -~ federal forest reserve in the San Bernardino Mountain chaparral. In Proc. Symp. on the Mountains. environmental consequences of fire and fuel management in Mediterranean ecosystems. The significant increase in the length of August 1-5, 1977, Palo Alto, CA. USDA Forest interval between fires in the Modern American Serv. Gen. Tech. Rep. WO-#. pp. 383-386 period is a result of fire control activities by U.S.F.S. 1940-79. National Fire Report, 1940-79. the U.S. Forest Service and the California Division USDA. Washington DC.

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