San Diego Management & Monitoring Program


Chaparral

Brief community description

Chaparral is comprised of evergreen drought-and fire-tolerant shrubs with sclerophyllus leaves [1] adapted to long, hot, dry summers and intermittent rain in winter. The MSP focus is on chaparral communities in the western part of San Diego County in the foothills, but not the mountains. Includes southern mixed chaparral, northern mixed chaparral, chamise chaparral, scrub oak chaparral, southern maritime chaparral, and the coastal sage-chaparral transition [2]. Southern mixed chaparral is part of the upper Sonoran mixed chaparral community of shrubs that are 1.5-3 m tall [2], with occasional patches of bare soil or a mosaic with sage scrub. Dominant plants in San Diego include Ceanothus spp., especially C. tomentosus var. olivaceus, as well as C. leucodermis and C. oliganthus. Granitic and mafic southern mixed chaparral are two different subtypes based on substrate. Northern mixed chaparral is part of the upper Sonoran mixed chaparral community of shrubs 2-4 m tall [2] with dense and nearly impenetrable vegetation, dominated by Quercus berberidifolia, Adenostoma fasciculatum, Arctostaphylos spp., and Ceanothus spp. Plants are typically deep rooted, usually with little or no understory vegetation, and often a considerable accumulation of leaf litter. Growth is highest in the spring and greatly reduced in winter at higher elevations. Flowering occurs from later winter to early summer. Chamise chaparral is dominated by 1-3 m tall A. fasciculatum. Mature sites are dense with very little herbaceous understory or litter. Scrub oak chaparral is a dense, evergreen chaparral up to 6 meters tall [2] dominated by Q. berberidifolia in San Diego County with over 50% cover. Usually occurs in small patches within a variety of other vegetation communities. Southern maritime chaparral, sometimes referred to as coastal mixed chaparral, is a low and fairly open chaparral found in the coastal fog belt. It is dominated by C. verrucosus and Arctostaphylos glandulosa ssp. crassifolia [2]. The coastal sage-chaparral transition community is a mix of sclerophyllous , woody chaparral species, and drought-deciduous, malacophyllous sage scrub species. A. fasciculatum and Artemesia californica are the codominant species [2].


Alliances

There are 15 chaparral alliances in the MSPA [4]. The southern mixed chaparral community includes some of the most abundant chaparral alliances: A. fasciculatum-Xylococcus bicolor, Arctostaphylos glandulosa, and Cenothus tomentosus. The chamise chaparral community with the A. fasciculatum alliance is second most abundant, followed by the scrub oak chaparral community with the Quercus berberidifolia x acutidens and Q. berberidifolia x acutidens-A. fasciculatum alliances.


Range wide dist. status

Southern mixed chaparral is found in coastal foothills of San Diego County and northern Baja California, usually below 910 m [2]. Northern mixed chaparral occurs more inland [1] and is found on Transverse and Peninsular Ranges of southern California on slopes away from the desert, usually below 1520 m. Chamise chaparral distribution is similar to northern mixed chaparral [2]. Scrub oak chaparral is found from western Sierran foothills and North Coast ranges to Baja California. Most often found in San Diego County on the Cleveland National Forest, ridges on the east end of Henshaw Valley, and in McCain Valley [2]. Southern maritime chaparral is restricted in San Diego County to coastal areas such as Torrey Pines State Reserve, along the San Dieguito River Valley, Rancho Santa Fe, and a few other scattered locations [2]. The coastal sage-chaparral transition community occurs along outer Coast Ranges and Peninsular Range from the Big Sur Coast south to Baja [2].


MSPA distribution

There are 709,024 acres of chaparral in the MSPA in all MUs, of which, 406,270 acres are conserved. The more inland MUs (9, 10 and 11) support 444,140 acres of chaparral with 282,191 acres (64%) conserved. MUs 3, 4, 5, and 8 have 108,169 acres (47%) conserved of the 228,806 acres of chaparral.


Habitat affinities

Southern mixed chaparral occurs on dry, rocky, and often steep north-facing slopes with little soil and moderate temperature [2]. Granitic southern mixed chaparral occurs on granitic soils while mafic southern mixed chaparral occurs on mafic or metavolcanic soils. Northern mixed chaparral is found on dry, rocky, and often steep north-facing slopes with minimal soil [2]. Often adjacent to and on rockier sites than oak woodland and grasslands; rockier but moister sites than coastal sage scrub; and warmer, rockier, and drier sites than broadleaved evergreen forest or lower montane coniferous forest. Chamise chaparral has similar site preference to southern and northern mixed chaparral, but on shallower, drier soils, and at lower elevations [2] and is often found on xeric slopes and ridges. Scrub oak chaparral sites are somewhat more mesic than other chaparral sites and often occur at higher elevations up to 1,525 m with substantial accumulations of leaf litter. In San Diego, elevation can vary and sites are typically north facing or with mesic slopes. Southern maritime chaparral occurs in weathered sands within the coastal fog belt [2]. The coastal sage-chaparral transition community is an intermediate between coastal scrub and chaparral communities [2].


Ecosystem processes

Northern mixed chaparral is adapted to repeated fires with many species responding by stump sprouting [2]. A dense cover of annual herbs is common the first growing season after a fire, followed in subsequent years by perennial herbs, short-lived shrubs, and the reestablishment of original dominant shrub species. Chamise chaparral is also adapted to repeat fires by stump resprouting [2]. Scrub oak chaparral often recovers from fire faster than other chaparrals due to the favorable mesic soils [2]. Fire appears necessary in southern maritime chaparral for continued reproduction of many characteristic species. The coastal sage-chaparral transition is usually a post-fire successional community.


Threats

Short fire return interval (5-10 yrs) have lead to type conversion from chaparral and coastal sage scrub to non-native annual grasslands [5, 6]. Urban development threatens chaparral through habitat loss and alteration [7]. Due to climate change, the climate in California is projected to become warmer and drier with more frequent, intense and prolonged drought [8]. Extensive chaparral shrub mortality has been attributed to intense and prolonged droughts [9, 10]. A changing regional climate is attributed to an upward shift in the distribution of chaparral species in the Santa Rosa Mountains of southern California [9]


Special considerations

Chaparral communities in the MSPA support 50 MSP species (see Vol2C Section 2 for full list).


Sources