Abstract Detail

Floristics & Taxonomy

Donovan, Daniel [1], Fisher, Amanda [2].

Vascular Plant Flora of Ladd Canyon, Santa Ana Mountains, California.

Southern California’s Santa Ana Mountains are a coastal range between Orange and Riverside counties, within the California Floristic Province global diversity hotspot. Ladd Canyon in the northern Santa Anas is an intriguing target for a floristic survey because it has relatively few access routes and has not been well explored. The steep terrain covers 18.2 km² in the Cleveland National Forest. Significant Pinus attenuata stands on the high ridges are associated with the only serpentine soil in the mountains. Local topography is thought to funnel wet marine air through the canyon, and the canyon has burned less frequently than the rest of the mountains, with no recorded burns in much of its area. A complete checklist of taxa could shed light on the effects of Ladd’s low human traffic, wetter microclimate, and low fire frequency. I predict that compared with the rest of the Santa Anas, Ladd Canyon will (1) because of low fire frequency, have fewer annual taxa; (2) because of lower human disturbance, have fewer invasive taxa; and (3) because of its microclimate, have more taxa with northern, coastal, and/or higher-elevation ranges. As of March 2022, I have made 56 trips to Ladd Canyon and 519 collections. The vouchered checklist has 276 taxa (16 based only on previous records). Sensitive taxa in Ladd Canyon include Lepechinia cardiophylla (CRPR 1B.2), Calochortus weedii var. intermedius (1B.2), Monardella hypoleuca ssp. intermedia (1B.3), Lilium humboldtii ssp. ocellatum (4.2), Romneya coulteri (4.2.), Polygala cornuta var. fishiae (4.3), and Lobelia dunnii ssp. serrata (NatureServe G3T3). There are 90 annual taxa (33%), compared with 39% annual taxa across the Santa Ana Mountains and 44% in San Mateo Canyon in the southern part of the range. There are 231 native, 25 naturalized, and 19 invasive taxa, yielding 16% non-native and 6.9% invasive taxa. The more frequently visited San Mateo Canyon has 20.1% non-native taxa, and the entire range 22.5%. Work to date has revealed new populations of sensitive taxa and suggests possible effects of low human traffic and fire frequency.

1 - 374 Mira Mar Ave., Long Beach, CA, 90814, United States
2 - California State University, Long Beach, Biological Sciences, 1250 Bellflower Blvd., Long Beach, CA, 90840, United States

Keywords:
California
Santa Ana Mountains
Ladd Canyon
Floristics.

Presentation Type: Poster
Number: PFT012
Abstract ID:992
Candidate for Awards:None