-Most species of Lupinus were found predominately to occur on moderate to steeply sloping hillsides. Occurrence of certain lupines is strongly correlated, either positively or negatively, with other plants and some negative associations may be ascribed to phytotoxins. Most lupines prefer coarse-textured soils within relatively narrow elevational limits. The pH range of most species was fairly narrow, possibly because symbiotic Rhizobium strains cannot tolerate wider levels. Considerable environmental variability coupled with human-created habitats has formed a basis for adaptive radiation and expanded distributions in this area. Lupinus is among the largest and most ecologically diverse genera in the Californian flora. Extensive adaptive radiation, which has presumably occurred since the middle-Pliocene (Raven and Axelrod, 1978), has allowed its species to inhabit virtually every terrestrial plant community in California. Although lupines have long been known to colonize disturbed sites, little information exists regarding specific habitat preferences. Pitelka (1977) investigated the energy allocation patterns of three lupines-an annual, an herbaceous perennial, and a shrub-which occur along the central California coast, and related different strategies to environmental preferences. Population dynamics of the same shrubby lupine (L. arboreus Sims) growing in the northern coastal scrub of California were also examined by Davidson and Barbour (1977) who found establishment and mortality closely related to native animal populations. The purpose of this study is to determine which plants occur in association with lupine species and the strength of the association, whether different lupines are adapted to specific slope angles and aspects, and the differences in edaphic properties (texture and pH) these various species exploit. STUDY AREA.-The major portion of the research area is located in Los Padres National Forest (Fig. 1). Its complex geology and highly varied topography provide a basis for diverse soil types, most of which are poorly developed. High relief predominates in the northern half due to uplift by fault-displacement. Sample sites range in elevation from 300 m near Castaic Junction to 2720 m on Mt. Pinos, the highest peak in the area. The regional climate is summer dry. Annual precipitation increases from about 38 cm in the lower coastal areas to nearly 70 cm at the crests of the eastern Santa Ynez and Topatopa Mountains. Farther north, precipitation diminishes to about 30 cm in Lockwood Valley but again increases on Mt. Pinos. Eastward toward the Mojave desert, Gorman has the lowest annual average of any rainfall station in the study area (28 cm). The unusual abundance and timing of precipitation in fall, 1972, and winter, 1973, resulted in very high germination and plant growth in the spring and following summer. Lupine populations were found growing among all major plant communities in this area. It appears the north-south gradient of precipitation largely controls community borders. Consequently, communities do not occupy constant altitudinal zones. E SOUTHWESTERN NATURALIST 27(4):369-397 NOVEMBER 19, 1982 This content downloaded from 157.55.39.210 on Tue, 13 Dec 2016 04:35:48 UTC All use subject to http://about.jstor.org/terms The Southwestern Naturalist FIG. 1.-Location of transects within the study area. Coastal sage scrub covers much of the southern portion at elevations below about 460 m, intergrading into chaparral above this, and into oak woodland in the eastern portion of the study area. Chaparral extends upward to about 1700 m, above which it is replaced by yellow pine forest which extends northward to the Pine Mountain axis. North of this approximate border, precipitation decreases sharply, and above 1100 m pinyon-juniper woodland replaces chaparral. Adjacent to both Lockwood and Cuddy Valleys, pinyon and juniper grow to 1750 m elevation, above which yellow pine is again found. The summit of Mt. Pinos has several species usually found in alpine communities but most are also found at lower elevations on the mountain. Sagebrush scrub occu370 vol. 27, no. 4 This content downloaded from 157.55.39.210 on Tue, 13 Dec 2016 04:35:48 UTC All use subject to http://about.jstor.org/terms O'Leary-Habitat Preferences of Lupinus Artemisia tridentata Nutt. Avena barbata Brott. Baeria chrvsostoma F. & M. Brassica niara (L.) Koch Bromus diandrus Roth.
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