Oaks are foundational species in much of California, and many oak populations in the state may be in jeopardy due to a lack of recruitment of young trees. Despite considerable interest in this problem, there have been few comprehensive surveys of all stages of oak development. We surveyed all stages of three oaks: Quercus lobata, Q. douglasii, and Q. agrifolia in a forest plot with mixed land-use in central coastal California. We found abundant seedlings of all oak species, but an apparent paucity of Q. lobata and Q. douglasii saplings. First year seedlings of all species were less abundant in parts of the study site with cattle grazing, but later-stage seedlings of Q. lobata and Q. douglasii were equally abundant across land-use types. Quercus agrifolia seedlings were associated with non-grazed areas; Quercus agrifolia late-stage seedlings in the grazed area were smaller and less abundant than in non-grazed areas. Quercus agrifolia seedlings of all stages tended to be clustered around conspecific mature trees. Quercus lobata late-stage seedlings, and to a lesser degree those of Q. douglasii, were often distant from any potential parent tree. These data indicate that young stages of the three species of oak have different spatial distributions and occur in different abundances at two sites with different grazing regimes. They are also consistent with a relative lack of regeneration in Q. lobata and Q. douglasii, although it remains to be determined that the small number of saplings of these species observed is insufficient to replace mortality of mature trees. This survey provides a baseline from which future resampling can assess the long-term demographic success of three Californian oak species.

Erigeron lemmonii A. Gray, restricted to Scheelite Canyon in the Huachuca Range, Arizona, has previously been proposed for federal listing as an endangered species but basic cytological and reproductive information has been wanting. The first chromosome count for the species is 2n  =  18, which is the common diploid number in Erigeron. Analyses of eight plants from five disparate sites within the population show that pollen averages 85.8% staining in cotton blue in lactophenol. Microscopic observation using differential interference contrast optics shows that E. lemmonii combines about equally monosporic and bisporic megagametophyte development within a single capitulum. Despite variability in developmental route, the egg apparatus among mature megagametophytes appears to be nearly uniform in structure. In greenhouse culture, isolated plants fail to set seed indicating that plants are probably self-incompatible. Controlled crosses yield seed, but variation in seed set intimates the possible presence of genetic barriers within the population.

This project sampled throughout Phacelia using the internal transcribed spacer region (ITS-1, ITS-2, and 5.8S gene) of nuclear ribosomal DNA (nrITS) and the chloroplast DNA gene (ndhF) to infer phylogenies for nuclear and plastid partitions. Nuclear and plastid partitions were incongruent in our analyses. Phylogenetic analyses (maximum parsimony, maximum likelihood, and Bayesian inference) recovered gene tree topologies similar to previous molecular studies. We corroborate incongruence between nuclear and plastid topologies for placement of some problematic groups (e.g., Draperia, Romanzoffia and “core” Phacelia subg. Pulchellae, Phacelia sect. Baretiana). Combined analyses resulted in better resolution than separate analyses, and in a topology that favored the separate plastid topologies. Romanzoffia was sister to a monophyletic Phacelia in the combined analyses. Our results support combining incongruent partitions in a combined analysis to seek support for internal nodes. Maximum likelihood analyses were used to infer ancestral chromosome numbers and identify gains, losses, polyploid doubling, and whole genome duplication events from published chromosome counts in the genus. The predicted base number for the genus was x  =  9, x  =  11, or x  =  12.

This paper describes plant zonation in a southern California riparian woodland and identifies the factors responsible for the zonation. Of the 25 common trees and shrubs in the Tijuana River Valley, three were numerically dominant: Baccharis salicifolia (Ruiz & Pav.) Pers., Salix lasiolepis Benth., and Salix gooddingii C. R. Ball, here referred to as BASA, SALA, and SAGO, respectively. Adults of these species displayed significant down-slope zonation, with BASA, SALA, and SAGO most abundant in the High, Intermediate, and Low zone, respectively. Among new recruits, SALA and SAGO seedlings displayed zonation similar to that of adults, indicating that the zonation of SALA and SAGO was established at the time of recruitment. In contrast, BASA seedlings were more broadly distributed than adults; they were abundant in all zones, particularly the Low zone where adults were rare, indicating that the zonation of BASA adults was established post recruitment. For SALA and SAGO, the timing of fruiting and timing of water-level decline were the factors producing adult zonation; the two species had nearly non-overlapping periods of seed production, and this led to zonation of their seedlings on the banks as water levels declined. The seedling zonation was then retained in the adults. Because factors affecting recruitment played an important role in their zonation, these two willow species provide a new example of the supply-side influencing community structure. For BASA, whose seedlings were widely distributed, zonation of adults was the result of poor seedling survivorship in the Low zone during the first winter and poor adult survivorship in the Intermediate zone later. Results of this study can help guide future riparian restoration projects in southern California. Based on the prolific natural recruitment and rapid development of dense, native-dominated stands, use of a natural restoration approach where possible is recommended instead of the more common horticultural approach.

Cordylanthus tenuis subsp. pallescens, Pallid Bird's-beak, is a rare plant of the Mount Shasta area of northern California. Recent reports of dozens of populations outside its limited expected range, observations of plants with morphology intermediate to other subspecies of C. tenuis, and populations that seemed to include individuals of more than one subspecies, raised questions about its rarity and taxonomic validity. Examining populations in the field suggested that many reported populations were misidentified because they were based on a single trait, often foliage color. The name C. t. subsp. pallescens should be restricted to populations in which all or most plants have the combination of traits expected of this taxon, including yellow-green foliage, four to eight flowers per cluster, and short, mostly non-glandular calyx hairs. In the context of other variation recognized at the subspecies level in C. tenuis, recognizing C. t. subsp. pallescens taxonomically is a reasonable choice, despite its very limited range.

Soils, timber site data, and the foliage of mature conifer trees were sampled at 16 Klamath Mountains sites with serpentine soils and four sites with gabbro soils. The basal areas of trees at the gabbro sites were greater than the basal areas at the serpentine sites. Tree height growth, based on old growth site curves, was significantly greater on the gabbro soils than on the serpentine soils. The main soil difference was about five times greater exchangeable Mg from the serpentine soils than from the gabbro soils. The higher Mg in serpentine soils was not reflected in higher concentrations of Mg in the foliage of yellow pine (Pinus spp.), Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), or incense cedar (Calocedrus decurrens [Torr.] Florins) trees on serpentine soils, but Ca was significantly higher in the Douglas-fir tree foliage on gabbro soils. The high Mg in the serpentine soils may interfere with the utilization of Ca by Douglas-fir trees causing their foliage to have lower Ca concentrations than in the foliage of Douglas-fir trees on gabbro soils. For each of the three tree species (yellow pine, Douglas-fir, and incense cedar), foliar N, P, and K concentrations were not appreciably different on serpentine versus gabbro soils. Although soil N and P were not determined, organic matter concentrations did not differ between serpentine and gabbro soils.

Campylopus introflexus (Hedw.) Brid. is a moss native to the southern hemisphere and well documented as an invasive species throughout Europe. The species was first collected in North America in 1967 in Del Norte Co., California, and now occurs primarily in coastal areas from Santa Barbara Co. to southern British Columbia. Herbarium specimens were assembled and verified to document the distribution of the species in western North America. Collection dates of specimens indicate a rapid invasion along the coast north and south from the first record, with a slower establishment of inland populations. The species is most prevalent in coastal, foggy areas. Many of the populations are associated with anthropogenic environments, but several populations appear to be invading relatively undisturbed sites. These are mostly characterized by poor soils along the coast, with the largest populations associated with Bishop Pine forests and stabilized sand dunes. A brief summary of ecological literature documenting the European invasion of C. introflexus suggests that the species, especially in the presence of disturbance, has the potential to negatively impact native bryophyte, lichen, and vascular plant species.

The life cycle of the widespread, cormous geophyte, Triteleia ixioides (W. T. Aiton) Greene subsp. anilina (Greene) L. W. Lenz (Themidaceae) was studied in the field over several years in coniferous forest sites in Butte County, CA. All sites, ranging from 1383 to 1774 meters in elevation, have a Mediterranean climate and loamy soils above Tuscan mudflow substrate. Flowering scape height, corm weight, and corm depth varied significantly. Old corms decreased in dry weight throughout the winter, as shoots, roots, and new corms grew. By spring, each old corm had produced a leaf and a flowering scape, was depleted of stored food, and had a new “replacement corm” (without roots) already developed on top of it. Fruit set varied from 38.5% to 89.1%, with significant differences among populations sampled in different years and sites. Seed set was low (overall mean 38.4%), but varied significantly among years and sites, ranging from 26.4% to 56.3%. Plants are partially self-compatible. Soil moisture was not limiting to seed set, nor was pollen vectors, except on cold days. The most important pollinator was a bee fly (Bombylius facialis, Bombyliidae), although native bees provided some pollination at higher sites. Ten-minute observation periods, during bee fly activity, showed up to 15 visits to plants in a square meter. Percent seed germination was high (88–100%), with germination after the first rains and seedling growth continuing during the cold months. Seedlings produced single leaves up to 60.4 mm long, and corms averaged 1.6 ± 0.1 mm wide at one site. Contractile roots, produced lateral to the primary roots, averaged 16.13 ± 1.00 cm long. Shrinking and wrinkling at the upper part of the contractile root pulled the newly formed corm deeper in the soil. Study of contractile roots in Triteleia and other geophytes may help illustrate adaptation to summer drought in Mediterranean California.

Geomorphic gradients of landforms and associated soil catenas in the Central Desert region of Baja California produce complex but repeatable patterns of plant community distribution and a diversity of plant functional groups distributed unequally over the gradient. We measured plant diversity and made three assessments of plant dominance in six plant communities associated with a gradient of geomorphic landforms. Dominance was assessed by plant cover, aboveground biomass, and aboveground water mass held by vegetation. Perennial plant cover was highest on northeast-facing rocky pediment slopes (54.6%) and lower bajada slopes (45.7%), and lowest on creosote bush flats (19.2%). The highest aboveground biomass of any community (25.07 t ha⁻¹) was present in wash woodlands heavily dominated by Prosopis glandulosa. This was more than ten times the biomass present in the creosote bush flats. The highest aboveground water mass contained in vegetation was present on the northeast- and southwest-facing rocky pediment slopes which each held more than 30.0 t H₂O ha⁻¹. This water mass was heavily contained in just two species of arborescent stem succulents, Pachycormus discolor and Fouquieria columnaris, neither of which utilizes crassulacean acid metabolism (CAM). High amounts of standing water mass on upper and lower bajada slopes were held by the arborescent cactus Pachycereus pringlei. The changing pattern of relative dominance of plant functional groups across this gradient of desert landforms reflects the morphological and ecophysiological traits associated with each group, and indicates strong assembly rules of community composition.

An exceptional dataset for over 12,000 Carnegiea gigantea collected by the Arizona Department of Game and Fish over two field seasons on a restricted military reservation was released to the authors for analysis, including a variety of variables for which little empirical evidence exists. Data on epidermal browning, physical damage due to fire, lightning, gunshot or topping, rodent girdling, bird cavities and other variables were assessed using primarily chi-square analysis. The main findings of this study include: (1) Plants with high amounts of epidermal browning were rather evenly distributed across height classes, although the very smallest plants (0–0.9 m) had substantially less epidermal browning. (2) Although past work has shown that epidermal browning is surely a function of solar radiation receipt, other variables (bird cavities, girdling, damage, branching) are statistically linked with browning, raising the possibility that other biotic and abiotic factors may hasten browning. (3) Bird cavities are better predicted by height than branches, likely due to decreased visibility and exposure to thermally tempering winds caused by branches, and improved defensive position and reduced exposure to heating from the surface associated with taller plants.

At the beginning of the 21st Century, deserts and woodlands of the southwestern United States were in the midst of a drought that contributed to massive die-offs for many plant species. In the northwestern Sonoran Desert, the drought contributed to extreme desiccation and mortality of cholla (Cylindropuntia) cacti. At low elevations (210–290 m), over half of the Cylindropuntia bigelovii, over 17% of the C. echinocarpa, 6% of the C. ramosissima, and less than 2% of the C. ganderi were dead by winter 2004/2005. At a higher elevation (∼820 m), 26% of C. bigelovii and 14% of C. ganderi were dead by winter 2005/2006. The lower mortality for C. bigelovii at the higher elevation site was likely due to milder temperatures and greater precipitation; the greater mortality for C. ganderi at the same site may be the result of freezing or frost damage to tissues during the drought. Differences in mortality among species at both elevations were attributed to several factors, including: intra- and interspecific competition, reproductive strategy, and shoot architecture. Based on this study and previous research, it is believed that C. bigelovii experiences periodic extensive die-offs in response to extreme droughts, whereas populations of the other three species apparently change little during such droughts.

Scouleria siskiyouensis Shevock & D. H. Norris, a new species restricted to rivers and streams in southwestern Oregon is described and illustrated. This species appears related to the widespread S. aquatica Hook. in Drummond of western North America but is distinguished by a combination of features including lamina bistratose except for a few cells at immediate leaf margin unistratose, leaves lanceolate to ovate-lanceolate and with leaf apex acute to acuminate.