In southwestern Oregon and northern California, Jeffrey pine (Pinus jeffreyi) savannas and Darlingtonia fens are part of a mosaic of serpentine soil-related plant communities separated by distinct ecotones. I characterized and quantified the biological and physical aspects of these transition zones. Changes in vegetation were distinguished across communities and across three sites, each a different time since fire, and water discontinuities appeared important for preserving these uniquely-adapted systems, while vegetation undergoes postfire succession from fen to shrub to savanna after approximately 100 years since fire. While many factors play a role in determining the composition and location of community boundaries, the role of water appears to be the most critical factor determining the structure and species composition of the fen and shrub communities in southwestern Oregon.

Tenderfoot Creek Experimental Forest (TCEF) is situated in the Little Belt Mountains of Montana, 120 km east of the Continental Divide. TCEF is composed of 3693 ha at elevations between 1840 and 2420 m and is dominated by lodgepole pine forest, which covers about 3366 ha, with interspersed floristically rich meadows. Our floristic inventory is based on collections and field observations made by Scott Mincemoyer during 1996–1999 and collections by Jennifer Birdsall during 2003–2005. We also include collections made by Earle Layser in 1992 and Jessica Fultz in 2002–2003. The vascular flora of TCEF consists of 312 species, representing 162 genera and 44 families. Twenty-seven exotic species occur in TCEF including Centaurea maculosa, Chrysanthemum leucanthemum, Cirsium arvense, and Tanacetum vulgare which are listed as noxious weeds in Montana. Phlox kelseyi var. missoulensis is found in the experimental forest and is listed as sensitive by the USDA Forest Service Northern Region.

The Sarraceniaceae are a small family of insectivorous herbs native to North and South America. The family is composed of three geographically separated genera, Heliamphora, Darlingtonia and Sarracenia. Recent molecular evidence suggests that Darlingtonia is sister to a Heliamphora-Sarracenia clade. The systematic relationships among the taxa within the genus Sarracenia are uncertain. Within the S. rubra and S. purpurea complexes, five and four infraspecific taxa have been named respectively. In this study, combined Internally Transcribed Spacer 2 and 26S large ribosomal subunit rRNA gene DNA sequences were used to infer phylogenetic relationships among the genera within Sarraceniaceae and the specific and subspecific taxa within Sarracenia. Results from this study support the sister relationship between Darlingtonia and a Sarracenia-Heliamphora clade. Within the genus Sarracenia, S. purpurea is sister to all remaining species. Additionally, the four named infraspecific taxa of S. purpurea are resolved in a well-supported clade. However, the five named subspecific taxa of S. rubra are part of a polytomy without discernable structure. This study suggests that S. purpurea ssp. purpurea var. burkii (which has been named a separate species as S. rosea) may be considered a distinct species. If so treated, then the number of species of Sarracenia stands at nine.

The Bromus carinatus complex comprises several cleistogamous taxa that have been recognized at a variety of taxonomic levels. Our study focused on three taxa: B. carinatus s.s., B. marginatus, and B. polyanthus, that have received varied taxonomic treatment. We mapped the collection sites of 673 specimens belonging to these taxa to determine whether their geographic distribution would support their recognition as species. We examined the characters customarily used to distinguish among the three entities: longevity, blade width, awn length, sheath vestiture, and lemma vestiture. The geographic data do not support the value of blade width as a taxonomic character but provide some support for use of awn length and the two vestiture characters. Of the three taxa, B. polyanthus, characterized as having glabrous sheaths and lemmas and, usually, short awns, was the most geographically distinct taxon. Bromus carinatus sensu stricto and B. marginatus showed some separation, the former being primarily a coastal taxon and the latter primarily an inland taxon. Based on our observations and published molecular data, we propose that B. carinatus and B. marginatus be treated as B. carinatus var. carinatus and B. carinatus var. marginatus (Nees ex Steud.) Barkworth & Anderton, comb. nov. respectively, and that B. polyanthus be treated as a species.

Various Salsola spp. have been introduced to the USA, and some of these are considered noxious or invasive in certain regions. The genus is taxonomically challenging, and recent morphological, cytological, and molecular work has shown that an unknown taxon, previously identified as S. tragus, but recently temporarily designated as Type B, with unknown origins, exists in California and Arizona. Type B's origins and identity are a point of concern for biological control efforts, as it is much less affected by fungal biological control agents than the sympatric invasive S. tragus. Initial studies in 2005 indicated that Type B is morphologically very similar to S. kali subsp. austroafricana which has been collected in southern Africa. Here we use DNA sequence data from a PEPC intron to compare USA and Old World specimens, and results indicate that S. kali subsp. austroafricana is genetically identical to Type B and distinct from S. tragus. It is unclear if S. kali subsp. austroafricana is native to southern Africa or to the northern hemisphere of the Old World, and further investigations in both regions are needed.

A gridline survey for exotic plant species was undertaken in 1983 and repeated in 2005 at the Desert Laboratory, a 352-ha natural area just west of downtown Tucson, Arizona, USA. Coordinate data gathered during the surveys were used to plot distributions, determine frequencies (number of coordinate locations), and assess percent change. Fifty-two exotic species were encountered in all, 34 in the first survey, 44 in the second. The proportion of ornamental exotics doubled over time, reaching 50% in 2005. Casual, naturalized, and invasive exotics comprised 44%, 40%, and 15% of species found during the surveys. Minimum residence time increased significantly from casual to naturalized to invasive species, suggesting that the longer a species was present, the more likely it was to surmount barriers to naturalization and invasion. In both 1983 and 2005, casual, naturalized, and invasive species differed in mean frequency by an order of magnitude, with casual species having the lowest frequencies and invasive species the highest. Between surveys, frequency of 18 species decreased; most other species increased in frequency. The recent surge in ornamental exotics, combined with temporal trends in invasiveness, indicates that the proportion of invasive species in the flora will increase with time.

The conservation of peripheral plant populations is paradoxical. Populations occurring on the edge of a species' range tend to be smaller, more isolated, and more genetically and ecologically divergent than central populations. The combination of these characteristics can impart novel evolutionary potential and local ecological significance, thus heightening their conservation value, while also making them less viable and more prone to local extinction. Public policy supports the conservation of peripheral populations, despite the commonness of the species elsewhere. However, the conservation of significant peripheral populations of nonlisted plants has been arbitrary and ineffective. The absence of explicit criteria to determine the conservation value of peripheral plant populations, the lack of finer-scale data on plant distributions, and a general unawareness of their value have hindered efforts to conserve them. We review the conservation value of peripheral plant populations and, using California as an example, describe regulatory methods to improve their conservation. We also propose a scheme to assess a population's conservation value.

In a 1922 monograph on the California chaparral, William S. Cooper called attention to some patches of chamise (Adenostoma fasciculatum) growing robustly on deep alluvial soils on the west side of the lower Sacramento Valley. He submitted that these patches were relicts of “the true regional climax,” suggesting that centuries of Indian burning accounted for the prevalence of grass instead of brush when the Sacramento Valley was first seen by Europeans. We examined available historical evidence and found that Cooper was right in concluding that the chamise patches he saw were vestiges of a much more extensive (ca. 4000 ha) aboriginal stand. Whether the controlling local influence was edaphic or anthropogenic, and whether the local pattern had any wider regional implications, are questions that remain open to speculation.

A new species of club cholla (Grusonia robertsii) endemic to the Vizcaíno Desert of Baja California Sur is described here for the first time. Distribution, associated vegetation, rarity, affinities to other related species, a botanical illustration, a key to the species in the genus Grusonia of the Lower California region, and a key for the generic reclassification of Opuntia sensu lato as recognized by Wiggins (1980) but currently treated as three different genera in the region are also presented.

Trichostema ruygtii is described from Napa County, California. It is closely related to T. lanceolatum Bentham but differs from that species most conspicuously in having much smaller flowers with notably shorter stamens. Both species occur in Napa County but occupy somewhat different habitats and have not been found growing together.

We used PCA of morphological characters to confirm the presence of an undescribed Calamagrostis species in Washington and Oregon that has historically been attributed to Calamagrostis vaseyi. We propose to name this grass Calamagrostis tacomensis. It is most similar to C. foliosa although it has often been confused with C. purpurascens and C. sesquiflora all of which have similar lemma awn characteristics (i.e., the awn relatively long, exserted, and bent). Calamagrostis tacomensis has been collected at high elevations (490–2170 m) in the Washington Cascades, the Olympic Peninsula and the Steens Mountains of Oregon. The name C. vaseyi has been misapplied to our new species. The description of C. vaseyi is similar to C. rubescens. We have studied the specimen that has been attributed to be the type of C. vaseyi and it is C. purpurascens. We lectotypify C. vaseyi.