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We investigated the phylogenetic relationships and taxonomic status of the castaneoid component (Lithocarpus and Chrysolepis) of the family Fagaceae that is endemic to the California Floristic Province (CA-FP). Over 7800 basepairs of nuclear and chloroplast DNA were analyzed in 17 taxa representing the breadth of phylogenetic diversity in the family. The genus Lithocarpus, as currently defined, is clearly polyphyletic due to the inclusion of L. densiflorus. Here, we designate this taxon as a new genus, Notholithocarpus, which can be recognized morphologically by its relatively small, subprolate pollen. Notholithocarpus is more closely related to Quercus, Castanea, and Castanopsis; Chrysolepis was resolved as the sister group to Lithocarpus sensu stricto. These results indicate that Notholithocarpus does not possess true ‘flower cupules,’ which define Lithocarpus sensu stricto, but like the oaks, the single flower per cupule is derived through the abortion of lateral flowers within each cupule. Further study is required to confirm this characteristic. A formal taxonomic treatment is presented with new combinations.
After a century of fire suppression, prescribed fire and mechanical thinning are widely used to restore mixed-conifer forests in California's Sierra Nevada, yet after these treatments, trees sometimes fail to regenerate on many sites, for several possible reasons. Notably, competition between shrubs and tree seedlings for scarce water during prolonged summer dry seasons is suspected to influence seedling survival, yet this hypothesis has been tested in few manipulated field experiments. We investigated the effects of vegetation patch types, root competition, putative mycorrhizal connections, soil moisture, and microclimate on the establishment of sugar pine (Pinus lambertiana) and white fir (Abies concolor) seedlings in an old-growth, mixed-conifer forest in the southern Sierra Nevada. Seedling survival rates were significantly higher under closed tree canopies than in patches dominated by manzanita (Arctostaphylos patula) shrubs. Treatments that allowed seedlings to connect with existing ectomycorrhizal networks did not enhance their survival. Isotope signatures suggest that mature conifer trees rely on water from deep soil layers (>50 cm), while shrubs and tree saplings (1–3 m in height) rely on water from shallower layers (0–50 cm) at the beginning of the season, but as soils become drier the shrub's and the sapling's primary zone of uptake shifts downward in the soil profile. These findings imply that shrubs may inhibit the survival of establishing tree seedlings until the seedlings have a deep enough root system to extract soil moisture from soil below 50 cm. Our study suggests that tree seedling survival may depend on a seedling's ability to compete with shrubs for scarce soil moisture in the near-surface soil layers.
The alpine zone of the White Mountains of California, defined as non-forested areas above 3500 m, includes 163 native species of vascular plants in an area of 106 km2. No invasive species have become well established. Nearly two-thirds of the native species occur in just seven families, led by the Asteraceae with 30 species. Six genera have five or more species, led by Carex with 14 species. Life forms of the flora are heavily dominated by broad-leaved herbaceous perennials (53%), followed in importance by graminoid perennials (22%) and mats and cushions (11%). Woody shrubs, chamaephytes (low subshrubs), and annuals are relatively few in number, and those species present are generally more characteristic of lower elevation communities. Fellfields form the characteristic habitat for 41% of the flora, while moist meadows and open slopes habitats characterize 24 and 22% of the flora, respectively. Only 31% of the flora is restricted in the White Mountains to the alpine zone, while nearly a third of the alpine flora has a range extending to lower elevations of the montane or cold desert zones below 2900 m. The alpine flora of the White Mountains shares over 70% of its species with the Sierra Nevada. Only three species are endemic to the alpine zone of the White Mountains: Draba californica, D. monoensis, and Potentilla morefieldii.
Arundo donax L. (Poaceae) is an invasive grass that severely degrades riparian habitats. It grows in many-stemmed clumps and, in California, spreads vegetatively only. Currently, A donax is thought to invade new areas through fragments broken from established clumps during flood events. But the role of flooding in generating fragments is based on anecdotal evidence only and has not been adequately studied. I examined A. donax clump break-up and reproduction via fragmentation in the Tijuana River Valley, California. I found that: (1) the majority of the new recruits from fragments grew from rhizome fragments (85% of 54) rather than stem fragments; (2) during the record rainfall of 2004–2005, flood waters damaged the rootstock of only a small proportion of clumps in the flood zone (7%; n = 46 clumps), and relatively few recruits from fragments subsequently became established in the valley at large (0.048 recruits 100 m−2); and (3) during emergency channel maintenance along one tributary, bulldozers severely damaged the rootstock of all clumps growing on the channel bank (n = 3 clumps), and many recruits from fragments subsequently became established downstream of the bulldozer activity (2.92 recruits 100 m−2; 61 times the number in the valley at large). These results indicate that, in the Tijuana River Valley, flood events only rarely break up A. donax rootstock and wash rhizomes downstream, and bulldozers play an important, and overlooked, role in the break-up and dispersal of A. donax. To reduce the spread of A. donax via rhizome fragments, regulatory agencies should require appropriate management practices when bulldozers are used in the presence of A. donax, and land managers should not use bulldozers when attempting to eradicate A. donax.
In California, the Vegetation Type Map (VTM) project of the 1930's has provided valuable historical vegetation data. Albert Wieslander led this effort to survey the forests of California in the 1930's. His crews surveyed over 150,000 km2, drawing detailed vegetation maps, taking 3000 photos and 17,000 vegetation plots. We developed a technique to digitize the Placerville 30′ quadrangle VTM, rendering it to a Geographic Information System (GIS). The map covers 2408.8 km2 of the west slope of the Sierra Nevada. In this area VTM crews identified 59 dominant plant species and eight genera or land cover classes and mapped their distribution into 3422 polygons. They identified recently disturbed areas that covered 13.5% of the landscape. We compared the digital VTM quad to CALVEG, a satellite-derived vegetation map from 1996. Land cover change for California Wildlife Habitat Relationship (WHR) vegetation types had occurred on 42.1% of the area. WHR types with the largest gains were: Montane Hardwood, Douglas-Fir, and Annual Grassland. Low elevation hardwoods, particularly Blue Oak Woodland (dominated by Quercus douglasii, Fagaceae), chaparrals and upper elevation conifers were the types that lost the most area. Differences in mapping techniques are unlikely to be the cause of this change because the analysis used controlled for map-based errors. Potential causes of the observed change at these physiognomic levels of classification include human perturbation, succession, and climate change.
A newly described local endemic species, Arctostaphylos ohloneana M.C. Vasey and V.T. Parker, is found scattered within populations of another geographically restricted manzanita species, Arctostaphylos glutinosa Schreiber, from the “Lockheed Chalks” area on siliceous shale ridges, northern Ben Lomond Mountain, western Santa Cruz County. This species is found in at least four scattered occurrences within the distribution of A. glutinosa on private property owned by the Lockeed Martin Corporation at the end of Empire Grade Road. Arctostaphylos ohloneana superficially resembles A. pungens and A. manzanita, but it presents distinctive characters that separate it from these two species. Unlike the tetraploid A. manzanita, A. ohloneana is diploid, and it lacks the distinctive nascent inflorescence of A. pungens. Since neither A. pungens nor A. manzanita occurs in the Santa Cruz Mountains, A. ohloneana is all the more remarkable by virtue of its distinctiveness compared to other nearby species.
A literature review and determination of specimens performed in conjunction with treatment preparations for the Flora of North America North of Mexico and the second edition of The Jepson Manual indicates that the names in use for two Arctotis species (Arctotideae: Asteraceae) occurring in California need updating. Venidium fastuosum (Jacq.) Stapf, a rare escape from cultivation, should be Arctotis fastuosa Jacq. (Pl. hort. schoenbr. 2: 20, pl. 166; 1797) and A. venusta Norl. (Bot. Not. 118: 406-7; 1965) is the correct name for a naturalized species previously determined as A. stoechadifolia P.J. Bergius.
Specimens (in FH and PC) of Cumathamnion sympodophyllum M.J. Wynne and K. Daniels (Delesseriaceae, Rhodophyta) made by C. G. Pringle at Cape Mendocino, northern California in 1882 are the first known collections of this rare monospecific genus. A collection (US) made by E.Y. Dawson from Trinidad Head, Humboldt County, and reported in 1965 as a “very compact, short-bladed” form of Delesseria decipiens J. Agardh is re-determined to be C. sympodophyllum. Records of C. sympodophyllum from Oregon, Washington, and British Columbia (Canada) are based on one collection from British Columbia, which cannot be verified. This taxon is most likely restricted to very exposed lower littoral rocky outcrops of Sonoma, Mendocino, and Humboldt counties in California.