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Quartz‐in‐garnet elastic geobarometry (QuiG) pressures in rocks from two Barrovian metamorphic terranes in the western US Cordilleran hinterland exceed pressures determined using chemical thermodynamics by 3–4 kbar. For this study, 135 quartz inclusions from the Funeral Mountains, California, were analysed using QuiG in five garnets from three locations representing metamorphic grades of upper greenschist, lower amphibolite, and middle amphibolite facies. From a second Barrovian terrane, the Wood Hills in northeastern Nevada, 125 quartz inclusions were analysed using QuiG in 14 garnets from a single rock sample metamorphosed to middle amphibolite facies. Pressures determined for rocks in the Funeral Mountains using QuiG and methods rooted in equilibrium thermodynamics yielded consistent pressure differences between locations, but QuiG pressures are higher. Similarly, QuiG pressures determined for rocks in the Wood Hills are higher than pressures determined by equilibrium thermodynamic approaches. Possible explanations for the pressure differences include garnet compositions not reflecting equilibrium, sources of error in thermodynamic calculations such as thermodynamic data or a‐X models, or an unknown source of systematic error that causes QuiG to overestimate pressures of entrapment. To test Raman spectroscopy's ability to reproduce inclusion pressures, pressures were calculated using Raman spectroscopy and synchrotron X‐ray diffraction, which yielded consistent pressures and support the use of the single mode‐shift of the 464 cm−1 band of quartz for geobarometry, which simplifies the method by assuming hydrostatic compression of quartz. These results are compared with pressures obtained using Grüneisen tensors and show consistency between these different approaches. [ABSTRACT FROM AUTHOR]

We present new P and S teleseismic tomography models of the upper mantle beneath California and Nevada. Improved tomographic methods and the incorporation of new data increase image resolution and seismic structure definition. Technical advancements include the use of 3‐D ray tracing, ray weighting and finite‐frequency sensitivity kernels. Together with the incorporation of modern crustal velocity models to account for crustal delay time, these tomographic advancements reveal slightly higher amplitudes and narrower structures beneath prominent tectonic features in California and Nevada. The addition of new data from the southern California Borderland and northwestern California are particularly useful. Based on our imaging results, we discuss the effects of temperature and partial melt on upper mantle seismic velocity beneath California and Nevada. We interpret the major seismically fast structures in our study area to be Juan de Fuca slab and its downward continuation beneath central Nevada and foundered Farallon lithosphere beneath the southern Sierra Nevada and Transverse Ranges. The seismically slow structures beneath the slab‐free window of northern California Coast Range, the Salton Trough extensional basin, and the Cascadia back arc, are all consistent with the presence of partial melting of decompressing mantle. The imaged seismically fast and slow anomalies imply buoyancy variations and melt productivity that ultimately act on the overlying crust. Plain Language Summary: We present new images of the structure of the upper mantle beneath California and Nevada based on the travel times of seismic waves from around the world. Modern methods and new data increase image resolution and seismic structure definition, and these advancements reveal stronger and narrower structures beneath prominent geologic features in California and Nevada. Based on our results we discuss the effects of temperature and partial melt on upper mantle seismic velocity beneath this region. We interpret structures in the upper mantle beneath central Nevada, the southern Sierra Nevada, the Transverse Ranges, and the Salton Trough. The imaged regions of faster seismic wave speeds are associated primarily with the Juan de Fuca‐Farallon slab. Structures imaged with slower seismic wave speeds indicate the presence of partial melt in the upper mantle. These seismic anomalies imply variations in the upper mantle that ultimately impact the overlying crust in California and Nevada. Key Points: We image upper mantle structures beneath California and Nevada with improved seismic techniques and an expanded data setThe major seismically fast anomalies likely represent fragments of Farallon oceanic lithosphereSlow anomalies are consistent with elevated temperatures and partial melt of decompressing mantle [ABSTRACT FROM AUTHOR]

We present a data‐driven approach to clustering or grouping Global Navigation Satellite System (GNSS) stations according to observed velocities, displacements or other selected characteristics. Clustering GNSS stations provides useful scientific information, and is a necessary initial step in other analysis, such as detecting aseismic transient signals (Granat et al., 2013, https://doi.org/10.1785/0220130039). Desired features of the data can be selected for clustering, including some subset of displacement or velocity components, uncertainty estimates, station location, and other relevant information. Based on those selections, the clustering procedure autonomously groups the GNSS stations according to a selected clustering method. We have implemented this approach as a Python application, allowing us to draw upon the full range of open source clustering methods available in Python's scikit‐learn package (Pedregosa et al., 2011, https://doi.org/10.5555/1953048.2078195). The application returns the stations labeled by group as a table and color coded KML file and is designed to work with the GNSS information available from GeoGateway (Donnellan et al., 2021, https://doi.org/10.1007/s12145-020-00561-7; Heflin et al., 2020, https://doi.org/10.1029/2019ea000644) but is easily extensible. We demonstrate the methodology on California and western Nevada. The results show partitions that follow faults or geologic boundaries, including for recent large earthquakes and post‐seismic motion. The San Andreas fault system is most prominent, reflecting Pacific‐North American plate boundary motion. Deformation reflected as class boundaries is distributed north and south of the central California creeping section. For most models a cluster boundary connects the southernmost San Andreas fault with the Eastern California Shear Zone (ECSZ) rather than continuing through the San Gorgonio Pass. Key Points: Unsupervised clustering methods provide a data‐driven way of analyzing and partitioning Global Navigation Satellite System observations of crustal deformationDeformation is distributed across the San Andreas fault system but is localized at the creeping section in central CaliforniaThe Southern San Andreas fault connects with the Eastern California Shear Zone rather than the rest of the San Andreas fault system [ABSTRACT FROM AUTHOR]

Recent high impact wildfires and droughts in California and Nevada have been linked to extremes in the Evaporative Demand Drought Index (EDDI) and Standardized Precipitation Evapotranspiration Index (SPEI), respectively. Both indices are dependent on reference evapotranspiration (ET0). Future changes in ET0 for California and Nevada are examined, calculated from global climate model simulations downscaled by Localized Constructed Analogs (LOCA). ET0 increases of 13–18% at seasonal timescales are projected by late century (2070–2099), with greatest relative increases in winter and spring. Seasonal ET0 increases are most strongly driven by warmer temperatures, with increasing specific humidity having a smaller, but noteworthy, counter tendency. Extreme (95th percentile) EDDI values on the 2‐week timescale have coincided with recent large wildfires in the area. Two‐week EDDI extremes are projected to increase by 6–10 times during summer and 4–6 times during autumn by the end of the century. On multiyear timescales, the occurrence of extreme droughts based on 3‐year SPEI below the historical fifth percentile, similar to that experienced during the 2012–2016 drought across the region, is projected to increase 3–15 times by late century. Positive trends in extreme multiyear droughts will further increase seasonal fire potential through degraded forests and increased fuel loads and flammability. Understanding how these drought metrics change on various climate timescales at the local level can provide fundamental information to support the development of long‐term adaptation strategies for wildland fire and water resource management. Plain Language Summary: Since the start of the 21st century, California and Nevada have observed extreme wildland fires and droughts that have caused devastating impacts to ecosystems and society. A common feature of these events has been very high atmospheric evaporative demand—the "thirst" of the atmosphere—which has largely been driven by increased air temperatures caused by anthropogenic climate change. This study examines projected changes in evaporative demand, which of the input variables are causing those changes and how the frequency of extreme wildfire potential and multiyear droughts will change. Evaporative demand is found to increase during all seasons, and increased temperatures drive most of that change. The likelihood of extreme wildfire potential based on 2‐week periods of elevated evaporative demand during summer and autumn increases substantially. A climatic water balance based on precipitation and evaporative demand indicates extreme 3‐year droughts that hold potential to deplete regional‐scale water supply also become much more likely. Future adaptation planning efforts for wildfire management agencies, forest management, and water resource managers should account for a greater likelihood of more extreme events. Key Points: All climate models show increasing reference evapotranspiration (ET0) through the end of the centuryIncreased air temperature has the greatest contribution to projected ET0 increasesExtreme ET0‐based wildfire potential and 3‐year droughts based on precipitation minus ET0 become much more frequent in the future [ABSTRACT FROM AUTHOR]

Trophic cascades are extensively documented in nature, but they are also known to vary widely in strength and frequency across ecosystems. Therefore, much effort has gone into understanding which ecological factors generate variation in cascade strength. To identify which factors covary with the strength of cascades in streams, we performed a concurrent experiment across 17 streams throughout the Sierra Nevada Mountains. We eliminated top consumers from experimental substrates using electrical exclusions and compared the strength of indirect effects of consumers on the biomass of primary producers relative to control patches. In each stream we 1) classified the dominant invertebrate herbivores according to life-history traits that influence their susceptibility to predators, 2) determined the abundance and diversity of algae and herbivores, and 3) measured production-to-biomass ratios (P:B) of the stream biofilm. This allowed us to assess three common predictions about factors thought to influence the strength of trophic cascades: cascade strength 1) is weaker in systems dominated by herbivores with greater ability to evade or defend against predators, 2) is stronger in systems characterized by low species diversity, and 3) increases with increasing producer P:B. When averaged across all streams, the indirect effect of predators increased the biomass of periphyton by a mean 60%. However, impacts of predators on algae varied widely, ranging from effects that exacerbated algal loss to herbivores, to strong cascades that increased algal biomass by 4.35 times. Cascade strength was not related to herbivore traits or species diversity, but decreased significantly with increasing algal diversity and biofilm P:B in a stream. Partial regression analyses suggested that the relationship between cascade strength and algal diversity was spurious, and that the only significant covariate after statistically controlling for cross-correlations was algal P:B. Our study contributes to the ongoing debate about why trophic cascade strength varies in nature and is useful because it eliminates factors that have no potential to explain variation in cascades within these stream ecosystems. [ABSTRACT FROM AUTHOR]

We studied home range and habitat selection of radio-marked adult California spotted owls (Strix occidentalis occidentalis) randomly selected from among the breeding population of owls in the central Sierra Nevada, California from June to October 2006. The most parsimonious home-range estimate for our data was 555 ha (SE = 100 ha). Home-range size was positively correlated with the number of vegetation patches in the home range (habitat heterogeneity). We used resource selection ratios to examine selection of vegetation types by owls within our study area. Owl home ranges contained a high proportion of mature conifer forest, relative to its availability, although the confidence interval for this estimate overlapped one. We also used resource selection functions (RSF) to examine owl foraging habitat selection. Relative probability of selection of foraging habitat was correlated with vegetation classes, patch size, and their interaction. Owls showed highest selection rates for large patches (>10 ha) of pole-sized coniferous forest. Our results suggested that spotted owls in the central Sierra Nevada used habitat that contained a high proportion of mature conifer forest at the home-range scale, but at a finer scale (foraging site selection) owls used other vegetation classes interspersed among mature forest patches, consistent with our hypothesis that spotted owls may use other forest types besides old growth and mature forests when foraging. Our study provides an unbiased estimate of habitat use by spotted owls in the central Sierra Nevada. Our results suggest that forest managers continue to protect remaining mature and old-growth forests in the central Sierra Nevada because owl home ranges contain high proportions of these habitats. However, our results also showed that owls used younger stands as foraging habitat so that landscape heterogeneity, with respect to cover types, may be an important consideration for management but we did not attempt to relate our findings to fitness of owls. Thus management for some level of landscape heterogeneity for the benefit of owls should proceed with caution or under an adaptive management framework. [ABSTRACT FROM AUTHOR]

Maurer, Edwin P., Levi D. Brekke, and Tom Pruitt, 2010. Contrasting Lumped and Distributed Hydrology Models for Estimating Climate Change Impacts on California Watersheds. Journal of the American Water Resources Association (JAWRA) 46(5):1024-1035. DOI: 10.1111/j.1752-1688.2010.00473.x Abstract: We compare the projected changes to streamflows for three Sierra Nevada rivers using statistically downscaled output from 22 global climate projections. The downscaled meteorological data are used to drive two hydrology models: the Sacramento Soil Moisture Accounting model and the variable infiltration capacity model. These two models differ in their spatial resolution, computational time step, and degree and objective of calibration, thus producing significantly different simulations of current and future streamflow. However, the projected percentage changes in monthly streamflows through mid-21st Century generally did not differ, with the exceptions of streamflow during low flow months, and extreme low flows. These findings suggest that for physically based hydrology models applied to snow-dominated basins in Mediterranean climate regimes like the Sierra Nevada, California, model formulation, resolution, and calibration are secondary factors for estimating projected changes in extreme flows (seasonal or daily). For low flows, hydrology model selection and calibration can be significant factors in assessing impacts of projected climate change. [ABSTRACT FROM AUTHOR]

Northern saw-whet owls (Aegolius acadicus) are secondary cavity-nesters and their dependence on snags has potential repercussions on forest management practices. Descriptive studies exist regarding habitat characteristics around saw-whet nest and roost areas, yet few studies have examined associations within larger areas or relative to snag characteristics (e.g., density). We conducted owl broadcast surveys and snag sampling during the spring and summer of 2006 and 2007 in the Lake Tahoe Basin of the central Sierra Nevada; we measured additional habitat variables from Geographic Information System layers. We modeled detection and occupancy probabilities for saw-whets using sampling and site covariates at survey sites. In addition, we used stepwise logistic regression to compare habitat characteristics at owl use sites and nonuse sites at 2 spatial scales. Detection probability was low in 2006 and decreased throughout the survey period; detection probability was slightly higher in 2007 and unaffected by day of survey. Probability of occupancy was affected by elevation and dominant tree species in 2007. Similarly, stepwise logistic regression indicated saw-whet occurrence was negatively correlated with the percentage of area dominated by white fir (Abies concolor) at both the macrohabitat (approx. 260 ha) and microhabitat (approx. 20 ha) scales and was positively correlated with the percentage of area containing open canopy at the microhabitat scale. We did not find correlations between saw-whet occurrence and snag characteristics. Current restoration projects in areas of the Sierra Nevada aim to decrease relative abundance of white fir and the number of snags in forest stands. We recommend continued monitoring of saw-whets to understand potential effects of these restoration activities. Our estimates of saw-whet occupancy and detection probabilities can be used by forest managers to determine necessary survey effort for reliable results when developing monitoring protocols. [ABSTRACT FROM AUTHOR]

1. Non-native trout have been stocked in streams and lakes worldwide largely without knowledge of the consequences for native ecosystems. Although trout have been introduced widely throughout the Sierra Nevada of California, U.S.A., fishless streams and their communities of native invertebrates persist in some high elevation areas, providing an opportunity to study the effects of trout introductions on natural fishless stream communities. 2. We compared algal biomass and cover, organic matter levels and invertebrate assemblages in 21 natural fishless headwater streams with 21 paired nearby streams containing stocked trout in Yosemite National Park. 3. Although environmental conditions and particulate organic matter levels did not differ between the fishless and trout streams, algal biomass (as chlorophyll a concentration) and macroalgal cover were, on average, approximately two times and five times higher, respectively, in streams containing trout. 4. There were no differences in the overall densities of invertebrates in fishless versus paired trout streams; however, invertebrate richness (after rarefaction), evenness, and Simpson and Shannon diversities were 10–20% higher in fishless than in trout streams. 5. The densities of invertebrates belonging to the scraper-algivore and predator functional feeding guilds were higher, and those for the collector-gatherer guild lower, in fishless than trout streams, but there was considerable variation in the effects of trout on specific taxa within functional feeding groups. 6. We found that the densities of 10 of 50 common native invertebrate taxa (found in more than half of the stream pairs) were reduced in trout compared to fishless streams. A similar number of rarer taxa also were absent or less abundant in the presence of trout. Many of the taxa that declined with trout were conspicuous forms (by size and behaviour) whose native habitats are primarily high elevation montane streams above the original range of trout. 7. Only a few taxa increased in the presence of trout, possibly benefiting from reductions in their competitors and predators by trout predation. 8. These field studies provide catchment-scale evidence showing the selective influence of introduced trout on stream invertebrate and algal communities. Removal of trout from targeted headwater streams may promote the recovery of native taxa, community structure and trophic organisation. [ABSTRACT FROM AUTHOR]

Arguments for collaborative rather than adversarial approaches to governance rest partly on two axioms: first, that collaborative approaches mitigate conflict to intermediate levels and second, that collaborative approaches help integrate science and values through various joint fact-finding strategies. Using questionnaire data in 1984 and 2001 of policy participants involved in Lake Tahoe water quality policy, this article investigates whether a shift from an adversarial to a collaborative policy subsystem is associated with (i) convergence in beliefs regarding water quality problems and policy proposals; and (ii) an increase in the use of science-based empirical beliefs and a decrease in the use of normative beliefs in supporting policy proposals. The findings send a mixed message to policymakers and researchers about science and collaboration. The analysis suggests that collaborative policy subsystems are associated with convergence in some beliefs between rival coalitions, but it also suggests that policy participants are no more likely to rely on science-based, empirical beliefs in collaborative than in adversarial policy subsystems. [ABSTRACT FROM AUTHOR]

The article discusses a study on sizes of runoff sediments linked to soil erosion in the Lake Tahoe basin in California and Nevada. It was noted that accumulation of nutrients and loss of clarity in the lake have resulted from runoff sediments from disturbed soil. Data used in the study included those for runoff, infiltration and runoff rates and average sediment concentration. It was found that particles of granitic soils are bigger than those of volcanic soils. The study also revealed that increasing slope have smaller particle size.

Biogeographical patterns within the California Floristic Province have been greatly affected by geological and climatic events. Here, we investigate the phylogeography of foxtail pine ( Pinus balfouriana) in an effort to date its range disjunction using molecular data and to further our understanding of phylogeographical patterns for plants within the California Floristic Province. The distribution of foxtail pine is characterized by a 500-km disjunction separating populations located in the Klamath Mountains from those in the southern Sierra Nevada. Previous authors suggested that this disjunction occurred approximately 4000–8000 years ago during the Holocene Xerotherm when western North America became warmer and drier. Those dates, however, are inconsistent with the morphological differences that separate regional populations into formally recognized subspecies. Using the coalescent-based isolation with migration model and DNA sequence data from the chloroplast, mitochondrial, and nuclear genomes, we evaluate several hypotheses addressing the timing of this range disjunction and its effects on subsequent patterns of gene flow. Results from all three genomes are largely consistent with Middle to Early Pleistocene divergence dates. Those dates correspond to the Sherwin glaciation, which was the largest Pleistocene glacial episode in the Sierra Nevada. Gene flow, moreover, was only documented using data from the chloroplast genome, suggesting that low levels of long-distance pollen dispersal ( Nem<0.5) have occurred since this divergence event. These results are extended to a discussion of the biogeographical development of subalpine forests in California. [ABSTRACT FROM AUTHOR]

The efficacy of in-stream nephelometric turbidometric as a surrogate for total suspended solids (TSS) and total phosphorus (TP) concentrations was evaluated for use in low turbidity (<50 NTU) subalpine watersheds at Lake Tahoe, California-Nevada, USA. Continuous turbidity records for the 1999, 2000 and 2001 snowmelt seasons and data from water quality samples (1982-2000) were examined to determine watershed sediment delivery dynamics. Strong correlations were found between turbidity and both TSS and TP concentration. The strong correlation indicates that turbidity can serve as a good surrogate for direct measurement in these watersheds. The watersheds displayed clockwise hysteresis: sediment flushing and depletion, on daily, seasonal and decadal time-scales. The hysteresis curves had strong concave shapes, indicating a sensitive response to peak flow. A pronounced seasonal trend was observed for the ratio of suspended sediment concentration (SSC)/discharge over time, indicating early season flushing of available sediment. Significant linear relationships (p < 0.051 were found for 12 of 17 years. Comparison of annual sediment rating curve coefficients indicated smaller coefficients during high sediment loading years and in the years following. The smaller coefficients are evidence of sediment depletion during high flow years. The effect of hysteresis on monitoring methods was illustrated by comparing turbidity estimates of TSS load with sediment rating curve estimates of SSC. After accounting for differences in SSC/TSS methods of analysis, daily loads calculated with turbidity methods were 58-98% of rating curve estimates for the spring snowmelt seasons of 1999-2001. [ABSTRACT FROM AUTHOR]

• Our primary goal was to determine whether detection of Rhizopogon internal transcribed spacer (ITS) groups is affected by the pine species used in seedling bioassays. Our secondary goal was to investigate composition of Rhizopogon spore banks in the Eastern Sierra Nevada of California, a previously unsampled region. • We used seedlings of Pinus contorta, Pinus jeffreyi, Pinus lambertiana, and Pinus muricata as bioassay plants and identified the Rhizopogon retrieved by internal transcribed spacer (ITS) sequence analysis. • We found that each of the pine species retrieved all of the abundant Rhizopogon ITS groups, but there were significant differences among pines in the richness of Rhizopogon ITS groups recovered. Pinus muricata recovered all ITS groups found in this study and was significantly better than P. lambertiana. Rhizopogon communities from the five sampled sites contained six to eight ITS groups per site, with two unique sequence groups and a higher abundance of the Rhizopogon ellenae and Rhizopogon arctostaphyli groups than at previously sampled sites. • These results show high cross-receptivity between Rhizopogon and pine species, and regional patterns in spore bank composition. [ABSTRACT FROM AUTHOR]

Aim The physiological requirements and tolerances of a species partially determine both its habitat preferences within a community and its broader geographic range. Therefore, we predicted that local ecology should be correlated with geographic distribution. We tested for a correlation between local ecology and range size, and we attempted to account for this correlation by the climate of the range. Location Bishop Creek Watershed, on the eastern side of the Sierra Nevada, California. Methods We recorded all plant species growing in each of 263 plots in the montane to alpine zones of the watershed. The local habitat preferences of 282 species were described in terms of wetness, elevation, soil, and amount of shade. The size and centre of the geographic range for each species were determined from regional floras. Results Wetness preference within the watershed was significantly correlated with range size. Specifically, plants of wet sites had larger ranges that extend to the north, whereas plants of dry sites tended to have smaller ranges centred to the east. The correlation between local wetness preference and range size was entirely explained by the location of the range centre of the species. Main conclusions A possible reason for the large ranges of mesophilic plants in our study area is that mesic habitats are continuous throughout the western Cordillera, while dry alpine habitats are isolated by valleys to the east. The correspondence between local ecology and geographic distributions implies evolutionary stasis in the niches of these plant species. [ABSTRACT FROM AUTHOR]

The Oligocene and Miocene Valley Springs Formation is one element in the middle to late Cenozoic alluvial fill of the Central Valley of California and represents a large fluvial depositional system that extended westward from sediment-filled palaeovalleys in the high Sierra Nevada to a piedmont alluvial plain under the present Central Valley. The Valley Springs Formation consists largely of tuffaceous mudrock, tuffaceous sandstone, polymict conglomerate and rhyodacitic tuff. The most prominent lithofacies in the formation is yellowish grey or greyish yellow, tuffaceous mudstone and claystone characterized by crude, commonly wavy layering or bedding, an irregular fracture, and common clay-lined partings, fissures, and small branching tubules. Petrographic and X-ray diffraction analysys of the composition, texture, fabric, mineralogy and organic content of an 8 m thick section of the tuffaceous mudrock lithofacies have provided evidence for an origin quite different from the earlier interpretations of this lithofacies as altered tuffs. Numerous rounded mudstone or claystone clasts in a detrital mud matrix, together with abundant freshwater microfossils (megaspores, chrysophyte cysts, diatoms and sponge spicules), indicates that the lithofacies is a mostly epiclastic sedimentary deposit. Root traces, fissuring, orientated clay skins lining pores and secondary surfaces, and mineralogical data are evidence of periodic exposure and desiccation The tuffaceous mudrock lithofacies of the Valley Springs Formation, interpreted in the context of the middle to lower regions of a piedmont alluvial system, most probably represents a complex of ephemeral lake and marsh environments on a low gradient alluvial plain. The referred abundance of shallow lakes, ponds and marshes implies a climate that was wetter than the semi-and climate of the region today. [ABSTRACT FROM AUTHOR]

Degradation of sagebrush habitat and a lack of information on current status motivated a petition to list the pygmy rabbit (Brachylagus idahoensis) as threatened or endangered under the Endangered Species Act. The petition brought on renewed interest in obtaining data on pygmy rabbits; however, pygmy rabbits are notoriously difficult to capture, especially in summer. We tested box-trap, net, noose-pole, and fabric-fence methods to capture pygmy rabbits in 4 areas of northern Nevada and eastern California, USA. We captured 25 different pygmy rabbits in 30 captures from April 2005 to July 2006. The combination of camouflaged box traps baited with canned green beans was 35% more successful and required less effort per captured rabbit than any other method. Noose-pole methods also were successful. These techniques provide an efficient method of capturing pygmy rabbits in summer when many remote field sites are most accessible. [ABSTRACT FROM AUTHOR]

The article discusses the research proposal which aims to conserve Dodecatheon jeffreyi against D. jeffreyanum (Primulaceae). The genera is believed to be widely scattered in the mountainous regions of Sierra Nevada and other places in the North America. In conjuntion with what precedes, these species are claimed to have been cultivated in the horticultural literature in most mountainous areas in the area mentioned.