Although prolonged seed retention, or serotiny, is believed to be an adaptation to highly variable environments such as the Mediterranean regions of California, no prior study has systematically investigated the prevalence of seed retention among California oaks (family Fagaceae), the dominant woody taxon in California foothill woodlands. We quantified the extent to which acorns were retained into and through the winter and spring within the canopy of five species of California oaks at Hastings Reservation, Monterey County. Significant serotiny was found in coast live oak (Quercus agrifolia) and, to a lesser extent, valley oak (Q. lobata), but was absent in blue oak (Q. douglasii), canyon live oak (Q. chrysolepis), and California black oak (Q. kelloggii). In both species where serotiny was observed, seed retention was primarily predicted by the size of the focal tree's acorn crop. In addition, serotiny in coast live oaks was more prevalent in dry years and when the overall acorn crop of coast live oaks was large. We found no evidence that acorn fall in these species is triggered by a specific environmental event. Prolonged seed retention in California oaks renders acorns available in the canopy to wildlife throughout the winter in some years with potentially significant effects extending beyond those of acorn abundance per se.

During 2008 and 2010, we conducted a floristic inventory of the aquatic vascular plants of Yellowstone National Park (YNP). Here, we report noteworthy records found during a survey of over 224 collecting locations within YNP. We documented 26 noteworthy species from 151 collections. These records represent rare, under-collected or newly located species in YNP, Montana, and Wyoming. New records include members of the Araceae (incl. Lemnaceae), Haloragaceae, Hydrocharitaceae, Isoëtaceae, Lentibulariaceae, Potamogetonaceae, and Typhaceae (incl. Sparganiaceae). During our fieldwork, we located two species new to Montana (Myriophyllum quitense and Potamogeton strictifolius) and three species new to Wyoming (Isoëtes echinospora, Najas flexilis, and Utricularia ochroleuca). We also found a single location for P. obtusifolius, a species known historically from Wyoming. In addition, we located P. zosteriformis, a species that had not been collected recently in Wyoming. We also found several species that were either new to the flora of YNP (Callitriche heterophylla, N. flexilis, Potamogeton obtusifolius, P. zosteriformis) or species previously collected in YNP, but were misidentified in herbarium records (Lemna gibba, P. strictifolius, Stuckenia vaginata, and U. ochroleuca). Our work also has greatly augmented the known collections of additional rare species in the Greater Yellowstone Ecosystem such as Lemna valdiviana, M. verticillatum, P. amplifolius, P. friesii, P. robbinsii, and U. minor. In addition, we found new sites for infrequently encountered or easily overlooked aquatic species including Ceratophyllum demersum (Ceratophyllaceae), Elatine rubella (Elatinaceae), Elodea nuttallii (Hydrocharitaceae), Ruppia cirrhosa (Ruppiaceae), and Subularia aquatica (Brassicaceae).

The impacts of ploidy level changes on plant physiology and ecology present interesting avenues of research, and many questions remain unanswered. Here, we examine the connections between cytotype, taxon, stomata characteristics, and environmental variables in black-fruited hawthorns of the Pacific Northwest (Crataegus ser. Douglasianae; Maleae, Amygdaloideae, Rosaceae). We explore the extent to which stomatal measurements can be used to predict ploidy level and how differences in ploidy level and stomata characteristics relate to geographic distributions. We sampled trees from across the geographic ranges of the putative sister taxa Crataegus suksdorfii (Sarg.) Kruschke (diploids and autotriploids) and C. douglasii Lindl. (tetraploids). We found that stomata differed between the two species, with tetraploid C. douglasii having larger average stomata sizes than diploid and triploid C. suksdorfii. We also obtained climatological and elevation data for the sites at which these samples were collected, and examined the associations between taxon, ploidy level, stomatal size and density, elevation, and environmental parameters. Our analyses indicate positive associations between stomatal size and latitude, and between ploidy level and elevation. Negative associations were found between temperature and precipitation variables and both ploidy level and stomatal size, particularly for the fall and winter quarters. There appeared to be no significant association between stomatal density and any of the environmental variables. Tetraploid C. douglasii occupied a wider range of environmental conditions than did either the diploids or the autotriploids.

Growth of photosynthetic portions of Discocactus shoots is seemingly not suppressed by cephalium formation, as vascular traces are prominent between the vascular cylinder and the circular juncture of cephalium and juvenile growth. Neither of these morphological traits has previously been documented in the Cactaceae. I therefore provide a pair of hypotheses consistent with these morphological traits and suggest ways to test these hypotheses, although do not test them myself. One hypothesis for these morphological traits is that the shoot vascular cylinder bifurcates when the cephalium first forms, with one cylindrical ‘branch’ of the vascular cambium terminating in the shoot apical meristem and the other concentric cylindrical ‘branch’ of the vascular cambium terminating in a circular meristem at the base of the terminal cephalium. A second hypothesis is that subapical development occurs very slowly surrounding a depressed shoot apical meristem in Discocactus. Vegetative portions of the shoot mature sufficiently slowly that the cephalium can be well formed even while juvenile areoles and photosynthetic internodes continue to grow and develop for several years after production by the juvenile phase of the shoot apical meristem.

The stand-replacing Charlton, OR wildfire of 1996 burned several vegetation transects established before the fire, providing an opportunity to document recovery in one upland and five wetland vegetation zones over a 12-year period. Total mean percent cover of vegetation recovered to about 48% of pre-burn levels by year 12. Total cover increased slightly in Carex fen, but decreased in the other five zones. Fire damage was inversely proportional to moisture gradient, and recovery more or less directly proportional to the gradient. Upland Tsuga mertensiana forest sustained the greatest damage and showed the least recovery by year 12, followed by seasonally-flooded Polytrichum commune moss bed, Xerophyllum tenax ecotone, Vaccinium uliginosum shrub swamp, grass-dominated fen, and Carex fen. A transient soil crust of early-seral bryophytes occurred in upland Tsuga mertensiana forest. Cover of shrub, forb, grass, and moss layers declined in vegetation zones at the drier end of the moisture gradient, but increased in grass and sedge-dominated zones at the wetter end of the gradient, at the expense of forb, grass, and sedge layers.

Disturbance often has the net effect of promoting invasive plant establishment, but the precise nature of the relationship between disturbance and invasion can depend on community context. We used simulated gopher mounds in bare and monoculture plots of three California native grasses (Bromus carinatus var. maritimus [Piper] C. L. Hitch., Festuca rubra L., and Calamagrostis nutkaensis [J. Presl] Steudel) to test the effects of mounds on seedling establishment and survival of the European perennial grass Holcus lanatus L. Soil disturbance treatments were crossed with manipulations of the plant canopy (shade cages in bare and Bromus plots vs. pinning back grass leaves in Festuca and Calamagrostis plots) to separate some of the positive and negative effects of natural mounds. Mean PAR measured in February at the soil surface varied from 11 to 969 µm/m²/s. As predicted, shade structures that decreased light availability but also increased soil moisture generally increased Holcus seedling establishment and survival in bare and Bromus plots. In contrast, Holcus seedling establishment increased in response to increased light availability and soil disturbance in Festuca and Calamagrostis plots, even where water availability was lower. Thus, the relative importance of light and water availability across plot types appeared to determine the effect of disturbance on invasive plant establishment. Ultimately, Holcus survival was low on mounds in bare plots and on unshaded mounds in Bromus plots, and similarly low numbers of Holcus seedlings survived across all treatment combinations in Festuca and Calamagrostis plots. Therefore, our results do not support the hypothesis that gopher mounds explain the invasion of Holcus in native-dominated coastal prairie sites.

Triteleia piutensis E. Kentner & K. Steiner is described as a new species from the Piute Mountains of the southern Sierra Nevada in Kern County, California where it is known from only two small populations. Both populations are located in openings in pinyon-juniper woodland on volcanically derived soils. It is distinguished from other Triteleia species that have stamens attached at two different levels by its erect, yellow, campanulate flowers with recurved lobes, its short ovary stalk, and a geographic range restricted to the extreme southern Sierra Nevada Mountains. A revised key to Triteleia species with stamens attached alternately at two levels is provided.

A gynodioecious hexaploid (n  =  33), Cylindropuntia chuckwallensis M. A. Baker & M. A. Cloud-Hughes, is newly described. Populations of C. chuckwallensis extend from the Eagle Mountains of Joshua Tree National Park, through the Chuckwalla Mountains of Riverside County, to the north side of the Chocolate Mountains in Imperial County, California, USA, and occur on a variety of substrates primarily between 400–1600 m (1312–5250 ft) elevation. Of the flowering individuals studied, 38% produced only pollen-sterile flowers. Flower color in C. chuckwallensis ranges from dark red-purple (33%) through orange (54%) to yellow (13%). For most individuals (93%) the style and filaments are dark red to light pink. Morphological measurements were made for 15 populations of Cylindropuntia, including four of C. chuckwallensis, four of C. echinocarpa, three of C. multigeniculata, and four of C. acanthocarpa. Multivariate analyses indicated that C. chuckwallensis possesses a unique combination of characters. Fewer than 3% of the 121 C. chuckwallensis individuals sampled were misclassified by discriminate function analysis, one as C. echinocarpa, and three as C. multigeniculata.