We studied the effect of white-tailed deer (Odocoileus virginianus Zimmermann) browsing and fire on diversity and number of prairie-forb flowering stems in a remnant tallgrass prairie in northern Illinois. Our study included two plots protected from deer browsing since 1992 and two unprotected plots. All plots were burned twice in late April of 1990 and 1991. Deer densities of 32–50 km⁻² (1992–96) declined to 7–9 km⁻² in 1998 and 1999 after controlled hunting. Similarity between protected and unprotected plots was initially 82%, declined to 49% during the period of high deer density, and increased to 68% in 2001 with managed hunting. Flowering stems for all forbs were tallied in 1998–2001. Diversity (Shannon index [H′] and effective number of stems [HO]) of flowering stems was higher on protected than on unprotected plots for all study years. Differences in composition and diversity between protected and unprotected plots were associated with interactions between fire and protection from deer browsing as measured by total number of flowering stems, which was significantly higher on protected than on unprotected plots in nonburn years (3.4–3.5-fold) but not in burn years (1.0–1.2-fold). The two leading species on protected plots (ashy sunflower [Helianthus mollis Lam.] and Culver's root [Veronicastrum virginicum (L.) Farw.]) tended to have fewer flowering stems in burn years and always had them in protected plots (54-fold and 70-fold higher in protected plots for the two species, respectively). For the second leading species on unprotected sites (wild quinine [Parthenium integrifolium L.]), the number of flowering stems was significantly higher in burn years (27-fold); however, there was no significant difference in the number of stems between protected and unprotected plots. These results show strong interactions between fire and deer-browsing disturbances in communities recovering from deer overabundance.

Plant responses to hydrology are central to understanding the structure of wetland plant communities and to informing restoration efforts. The objectives of this study were to examine ecological responses of emergent plant species to water depth in a freshwater wetland in south-central New York (USA) and to test growth responses and associated nutrient relations for emergent species exposed to controlled water depths without interspecific competition in a greenhouse experiment. Field observations quantified the distribution of wetland plants in relation to water depth at Harpur Pond in the Binghamton University Nature Preserve. Presence or absence of plant species was noted in 0.25-m² quadrats, along 11 transects extending from the upland limit of emergents to their greatest depth in the pond. Ten of the 12 most frequent taxa showed significantly nonrandom distributions (P < 0.05). For example, Boehmeria cylindrica and Persicaria sagittata were more frequent > 0.2 m above the median water level, whereas Sparganium americanum and Leersia oryzoides were more frequent near it. In contrast, Eleocharis palustris was evenly distributed across the approximately 0.6-m elevational range. Species richness decreased significantly from the upper and middle ends to the lower end of the hydrological gradient, and plant community composition at the highest elevation was 80% dissimilar to that below the median water level. The greenhouse experiment was conducted to examine the effects of small-scale differences in water depth (−11 cm, −8 cm, −2 cm, and 3 cm in relation to the soil surface) on the growth and nutrient concentrations of transplanted ramets of five common wetland plant species: Juncus effusus, Scirpus cyperinus, L. oryzoides, Glyceria grandis, and S. americanum. After 45 days of growth, S. americanum had accumulated 96% greater biomass at 3 cm below the water level than at 11 cm above (P = 0.03 from one-way ANOVA), showing that minor differences in water depth can be important to plant success. Water depth did not significantly affect growth for the other four species. Greater biomass was correlated with lower tissue nitrogen concentration for S. americanum, L. oryzoides, and G. grandis and with lower phosphorus concentration for L. oryzoides and G. grandis, indicating that growth may result in nutrient dilution within tissues.

This study characterized associations between climate variables and radial growth of white ash (Fraxinus americana L.) at 12 sites along a longitudinal climate gradient in the eastern USA. Growth responses of this species to climate stresses have not been well documented, and this study sought to improve understanding of how climate change might affect white ash. Total annual ring-width data were obtained for trees at all sites, and data for earlywood and latewood width were obtained at six sites. Pearson's correlation coefficients were computed among radial growth indices and temperature, precipitation, and Palmer drought severity index (PDSI). Total ring width was positively correlated with precipitation and PDSI and negatively correlated with temperature during the months of May to July, when most radial growth occurs. These spatially replicated correlations indicate that white ash growth is most strongly influenced by drought stress in the first half of the growing season. Correlations between climate variables and latewood width were the same as for total ring width; latewood width explained 98% of the variation in total ring width. Earlywood width exhibited less interannual variation than latewood width did and was weakly correlated with climate variables for months before leaf-out was complete but not after. These correlations were consistent with the ecology and carbon allocation patterns of other tree species with ring-porous wood anatomy. The effect of climate change on white ash growth will depend on how changes in the balance between increasing temperature and precipitation alter the frequency and intensity of early growing-season droughts.

Fixed-width buffer zones on rivers and streams are designed to protect the diverse riparian community and its important function in the ecosystem. However, recent data suggest that riparian areas of some western forests have become more fire prone because of restrictions on fuel reduction treatments within buffer zones. Surprisingly little is known about where and how the plant community transitions from riparian to upland vegetation, but understanding that transition would inform the restoration of riparian forest structure and function and its associated management applications (e.g., prescribed fire or mechanical thinning) that may be necessary to achieve restoration. Using data collected from the Kings River Experimental Watersheds, we assessed the transition in plant structure and composition from riparian near-stream areas to upland locations, in mixed-conifer and red fir forests on headwater streams of the southern Sierra Nevada, CA. Our data strongly support the conclusion that the riparian zone, as evidenced by the riparian plant community, extends beyond 10 m from the stream on these narrow, first- and second-order streams. The herbaceous community at 10 m from the stream was distinct from the upland community and had greater similarity to locations closer to the stream in mixed-conifer forest. Species richness was three to four times greater in riparian areas compared with upland areas, and there was little overlap of the more-abundant herbaceous species. In addition, riparian forests were generally denser, with smaller trees in mixed-conifer forest, but had similar stand structure to upland forests in red fir forest. Differences between mixed-conifer and red fir forests may reflect different departures from the historical fire regime in these two community types. Compared with riparian areas of wetter climates, riparian areas of dry climates, such as the Sierra Nevada, may harbor even greater species diversity relative to nearby upland areas, indicating that buffer zones of restricted management may be justified in these forests if the goal is the preservation of biodiversity. However, perhaps more important, these findings, along with recent literature, highlight the need to identify site-specific goals when undertaking restoration of riparian forests in the western USA: herbaceous biodiversity, fuels reduction, historic tree composition and structure, and/or water quality.

Structural features of cypsela are important to certain tribes of Asteraceae; thus, the ontogeny of the fruit (only the pericarp) of 10 weedy Asteraceae species was determined concerning the contribution to increase the knowledge of the fruit development in Asteraceae. The species analyzed are Conyza bonariensis L. (Cronquist.), Cosmos sulphureus Cav., Eclipta alba L. Hassk., Elephantopus mollis Kunth., Emilia sonchifolia L. DC., Galinsoga quadriradiata Ruiz & Pav., Erechtites valerianifolius (Wolf) DC., Parthenium hysterophorus L., Praxelis clematidea (Griseb) R.M. King & H. Rob and Sigesbeckia orientalis L. The mesocarp in the cypsela structure shows variation in the number of layers, the cell layer arrangement of the sclerenchyma and parenchyma, and the presence of phytomelanin that is especially striking. The mesocarp traits of Heliantheae alliance species are homogeneous, and it has been suggested that the derived character phytomelanin may not have the same evolutionary history in species belonging to the same tribe. It is noteworthy that Cichorioideae cypsela has the same general structure as that of Asteroideae.

Recent studies have shown the laticifers of Apocynaceae, previously classified as nonarticulated, indeed are articulated, anastomosing laticifers whose transverse walls dissolve rapidly and entirely, although doubts about their growth mode still persist. To better understand the mode of laticifer growth and differentiation in this family, we studied its development in Allamanda blanchetii using anatomical and ultrastructural analyses. Our results showed that laticifers are formed by a row of cells that join each other through dissolution of the transverse walls from the center to the periphery. The laticifers originate from ground meristem and procambium; the laticifers in the different tissues connect through lateral fusion, generating a laticifer network. The laticifers occur in the cortex, pith, and vascular system of the shoot, mesophyll, and vascular bundles of the leaves. There is no apical growth, and all the organelles observed in the apices of the laticifers play a role in the production of latex or in the dissolution of the terminal walls between the cells that compose the laticifer. The latex is composed of many metabolites produced mainly in the endoplasmic reticulum and plastids. Mitochondria are abundant, and dictyosomes are scarce. The vacuome is prominent from the start of laticifer differentiation, and many small vacuoles and vesicles transport the secretion from cytosol into the central vacuole, where an emulsion of substances is stored. The articulated, anastomosing laticifers of A. blanchetii have no subcellular mechanism for production of a cell wall in a polarized manner or dissolution of middle lamella of the cells which surround the laticifer tip, proving that there is no intrusive growth in this secretory structure.

Study of reproductive patterns of understory species is of great importance because they influence the regeneration dynamics of a forest, and the biogeographic origin of these species will also define their responses to environmental conditions. In this study, we answer the following questions: Are there temporal patterns in the reproductive phenology of understory species? If so, what are the variables that influence them? How do the reproductive patterns of the species differ according to their biogeographic origin? To answer these questions, in the Abies religiosa forest in the Magdalena River Basin, Mexico City, we determined the flowering and fruiting patterns of 55 species using multivariate analyses. Spearman's correlations were calculated between the patterns found and the environmental variables, and Augspurger's synchrony indexes were also calculated. Our results showed three flowering and three fruiting patterns. The correlations showed a significant and positive relationship between flowering and precipitation during the rainy season. A significant and negative relationship was found between dry season fruiting pattern and soil moisture. The highest values of flowering and fruiting for both introduced species and native weeds occurred in different months than for characteristic understory species. Our results suggest strong relationships between reproductive patterns and biotic factors, mainly those related to species growth form and biogeographic origin. This is the first phenology study of this area, and it forms a basis for generation of hypotheses related to forest management and conservation.

We hypothesized that in the oligotrophic, acid soils of the New Jersey Pine Barrens, where native diversity and invasability appear to be low, the weathering of concrete block construction material over time has reduced resistance to plant species' invasion by reducing soil acidity. We also sought to determine whether alien species' success in disturbed Pine Barrens soil differs from that of the non–Pine Barrens North American plant species whose presence in the region is associated with anthropogenic soil disturbance. In the field, species richness of native Pine Barrens species, non–Pine Barrens species, and alien species was determined along with current-year aboveground biomass production and soil pH along transects extending from concrete block buildings and from paired control transects without concrete block buildings. Soil inorganic nitrogen was measured near and far from buildings. Additionally, a pot study using native soil amended with ground concrete was conducted to determine its effect on pore-water pH. Richness was significantly greater near buildings, with alien species concentrated within 6 m of buildings. Alien plant biomass was greater within 3 m of buildings than farther along the transects; however, productivity along the transects did not vary. Soil pH was elevated within 7.5 m of buildings and soil nitrate concentration was greater near buildings. The ground-concrete soil amendments were found to significantly elevate pore-water pH. We conclude that disturbed habitats with acid soil conditions possess a degree of ecosystem resistance to alien plant species establishment. However, this may be overcome by raising the soil pH.

We utilize fruit and seed morphology to help clarify the taxonomy of the Chenopodium neomexicanum complex. All previously synonymized taxa are recovered, and one new species within this complex, Chenopodium sonorense Benet-Pierce & M. G. Simpson, is described. For all members of the complex we present a descriptive characterization. We include a dichotomous key for members of this species complex, integrating both reproductive and vegetative characters.

We conducted the first comprehensive floristic study of the lichens and allied fungi of Salmonier Nature Park on the Avalon Peninsula in Newfoundland, Canada. By comparing our results to those from other provincial parks in Newfoundland, we show that Salmonier Nature Park has a regionally rich lichen biota that includes several uncommon species. We carry out an assessment of landscape-level drivers including geographic location and land cover diversity to determine whether lichen richness corresponds to patterns at the landscape extent. Within Salmonier, one species (Erioderma pedicellatum) is listed as “special concern” by the federal Committee on the Status of Endangered Wildlife in Canada and “critically endangered” by the International Union for Conservation of Nature. Two species are new to the island of Newfoundland: Phaeophyscia ciliata and Stereocaulon subcoralloides. Six species are new to the province of Newfoundland and Labrador: Ephebe hispidula, Muellerella lichenicola, Mycoblastus sanguinarioides, Placynthium flabellosum, Usnea flammea, and Xanthoparmelia angustiphylla. Our results provide baseline knowledge that allows changes in the lichen community to be monitored, the discovery of new species in the park to be acknowledged, regional distributions and frequencies to be better understood, and accurate comparisons to be made with other parks.