Thesis (Ph. D.)--University of California, Berkeley, 2006. / Includes bibliographical references.

Taiwan is an island surrounded by sea. Due to the topography, the coastal wetlands distribute almost around the west seashore, and some at the estuary of the east seashore. The coastal wetland is a transitional area between territory ecosystem and marine ecosystem. The environment of the coastal wetland is influenced by tide and season, thus the distribution of vegetations here exhibits a dynamic equilibrium. This study attempts to investigate the distribution and composition of the vegetation and the appearance of the habitat environment at the coastal wetland of Taiwan. According to the results, 173 species belonging to 50 families have been recorded. This indicates that the diversity of the marsh vegetation at the coastal wetland is low. Most of the species belong to Gramineae, Compositae and Cyperaceae. Paspalum vaginatum and Phragmites karka are the most dominant plant at coastal marsh environments. According to the results of detrended correspondence analysis (DCA) and cluster analysis (CA), 16 vegetation types including one subtype and one transitional type are classified. The habitats of these vegetation types can be classified into five types, namely tidal fresh water marsh, fresh water-salt marsh, wet meadow, salt marsh and submerged environment. Most of these vegetation types have only one major dominant species. The distribution of the marsh vegetation features a belting pattern, which is mainly limited by the maximum of their salt tolerance from coastal toward inland, or estuary toward headwaters. Subsequently, it can by influenced by soil moisture and pH value. Furthermore, the vegetations are influenced by many additional environmental factors, resulting in a mosaic distribution of vegetation types. The marsh vegetation is processing at an unstable and developing period. Because the coastal wetland is seriously disturbed by human activities, the environmental variation becomes greater. Therefore, the transitional vegetations were observed frequently. Finally, the development pressure due to economic demand is the major cause that makes coastal wetland disappeared. It is urgently needed to protect this sensitive natural resource.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [69]-72).

This study examines modern relationships among salt marsh plant species and their pollen in three salt marshes located on the northwest coast of the Bay of Fundy, New Brunswick. Linear regression analysis of pollen in 35 surface sediment samples and vegetation cover on small (<15 m) and broad (>15 m) scales show that, with the exception of Poaceae and Cheno Am, pollen corresponds well with fine-scale patterns of salt marsh vegetation. Scatter diagrams of paired pollen and cover data illustrate that cover of Triglochin is over-represented by its pollen, Glaux is under-represented, and Poaceae, Cheno Am, and Plantago are inconsistent. Tidal mixing and differential inputs from local, regional, and extra-regional sources with elevation limit the establishment of plant-pollen relationships for Cheno Am and Poaceae but not for other taxa. Comparison of 35 modern analogs from five vegetation zones using squared chord distance show that zones are distinct such that the marsh-terrestrial interface can be tracked with the greatest degree of certainty in a salt marsh paleo-ecological record and other marsh zones can be tracked when a conservative threshold of dissimilarity is used.

Thesis (M.S.)--Oregon State University, 1992. / Typescript (photocopy). Includes bibliographical references (leaves 105-112). Also available via the World Wide Web.

No description available.

Water levels of Malheur Lake in southeastern Oregon fluctuate widely with seasonal and cyclic climatic changes. Seven years of severe flooding from 1978 to 1984 produced the highest water levels in recorded history and covered almost all marsh vegetation. Seven years of drought followed the flooding, and by 1992 the water level had dropped to the lowest point in nearly 60 years. A survey of vegetation colonizing the lakeshore as flood water receded was conducted from 1989 to 1992 to describe the reestablishment of marsh vegetation. Six transects were placed in three different ecological units of the lake. Frequency and cover data for each plant species were recorded. Recruitment from seed banks produced germination the first year of annual, mud flat species followed the second year by perennial emergent seedlings. The emergent seedlings generally did not survive the drought as water levels continued to recede. The seeds of introduced Eurasian species were distributed by wind, became lodged in the cracks of drying mud flats and then germinated following winter rains. The central ecological unit, fed by both the Blitzen and Silvies Rivers, did not show severe effects of drought and species of emergent vegetation grew without apparent signs of drought stress.

The low-lying topographic nature of salt marshes makes plants in these communities particularly vulnerable to increased salinity and inundation exposure associated with sea level rise. Both increased salinity and inundation have been cited as major causes of reduced plant performance and survival in marsh and areas fringing marsh. In addition to limitations imposed by physical stress, interspecific interactions have also been shown to mediate the performance and survival of salt marsh and salt marsh fringing species. The Stress Gradient Hypothesis (SGH) postulates that species interactions shift from competitive to facilitative as stress levels increase and predicts that (a) the frequency and intensity of facilitative interactions increase as conditions become more stressful for plants and (b) the strength of competitive interactions increases as abiotic stress levels diminish. The SGH has been rigorously tested to examine how both the frequency and intensity of species interactions change under varying physical stress levels. Studies conducted in salt marsh systems have shown facilitation to be as strong of a driving force as competition in influencing plant performance and survival and have shown that while competition appears to be the pervasive force in the less physically stressful terrestrial zones fringing salt marshes, facilitation influences the performance and survival of species in harsher marsh areas. Under conditions of sea level rise, it remains unclear if the nature of interspecific interactions would shift as stress levels change. This research endeavors to examine the interplay between abiotic stresses and biotic interactions under conditions of increased salinity and inundation exposure. The first study presented here investigated the effects of increased inundation and soil salinity associated with sea level rise on four salt marsh fringing species, and assesses how competition and facilitation impact survival of salt marsh fringing plant survival under these changing conditions. All plant species experienced reduced growth and photosynthetic inhibition below their current distributional positions, both in the presence and absence of neighboring above ground vegetation. The findings also signal a potential shift in the nature of interspecific interactions from competition to facilitation to neutral as plants begin to experience increased salt and inundation exposure. The second study aimed to disentangle the effects of increased soil salinity and increased soil moisture on four salt marsh fringing species, and to examine the effects of plant neighbors. The results showed that fringe plants exposed to increased inundation experienced a two-fold reduction in performance and survival over 750 g pure salt addition, suggesting that inundation may be a more important limiting factor than salinity with rising sea levels. Landward transplants at the forest-fringe margin exposed to lower soil salinity and decreased inundation exhibited a three-fold increase in performance and survival when compared to controls. Neighbor manipulation studies, which consisted of trimming neighboring vegetation to ground level, again suggested that interspecific interactions in salt marsh fringing species may shift from competitive to facilitative with climate-induced sea level rise. Overall, our findings suggest that salt marsh fringing species may not be able to tolerate changing conditions associated with sea level rise and their survival may hinge on their ability to migrate towards higher elevations. The final experiment tested the Stress Gradient Hypothesis and investigated the relative importance of facilitation and competition in a salt marsh system under varying stress levels. This study also ascertained whether salt or inundation exposure is the primary influence on salt marsh plant performance and survival. As in previous studies, our findings suggest that many salt marsh plants don't require, but merely tolerate harsher abiotic conditions. The results showed that plants at higher elevations were depressed by strong competitive pressure from neighboring fringe species while plants at lower elevations benefited from the presence of neighbors. Collectively, the results of these studies indicate that species interactions are an integral driver of plant distribution in salt marsh communities. Furthermore, our findings indicate that changing stress levels may not always result in a shift in the nature of interspecific interactions. These studies have endeavored to show that the interplay between competition and facilitation interacts with physical processes to determine the growth and performance of both fringe and marsh plant species. The paucity of studies examining the roles of species interactions and changing abiotic stress levels on multiple salt marsh and salt marsh fringing species warrants the need for additional research. The responses of salt marsh and salt marsh fringing species to sea level rise can not only serve as very valuable and sensitive indictors of climate change, but will also aid in predicting the future location of the marsh-fringe-forest ecotone, which is predicted to shift inland as sea levels continue to rise.

Understanding the maintenance of sexual systems is of great interest to evolutionary and ecological biologists because plant systems are extremely varied. Plant sexual systems have evolved to include not only complete plants with both male and female reproduction occurring on one plant (i.e., monoecious and hermaphroditic) but also plants with male and female function on separate plants (dioecious). The dioecious reproductive system can be used to test theories on niche differentiation given that having separate plants potentially allows for the exploitation of a broader niche. This increase in the realized niche is due to the ability for separate sexes to occupy different niches, which may occur in different physical habitats. Some dioecious plants have been shown to occur in areas biased to nearly 100% male or nearly 100% female, called spatial segregation of the sexes (SSS). Occupying a broader niche could increase fitness in some species when the separation is used for one sex to gain access to resources that increase reproductive success and/or if the separation inhibits deleterious competition. These two mechanisms have been previously proposed for the evolution of SSS in dioecious plants. The first mechanism suggests that males and females have evolved to occupy different niches due to differences in reproduction (sexual specialization). The hypothesis for the sexual specialization mechanism is that females should have higher fitness in female-majority sites and males should have higher fitness in male-majority sites. The second mechanism states that males and females occupy different niches due to competition between the sexes (niche partitioning). The hypothesis for niche partitioning states that inter-sexual competition should decrease fitness more than intra-sexual competition. These mechanisms are not mutually exclusive. In our research we use the salt-marsh grass Distichlis spicata as our study species because this plant is dioecious and because molecular markers have been developed to determine the sex of juvenile plants. These molecular markers are important for testing the niche partitioning hypothesis for SSS in juveniles. Furthermore, previous work in California has shown that plants occur in areas nearly 100% female and nearly 100% male called spatial segregation of the sexes (SSS). The previous research also showed that female-majority sites were higher in soil phosphorus than male-majority sites. We conduct all research, presented in the proceeding chapters, on Distichlis spicata in the Sand Lake estuary near Pacific City, Oregon and in the laboratory at Portland State University. In Chapter 1 we used field data to answer two questions: (1) Does Distichlis spicata exhibit SSS in Oregon, and (2) If SSS is occurring, do differences occur in plant form and function (sexual specialization) in reproductive female and male plants in female-majority and male-majority sites? We used a sex ratio survey and collected field data on reproductive males and females. Our results show that there are female-majority and male-majority areas and SSS is occurring in the Sand Lake Estuary. Results from our native plant data suggest that reproductive females perform better in female-majority sites compared to male-majority sites which could suggest that sexual specialization is occurring in females. We currently have a long term field reciprocal transplant experiment in place to further address this hypothesis. In Chapter 2 we use field dada to address the following questions: (1) Does site-specific soil nutrient content occur in August, when females have set seed? (2) Does sex-specific mycorrhizal colonization occur in reproductively mature plants? (3) Does sex-specific mycorrhizal colonization vary seasonally in natural populations? Inside the roots of D. spicata a symbiotic relationship is formed between plant and arbuscular mycorrhizal fungus (AM). The AM- plant relationship has been shown to thrive in phosphorus limited areas because the mycorrhizal fungus increases nutrient access to the plant. We analyzed the results of the field soil nutrient content and mycorrhizal colonization in roots of native Distichlis spicata from male-majority and female-majority sites. The root colonization included staining roots with trypan blue and viewing sections of the roots under the microscope. Our results show that female- majority sites are higher in phosphorus and are found to have higher AM colonization than male- majority sites in the field. In Chapter 3 we then reciprocally transplanted D. spicata plants in the field to address the following questions: (1) Does niche partitioning occur in D. spicata, and (2) If niche partitioning is occurring, which plants are competing more? Our reciprocal transplant experiment included seeds grown in intra-sexual, inter-sexual and no competition in cones, planted directly into the field, and allowed to grow for 15 months. After the 15 months was over we measured survival, dry weight and root/shoot ratio. The design of the experiment was to determine the effects of competition (intra-sexual and inter-sexual) and no competition on (single male and female) on survival, biomass and root/shoot ratios. Our results show that niche partitioning is occurring and plants in inter-sexual competition have significantly less biomass then intra-sexual competitors. In, Chapter 4, we conduct a laboratory experiment to address the following questions: (1) Do plants show plasticity in their response to root exudates of the competing plant in regards to the sexual phenotype of the competitor? (2) Do plants show plasticity in their response to root exudates of the competing plant with respect to the relatedness of the competitor? We use sterile seeds grown in 24-well plates containing liquid media. For each competing plant, we picked plants up out of the wells and into the competing plants wells so that plants only experienced media that the competing plant had grown. At no time do roots ever come into contact with one another. We measured primary root length, number of lateral roots, the number of root hairs, root/shoot ratio and total dry weight. We analyzed the study two different ways, one for sexual type competition (inter-sexual, intra-sexual, none) and for plant relationship (KIN, STRANGER and OWN). The results for the sexual type competition found that inter-sexual competition was greater for root/shoot ratio and dry weight. The results for plant relationship competition found that kin plants had a significantly greater number of lateral roots and a significantly longer primary root. The last chapter, Chapter 5, includes a summary of our conclusions. Our study found SSS occurring in the Sand Lake Estuary in Oregon with female-majority sites higher in phosphorus and root colonization higher in percent colonization of arbuscular mycorrhizal fungi compared to male-majority sites. Based on the sexual specialization hypothesis as a mechanism for SSS, we found that females had greater fitness in female-majority sites compared to male-majority sites, suggesting that sexual specialization is occurring in reproductive females. We then tested the niche partitioning hypothesis for SSS, and we found consistent lab and field results suggesting that niche partitioning due to inter-sexual competition is an explanation for why females and males D. spicata plants spatially segregate themselves at the juvenile life history stage. Furthermore, we found that plants that have the same mother had a significantly greater number of lateral roots and a significantly longer primary root. These results suggest that KIN plants respond differently to one another compared to plants paired with a plant not from the same mother (STRANGER) or when the plant is alone (OWN).

Salt marshes provide critical ecosystem services, such as shoreline stabilization, biogeochemical cycling and habitat for wildlife, to much of the world's population living on the coasts. Emergent vascular plants are a critical component of these ecosystems. This study was a comprehensive effort to gain a better understanding of the ecology of salt marsh plants in the Nueces River delta on the south Texas coast. This knowledge is essential to understand the potential anthropogenic impacts on salt marshes, including sea-level rise, global warming, reduced freshwater inflow and coastal erosion. A combination of remote sensing analysis, field studies and experiments were used to allow analysis across spatial scales ranging from landscape patterns of vegetation to leaf level measurements of the dominant species. A novel method of image classification was developed using high-resolution multi-spectral imagery integrated with ancillary data to map the major plant communities at a landscape scale. This included a high marsh assemblage composed primarily of Spartina spartinae and a low marsh community dominated by Borrichia frutescens and Salicornia virginica. Geospatial analysis determined that the location of these plant communities was related to the distance from the tidal creek network and elevation. The B. frutescens and S. virginica assemblage was more abundant at lower elevations along the waters edge, making it vulnerable to loss from shoreline erosion. At a finer spatial scale, gradient analysis was utilized to examine the relationship between elevation, which creates environmental gradients in salt marshes, and species distribution. I discovered that elevation differences of less than 5 cm can influence both individual species and plant community distribution. One interesting finding was that the two dominant species, B. frutescens and S. virginica, share similar responses along an elevation gradient yet are observed growing in monotypic adjacent zones. I constructed a large reciprocal transplant experiment, using 160 plants at 4 sites throughout the marsh, to determine what causes the zonation between these two species. The results of this study found that S. virginica fared well wherever it was transplanted but was a weak competitor. B. frutescens survival was significantly lower in the S. virginica zone than in its own zone suggesting that abiotic factors are important in determining the zonation of this species. However, high spatial and temporal variability existed in environmental parameters such as salinity. This variability may have been caused by the semi-arid climate and irregular flooding typical in the Nueces Marsh. Therefore, I utilized a greenhouse experiment to directly test the importance of the two dominant physical factors in salt marshes, flooding and salinity. The results found that for B. frutescens the effects of flooding were not significant, however salinity at 30% reduced growth. Salinity did not influence growth of S. virginica. The greater ability of S. virginica to tolerate salinity stress has important implications because reduced freshwater inflow or climate change can increase porewater salinity, thus favoring the expansion of S. virginica, and altering the plant community structure. / text