Nitrogen enrichment of plant communities is known to have big impact on declines in plant diversity and increase of biomass production. Though nitrogen is an important nutrient in the life cycle of a plant it is also problematic when the availability of nitrogen is continually high. When enrichment of nitrogen is continual, the increase in biomass and height from competitive plant species result in shading, which contribute to diversity loss in plant communities. Some nitrogen-favoured plants are long-lived and have the possibility to store seed banks in the ground until conditions are more favourable. Little is known about what role historic fertilization have on plant communities that are being re-fertilized. The aim with this study was to re-fertilize vegetation plots and compare those with vegetation plots that have not been fertilized before. The study site was vegetation plots on a meadow in Strycksele, Västerbotten, Sweden. Some plots had been fertilized from year 1996 until 2000 and scientific studies with re-fertilization started in 2019 and is ongoing. The vegetation response from re-fertilization and newly fertilization was assessed by investigating species diversity and biomass. The results showed no significant difference between re-fertilized and newly fertilized plots in either species diversity or biomass, but there was significant higher biomass in newly fertilized plots than control plots which had not been fertilized 2019-2021. For future studies there would be of high interest to look at potential differences in functional group composition in plant communities that are being re-fertilized compared to newly fertilized plant communities.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / The study aimed to differentiate the effect of rainfall and grazing on the compositional change of savanna grasslands, and to explain responses in terms of the life history patterns of the main species, An extinction prone perennial grass under heiry grazing was identified as a palatable, obligate seed reproducer with low seed production and poor dispersal (e.g. Themeda triandra and Reteropogon contortus), wnich could become extinct if the established population and the seed bank were eliminated. Aristrida species were expected to show the converse pattern. Grazing was manipulated for three or five years, and rainfall for one year, on a sandveld site, and two clay soil sites which supported the same species in different amounts, respectively. (Abbreviation abstract) / Andrew Chakane 2019

I investigated percent coverage, plant height, species richness, and woody stem density in plant communities in ten study plots during spring and fall (2010-2012) within 3 different treatments (continual mowings, one fall mowing, and one fall mowing with native wildflower seeds) on highway 25 right-of-way in Oktibbeha and Winston counties, Mississippi. I recorded 277 plant species including native and non-native forbs, legumes, grasses, rushes/sedges, and woody plants. Non-native agronomic grasses exhibited greatest coverage greater than 90 percent occurring in all treatments. Percent coverage of plants less than 0.46m height category exceeded 100 while, greater than 0.46m plant height categories averaged 55 percent. Woody stem density ranged from 7,772 year 1 to 10,025 stems/hectare year 2. I detected no significant differences in plant height or woody stems among treatments. One mowing per year retained agronomic plant cover for erosion control and annual cost savings up to 75 percent for roadside maintenance.

No description available.

The distribution and occurrence of plant species within a given region provides insight into the many environmental properties of that region. Although much research has been conducted on plant communities and associated environmental properties, few studies have been conducted on the characteristics of individual plants within those communities. Calcareous fens are wetlands formed by the upwelling of mineral-rich groundwater and often are associated with many unique plant communities and rare species of flora and fauna. Although many studies have documented the vegetation patterns and associated environmental gradients of these fens, none have isolated the specific hydrogeochemical conditions associated with individual species, nor have any studies attempted to document and compare the individual physiological response of species to elevated environmental calcium levels. This research was conducted to estimate environmental calcium requirements for rare as well as common indicator species of calcareous fens of Massachusetts and to examine the relationship between the accumulation of calcium in the tissues of these species to calcium availability in their environment. These factors will be important when determining required conditions for fen restoration and will further the understanding of why these species often only occur in calcareous fens. Eight calcareous fen study sites at three different locations were established where calciphiles occur in western Massachusetts. In each site, data were collected on the vegetation patterns and associated soil chemistry, water chemistry, and hydrology. In addition, plant tissues were collected and analyzed for calcium. Species distributions were evaluated as to whether they increased in abundance as environmental calcium did or whether they appeared to occur only once a specific calcium threshold was met. In addition, the concentrations of calcium in the tissues were used to determine the extent to which those plants accumulated calcium and how those levels related to levels of calcium in the substrate environment and to their overall distributions. It was found that certain calciphiles are calcium specialists, i.e. they are more abundant when environmental calcium levels are elevated, absorb greater quantities of calcium and those quantities correlate to the available environmental supply. These species include Parnassia glauca, Packera aurea, Geum rivale and Carex granularis. Of these, Geum rivale and Carex granularis, as well as Carex sterilis, did not occur below calcium concentrations of 48 mg.L-1. However, other calciphiles are calcium generalists, i.e. they are tolerant of elevated calcium levels but show no other relationship with respect to growth or accumulation. These species include Carex flava, Carex hystericina, Juncus nodosus, Solidago patula, Solidago uliginosa, and Symphyotrichum puniceum. In addition, some wetland generalists maintain elevated calcium levels (Symplocarpus foetidus and Mentha arvensis) whereas most others do not (Thelypteris palustris and Fragaria vesca). Of the calciphile and wetland generalist species, some appear to increase in abundance in calcareous fens in relation to increases in accessory benefits (Dasiphora fruticosa and Juncus brachycephalus with pH; Thelypteris palustris and Carex flava with magnesium and possibly Equisetum fluviatile with iron). Combined, these findings characterize the growth habits and calcium accumulation of species that grow in calcareous fens and indicate that calciphiles have varying degrees of dependence on calcium.

No description available.

Moderate livestock grazing is often identified as a useful management tool for sustaining biodiverse grassland communities and has long been practiced in Scandinavian mountains. Despite of a growing number of studies focusing on grazing effects along elevational gradients worldwide, there is still limited knowledge of how grazing intensity varies over time and how it affects plant communities on species and functional group level. Moreover, the majority of existing studies are conducted in enclosures with controlled stocking rate, while free-range grazing with a highly varied livestock number is the common practise in Scandinavia. Therefore, the aim of this study was to quantify free-range grazing intensity over the growing season along an elevational gradient and to evaluate how grazing affects plant communities on species, functional group and community level. In order to quantify grazing intensity, we conducted a grazer exclusion experiment along an elevational gradient in Norway in the growing season of 2019. We quantified grazing intensity as the difference in dry above-ground biomass between grazed and caged plots and analyzed plant composition on community and functional group level as well as recorded species-specific grazing damage and potentially influential abiotic factors. To capture the effects of temporal variation in grazing we also relocated caged and grazed plots in four-week intervals during the growing season. We demonstrated that grazing intensity gradually decreased with elevation and elevation explained 77% of the variation in grazing among sites. Lower grazing intensity at high elevation is likely related to decreasing plant productivity and differences in plant community composition along the gradient. Grazers reduced the biomass of graminoids and forbs in the intensively grazed lower sites. Grazing damage varied among sites for five of the eight most commonly grazed plant species, which was mainly driven by a higher grazing damage in the intermediate site (900m a.s.l.). Selective grazing was observed in three sheep-dominated study sites. Grazing intensity did not significantly vary during the growing season at any site, possibly due to weak temporal effects of an overall short growing season. In accordance with other studies, we demonstrated that grazing homogenized plant community composition in actively grazed sites that were relatively species rich. To conclude, livestock grazing can help maintain biodiverse semi-natural grasslands, yet when grazing is applied as a management tool in the mountainous landscapes, we suggest considering that grazing intensity, and therefore its effects, will vary with elevation.

Utah Lake is a shallow eutrophic lake located in central Utah. It is characterized by high nutrient and silt loads and by large algal blooms in late summer and early fall. Phytoplankton samples and environmental data were taken from June through August 1974. Phytoplankton species were identified and then quantified in a Palmer counting cell. Environmental continuum theory was employed to describe algal succession and regression analysis was used to discover interactions between algal communities and the environment. Phytoplankton communities in June were characterized by high species diversity. As the lake environment became stressed in late summer due to higher turbidity, nutrient levels, and pH and decreases in available inorganic carbon,species diversity decreased. By August, the phytoplankton flora was composed essentially of only two species, Ceratium hirundinella and Aphanizomenon flos-aquae.

One knowledge gap hindering prairie restoration is uncertainty about when a restored prairie communities sufficiently resemble remnant prairie. I surveyed plant communities in remnant prairies, prairies > 5 years post-restoration, and prairies ≤ 5 years post-restoration in Mississippi. Remnants had the greater species richness. Restored prairies had less cover of woody plants and forbs but greatest non-natives. Restored prairies were not similar to remnant prairies (similarity index = 28.9 - 25.9%), primarily because restored prairies had fewer prairie forbs. Thus, restoration may take decades. Transplanting locallyapted prairie forbs into restored prairies may accelerate restoration, but this has not been evaluated adequately. I transplanted a prairie forb (Liatris pycnostachya) into prepared beds, oldields, and restored prairies. Prepared beds had greater growth and seed production, but survival and flowering was high in oldields and restored prairies. Augmenting restored prairies with locallyapted forbs has promise for accelerating prairie restoration.

The aquatic and semi-aquatic plant communities of Utah Lake, Utah County, Utah are discussed. This discussion includes the methods of describing and delimiting the major vascular plant communities, the descriptions of the present existent communities, and the determination of the vegetational changes, particularly since 1925. The vegetation around Utah Lake is divided into plant communities. Each community is discussed using: (a) quantitative data, (b) field observations, (c) general and specific locations of the community, and (d) interrelationships and trends of the community. Historical vegetational changes of Utah Lake plant communities are discussed. In this discussion, the plant communities described by Cottam in 1925 are examined in broad outline and then in detail. In 1968, twenty-nine plant communities had developed from fifty-six per cent of the associations and twenty-nine per cent of the societies that were described by Cottam in 1925.