The effects of varying concentrations of two chelators: EDTA, citric acid (CA), and phosphorus on the accumulation of arsenic in soil by two perennial grasses, Leersia oryzoides and (rice cut-grass) Festuca arundinacea (tall fescue). Each experiment was run for eight weeks, after which plants were harvested, oven-dried, digested in acid and analyzed using an ICP-OES. Phosphorus soil amendments were applied as 0, 15, 30, 60, 120 mg P/kg soil. For the first chelator experiment, CA and EDTA concentrations of 0, 2.5, and 5.0 mmol/kg soil were added in pulse form to the soil. In the second chelator experiment, concentrations of CA were added in 0, 2.0, 4.0 mmol/kg soil and EDTA was added as 0, 0.25, 0.50 mmol/kg soil. Both plant species accumulated enough arsenic in the root and shoot tissues to be considered at hyperaccumulator species. Citric acid produced comparable results with EDTA, and is considerable much safer for the environment than any synthetic chelator. Certain soil amendments (citric acid and phosphorus) and hyperaccumulator species used in this study warrant further research in the field.

Streams are classified into perennial, intermittent, and ephemeral streams based on flow durations. Perennial stream is the basic network, while intermittent or ephemeral stream is the expanded network. Connection between perennial stream and base flow at the mean annual scale exists since one of the hydrologic functions of perennial stream is to deliver runoff even in low flow seasons. The partitioning of precipitation into runoff and evaporation at the mean annual scale, on the first order, is captured by the ratio of potential evaporation to precipitation (Ep/P called climate aridity index) based on the Budyko hypothesis. The primary focus of this thesis is the relationship between base flow and perennial stream density (Dp) in the Budyko framework. In this thesis, perennial stream density is quantified from the high resolution National Hydrography Dataset for 185 watersheds; the climate control (represented by the climate aridity index) on perennial stream density and on base flow is quantified; and the correlation between base flow and perennial stream density is analyzed. Perennial stream density declines monotonically with the climate aridity index, and an inversely proportional function is proposed to model the relationship between Dp and Ep/P. This monotonic trend of perennial stream density reconciles with the Abrahams curve, and the perennial stream density is only a small portion of the total drainage density. The dependences of base flow ratio (Qb/P) and the normalized perennial stream density on the climate aridity index follow a similar complementary Budyko-type curve. The correlation coefficient between iv the ratio of base flow to precipitation and perennial stream density is found to be 0.74. The similarity between the base flow and perennial stream density reveals the co-evolution between water balance and perennial stream network.

Cranberry (Vaccinium macrocarpon Ait.) is a woody perennial crop that can remain productive for decades. Competition for resources between cranberries and weeds can depress cranberry farm yields, resulting in large annual crop losses. Renewed interest in reducing chemical inputs into cranberry systems has provided the motivation to evaluate methods, such as flame cultivation (FC), as potential nonchemical options for weed control. Also known as thermal weeding, FC exposes plants to brief periods of high temperature that causes the water in the plant tissue to expand rapidly, rupturing plant cells and leading to necrosis. Various FC methods have been used successfully in annual crops as both a preemergence and postemergence weed control, but few scientific reports have been published on the use of FC on perennial weeds in a woody perennial crop system. Dewberry (Rubus spp.), sawbrier (Smilax glauca), and common rush (Juncus effusus) are cranberry weeds that are difficult to control, spread quickly and can cause significant crop loss. Flame cultivation may be an effective non-chemical means for controlling these weeds in cranberry systems. FC would ideally be used as a spot treatment for weeds growing in the cranberry canopy, as well as on larger non-production areas where cranberry vines are not as abundant, such as bog edges, ditches, and dikes. Using FC to treat weeds within the cranberry canopy will likely cause localized damage to cranberry plants immediately surrounding the weeds, thus cranberry response to FC is also of interest. The following experiments were designed to examine the response of weeds and cranberry plants to FC. Perennial plants rely on reserves of nonstructural carbohydrates (NSC) for growth and survival, thus the efficacy of FC treatments to weeds will likely be impacted by the timing and frequency of treatments as they relate to the specific carbohydrate cycles of targeted weeds, such as dewberry. An additional experiment studied the seasonal fluctuations of NSC in dewberry roots. Cranberry growers were also surveyed on their past experiences with FC, as well as their willingness to adopt FC if proven an effective method for controlling weeds.

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No description available.

No / Recurrent fires have a considerable potential to influence the structure and composition of savanna vegetation. In Mole National Park in Ghana, the policy is to burn the vegetation annually early in the dry season. This study aimed to assess the effects of these perennial fires on the trees and shrubs of the Park. To achieve this, scars on tree bole bases as well as mortality and top-kill to trees ¿ 2 m tall resulting from perennial fires were assessed in twenty 50 m x 50 m plots in the savanna vegetation near Grupe camp at the south-western section of the Park. Fire scars on tree bole bases were widespread, but were significantly more frequent on large trees (> 5 m tall) than small ones (< 2 m tall). Also, certain tree species, notably Burkea africana and Detarium microcarpum were more prone to scarring. The greater proportion of the scars had reached an advanced stage and the affected individuals were either moribund or were likely to be killed by subsequent fires or toppled by the wind. Contrary to the popular opinion that fire generally affects tree recruitment and not adult survival, fire-induced mortality and top-kill to large trees (> 5 m tall) was widespread among all the tree species, particularly Acacia dudgeoni, Burkea africana, Detarium microcarpum and Vitellaria paradoxa. These fire impacts will likely lead to changes in the relative abundance of the constituent tree species as well as a decline in the density of woody elements in the plant community as a whole unless burning frequency is reduced. The areas for which these predicted vegetation changes are valid can be generalized to include the vegetation in the northern half of the Park where similar conditions of high fuel load and intense fires are likely to prevail.

Research subject Process of preparation and processing of perennial grass (cocksfoot, tall fescue and reed canary grass) biomass into biogas. Objectives 1. To analyse the possibility and identify the energy potential of processing of perennial grass (cocksfoot, tall fescue and reed canary grass) biomass silage into biogas. 2. To assess energy consumption during the process of preparation and processing of perennial grass biomass into biogas and draw up the energy balance. 3. To identify environmental impact of preparation and processing of perennial grasses into biogas. / Darbo tikslas Ištirti daugiamečių žolių (paprastųjų šunažolių, nendrinių eraičinų ir nendrinių dryžučių) biomasės naudojimo galimybes biodujų gamybai, įvertinant žaliavos gamybos energinį balansą ir įtaką aplinkos taršos mažinimui.   Darbo uždaviniai 1. Ištirti daugiamečių žolių (paprastųjų šunažolių, nendrinių eraičinų ir nendrinių dryžučių) biomasės siloso perdirbimo į biodujas galimybę ir nustatyti energinį potencialą. 2. Įvertinti daugiamečių žolių biomasės paruošimo ir perdirbimo į biodujas metu, patiriamas energijos sąnaudas ir sudaryti energijos balansą. 3. Nustatyti daugiamečių žolių paruošimo ir perdirbimo į biodujas įtaką aplinkai.

Doctor of Philosophy / Department of Biology / David C. Hartnett / Perennial grass populations propagate vegetatively via the belowground bud bank. Climate, photosynthetic pathway, and growth form impact bud production, longevity, and dormancy; leading to alterations in bud bank and tiller dynamics. Previous research in mesic C₄-dominated tallgrass prairie revealed that a C₄ grass had greater bud longevity and differing bud bank dynamics than a C₃ species. This study examined the bud bank dynamics of rhizomatous and caespitose grasses in a more arid C₃ dominated prairie to gain insights into how bud banks differ among grass species, growth forms, and environments, and the relationship between bud bank characteristics and grass architecture and growth patterns. The bud bank and tiller dynamics of four perennial grasses in the C₃-dominated northern mixed grass prairie were examined over 15 months. The C₃ caespitose and rhizomatous grasses produced similar numbers of buds per tiller and their bud longevity was [greater than or equal to] 2 years. Tiller longevity drove the turnover within the bud bank of the dominant C₃ caespitose grasses Hesperostipa comata and Nassella viridula. Their polycyclic tillers (tillers that lived for more than one year) created multi-aged bud banks. The rhizomatous C₃ grass Pascopyrum smithii also had a multi-aged bud bank because buds were able to live longer than its annual tillers. Differences between caespitose and rhizomatous C₃ grass bud banks were driven by differences in tiller and rhizome production and spatial distribution. Responses to water availability fluctuations are likely buffered by the maintenance of polycyclic tillers in the caespitose grasses and flexible timing of annual tiller recruitment in the rhizomatous grass. The C₄ rhizomatous grass Andropogon gerardii had similar phenology to populations in its tallgrass prairie range center. Despite declines in bud production per tiller and lowered flowering probability in mixed-grass prairie, A. gerardii maintained a multi-aged bud bank and a positive population growth rate via vegetative reproduction at both the center and edge of its range. Bud bank dynamics of different growth forms and photosynthetic pathways, as they offer insight into the control of grass population dynamics and production, will enhance understanding of the mechanisms by which management practices and environmental change can alter perennial grasslands.

No description available.

A firn aquifer is a type of englacial water storage that forms when surface meltwater fills up the pore space in porous firn. If the retention time exceeds one year the feature is regarded as perennial. The melt and accumulation rates as well as the available pore space determine the formation and extent of the firn aquifer. Flow of water within the aquifer caused by gradients in hydraulic potential leads to redistribution of water and consequently to a change in the level of the water table. This thesis focuses on a perennial firn aquifer on the Lomonosovfonna ice field on Svalbard. Spatial and temporal variations in the depth to the water table as well as variations in reflectivity strength of the water table are analysed using data from ground penetrating radar surveys along with MATLAB and ArcGIS software tools. The results show a clear connection between surface topography, steepness of its slopes and depth to the water table. It is also proved that the depth varies between different years. During the four years of study, the water table in the area rose closer to the surface. The results also show that the reflections from the top of the water table are stronger and more frequently detected in areas with gentler water table slopes. A similar correlation is true for the surface topography slope, where a gentler slope shows a stronger reflectivity. The results support the previous research done on Holtedahlfonna’s aquifer on Svalbard as well as aquifers on Greenland. / En firnakvifer är en typ av englacial vattenlagring som formas när smältvatten från en glaciärs yta fyller upp porutrymmen i porös firn. När retentionstiden överskrider ett år betraktas akviferen som flerårig. Smält- och ackumulationshastigheten samt det tillgängliga porutrymmet avgör bildningen och utsträckningen av akviferen. Vattenflödet i akviferen orsakad av gradienter i hydraulisk potential leder till omfördelning av vattnet och därmed till förändringar i vattenytans nivå. Denna uppsats fokuserar på en akvifer på isfältet Lomonosovfonna på Svalbard. De rumsliga och tidsmässiga variationerna i djupet till vattenytan samt de rumsliga variationerna i reflektivitetsstyrkan från vattenytan analyseras med hjälp av georadarmätningar samt MATLAB- och ArcGIS-mjukvaror. Resultaten visar ett tydligt samband mellan yttopografin, dess lutning samt djupet till vattenytan. Dessutom är det bevisat att djupet varierar mellan olika år. Under den fyra år långa undersökningssperioden har vattenytan i mätområdet stigit. Vidare visar resultaten att reflektioner från vattenytan är starkare och mer frekvent observerade i områden där vattenytans lutning är svag. En liknande korrelation gäller också för yttopografin, där svagare lutning ger upphov till en starkare reflektivitet. Resultaten stödjer den tidigare forskningen gjord både på akviferen på Holtedahlfonna på Svalbard och akviferer på Grönland.