Seston is the complex of organic and inorganic particles suspended in the water column in stream ecosystems. This detrital pool is a significant vector of energy and nutrients from headwaters to the ocean. Many of the processes involved in seston generation in streams involve the terrestrial ecosystems they drain. My objective was to determine how land use influences seston quality. Seston was collected from 9 streams along a gradient of catchment forest cover, draining 3 land-use categories: forested, agricultural, and residential. Quality variations were determined through the physical composition (size classes and concentration), chemical composition (carbon, nitrogen, and phosphorous) and organic content of seston, as well as microbial respiration of associated assemblages and growth rates of Chironomus tentans fed seston. There was more seston in streams draining less forested catchments but proportionally that material was less organic. Ultrafine particles dominated seston size classes at all sites and was higher in streams with less catchment forest cover. Phosphorous content of seston, as a % of ash free dry mass, and dissolved P in the water were higher in more disturbed streams, and C:N and N:P ratios of seston were higher in forested streams. Microbial respiration and instantaneous growth rates of C. tentans were highest on residential seston, indicating seston from those streams was more bioavailable. These results indicate that the quality of seston in stream ecosystems is linked to terrestrial processes and influenced by land use. / Master of Science

Oxygen uptake rates by fine benthic organic matter were measured on samples from two Appalachian mountain streams to determine the effects of land use patterns on microbial respiration. Both Coweeta Creek in western North Carolina, and Wolf Creek in western Virginia, flow through national forest, agricultural land and scattered residential areas. Seven sites were sampled at six to ten week intervals over one year. Land use was determined using infrared aerial photographs. ARC/INFO was used to obtain land use areas for various land uses. Oxygen uptake rates were measured using a Gilson differential respirometer, at ambient temperature and 20°C. Temperature was the most important factor influencing oxygen uptake rates in both streams, with oxygen uptake rates consistently lower at ambient temperatures than 20°C. Oxygen uptake rates were higher in Wolf Creek than Coweeta Creek and were higher at sites that drained agricultural areas. Nitrates increased as the percent of agriculture increased in Wolf Creek, but not in Coweeta Creek. Nitrates were positively correlated with oxygen uptake / Master of Science

Fertilization is a common, cost effective treatment for increasing forest productivity within managed forests of the southeastern United States. However, little is known about how fertilization affects the below-ground processes that drive soil CO2 efflux in loblolly pine (Pinus taeda L.). A thorough understanding of below-ground carbon dynamics is necessary for the estimation of net ecosystem productivity and the carbon storage potential of these managed systems. In April 2004, we began monitoring total soil CO2 efflux (EC), heterotrophic (RH), and root respiration (RR) in response to fertilization with diammonium phosphate (DAP). Respiratory components were measured prior to fertilization, weekly following fertilization, and bi-weekly after respiratory components stabilized using a dynamic closed chamber and an infrared gas analyzer. We found that EC differed significantly (P<0.0001) between fertilized and unfertilized plots, but the direction was dependent on date. In the early period of the study, fertilized plot values were lower than control plots. However, by the latter periods fertilized plot values returned to control levels except for one sampling date in March 2005 when fertilized plot values were greater then control plots. Heterotrophic respiration was consistently and significantly (P=0.0002) lower in fertilized plots. Root respiration was significantly (P=0.0597) increased in fertilized plots when analyzed over the study and showed a 20% increase due to fertilization. We concluded that an increase in RR and possibly root biomass was enough to balance the decrease in RH leading to no difference in EC later in the growing season. We performed a pair of greenhouse studies to observe the effects of fertilization in the form of diammonium phosphate (DAP) on RR. The objectives were to determine how nutrient additions initially affect RR in one-year-old loblolly pine seedlings. Secondly, we wanted to determine if Captan [N-(trichloromethylthio) cyclohex-4-ene-1, 2-dicarboximide], a mild fungicide, could be used to reduce or eliminate ecto-mycorrhizae upon visual inspection. Both studies showed that initially, at a high rate (100 ppm N and 49 ppm P) of fertilization, RR was significantly (P<0.10) increased relative to seedlings that did not receive fertilization. This increase was only temporary with rates returning to, or decreasing below, control levels by the end of the study. No consistent trend was found between low (25 ppm N and 13 ppm P) and moderate (50 ppm N and 25 ppm P) rates of fertilization. Captan was shown to generally have no affect on RR. Captan and fertilization both showed (visual inspection) a decrease in fine-roots and mycorrhizae, which could explain the reduction in respiration rates observed in these treatments by the end of the studies. / Master of Science

Soil organic matter is important as storage for carbon and nutrients, supporting soil structure, and as a filter for pollutants entering the soil ecosystem. The recovery of soil organic matter in depleted soils can take decades, or even hundreds of years. It has been assumed that in non-eroding pasture, soil carbon levels either increase or not change over time. However, some recent studies have suggested that fertiliser addition to pasture soils may contribute to decreases in soil carbon content. My hypotheses were: 1. As P fertiliser loadings increase the soil carbon content and C:N ratio will decrease. 2. Changes in C pools will be greater in the more active pool (readily available carbon, and microbial biomass carbon) within the soil total carbon The study was undertaken at a long term fertiliser trial, established in 1980, at the Whatawhata Hill Country Research Station west of Hamilton, New Zealand. The fertiliser trial has P fertiliser application rates maintained since 1984. Olsen P, total C, total N, labile carbon, respirable carbon, specific respiration rate, microbial biomass C, microbial quotient, mineralised N, microbial biomass N, microbial N quotient, and mineralised N per microbial biomass nitrogen, C:N ratio, and soil pH were measured on soil samples collected from 12 paddocks with six P fertiliser loading (0, 10, 20, 30, 50, 100 kg P ha-1 yr-1). As expected, the available P (Olsen P) increased significantly (P less than 0.001) with increasing P fertiliser application rate. Total carbon, labile carbon, and total nitrogen all decreased significantly (P less than 0.05) with increasing P fertiliser application. No significant relationships were found between P fertiliser and respirable carbon, microbial carbon, microbial (C) quotient, microbial specific respiration, microbial nitrogen, microbial (N) quotient, mineralised N, or C:N ratio. The first hypothesis was rejected as the C:N ratio did not change with increased P fertiliser application. However, both C and N decreased with increased P fertiliser application. The second hypothesis was, therefore, accepted in part because there was a decrease in labile carbon (readily available carbon) and total carbon, with P fertiliser application, but no relationship was evident for the respirable carbon and microbial biomass.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The study was conducted in four distinct classes of soils, namely Yellow Latosol (LAD), Hapludox (RH), Entisol (RQo) and Acrudox typical (LAw), all under savannah vegetation. Four samples were collected per area, in two depths (0-10 and 10-20 cm) and three seasons (summer, winter and spring). An analysis was made on soil chemical and physical and chemical analysis of litter and biochemical. The parameters were: the CO2 flux, microbial respiration, activity of urease and &#946;-glucosidase, the percentage of leaf litter decomposition and total organic carbon (COT). The sites analyzed showed significant differences regarding the chemical properties of soil. The Law soil had the highest CO2 fluxes in times and the minors observed for RQo. No correlation of flow with the concentration of nutrients in the litter. In layer 0 -10 cm, the flow of CO2 was positively correlated with COT, N, K, C / N and C / P. The correlation in the layer 10- 20 cm was positive for the COT and N. The additions of 0.1 and 1% of litter were not sufficient to determine the potential carbon mineralization, only the addition of 10% showed satisfactory results with soil RH presented the largest percentage and was observed for RQo. The major differences in respiration in these soils were observed after the addition of 10% of litter, especially for the RQo. The yield respiratory decreased with increased amount of litter added and the soil had the highest yield for Lad respiratory. The largest differences in yield were observed in the addition of 0.1% of litter. With respect to enzyme activity, the greatest differences were observed in the addition of 10% litter, and soil RQo showed higher activity of the enzyme &#946;-glucosidase and soil RH showed higher activity of the enzyme urease. / O trabalho foi conduzido em quatro classes de solos, a saber: Latossolo Amarelo distrófico (LAd), Latossolo Vermelho distroférrico (LVdf), Neossolo Quartzarênico órtico (RQo) e Latossolo Amarelo ácrico (LAw), todos com vegetação do tipo cerradão. Foram coletadas quatro amostras por área, em duas profundidades (0-10 e 10-20 cm) e em três épocas (verão, inverno e primavera). Foram feitas análises químicas, físicas e bioquímicas para caracterização das amostras de solos e análises químicas da serapilheira. Os parâmetros avaliados foram: fluxo de CO2, respiração microbiana, atividade de urease e &#946;-glicosidase, percentual de decomposição de serapilheira e carbono orgânico total (COT). Os sítios analisados apresentaram diferenças expressivas quanto às propriedades químicas do solo. O solo LAw apresentou os maiores fluxos de CO2 nas épocas e profundidades analisadas e o solo RQo os menores. Não foi observada correlação do fluxo com os teores de nutrientes na serapilheira. Na camada de 0-10 cm, o fluxo de CO2 correlacionou-se positivamente com as variáveis de COT, N, K, C/N e C/P. A correlação na camada de 10-20 cm foi positiva para o COT e N. As adições de 0,1 e 1% de serapilheira não foram suficientes para determinar o potencial de mineralização do carbono. Apenas a adição de 10% mostrou resultados satisfatórios, tendo o solo LVdf apresentado o maior percentual e o RQo o menor. As maiores diferenças quanto a respiração nesses solos foram observadas quando da adição de 10% de serapilheira, com destaque para o solo RQo. O rendimento respiratório decresceu com aumento da quantidade de serapilheira adicionada, sendo que o solo LAd apresentou maior rendimento respiratório. As maiores diferenças no rendimento foram observadas na adição de 0,1% de serapilheira. Com relação a atividade enzimática, as maiores diferenças foram observadas na adição de 10% de serapilheira, sendo que o solo RQo apresentou maior atividade da enzima &#946;-glicosidase e o solo LVdf apresentou maior atividade da enzima urease. / Mestre em Agronomia

No description available.

Continental shelves located along eastern boundary currents occupy relatively small volumes of the world’s oceans, yet are responsible for a large proportion of global primary production. The Oregon coast is among these ecosystems. Recent analyses of dissolved oxygen at shallow depths in the water column has suggested increasing episodes of hypoxia and anoxia, events that are detrimental to larger macro-faunal species. Microbial communities, however, are metabolically diverse, capable of utilizing alternative electron donors and acceptors, and can withstand transient periods of low dissolved oxygen. Understanding the phylogenetic and metabolic diversity of microorganisms in these environments is important for assessing the impact hypoxic events have on local and global biogeochemistry. Several molecular ecology tools were used to answer questions about the distribution patterns and activities of microorganisms residing along the coast of Oregon in this dissertation. Ribosomal rRNA fingerprinting and sequence analyses of samples collected during 2007-2008 suggested that bacterial community structure was not substantially influenced by changes in dissolved oxygen. However, substantial depth dependent changes were observed, with samples collected in the bottom boundary layer (BBL) displaying significant differences from those collected in the surface layer. Phylogenetic analyses of bacterial rRNA genes revealed novel phylotypes associated with this area of the water column, including groups with close evolutionary relationships to putative or characterized sulfur oxidizing bacteria (SOB). Analysis of metagenomes and metatranscriptomes collected during 2009 suggested increasing abundances of chemolithoautrophic organisms and their activities in the BBL. Thaumarchaea displayed significant depth dependent increases during the summer, and were detected at maximal frequencies during periods of hypoxia, suggesting that nitrification maybe influenced by local changes in dissolved oxygen. Metagenomic analysis of samples collected from 2010 revealed substantial variability in the metabolic potential of the microbial communities from different water masses. Samples collected during the spring, prior to upwelling clustered independently of those collected during the summer, during a period of upwelling, and did not display any clear stratification. Samples collected during the summer did cluster based on depth, consistent with previous observations, and increases in the relative abundances of chemolithotrophic gene suites were observed in the BBL during stratified conditions, suggesting that the metabolic potential for these processes is a repeatable feature along the Oregon coast. Overall, these observations suggest that depth impacts microbial community diversity, metabolic potential, and transcriptional activity in shallow areas of the Northeast Pacific Ocean. The increase in lithotrophic genes and transcripts in the BBL suggests that this microbial community includes many organisms that are able to use inorganic electron donors for respiration. We speculate that the dissolved organic material in the BBL is semi-labile and not available for immediate oxidation, favoring the growth for microorganisms that are able to use alternative electron donors. / Graduation date: 2012

The aim of the study was to determine the influence of phenolics content and inoculation with soil extract on microbial respiration, on the phenoloxidase (PhOx), peroxidase (PerOx) and newly Mn-peroxidase (MnP) activity in two dominating litter samples (Calamagrostis villosa and Picea abies) differing in phenolics content from Plešné and Čertovo lake watersheds. At PhOx and PerOx activity, the dependence on incubation temperature with L-DOPA was estimated. PhOx and MnP activities significantly increased with higher content of hardly decomposable phenolics, but decreased with water extractable phenolics content. Inoculation with soil extract had no influence on microbial respiration, enzyme activity, nor on decomposition of phenolics. Microbial respiration was significantly higher at 10°C, but average enzyme activity was comparable at 0 and 10°C. PhOx activities had temperature optimum higher than 22°C, while PerOx activities had temperature optimum at 0 - 15°C.

No description available.