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No description available.

The influence of parent lithology on the development of soil biogeochemical environments and their microbial diversity is explored by characterising soil profiles with respect to their mineral, solution and organic chemistry. Soil profiles were collected from a total of 17 sites, above basalt, granodiorite, shale, sandstone and limestone, across Northern Ireland. The soil system developed above basalt was examined to assess the development of soil bio-physicochemical properties and microbial diversity through the profile. These basalt soils showed two distinct horizons have developed in the previous 15’000 years, where soils from the top 20 cm of the profile were highly influenced by the interactions of soil minerals with soil organic and biological processes. In line with the observed differences in soil properties the microbial community structure varied; in the surface soils the community composition was dominated by root-associated bacteria. However the relative abundance of phyla affiliated with nutrient-limited conditions increased in samples from the base of the profile. Detailed examination of the soil profiles above granodiorite, shale, sandstone and limestone revealed large variations in soil geochemistry between profiles, reflecting the mineral geochemistry of the parent rock. Molecular analysis of SOM revealed compositional changes with depth were comparable between profiles; however TOC concentrations were consistently higher in the soil profiles above basalt suggesting greater stabilisation of SOM in these soils. The chemistry of the soil waters was not reflective of the parent rocks; however variations in soil texture, specifically the abundance of less reactive residual minerals in the sandstone and limestone soils, led to higher concentrations of soluble elements in these soils. Soil pH and DOC were found to have a large control on buffering the release of free Al, Cr and Fe ions into solution. The microbial communities in near-surface soils were similar to each other, regardless of lithology, and were dominated by Proteobacteria, Actinobacteria, and Acidobacteria. However microbial diversity shifted with depth; the abundance of Actinobacteria decreased and Nitrospirae increased, and between rock types where soils next to the basalt, shale and granodiorite bedrock contained sequences affiliated with novel Candidate Phyla AD3 and GAL15. In these soils differences in SOM composition were the main driver of the observed variation with depth, however where labile SOM was depleted, mineral and solution geochemistry may have a larger control on the community composition. To assess the influence of parent lithology on selenium mobility, soils above basalt and granodiorite were amended with sodium selenate. Under anaerobic conditions, the proportion of soluble selenate removed varied (39-77 %) depending on the sample through a combination of abiotic and microbial reduction processes. However, under aerobic conditions, larger concentrations of selenate remained in solution (79-100%).

Recent work in microbial ecology has focused on elucidating controls over biogeographic patterns and connecting microbial community composition to ecosystem function. My objective was to investigate the relative influences of landscape legacies and contemporary environmental factors on the distribution of soil microbial communities and their contribution to ecosystem processes across a glacial till sequence in Taylor Valley, Antarctica. Within each till unit, I sampled from dry areas and areas with visible evidence of recent surface water movement generated by seasonal melting of ephemeral snow packs and hillslope ground ice. Using T-RFLP 16S rRNA gene profiles of microbial communities, I analyzed the contribution of till and environmental factors to community similarity, and assessed the functional potential of the microbial community using extracellular enzyme activity assays. Microbial communities were influenced by geochemical differences among both tills and local environments, but especially organized by variables associated with water availability as the first axis of an NMDS ordination was strongly related to shifts in soil moisture content. CCA revealed that tills explained only 3.4% of the variability in community similarity among sites, while geochemical variables explained 18.5%. Extracellular enzyme activity was correlated with relevant geochemical variables reflecting the influence of nutrient limitation on microbial activity. In addition, enzyme activity was related to changes in community similarity, particularly in wet environments with a partial Mantel correlation of 0.32. These results demonstrate how landscape history and environmental conditions can shape the functional potential of a microbial community mediated through shifts in microbial community composition. / Master of Science

In Peru, nearly 32 million people rely heavily on human-made coastal irrigation agricultural hubs that rely on water from melting glaciers, snowpack, and rain transported by rivers and canals from high in the Andes. However, Peru’s water resources are in a vulnerable state as climate change has shifted rainfall patterns causing glacier retreat affecting nearly the loss of one-third of the glaciers. In recent decades, an increase and expansion of irrigation projects in Peru require agriculture practices to consider environmental impacts directly. Now is the time to explore the sustainability of the desert agroecosystems and understand how different water management practices influence the supporting soil’s health so decision-makers can plan for future change in water resources and any feedbacks to the productivity of the soils. Over the past 40 years, Peru has led some of the largest scale water management projects on earth to convert infertile coastal desert soils into irrigated agricultural land. Still, these efforts can come at a severe local cost with impacts to groundwater quality, salination of the soil, toxic concentrations of trace metals due to evaporation, and overuse of fertilizer and pesticides. This thesis presents a study to assess how drip irrigation impacts desert soil chemistry within one of Peru’s desert irrigation projects in Arequipa’s southern district. We explored a chronosequence of drip irrigation in vineyards of 9-, 16- and 35- years. Results showed that both soil carbon and salinity accumulated progressively over time but that spatial accumulation patterns were influenced by proximity to the irrigation drip line. By 35 years, salinity levels exceeded what would be tolerances for most crops. Trace metals, such as Mn, Zn, and Ni, increased with time under drip irrigation and have significant relationships with Fe, present in the highest concentrations, seemingly controlling the patterns due to co-precipitation. However, no trace metals were found in quantities that would exceed Peru’s limits for agricultural soils. While drip irrigation is considered a water conservation strategy and widely promoted in the region over other irrigation techniques like high water volume furrow irrigation, its use may accelerate localized negative impacts to surface soil health. These progressive changes highlight the need for effective monitoring and salinity mitigation strategies in the region. This project is part of the bilateral technical program between Purdue University and Universidad Nacional San Agustín (UNSA) called the Arequipa Nexus Institute for Food, Water, Energy, and the Environment.

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Die geochemischen Verhältnisse der Böden des Erzgebirge und Vogtlandes werden auf der Grundlage der komplexen geochemischen Analyse von ausgewählten, flächenrepräsentativen Bodenprofilen auf Hauptgesteinen des Untersuchungegebietes charakterisiert. Die Wirkungsweisen vorhandener Einflussfaktoren (Gesteinschemismus, Bodengenese, Bodennutzung) werden untersucht und bewertet. Die Untersuchungen stellen eine Grundlage für die Ableitung von geologisch bedingten regionalen Hintergrundbelastungen dar. / A characterization of the soil geochemistry of the Erzgebirge and Vogtland Regions (Saxony) is provided on the basis of the investigation of characteristic soil profiles on major bedrock types of the area. Different factors of influence (rock geochemistry, soil formation, land utilization) are investigated and evaluated. The investigation provides essential information for the development of regional background concentrations.

Die geochemischen Verhältnisse der Böden des Erzgebirge und Vogtlandes werden auf der Grundlage der komplexen geochemischen Analyse von ausgewählten, flächenrepräsentativen Bodenprofilen auf Hauptgesteinen des Untersuchungegebietes charakterisiert. Die Wirkungsweisen vorhandener Einflussfaktoren (Gesteinschemismus, Bodengenese, Bodennutzung) werden untersucht und bewertet. Die Untersuchungen stellen eine Grundlage für die Ableitung von geologisch bedingten regionalen Hintergrundbelastungen dar. / A characterization of the soil geochemistry of the Erzgebirge and Vogtland Regions (Saxony) is provided on the basis of the investigation of characteristic soil profiles on major bedrock types of the area. Different factors of influence (rock geochemistry, soil formation, land utilization) are investigated and evaluated. The investigation provides essential information for the development of regional background concentrations.