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%).

Orientador: Mara Cristina Pessôa da Cruz / Coorientador: Edson Luiz Mendes Coutinho / Banca: Felipe Batistella Filho / Banca: Flávia Fernanda Simili / Banca: José carlos Barbosa / Banca: Itamar Andrioli / Resumo: A intensificação da produção dos animais em sistemas confinados gera uma alta produção de esterco bovino que pode contribuir para o fornecimento de nutrientes. Além de proporcionar melhorias em atributos químicos e físicos do solo. Diante deste contexto trabalhou-se com a hipótese de que o esterco bovino pode substituir total ou parcialmente o fertilizante nitrogenado industrial na adubação do capim-tifton 85. Assim, o objetivo com o presente trabalho foi avaliar o efeito da combinação nitrogênio x esterco da produção de capim-tifton 85 e em atributos químicos e físicos do solo. O experimento foi instalado durante os anos agrícolas 2013-2014 e 2014-2015. Os tratamentos consistiram de cinco doses de nitrogênio (N): 0, 50, 100, 200 e 300 kg ha-1, e cinco doses de esterco (E): 0, 10, 20, 40 e 60 Mg ha-1 combinadas em esquema fatorial. As doses de 300 kg ha-1 de N e 40 Mg ha-1 de E proporcionaram a maior produção de massa seca (10.469 kg ha-1) e altura (75,10 cm) em 2013-14. A associação das maiores doses de esterco e nitrogênio resultaram em melhor desempenho da forrageira em relação a produção de massa seca total (13.305 kg ha-1). Houve aumento de 71 e 88% de acúmulo de nitrogênio no capim-tifton 85 no ano agrícola 2013-14 e, aumento de 126 e 163 em 2014-15, com o uso de esterco e de N-ureia, respectivamente. A recuperação aparente de N com o uso de esterco foi maior no segundo ano de avaliação. Com o uso de N-ureia não houve variação nos teores de carbono orgânico do solo e na... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intensified production of animals in confined systems generates a high production of cattle manure that can contribute to the nutrient supply. In addition to providing improvements in soil chemical and physical attributes. In this context, we worked with the hypothesis that bovine manure can totally or partially replace industrial nitrogen fertilizer in fertilization of tifton grass 85. Thus, the objective with the present work was to evaluate the effect of the nitrogen and manure combination of tifton 85 grass production and on soil chemical and physical attributes. The experiment was installed during the agricultural years 2013-2014 and 2014-2015. The treatments consisted of five doses of nitrogen (N): 0, 50, 100, 200 and 300 kg ha-1, and five manure doses (E): 0, 10, 20, 40 and 60 Mg ha-1 combined in factorial scheme. The doses of 300 kg ha-1 of N and 40 Mg ha-1 of E provided the highest dry mass production (10,469 kg ha-1) and height (75,10 cm) in 2013-14. The association of the highest doses of manure and nitrogen resulted in better forage performance in relation to the production of total dry mass (13,305 kg ha-1). There was an increase of 71 and 88% of nitrogen accumulation in Tifton 85 grass in the agricultural year 2013-14 and, increased 126 and 163 in 2014-15, respectively. The apparent recovery of N with use of manure was greater in the second year of evaluation. With the use of N-urea, there was no change in soil organic carbon and forms of carbon associated with minerals and particulate. The use of 60 Mg ha-1 of manure for two consecutive years increased the stability (94.96%) and the weighted average diameter of the aggregates (4.86 mm) and decreased soil resistance to penetration (0.99 MPa) due to the 35% increase in soil carbon content. / Doutor

Tillage increases erosion rates and diminishes the quality of soils but has traditionally been a way to manage weeds and prepare a seedbed. No-till vegetable production can ameliorate the ill-effects of tillage in an economically effective way but has not been studied much in California. The objective of this thesis was to determine the viability of no-till vegetable cropping on the Central Coast of California. Tomatoes were grown in no-till and conventionally tilled treatments. Total yield, fruit weight, weed emergence, soil bulk density, soil aggregate stability, and soil organic carbon content were measured and compared. Yields and soil tests in both treatments were similar while weed emergence in the tilled plots was significantly higher than in no-till plots. The results may help vegetable producers determine how to make vegetable production on the Central Coast more sustainable.

abstract: Soil organic carbon (SOC) is a critical component of the global carbon (C) cycle, accounting for more C than the biotic and atmospheric pools combined. Microbes play an important role in soil C cycling, with abiotic conditions such as soil moisture and temperature governing microbial activity and subsequent soil C processes. Predictions for future climate include warmer temperatures and altered precipitation regimes, suggesting impacts on future soil C cycling. However, it is uncertain how soil microbial communities and subsequent soil organic carbon pools will respond to these changes, particularly in dryland ecosystems. A knowledge gap exists in soil microbial community responses to short- versus long-term precipitation alteration in dryland systems. Assessing soil C cycle processes and microbial community responses under current and altered precipitation patterns will aid in understanding how C pools and cycling might be altered by climate change. This study investigates how soil microbial communities are influenced by established climate regimes and extreme changes in short-term precipitation patterns across a 1000 m elevation gradient in northern Arizona, where precipitation increases with elevation. Precipitation was manipulated (50% addition and 50% exclusion of ambient rainfall) for two summer rainy seasons at five sites across the elevation gradient. In situ and ex situ soil CO2 flux, microbial biomass C, extracellular enzyme activity, and SOC were measured in precipitation treatments in all sites. Soil CO2 flux, microbial biomass C, extracellular enzyme activity, and SOC were highest at the three highest elevation sites compared to the two lowest elevation sites. Within sites, precipitation treatments did not change microbial biomass C, extracellular enzyme activity, and SOC. Soil CO2 flux was greater under precipitation addition treatments than exclusion treatments at both the highest elevation site and second lowest elevation site. Ex situ respiration differed among the precipitation treatments only at the lowest elevation site, where respiration was enhanced in the precipitation addition plots. These results suggest soil C cycling will respond to long-term changes in precipitation, but pools and fluxes of carbon will likely show site-specific sensitivities to short-term precipitation patterns that are also expected with climate change. / Dissertation/Thesis / Masters Thesis Biology 2019

<p>Plant microbiomes are increasingly recognized for their potential to help plants with critical functions such as nutrient acquisition. Nitrogen is the most limiting nutrient in agriculture and growers apply substantial amounts to meet crop needs. Only 50% of N fertilizers are generally taken up by plants and the rest is subject to loss which negatively affects environmental quality. Organic fertilizers such as cover crops and animal manure can help reduce this loss, though these materials must mineralize via microbial mediated processes before they are available for plant uptake, which makes managing fertility using these sources difficult. Some plants can scavenge nutrients from organic materials by stimulating positive priming processes in soil. Carrot (<i>Daucus carota.</i> L) is known as an N scavenging crop, making it an ideal model crop to study these interactions. In a greenhouse trial, soils were amended with an isotopically labeled corn residue to track N movement, and planted with one of five carrot genotypes expected to differ in nitrogen use efficiency (NUE). Changes in soil b-glucosidase activity, ammonium (NH₄⁺-N) and nitrate (NO₃^--N) concentrations, soil bacterial community composition, weight and carbon and N concentrations, and total δ¹⁵N of above and below ground carrot biomass were determined. Results indicate that there are genetic differences in the ability of carrots to promote priming under N limited conditions, which could be exploited to enhance NUE in carrots. Soil microbial communities differed between genotypes, indicating that some of these microbes could play a role in the differential N scavenging responses observed, and/or contribute to other important functions such as resistance to pests. Endophytic microbes residing inside carrot taproots also have potential to contribute to NUE and other benefits, but are notoriously difficult to isolate and culture. New next generation sequencing technologies have revolutionized the study of microbiomes, though using these tools to study bacterial endophytes in plants is still difficult due to co-amplification of plant organelles. Consequently, a second study was conducted to determine if subjecting carrot tissues to hollow fiber microfiltration followed by enzymatic digestion could enhance recovery and amplification of bacterial endophytes. Carrot taproot digests were subject to amplification using a standard V3-V4 16S primer set, as well as two alternative (blocking and mismatch) primer sets that have prevented amplification of plastids/mitochondria in other plant species. Results indicate that the microfiltration/digestion procedure can increase the number of bacterial endophyte OTUs assigned and could be further optimized for use in carrots. The blocking and mismatch primer sets were not as effective in blocking co-amplification of plant products as they are in other studies, possibly due to the presence of a high number of chromoplasts in carrot tissues. Taxonomic assignment of bacterial endophytes differed significantly between the primer sets, indicating that multiple primer sets may be needed to fully characterize these communities in carrots. The enzymatic digestion procedure could artificially inflate certain taxa, which could be helpful if targeting specific taxa. These studies demonstrate that carrots are intimately connected with microbes residing in the soil and within their taproots, and further exploration of these plant-soil-microbial relationships could enhance the yield and sustainability of carrot production systems.</p>

The soil microbial community has a major impact on ecosystem processes on a global scale. Anthropogenic stress has a significant effect on the composition, biomass and activity of the microbial community. In addition, this effect depends not only on the anthropogenic activity, but also on the environmental conditions. Modern analytical and molecular methods, including the use of biochemical markers, can be well used to monitor changes in the microbial community. These methods do not monitor the community directly, but detect the substances that are secreted and transformed by microbes and, last but not least, those that are part of them. The amount of these biochemical markers reflects the biomass, condition and taxonomic composition of a particular microbial community. In the presented work, these markers were used to monitor the response of microorganisms in various ecosystems which are affected directly or indirectly by human activity. The results of the dissertation are presented in four articles. Three of them have been published in international journals with IF and one is prepared in the form of a manuscript for publication. The first publication presents the results of research exploring the impact of traditional agriculture in Papua New Guinea on the soil microbial communities, soil...

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21470号 / 農博第2313号 / 新制||農||1064(附属図書館) / 学位論文||H31||N5165(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 北山 兼弘, 教授 本田 与一, 教授 舟川 晋也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems, which plays an important role in climate change by regulating atmospheric carbon dioxide. Sweden’s forest management has led to a decrease in old growth forests. This change in land use can affect SOC levels in these forests. This report quantified SOC stocks among different wetness classes in 10 old growth forests across multiple regional environmental gradients in Sweden. I tested for the effects of some different environmental factors on SOC: temperature, precipitation, altitude, stem basal area, latitude, and normalized difference vegetation index. Soil measurements were taken from three different horizons: the O-, E-, and B-horizon. The results showed that the mean SOC stock in old growth forests (5.25 ± 0.60 kg m-2)  is a bit higher than the regional average (4.1 ± 0.5 kg m-2) and that local variation within forests, mainly due to hydrology, appears to drive variation that is often as big or larger than regional variations. There were no significant differences between the different forests, but there were significant differences found between the different wetness classes. There were several correlations found between the different regional environmental factors and SOC stocks. The most prominent relationship was a positive link between the O-horizons’ SOC stocks and temperature (R2adj = 0.58). Overall, these results indicate that SOC stocks in old growth forests are affected by both soil wetness at a local scale and air temperature at a regional scale; and that they might contain a slightly larger amount of SOC than managed forests.

This study looks at relationships along the hydrologic gradient between and within six pools; including the vegetation community, soil characteristics and hydrology. Pool conditions were monitored weekly throughout the 2011 and 2012 growing seasons. Each pool was equipped with permanent platinum-tipped redox probes to quantify the severity and duration of soil reduction. We described and analyzed 12 soil profiles in each pool, distributed in summit/upland, basin, and rim/transition positions as defined by the high water line. The pools were systematically surveyed for understory vegetation during the 2012 growing season. Vegetation patterns varied between study areas. No clear pattern of unique vegetation was evident from an ordination of the gradient communities. Time series redox potential data showed a visual relationship to water table fluxuation, but also a dampening effect from soil organic matter content in the basin positions.

Farmers have been disrupting the carbon cycle ever since humans started converting forests to agricultural lands. But are there farming practices that can be applied to increase the carbon storage in the soil and subsequently counteract increasing carbon dioxide levels in the atmosphere? In this study I investigate if soil organic matter (SOM) and soil organic carbon (SOC) change with longer interruption between tillage events. The study was conducted by studying SOM concentrations and SOC pools in eight fields with different time since tillage (1 to 14 years). I found that SOM concentrations increased in the O horizon of the studied soil in response to increased time since tillage. Here, SOM concentrations were on average around 13 % one year after tillage, while fourteen-year-old farmland had a concentration around 15 %. In similar, SOC pool increased from around 0.1 kg C m-2 in the O horizon of 1 year old soil to 0.33 kg C m-2 14 years after tillage. While both SOM concentrations and SOC pools increased in the O horizon over time since tillage, the SOM concentration and SOC pools decreased in the subsoil. I found no net sequestering of SOC in response to less frequent tillage in comparison to more frequency tillage. My conclusion is that limiting tillage to 14-year cycles is not enough to increase carbon sequestration.