Salt marshes role in Phosphorus cycling: importance to natural remediation of estuarine systems

Tese de mestrado. Biologia (Biologia Celular e Biotecnologia). Universidade de Lisboa, Faculdade de Ciências, 2012Os sapais são zonas intertidais onde ocorre acumulação de sedimentos finos devido à sua localização em ambientes protegidos como os estuários. Apesar de já terem sido considerados zonas sem qualquer valor, o seu papel na defesa da linha costeira, tal como conservação da biodiversidade, funcionando como abrigo, zona de nidificação e fonte de alimento para vários animais é extremamente relevante. Para além destas funções os sapais também têm a capacidade de reter poluentes, nomeadamente metais pesados ou nutrientes em excesso que possam levar à eutrofização. Tanto o Azoto como o Fósforo podem ter efeitos negativos por levarem ao aumento excessivo da produção primária e consequentemente à depleção de oxigénio dos sistemas. As plantas halófitas que colonizam os sapais têm a capacidade de impedir a passagem de fósforo para a coluna de água através da oxigenação das camadas superficiais dos sedimentos. Estas plantas constituem uma importante ferramenta na remediação da eutrofização nestes sistemas já que, para o seu crescimento, necessitam de tomar fósforo do sedimento e também porque a sua presença aumenta a capacidade do sedimento para adsorver fósforo. O sistema radicular das plantas promove a criação de um ambiente favorável ao crescimento da comunidade microbiana devido à oxigenação do sedimento e à produção de exsudados radiculares. O estado da comunidade microbiana pode ser avaliado através da determinação de atividades enzimáticas como é o caso da desidrogenase que é uma enzima intracelular que reflete a respiração microbiana. A comunidade microbiana existente no sedimento é crucial no ciclo de nutrientes já que produz enzimas envolvidas na mineralização da matéria orgânica. É o caso das fosfatases que são um grupo de enzimas responsáveis por hidrolisar o fósforo orgânico de forma a obter ortofosfato que pode ser absorvido pelas células. Os objetivos principais desta tese são a determinação dos fatores biogeoquímicos que influenciam a atividade da comunidade microbiana como um todo e em particular os fatores que influenciam a atividade da fosfatase tal como o seu papel no ciclo biogeoquímico do fósforo em sedimentos de sapais do estuário do Tejo. Para tal, as variações sazonais na atividade da desidrogenase foram avaliadas, assim como as diferenças de atividade nos sedimentos colonizados pelas espécies vegetais mais abundantes no estuário do Tejo (Halimione portulacoides, Sarcocornia fruticosa e Spartina maritima). Nestes sedimentos avaliou-se o conteúdo em matéria orgânica, pH, humidade relativa e salinidade de forma a perceber quais os parâmetros que influenciam a atividade microbiana. A atividade da desidrogenase varia ao longo do ano, sendo possível observar um pico de atividade no Inverno e é influenciada pelos vários fatores avaliados, em particular pelo pH e pela humidade relativa dos sedimentos. A espécie de halófito que coloniza o sedimento também mostrou ser um fator importante na atividade microbiana. A atividade das diferentes isoformas de fosfatase presentes no sedimento colonizado por plantas (Halimione portulacoides, Sarcocornia fruticosa, Sarcocornia perennis e Spartina maritima) e sedimento não vegetado também foi avaliada de forma a perceber os processos de mineralização do fósforo que ocorrem no sedimento. Com o mesmo fim, também foram avaliados os fatores biogeoquímicos que podem influenciar estes processos. Desta forma, foram encontradas diferenças entre sedimentos colonizados e não colonizados por vegetação superior, nomeadamente na atividade das fosfatases e o conteúdo de fósforo, indicando que os halófitos testados aumentam a capacidade do sedimento para reter o fósforo. No entanto, não se encontraram diferenças significativas entre sedimentos colonizados pelas diferentes espécies. A atividade total da fosfatase no sedimento depende sobretudo da fosfatase ácida que depende sobretudo do pH e do conteúdo em ácidos húmicos do sedimento. A quantidade de fósforo inorgânico presente no sedimento também influencia a atividade da fosfatase. Deste modo, a atividade microbiana tem um papel importante no ciclo biogeoquímico de fósforo, especialmente devido à atividade da fosfatase ácida. A atividade microbiana do sedimento tanto no seu todo, como no caso da fosfatase, é influenciada pelo pH e pelo coberto vegetal. Assim, quando se considera os sapais como fatores-chave na remediação natural da eutrofização, é importante ter em conta a sazonalidade e a cobertura vegetal que influenciam a comunidade microbiana do sedimento.Salt marshes have been shown to act as a sink for pollutants, such as excess nutrients that cause eutrophication, like nitrogen and phosphorus. Halophytes have been known to block phosphorus efflux. Sediment microbial communities are involved in nutrient cycle due to the action of extracellular enzymes such as phosphatase. Microbial community status can be assessed through the measurement of dehydrogenase that is an intracellular enzyme that provides information about microbial community status. The main objectives of the present thesis are to understand the biogeochemical factors underlying sediment microbial community activities on its hole and in particular the phosphatase activity and its role on phosphorous biogeochemical cycle in salt marsh sediments from the Tagus estuary. The possible seasonal effects on and the biogeochemical factors influencing dehydrogenase activity in salt marsh sediments were assessed. A peak in dehydrogenase activity was found during the winter and dehydrogenase activity was found to be influenced by several factors, mainly water content and pH. The biogeochemical sediment drivers that control phosphatase activities, how the different isoforms are controlled and its influence on the enzyme-mediated phosphorous cycling processes in salt marshes were studied. Bare sediments differed significantly from vegetated sediments in respect to several characteristics such as pH, total and acid phosphatase activities, water content, humic acids and organic matter contents, however, no significant differences were found among vegetated sediments. Acid phosphatase was the most active pH-isoform and its activity was driven mostly by pH and humic acid content, although inorganic phosphorus was also found to have a clear relation with phosphatase activity. Salt marshes may have a key role to achieve ecosystem natural remediation being important to take seasonal variability and plant coverage into account when considering the efficiency of these remediation processes

3rd Conference on Ecology of Soil Microorganisms

We are pleased to welcome you to the 3rd conference on the Ecology of Soil Microorganisms in Helsinki, Finland. The two previous meetings were organized in Prague in 2011 and 2015 by Petr Baldrian. We are delighted to see that as many participants, 400 are joining us also under the midnight sun. During the meeting, soil science will be linked with traditional microbiology and modern genomic, transcriptomic and proteomic analysis tools, extending from the soil-microbe interphase to their interactions with plants. Indeed, one important goal of the conference is to inspire us to bring forward new dimensions in the characterization of the interplay between soil microbial ecology and larger-scale processes in various ecosystems. In this meeting we will cover not only the role of soil microbiota but also their viruses. We hope that you take a moment to think of recent studies that have begun to unearth relationships found between soil microbes, plant performance and even human health. Sustainability of soils and their role in mitigation of climate change are key challenges for preserving life on Earth. As microbes are living functional components of soils, our focus during the week could not be timelier. The organizers and the host organization Natural Resources Institute Finland wish you a fruitful and invigorating conference. We are excited that you have joined us here in Helsinki to promote state-of-the-art research in soil ecology under the northern midsummer madness!201

Effects of softwood biochars on soil biota in medium-term field experiments in Finland

Biochar soil amendment could be used to sequester carbon, enhance soil fertility and potentially increase crop yields. It can have significant impacts on soil organic carbon levels and physicochemical conditions, which consequently affect soil micro- and macro-biota. It is therefore important to understand how key biological components in the soil such as microbial and earthworm communities response to biochar application in the long-term. This study was conducted in Southern Finland in a fertile Stagnosol and a nutrient deficient Umbrisol, four and five years after biochar amendment, respectively. Biochars were produced from spruce (Picea abies (L.) H.Karst.) and pine (Pinus sylvestris L.), and applied at the rates of 10 and 30 t ha-1, respectively. Earthworms and soil samples for microbial analyses were collected in September 2015. Soil microbial communities were studied by using phospholipid fatty acid profiling and 16S rRNA gene amplicon sequencing. Casts from the sampled earthworms were collected to investigate the consumption of biochar and the potential of earthworm bioturbation to affect biochar distribution. Additionally, greenhouse gas emissions from soil were measured. Biochar and fertilizer treatments or their interaction had no statistically significant effects on the earthworm abundance, community composition or greenhouse gas emissions in either field. Earthworms had ingested biochar as earthworm casts from biochar treated-plots contained significantly more black carbon than those in the control plots, demonstrating that earthworm bioturbation is a potentially important factor in the translocation of applied biochar in the soil profile. Microbial community structure data will be presented in the final presentation.Non peer reviewe

Impact of burn severity on soil properties in a Pinus pinaster ecosystem immediately after fire

P. 1-11We analyse the effects of burn severity on individual soil properties and soil quotients in Mediterranean fire-prone pine forests immediately after a wildfire. Burn severity was measured in the field through the substrate stratum of the Composite Burn Index and soil samples were taken 7–9 days after a wildfire occurred in a Pinus pinaster Ait. ecosystem. In each soil sample, we analysed physical (size of soil aggregates), chemical (pH, organic C, total N and available P) and biological (microbial biomass C, b-glucosidase, urease and acid phosphatase activities) properties. Size of aggregates decreased in the areas affected by high burn severity. Additionally, moderate and high severities were associated with increases in pH and available P concentration and with decreases in organic C concentration. Microbial biomass C showed similar patterns to organic C along the burn severity gradient. The enzymatic activities of phosphatase and b-glucosidase showed the highest sensitivity to burn severity, as they strongly decreased from the low-severity scenarios. Among the studied soil quotients, the C : N ratio, microbial quotient and b-glucosidase : microbial biomass C quotient decreased with burn severity. This work provides valuable information on the impact of burn severity on the functioning of sandy siliceous soils in fire-prone pine ecosystems.S

Influence of land use on abundance, function and spatial distribution of N-cycling microorganisms in grassland soils

This thesis focuses on the influence of land use on the abundance, function and spatial distribution of N-cycling microorganisms in grassland soils, but also on soil biogeochemical properties, as well as on enzyme activities involved in the carbon-, nitrogen-, and phosphorous cycle. The objective of this thesis was tackled in three studies. All study sites that were investigated as part of this thesis were preselected and assigned according to study region and land use within the framework of the Exploratories for Functional Biodiversity Research The Biodiversity Exploratories of the Deutsche Forschungsgemeinschaft priority program 1374. The first study addressed the question whether land-use intensity influences soil biogeochemical properties, as well as the abundance and spatial distributions of ammonia-oxidizing and denitrifying microorganisms in grasslands of the Schwäbische Alb. To this end, a geostatistical approach on replicated grassland sites (10 m × 10 m), belonging to either unfertilized pastures (n = 3) or fertilized mown meadows (n = 3), representing low and high land-use intensity, was applied. Results of this study revealed that land-use intensity changed spatial patterns of both soil biogeochemical properties and N-cycling microorganisms at the plot scale. For soil biogeochemical properties, spatial heterogeneity decreased with higher land-use intensity, but increased for ammonia oxidizers and nirS-type denitrifiers. This suggests that other factors, both biotic and abiotic than those measured, are driving the spatial distribution of these microorganisms at the plot scale. Furterhmore, the geostatistical analysis indicated spatial coexistence for ammonia oxidizers (amoA ammonia-oxidizing archaea and amoA ammonia-oxidizing bacteria) and nitrate reducers (napA and narG), but niche partitioning between nirK- and nirS-type denitrifiers. The second study aimed at whether land-use intensity contributes to spatial variation in microbial abundance and function in grassland ecosystems of the Schwäbische Alb assigned to either low (unfertilized pastures, n = 3), intermediate (fertilized mown pastures, n = 3), or high (fertilized mown meadows, n = 3) land-use intensity. Plot-scale (10 m × 10 m) spatial heterogeneity and autocorrelation of soil biogeochemical properties, microbial biomass and enzymes involved in C, N, and P cycle were investigated using a geostatistical approach. Geostatistics revealed spatial autocorrelations (p-Range) of chemical soil properties within the maximum sampling distance of the investigated plots, while greater variations of p-Ranges of soil microbiological properties indicated spatial heterogeneity at multiple scales. An expected decrease in small-scale spatial heterogeneity in high land-use intensity could not be confirmed for microbiological soil properties. Finding smaller spatial autocorrelations for most of the investigated properties indicated increased habitat heterogeneity at smaller scales under high land-use intensity. In the third study, the effects of warming and drought on the abundance of denitrifier marker genes, the potential denitrification activity and the N2O emission potential from grassland ecosystems located in the Schwäbische Alb, the Hainich, and the Schorfheide region were investigated. Land use was defined individually for each grassland site by a land-use index that integrated mowing, grazing and fertilization at the sites over the last three years before sampling of the soil. It was tested if the microbial community response to warming and drought depended on more static site properties (soil organic carbon, water holding capacity, pH) in interaction with land use, the study region and the climate change treatment. It was further tested to which extent the N2O emission potential was influenced by more dynamic properties, e.g. the actual water content, the availability of organic carbon and nitrate, or the size of the denitrifier community. Warming effects in enhanced the potential denitrification of denitrifying microorganisms. While differences among the study regions were mainly related to soil chemical and physical properties, the land-use index was a stronger driver for potential denitrification, and grasslands with higher land use also had greater potentials for N2O emissions. The total bacterial community did not respond to experimental treatments, displaying resilience to minor and short-term effects of climate change. In contrast, the denitrifier community tended to be influenced by the experimental treatments and particularly the nosZ abundance was influenced by drought. The results indicate that warming and drought affected the denitrifying communities and the potential denitrification, but these effects are overruled by study region and site-specific land-use index. This thesis gives novel insights into the performance of N-cycling microorganisms in grassland ecosystems. The spatial distribution of soil biogeochemical properties is strongly dependent on land-use intensity, as in return is the spatial distribution of nitrifying and denitrifying microorganisms and the ecosystem services they perform. Yet, future work will be necessary to fully understand the interrelating factors and seasonal variability, which influence the ecosystem functioning and ecosystem services that are provided by N-cycling soil microorganisms at multiple scales.Diese Arbeit befasst sich mit dem Einfluss von Landnutzungsintensität von Grünländern auf die Abundanz, Funktion und räumliche Verteilung von Stickstoff umsetzenden Bodenmikroorganismen, sowie dem Einfluss der Nutzungsintensität auf biogeochemische Bodeneigenschaften und Enzymaktivitäten des C-, N- und P-Kreislaufs. Die Fragestellung dieser Arbeit wurde in drei Studien bearbeitet, die im Rahmen des DFG Schwerpunktprogrammes 1374 Biodiversitäts-Exploratorien durchgeführt wurden. Die erste Studie sollte klären, wie sich die Landnutzungsintensität auf biogeochemische Bodeneigenschaften, Abundanz und räumliche Verteilung von Nitrifizierern und Denitrifizierern in Grünländern der Schwäbischen Alb auswirkt. Dafür wurde auf Grünländern (10 m × 10 m) mit replizierten Nutzungsintensitäten (ungedüngte Weiden, n = 3; gedüngte Mähwiesen, n = 3) ein geostatistischer Ansatz angewandt. Die Ergebnisse zeigen, dass die Landnutzungsintensität die räumliche Verteilung der biogeochemischen Bodeneigenschaften und die der Stickstoff umsetzenden Mikroorganismen auf der Plot-Ebene beeinflusste: Die räumliche Heterogenität nahm für die untersuchten Bodenparameter mit zunehmender Landnutzungsintensität ab. Im Gegensatz dazu konnte eine Zunahme der räumlichen Heterogenität für Ammoniak oxidierende Mikroorganismen und nirS-Denitrifizierer bei steigender Landnutzungsintensität gezeigt werden. Diese Ergebnisse indizieren, dass auf der Plot-Skala andere abiotisch / biotisch Faktoren als jene, die in der Studie erfasst wurden, die räumliche Verteilung dieser Mikroorganismen bedingen. Weiterhin wurde gezeigt, dass Nitrifizierer (amoA AOA und amoA AOB) und Nitrat-Reduzierer (napA und narG) koexistieren, während nirK- und nirS-Denitrifizierer unterschiedliche ökologische Nischen besetzen. Die zweite Studie thematisierte den Einfluss von Landnutzungsintensität auf die räumliche Variabilität mikrobieller Abundanz und Funktion in Grünlandböden der Schwäbischen Alb. Die Landnutzung war 3 Stufen zugeordnet: niedrig (ungedüngte Weiden, n = 3), mittel (gedüngte Mähweiden, n = 3) und hoch (gedüngte Mähwiesen, n = 3). Ein geostatistischer Ansatz erlaubte es, auf der Plot-Ebene (10 m × 10 m) die räumliche Heterogenität von biogeochemische Bodeneigenschaften, mikrobieller Biomasse und von Enzymen des C-, N-, und P-Kreislaufes zu untersuchen. Die geostatistische Analyse der chemischen Bodeneigenschaften ergab räumliche Autokorrelationen (p-Range), die innerhalb der maximalen Beprobungsdistanz lagen. Eine größere Variation der p-Ranges für mikrobiologische Bodenparameter indizierte räumliche Heterogenität auf unterschiedlichen Ebenen. Die erwartete Abnahme kleinskaliger räumlicher Heterogenität mikrobieller Parameter konnte nicht bestätigt werden da für die meisten Kenngrößen eine geringere räumliche Autokorrelation bei hoher Landnutzungsintensität gefunden wurde. Dies lässt den Schluss zu, dass bei hoher Landnutzungsintensität eine erhöhte, kleinskalige Habitat-Heterogenität vorliegt. In der dritten Studie wurde untersucht, wie sich Bodenerwärmung im Frühjahr und Dürre im Sommer auf die Abundanz denitrifizierender Bakterien sowie das N2O-Emissionspotenzial in drei Grünlandökosystemen auswirken. Das Studiendesign wurde in replizierten Grünlandflächen unterschiedlicher Landnutzung und unterschiedlicher geographischer Herkunft umgesetzt (Schwäbische Alb, Hainich und Schorfheide). Die Landnutzung war für jedes Grünland durch einen individuellen Landnutzungsindex definiert der Mahd, Beweidung und Düngung während der letzten drei Jahre vor der Probennahme berücksichtigte. Es wurde untersucht, ob die von Erwärmung und Dürre induzierten Effekte von statischen Standorteigenschaften (z.B. organischer Kohlenstoffgehalt, Wasserhaltekapazität oder pH-Wert) in Zusammenhang mit der Landnutzung abhängen, und in wie weit die potentielle Denitrifikation von dynamischen Standorteigenschaften (z.B. aktueller Bodenwassergehalt, organischer Kohlenstoff, Nitrat) und der Abundanz der Denitrifizierer selbst beeinflusst ist. Erwärmung steigerte die Aktivität der Denitrifizierer und führte zu erhöhter potentieller Denitrifikation. Die Unterschiede zwischen den Untersuchungsgebieten wurden hauptsächlich durch bodenchemisch-physikalische Eigenschaften erklärt. Der Landnutzungsindex war ein starker bestimmender Faktor für die potentielle Denitrifikation und Flächen mit einem höheren Flächennutzungsindex zeigten ein erhöhtes Potential für N2O-Emissionen. Während die mikrobielle Gemeinschaft (16S rRNA Abundanz) das Potential hatte Effekte der experimentellen Erwärmung und Dürre aufzufangen, zeigten die Denitrifizierer und hier insbesondere nosZ-Denitrifizierer eine Reaktion auf das Dürreexperiment. Insgesamt zeigten Grünländer mit hohem Landnutzungsindex ein größeres Potential zu erhöhten N2O-Emissionen als Flächen mit niedrigerem Nutzungsindex, und die Ausprägung der Effekte auf die denitrifizierenden Mikroorganismen waren hauptsächlich von der Untersuchungsregion und dem Landnutzungsindex abhängig. Diese Arbeit erweitert die Kenntnisse über die Funktion und Rolle Stickstoff umsetzender Mikroorganismen in Grünland-Ökosystemen. Die räumliche Verteilung von biogeochemischen Bodenparametern wird von der Landnutzungsintensität beeinflusst und wirkt sich auf die räumliche Verteilung der Nitrifizierer und Denitrifizierer sowie deren Ökosystemleistungen aus. Um die vielfältigen Ökosystemfunktionen, die von Stickstoff umsetzenden Bodenmikroorganismen bewältigt werden auf allen Ebenen zu verstehen, sind jedoch weitere Untersuchungen notwendig, um beispielsweise die zeitliche Variabilität dieser Funktionen besser zu verstehen

Nutrient Cycling-Tree Species Relationships in Appalachian Forests

Since the colonization of North America by Europeans, ecosystems in Appalachia and across the continent have been in a prolonged state of flux. Areas particularly rich in natural resources, such as Appalachia, have historically borne the brunt of these swift changes, often with devastating consequences. Downwind of much of the power generation facilities of the Ohio Valley, Appalachian forests have been geographically predisposed to high rates of acidic deposition, a circumstance mitigated by the passage of Clean Air Legislation beginning in the 1970s. Nevertheless, decades of elevated nitrogen (N) and sulfur (S) inputs had a profound impact on the ecology and biogeochemistry of these forests. While inputs of these important plant nutrients can provide fertilization effects on plant life, the acidic N and S forms deposited in precipitation also result in a variety of negative outcomes. Plant nutrition can be influenced by acidic inputs in a variety of ways, including modifications to decomposition processes. Microbially-mediated decomposition results in the liberation of nutrients from organically-bound, often recalcitrant forms. When nutrients are abundant due to acidic deposition or by tree species effects such as N fixation and/or readily decomposable low C/N litter, decomposition processes may be suppressed. Since extracellular soil enzymes (ESEs)–the biomolecules responsible for mediating many of the rate-limiting transformations in terrestrial nutrient cycling–are metabolically expensive, and their synthesis and activities tend to be suppressed under nutrient fertilization. In Chapter 2, I present a literature review of ESE activities in the context of their ecosystem function and responses to disturbance, such as different types of pollution episodes, including acidic deposition. In addition to alterations to forest soil decomposition processes, acidic deposition may have other consequences on forest biogeochemistry. Poorly-buffered forest soils are particularly vulnerable to losses of essential nutrient cations, overriding any potential benefits from plant fertilization effects. In addition, the liberation of phytotoxic aluminum cations in an acidifying soil substrate can be extremely detrimental to plant growth. I hypothesize in Chapter 3 that I will observe declines in soil and foliar nutrient element concentrations as modeled estimates of cumulative historic N deposition in high-elevation red spruce forests increase. Likewise, Chapter 4 considers the effects of acidic deposition in the same ecosystem, testing the hypothesis that ESE activities will decline in concert with a legacy fertilization effect still present in high elevation red spruce forest soils. Lastly, I examine the relationships between plant functional guilds and soil processes using the Stand Initiation and Diversity Experiment (SIDE) at Point Pleasant, West Virginia. I hypothesize that I will observe differences in ESEs in plots dominated by different functional guilds of woody tree species: those bearing arbuscular mycorrhizal symbioses, ectomycorrhizal symbioses, and those capable of fixing N. This research will investigate the interplay between anthropogenic disturbances to ecosystem processes, legacy effects due to historic disturbances, tree species effects on ecosystem processes, and the role of tree species functional guilds on ESE profile and decomposition. Observing the effects of past disturbances will provide insight on the nature of contemporary and future changes to natural systems

Enhancing Phosphorus Uptake in Sugarcane: A Critical Evaluation of Humic Acid and Phosphorus Fertilizers Effectiveness

Our research conducted in an area characterized by alkaline, lime-abundant soils investigated the potential of utilizing phosphorus fertilizer and humic acid to enhance phosphorus absorption in sugarcane crops. The results indicated that the application of phosphorus fertilizer significantly increased the total and bioavailable phosphorus in the rhizospheric soil, despite observing a decrease in phosphatase enzyme activity. An important observation was the considerable growth of active carbon, a crucial soil health indicator, under the influence of humic acid treatments. The findings also demonstrated an enhancement in phosphorus absorption by sugarcane due to the synergistic application of humic acid and phosphorus fertilizer at both harvest periods. Interestingly, humic acid treatments, when applied through immersion, were found to be more effective than soil applications, implying a greater impact on root absorption processes. The findings underline the potential of integrating humic acid into sugarcane cultivation for better phosphorus absorption. Our study offers valuable insights for improved soil management strategies, and could potentially pave the way towards more sustainable agricultural practices. However, we also recommend further investigation into alternative methods of humic acid application and its usage at different stages of plant growth. Such exploration could provide a comprehensive understanding of the potential benefits and most effective utilization of humic acid in agriculture, especially in regions with similar soil characteristics as West Azarbaijan, Ira

Ecophysiological field studies of phosphorus nutrition of beech (Fagus sylvatica)

Phosphor (P) ist ein wesentliches Element für die Pflanzenernährung, da es für viele essentielle Biomoleküle wie Nukleotide, Membranlipide und ATP benötigt wird. Pflanzen nehmen P als anorganisches Phosphat (Pi) aus Bodenlösungen auf. Diese P-Ressource ist im Boden aufgrund geringer Diffusionsraten, Sequestrierung durch Bodenmineralien oder Bindung an organische Stoffe häufig begrenzt. Ein wichtiger Aspekt der P-Ernährung ist die Symbiose von Pflanzen mit Ektomykorrhizapilzarten (EMF). EMF tragen zur P-Ernährung bei, indem sie chemische Verbindungen sekretieren und die Bodenexploration durch extrametrische Hyphen erweitern. Obwohl Waldbäume im Allgemeinen an einen niedrigen Nährstoffgehalt im Boden angepasst sind, wurde in jüngsten Studien ein Rückgang der P-Konzentrationen von Buchenblättern in ganz Europa festgestellt (Fagus sylvatica L.). Die Gründe für den Trend zur Abnahme von P in Buche sind unbekannt. Daher analysierten wir die P-Aufnahmestrategien und den Ernährungszustand von Buchen und EMF unter Bedingungen mit niedrigem P (LP), mittlerem P (MP) und hohem P (HP), um die P-Effizienz von Buche und Mykorrhiza, sowie Störungen der Buchen P-Versorgung durch abiotische Veränderungen zu untersuchen. Insbesondere untersuchten wir Aspekte der P-Aufnahme, einschließlich Phosphataseaktivitäten, die Aufnahme von radioaktiv markiertem P, sowie Gesellschafts-Analysen von EMF unter verschiedenen Verfügbarkeiten von Makronährstoffen. Die folgenden Fragen wurden behandelt: a) Ist die Effizienz der P-Aufnahme und Allokation zu Buchenwurzeln unter LP höher als unter HP-Bedingungen? Da die vertikale Verteilung der P-Bestände zwischen HP- und LP-Wäldern unterschiedlich ist, haben wir auch die Bodenschichten in der organischen Schicht und in mineralischen Boden getrennt. b) Wie wichtig ist neuer photoassimilierter Kohlenstoff für die P-Ernährung? Führt der Kohlenhydratmangel zu einer Verringerung der P-Wurzelkonzentrationen mit stärkeren Auswirkungen unter LP- als unter HP-Bedingungen? c) Wie wirken sich P- und N-Verfügbarkeiten unter verschiedenen P-Bedingungen auf boden- und wurzelassoziierte Pilzgemeinschaften und die funktionelle Zusammensetzung dieser in verschiedenen Kompartimenten (Boden, Wurzel) aus? Diese Studie nutzte die Infrastruktur des Internationalen Kooperationsprogramms zur Bewertung und Überwachung der Auswirkungen der Luftverschmutzung auf Wälder (ICP-Wälder). Vom Level II-Standort von ICP Forests sind grundlegende Parameter für Böden und Bestände zugänglich. Wir haben drei Waldstandorte der Stufe II in ganz Deutschland genutzt, die mit mehr als 100 Jahre alten monospezifischen Buchenbeständen bestückt sind. LP befindet sich im Landkreis Celle in Niedersachsen (52°50'21.7" N 10°16'2.3" O, 115 m ü.M.), MP befindet sich im Distrikt Mitterfels in Bayern (48°58'34.1“ N 12°52'46.7“ O, 1023 m ü.M.) und HP befinden sich im Biosphärenreservat 'Bayerische Rhön' in Bayern (50°21'7.2" N 9° 55'44.5" O, 801 bis 850 m ü.M.). Die Standorte unterscheiden sich signifikant in ihrer Boden-P-Konzentration im Bereich von 195 mg kg-1 bis 2966 mg kg-1 des A-Horizonts (0-5 cm). Die Standorte unterscheiden sich in der Textur der mineralischen Oberböden sowie in der Humusform und -dicke. Der P-Gradient ergibt sich aus unterschiedlichen Ausgangsmaterialien der Böden. Trotz der P-Unterschiede behalten die Buchen eine ähnliche Konzentration an Blatt-P bei, die von 1,21 mg g-1 dw bis 1,66 mg g-1 dw reicht. a) Um die Effizienz der P-Aufnahme zu untersuchen, verwendeten wir intakte Bodenkerne, einschließlich der organischen und mineralischen Schicht von LP- und HP-Standorten. Diese intakten Bodenkerne wurden mit 33P markiert und 24 Stunden inkubiert. Das Hauptergebnis war, dass der Hauptpool von aufgenommenem P durch Buchen aus verschiedenen Schichten zwischen kontrastierenden Boden-P-Konzentrationen aufgenommen wurde. Während Buchen von LP-Standorten das meiste P aus der organischen Auflage gewinnen, gewinnen Buchen von HP-Standorten das meiste P aus dem mineralischen Oberboden. Dieses Ergebnis spiegelte sich auch in der P-Anreicherung der Ektomykorrhizawurzelspitzen der HP- und LP-Standorte wider. Die Bedeutung von Ektomykorrhizawurzelspitzen für die P-Aufnahme wurde im Gegensatz zu nicht-Mykorrhizawurzelspitzen gezeigt. Diese waren selten und zeigten eine geringere Anreicherung mit neuem P. Die P-Aufnahme der Buchen korrelierte mit der Anreicherungseffizienz von Ektomykorrhizawurzelspitzen und bestärkt die Relevanz von Mykorrhizawurzelspitzen für die Wurzel-P-Versorgung. b) Um den Einfluss von photoassimiliertem Kohlenstoff auf die P-Aufnahme zu untersuchen, haben wir den Transport zu den Wurzeln unterbrochen, indem wir junge Buchen unter LP- und HP-Bedingungen geringelt haben. Wir untersuchten die Folgen des Ringelns in Wurzeln, Boden und Mikroben eine Woche und zwei Monate nach der Behandlung. Um den Einfluss des Ringelns auf die P-Aufnahme zu testen, führten wir im Labor ein 32P-Aufnahmeexperiment mit jungen Buchen durch. Das Experiment mit radioaktivem Tracer quantifizierte die verringerte P-Aufnahme von Feinwurzeln. Das Ringeln führte zu einer erhöhten sauren Phosphatase- und PEPC-Aktivität in Feinwurzeln. Zusätzlich wurden Buchen durch Ringeln mit einer abnehmenden Anzahl lebenswichtiger Wurzelspitzen und Feinwurzelbiomasse belastet, wodurch die P-Aufnahmekapazität verringert wurde. An dem LP-Standort zeigten Ektomykorrhizen eine erhöhte Aktivität der extrazellulären sauren Pphosphatase als Reaktion auf das Ringeln. Darüber hinaus war die Genhäufigkeit von P-Transportern und von Genen für die P-Mineralisierung im Boden infolge des P- und C-Mangels an dem LP-Standort als Reaktion auf das Ringeln erhöht. Während bei HP nur erhöhte Phosphatase- und PEPC-Aktivitäten von Pflanzenmaterial beobachtet wurden, wurden bei LP selbst im umgebenden Boden viele Anpassungen festgestellt. Wir schließen daraus, dass die P-Konzentrationen von Mikroben und Feinwurzeln aufgrund einer erhöhten P-Aufnahme, einer internen P-Verlagerung und einer Verringerung der Biomasse unter HP- und LP-Bedingungen aufrechterhalten werden können. c) Um die Rolle der Verfügbarkeit von P und N im Boden als Treiber für Pilzgemeinschaften in Boden und Wurzeln zu untersuchen, verwendeten wir ein drei jähriges Düngeexperiment nach Zugabe von P (50 kg ha-1) und regelmäßigen Zugaben von N (5 mal 30 kg ha-1) oder die Kombination der P+N-Behandlungen. Die experimentellen Düngungen wurden an Parzellen in den HP-, MP- und LP-Wäldern durchgeführt, und mit KCl behandelte Parzellen dienten als Kontrollen. Wir analysierten die Veränderungen der Pilzgemeinschaften des Bodens und der Feinwurzeln mit Illumina MiSeq und die nutzten die Morphotypisierung von EMF von Wurzeln, aus der organischen Auflage und des mineralischen des Frühjahrs und Herbstes. Die Düngung mit P erhöhte die labile P-Konzentration im Boden und die gesamt P-Konzentration der Wurzeln. Die Düngung mit N wirkte sich nur auf Ammonium bei LP in der organischen Schicht aus, während bei MP und HP oder in den mineralischen Oberböden der Wälder keine Veränderungen auftraten. Weiterhin verringerte die N Düngung den gesamt P Gehalt der Wurzeln des P-armen Standortes. Weder die P- noch die N-Düngung erhöhte den Pilzreichtum (Richness) der Ektomycorrhizen, aber ihre relative Abundanz wurde durch die Zugabe von P oder N im Vergleich zu saprotrophen Pilzen erhöht. Die mit Wurzeln oder Boden assoziierten Pilzgemeinschaften und Arten (analysiert durch Illumina-Sequenzierung) zeigten jedoch keine signifikanten Veränderungen der Zusammensetzung, wenn sie auf der Ebene von 97% Sequenzidentität (operative taxonomische Einheiten) untersucht wurden. Auf der phylogenetischen Klassifikation der Ordnungen beobachteten wir eine moderate Abnahme der Häufigkeiten der Ordnungen Russulales (P + N), während Boletales (P) zunahm. Russulales und Boletales enthalten hauptsächlich mykorrhizalbildende Pilze. Kurzzeitige Änderungen der N und P Einträge hatten somit keine Einflüsse auf die Pilzgemeinschaften, wohingegen langfristige Belastungen mit Nährstoffeinträgen, möglicherweise zu signifikanten Änderungen des vorhandenen Mykobioms führen könnten. Zusammenfassend lässt sich sagen, dass die Ergebnisse dieser Arbeit die Anpassung der P-Effizienz von Mykorrhizapilzen an die Verfügbarkeit von P im Boden entwirren und die Komplexität biotischer und abiotischer Faktoren hervorheben, die die P-Versorgung von Bäumen in Waldökosystemen steuern. Die Ökosysteme der Buchenwälder zeigten je nach Verfügbarkeit von P unterschiedliche Strategien, um mit verschiedensten Umweltbedingungen ihre P Versorgung aufrecht zu erhalten. Wir bieten Einblicke in P-Akquirierungs- und P-Recycling-Strategien durch den Vergleich der LP- und HP-Bedingungen von Buchenwäldern und ihrer jeweiligen EMF-Gemeinschaft. Recyclingstrategien sind gekennzeichnet durch die P-Aufnahme von Buchen und die P-Anreicherung von EMF aus der organischen Auflage, in der sich die Feinwurzelmasse und lebenswichtige ektomykorrhisierte Wurzelspitzen ansammeln. Akquisitionsstrategien werden durch P-Aufnahme von Buche und P-Anreicherung von EMF aus dem mineralischen Oberboden identifiziert, in dem sich Feinwurzelmasse und lebenswichtige ektomykorrhisierte Wurzelspitzen zusammenballen. Jede Strategie hat ihre eigenen Pilz-EMF-Gemeinschaften, die die P Solubilisierung aus organischer Substanz unter LP-Bedingungen oder aus mineralischem Boden unter HP-Bedingungen verbessern.Phosphorus (P) is an essential element for plant nutrition because it is required for many essential biomolecules such as nucleotides, membrane lipids and ATP. Plants take up P as inorganic phosphate (Pi) from soil solutions. This P resource is usually scarcely available in soil due to low diffusion rates, sequestration by soil minerals or binding to organic matter. An important aspect of P nutrition is the symbiosis of plants with ectomycorrhizal fungal species (EMF). EMF contribute to P nutrition by secretion of chemical compounds and extending soil exploration by extrametrical hyphae. Although forest trees are generally adapted to low nutrient in soil, recent studies detected decreasing P concentrations of beech leaves across Europe (Fagus sylvatica L.). The reasons for the trend of declining P in beech are unknown. Here, we analysed the P uptake strategies and nutritional status of beech and EMF under low P (LP), medium P (MP) and high P (HP) conditions to examine plant and mycorrhizal P efficiencies, as well as disorders of P supply by abiotic interferences to beech. Specifically, we examined aspects of P uptake including phosphatase activities, uptake by radioactively labeled P, as well as community analyses of EMF under different availabilities of macronutrients. The following questions were addressed: a) Is the efficiency for P uptake and allocation to beech roots higher under LP than under HP conditions? Since the vertical distribution of P stocks differs between HP and LP forests, we also separated soil layers in the organic layer and the mineral topsoil. b) How important is recently photoassimilated carbon for P nutrition? Does carbohydrate depletion leads to decreased root P concentrations, with stronger effects under LP than under HP conditions? c) How do P and N availabilities affect soil and root associated fungal communities and functional composition in different compartments (soil, root) under different P conditions? This study used the infrastructure of the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). From Level II site of ICP Forests basic parameters for soils and stands are accessible. We used three Level II forest sites across Germany, which are stocked with more than 100-year-old mono-specific beech stands. LP is located at the district Celle in Lower Saxony (52°50'21.7"N 10°1.6'2.3"E, 115 m a.s.l.), MP is located at the district Mitterfels in Bavaria (48°58'34.1"N 12°52'46.7"E, 1023 m a.s.l.) and HP is located at the biosphere reservation ‘Bayerische Rhön’ in Bavaria (50°21'7.2"N 9°55'44.5"E, 801 to 850 m a.s.l.). The sites differ significantly in their soil P concentration ranging from 195 mg kg-1 to 2966 mg kg-1 of the A horizon (0-5 cm). The sites differ in the texture of the mineral topsoils as well as the humus form and thickness. The P gradient is a result of different parent materials of the soils. Despite the P differences the beeches maintain similar concentrations of foliar P ranging from 1.21mg g-1 dw to 1.66 mg g-1 dw.a) To investigate the P uptake efficiency, we used intact soil cores including the organic and mineral layers from LP and HP sites. These intact soil cores were labeled with 33P and incubated for 24 hours. The main result was that the main pool of P acquired by beech, was taken up from different layers between contrasting soil P concentrations. While beech from LP sites acquires most P from the organic layer, beech from HP sites acquire most P from the mineral layer. This result was also reflected by the P enrichment of ectomycorrhizal root tips at the HP and LP sites. The importance of ectomycorrhizal root tips for P uptake was shown in contrast to non-mycorrhizal root tips, which were rare and exhibited lower enrichment with new P. Beech P uptake correlated with the enrichment efficiency of ectomycorrhizal root tips, demonstrating the relevance of mycorrhizal P acquisition for root P supply. b) To investigate the impact of photoassimilated carbon on P uptake, we interrupted the transport to the roots by girdling of young beech trees under LP and HP conditions. We studied the consequences of the girdling in roots, soil, and microbes one week and two months after the treatment. To test the influence of girdling on P uptake we conducted a 32P uptake experiment with young beech trees in the laboratory. The radioactive tracer experiment showed that P uptake of fine roots was reduced after girdling. Girdling resulted in increased acid phosphatase and PEPC activity in fine roots. The girdled trees had a decreased number of vital root tips and less fine root biomass, thus, reducing P uptake capacity compared with controls. At the LP site, ectomycorrhizas exhibited increased extracellular acid phosphatase activity in response to girdling. In addition, gene abundances of P-transporters and of genes for P mineralization were increased in the soil as a consequence of P and C starvation at the LP site in response to girdling. Among the tested variables, at HP only increased phosphatase and PEPC activities in roots were observed, while at LP many adaptation responses were detected, even in the surrounding soil. We conclude that P concentrations of microbes and fine roots can be maintained due to increased P uptake, internal P relocation and a reduction of biomass at HP and LP conditions. c) To investigate the role of P and N availability in soil as drivers for fungal communities in soil and roots, we used a fertilization experiment three years after addition of P (50 kg ha-1) and regular additions of N (5 times 30 kg ha-1) or the combination of the P+N treatments. The experimental treatments were conducted on plots in the HP, MP and LP forests and KCl treated plots served as the controls. We analysed the changes of fungal communities with Illumina MiSeq of soil and fine roots and morphotyping of EMF from roots grown in the organic and the mineral layer in spring and fall. Fertilization with P increased the labile P concentration in soil and the total P concentration in roots. Fertilization with N only affected ammonia at LP in the organic layer, whereas no changes occurred at MP and HP or in the mineral topsoils of the forests. N further decreased total P of root at the low P site. P and N fertilization didn’t affect ectomycorrhizal species richness but increased their relative abundance compared to that of saprotrophic fungi. However, the fungal communities and taxa associated with roots or soil (analysed by Illumina sequencing) did not show significant compositional changes, when studied at the level of 97% sequence identity (operational taxonomic units). At the phylogenetic classification of orders, we observed moderate decreases in the abundances of Russulales (P+N), whereas Boletales (P) increased. Russulales and Boletales contain mainly mycorrhizal forming fungi. Short-term changes in N and P inputs were resisted by fungal communities, whereas chronic exposure to enhanced nutrient inputs may lead to significant changes of the resident mycobiome structures. In conclusion, the results of this thesis disentangle adaptation of mycorrhizal P efficiencies to soil P availability and highlight the complexity of biotic and abiotic factors that govern P supply to trees in forest ecosystems. Beech forest ecosystems revealed distinct strategies depending on the P availability to cope with varying environmental conditions. We provide insight in P acquiring and P recycling strategies by the comparison of LP and HP conditions of beech forests and their respective EMF community. Recycling strategies are characterized by P uptake of beech and P enrichment of EMF from the organic layer, where fine root mass and vital ectomycorrhized root tips are accumulated. Acquiring strategies are identified by P uptake of beech and P enrichment of EMF from the mineral topsoil, in which fine root mass and vital ectomycorrhized root tips are clustered. Each strategy has its unique fungal EMF communities, improving solubilization from organic matter under LP condition or from mineral soil under HP conditions.2021-10-2

Relationships between succession and community structure and function of Alnus-associated ectomycorrhizal fungi in Alaskan boreal forests

Thesis (M.S.) University of Alaska Fairbanks, 2016Rates of production and carbon cycling in northern ecosystems depend heavily on nitrogen (N) availability across the landscape. Since much of the available N enters these systems through biological N-fixation, Alnus, with its capacity to fix large amounts of N, plays a critical role in ecosystem response to environmental change. However, because of its high phosphorus (P) demands, the abundance, distribution, and N-fixing capacity of Alnus is tightly controlled by the availability of P and its ability to assimilate P by associating with ectomycorrhizal fungal (EMF) symbionts. We assessed the potential of A. tenuifolia-associated EMF to access organic P forms of varying complexities. More than half of the community on A. tenuifolia were individuals from the genera Alnicola and Tomentella, indicating that the community of EMF on Alnus is a relatively distinct group of host-specific ectomycorrhizal fungi. However, the aggregated acid phosphatase, phosphodiesterase and phytase activities of the Alnus-EMF community were not dramatically different from other boreal plant hosts on the root tip level. We detected variability in the activities of the two Alnus dominants to mobilize acid phosphatase and phosphodiesterase. However, it appears that contrary to the hypothesis that nitrogen-fixing species would associate with EMF types well suited to P acquisition, the potential acid phosphatase activity of Alnicola luteolofibrillosa was significantly below the community mean. Our finding that enzyme activities of Alnus-EMF are not substantially greater than those found on other plant hosts suggests that if host specific EMF on Alnus facilitates P mobilization and uptake, the steps between P hydrolysis and assimilation into plant tissue as well as other pathways of P acquisition may be of greater importance in determining P provisioning to Alnus by EMF

The Consequences of Environmental Properties and Tree Spatial Neighborhood on Post-Fire Structure of Forest in Yosemite National Park

Separating the contribution of habitat filtering and dispersal mechanisms in forming species distribution remains a challenge in community ecology. Despite the effect of environmental variables in structuring communities, only restricted numbers of them were considered as a habitat dissimilarity. In Chapter 2, I used topography and soil properties to define habitats within the Yosemite Forest Dynamics Plot (YFDP). The soil enzymes were added in soil samples due to their important role in releasing nutrients into the soil environment. The preference of eleven species to a specific habitat were examined. Also, the relative importance of habitat filtering and dispersal limitation were examined. I found that more species associated with habitats defined by soil properties compare to those associated with topographically defined habitat. In addition, the contribution of dispersal process was greater in explaining change in species composition. In Chapter 3, I studied the underlying processes in shaping four abundant species spatial arrangement in YFDP. I examined the effect of habitat heterogeneity, dispersal process, fire event, interaction of adults on juveniles, and negative density dependence (as a result of increasing density) in shaping species spatial distribution. My results suggest that dominant species spatial patterns are partially explained by topographic variables, dispersal limitation, biotic interactions, and fire history