abstract: Biological soil crusts (BSCs), topsoil microbial assemblages typical of arid land ecosystems, provide essential ecosystem services such as soil fertilization and stabilization against erosion. Cyanobacteria and lichens, sometimes mosses, drive BSC as primary producers, but metabolic activity is restricted to periods of hydration associated with precipitation. Climate models for the SW United States predict changes in precipitation frequency as a major outcome of global warming, even if models differ on the sign and magnitude of the change. BSC organisms are clearly well adapted to withstand desiccation and prolonged drought, but it is unknown if and how an alteration of the precipitation frequency may impact community composition, diversity, and ecosystem functions. To test this, we set up a BSC microcosm experiment with variable precipitation frequency treatments using a local, cyanobacteria-dominated, early-succession BSC maintained under controlled conditions in a greenhouse. Precipitation pulse size was kept constant but 11 different drought intervals were imposed, ranging between 416 to 3 days, during a period of 416 days. At the end of the experiments, bacterial community composition was analyzed by pyrosequencing of the 16s rRNA genes in the community, and a battery of functional assays were used to evaluate carbon and nitrogen cycling potentials. While changes in community composition were neither marked nor consistent at the Phylum level, there was a significant trend of decreased diversity with increasing precipitation frequency, and we detected particular bacterial phylotypes that responded to the frequency of precipitation in a consistent manner (either positively or negatively). A significant trend of increased respiration with increasingly long drought period was detected, but BSC could recover quickly from this effect. Gross photosynthesis, nitrification and denitrification remained essentially impervious to treatment. These results are consistent with the notion that BSC community structure adjustments sufficed to provide significant functional resilience, and allow us to predict that future alterations in precipitation frequency are unlikely to result in severe impacts to BSC biology or ecological relevance. / Dissertation/Thesis / M.S. Biology 2013

In the last years, microbial ecologists have dramatically increased their efforts to elucidate the \"black box\" of patterns and processes that modulate the diversity and functionality of soil microorganisms, examining their genetic diversity (e.g. through metagenomic) and measuring their functional characteristics. The aim of this thesis was to evaluate the interaction of the ecological processes of dispersion, diversification, selection and genetic drift on (1) the soil microbial communities, after conversion of forest to grassland or no-till cropping in long-term and (2) on the microbial communities in the rhizosphere of soybean in long-term no-till system. The cultivation of grassland in long-term led to a homogenizing selection of microbial communities, reducing beta-diversity, with consequent changes in the soil functions related to stress. No-till long-term led to minor changes of diversity, maintaining the functions found in the forest. The soybean plant has shown homogenizing power selection, and this increased with time. However, the functions selected in the rhizosphere were maintained, indicating functional resilience. / Nos últimos anos, ecologistas microbianos aumentaram drasticamente seus esforços para elucidar a \"caixa preta\" dos padrões e processos que modulam a diversidade e funcionalidade dos microrganismos do solo, examinando sua diversidade genética (e.g. através de metagenômica) e medindo suas características funcionais. O objetivo dessa tese foi avaliar a interação dos processos ecológicos de dispersão, diversificação, seleção e deriva gênica, sobre (1) as comunidades microbianas do solo, após a conversão da floresta em pastagem ou plantio direto, em longo período e (2) sobre as comunidades microbianas da rizosfera de soja, em sistema de plantio direto, em longo período. O cultivo de pastagens em longo período levou a uma seleção homogeneizante das comunidades microbianas, reduzindo a beta-diversidade, com conseguinte alteração em funções no solo relacionadas ao estresse. O plantio direto em longo período levou a uma menor alteração da diversidade, com manutenção das funções encontradas na floresta. A planta de soja demonstrou poder de seleção homogeneizante, e este aumentou com o tempo. Contudo, as funções selecionadas na rizosfera foram mantidas, indicando resiliência funcional.

In the last years, microbial ecologists have dramatically increased their efforts to elucidate the \"black box\" of patterns and processes that modulate the diversity and functionality of soil microorganisms, examining their genetic diversity (e.g. through metagenomic) and measuring their functional characteristics. The aim of this thesis was to evaluate the interaction of the ecological processes of dispersion, diversification, selection and genetic drift on (1) the soil microbial communities, after conversion of forest to grassland or no-till cropping in long-term and (2) on the microbial communities in the rhizosphere of soybean in long-term no-till system. The cultivation of grassland in long-term led to a homogenizing selection of microbial communities, reducing beta-diversity, with consequent changes in the soil functions related to stress. No-till long-term led to minor changes of diversity, maintaining the functions found in the forest. The soybean plant has shown homogenizing power selection, and this increased with time. However, the functions selected in the rhizosphere were maintained, indicating functional resilience. / Nos últimos anos, ecologistas microbianos aumentaram drasticamente seus esforços para elucidar a \"caixa preta\" dos padrões e processos que modulam a diversidade e funcionalidade dos microrganismos do solo, examinando sua diversidade genética (e.g. através de metagenômica) e medindo suas características funcionais. O objetivo dessa tese foi avaliar a interação dos processos ecológicos de dispersão, diversificação, seleção e deriva gênica, sobre (1) as comunidades microbianas do solo, após a conversão da floresta em pastagem ou plantio direto, em longo período e (2) sobre as comunidades microbianas da rizosfera de soja, em sistema de plantio direto, em longo período. O cultivo de pastagens em longo período levou a uma seleção homogeneizante das comunidades microbianas, reduzindo a beta-diversidade, com conseguinte alteração em funções no solo relacionadas ao estresse. O plantio direto em longo período levou a uma menor alteração da diversidade, com manutenção das funções encontradas na floresta. A planta de soja demonstrou poder de seleção homogeneizante, e este aumentou com o tempo. Contudo, as funções selecionadas na rizosfera foram mantidas, indicando resiliência funcional.

Områden som antas vara förorenade utreds idag med hjälp av Naturvårdsverkets vägledning för förorenade områden. Vägledningsmaterialet baseras till stor del på miljömålet giftfri miljö och vilka risker ett förorenat område kan utgöra för människor och ekosystem. Soil Security-konceptet är relativt nytt och är främst utvecklat för att bedöma jordbruksmarker och bygger på att jordförvaltningen ska leda till att jordresursen bevaras eller förbättras. I detta projekt har en utvärdering utförts om Soil Security-konceptet skulle kunna användas för att arbetet med förorenade områden ska leda mot hållbarhet. Nio indikatorer som alla indikerar att biomassaproduktion fungerar har tagits fram och sedan använts som underlag för jämförelsen mellan Naturvårdsverkets vägledning och Soil Security-konceptet. Dessa indikatorer har även använts för att utreda vad som utförs i det praktiska arbetet med förorenade områden. En analys av hur markmiljön värderas i det praktiska arbetet och om de åtgärder som utförs leder till fungerande markekosystem har också genomförts. Slutligen har Magdalena Gleisner på Naturvårdsverket intervjuats eftersom projektet har en koppling till den utvärdering de utför av vägledningsmaterialet. Vid jämförelse av utgångspunkterna bakom Soil Security-konceptet och Naturvårdsverkets vägledning hittades både skillnader och likheter. I stora drag är Naturvårdsverkets vägledning främst inriktad på vilka risker en förorenad jord kan utgöra och ser inte jorden som ett skyddsobjekt som behöver skyddas eftersom den kan utföra funktioner som är till nytta för människor och ekosystem. I Soil Security- konceptet är utgångspunkten att skydda markfunktioner för att de senare ska kunna bidra till att lösa globala samhällsutmaningar som exempelvis säker tillgång på livsmedel och vatten. När ramverken jämfördes med avseende på indikatorerna för biomassaproduktion fanns de flesta av indikatorerna med i Naturvårdsverkets vägledning, antingen direkt eller indirekt. Hur indikatorerna sedan analyserades för att bedöma jordens tillstånd var den största skillnaden mellan ramverken. I Soil Security- konceptet används indikatorerna för att avgöra om växtetablering kan ske och även jordens status, medan i Naturvårdsverkets vägledning bedöms istället vilka risker föroreningarna kan utgöra. Tre praktiska fall har också utvärderats och i dessa har Naturvårdsverkets vägledning följts till största delen. Markmiljön har bedömts skyddas av åtgärderna i två av tre fall, dock är det enda kravet på återfyllnadsmaterialet att det inte bidrar till ökade föroreningshalter. För att markfunktioner ska fungera och åtgärderna ska leda mot hållbarhet krävs även att markmaterialet exempelvis har en god jordtextur, ett gynnsamt pH-värde och innehåller näring. För att arbetet med förorenade områden ska leda mot hållbarhet behövs en ny vägledning där Soil Security-konceptet beaktas, nya studier tas fram och delar av den gamla vägledningen används. / In this project, today’s work with contaminated sites was evaluated. In Sweden when assessing sites that probably are contaminated, a guideline made by the Swedish EPA is used. This guideline was compared with the soil security concept both by comparing the foundations, and which indicators that differs between the frameworks. The differences in the foundations were that in the Swedish EPA guideline focus is on the risks contaminated sites could have on humans and ecosystems. The soil security concept on the other hand focuses in functioning soil functions to contribute in global societal challenges. In the comparison evaluating the indicators, nine indicators for the soil function production of biomass were formulated. All of the indicators are mentioned in the soil security concept and even in the Swedish EPA guidelines most of them are mentioned either direct or indirect. The biggest differ between the frameworks is how the indicators are analyzed. In the Swedish EPA guidelines, the risks the indicators could provide are analyzed, while in the soil security concept the indicators are analyzed to know if plants can be established in the area. The practical work with contaminated sites was also evaluated in the project. The same indicators where used to see if differences could be found between the actual work and the Swedish EPA guidelines. Three studies were evaluated and they followed most of guidelines. The soil ecosystem was assessed to be protected in two of the three studies, even though the filling material that could be used only has one requirement that it not contributes to increasing contamination levels. This could lead to non-sustainability due to soil material that is incapable of plant establishment and other important soil functions. If the work with contaminated sites should reach sustainability a new framework needs to be produced which has parts from the Swedish EPA guidelines, the soil security concept and even new research.