The nature of the microbial communities inhabiting the deeper soil horizons is largely unknown. It is also not clear why subsurface microorganisms do not make faster use of organic compounds under field conditions. The answer could be provided by a reciprocal soil transfer experiment studying the response of transferred soils to fluctuations in microclimate, organic inputs, and soil biota. The subproject P9 will be responsible for the establishment of reciprocal transfer experiments offering a strong link between subgroups interested in organic matter quality, transport of organic substances, as well as functions of the soil microbial community. A single, high molecular weight substrate (13C labelled cellulose) will be applied at two different levels in the pre-experiment to understand the dose-dependent reaction of soil microorganisms in transferred surface and sub-soils. Uniformly 13C labelled beech roots - representing complex substrates - will be used for the main reciprocal soil transfer experiment. We hypothesize that transferring soil cores between subsoil and surface soil as well as addition of labelled cellulose or roots will allow us to evaluate the relative impact of surface/subsurface habitat conditions and resource availability on abundance, function, and diversity of the soil microbial community. The second objective of the subproject is to understand whether minerals buried within different soil compartments (topsoil vs. subsoil) in the field contribute to creation of hot spots of microbial abundance and activity within a period of two to five years. We hypothesize that soil microorganisms colonize organo-mineral complexes depending on their nutritional composition and substrate availability. The existence of micro-habitat specific microbial communities could be important for short term carbon storage (1 to 6 years). The third objective is to understand the biogeography and function of soil microorganisms in different subsoils. Parent material as well as mineral composition might control niche differentiation during soil development. Depending on size and interconnectedness of niches, colonization and survival of soil microbial communities might be different in soils derived from loess, sand, terra fusca, or sandstone. From the methodological point of view, our specific interest is to place community composition into context with soil microbial functions in subsoils. Our subgroup will be responsible for determining the abundance, diversity, und function of soil microorganisms (13C microbial biomass, 13C PLFA, enzyme activities, DNA extraction followed by quantitative PCR). Quantitative PCR will be used to estimate total abundances of bacteria, archaea and fungi as well as abundances of specific groups of bacteria at high taxonomic levels. We will apply taxa specific bacterial primers because classes or phyla might be differentiated into ecological categories on the basis of their life strategies.
Various species of pest insects cause substantial damage to agriculture every year, or transmit deadly diseases to animals and humans. A successful strategy to control pest insect populations is based on the Sterile Insect Technique (SIT), which uses the release of mass-reared, radiation sterilized male insects to cause infertile matings and thus reduce the pest population level. However, irradiation is not applicable to every insect species. Thus, new strategies based on genetic modifications of pest insects have been developed or are currently under investigation.The goal of the proposed research is to improve the development and ecological safety of genetically engineered (GE) insects created for enhanced biological control programs, including the SIT and new strategies based on conditional lethality. A major concern for GE insect release programs is transgene stability, and maintenance of their consistent expression. Transgene loss or intra-genomic movement could result in loss of strain attributes, and may ultimately lead to interspecies movement resulting in ecological risks. To address potential transgene instability, a new transposon vector that allows post-integration immobilization will be tested in the Mediterranean, Mexican and Oriental fruit fly tephritid pest species. In addition, the system will be established in the mosquito species Aedes and Anopheles - carriers of dengue and malaria.Random genomic insertion is also problematic for GE strain development due to genomic position effects that suppress transgene expression, and insertional mutations that negatively affect host fitness and viability. Diminished transgene expression could result in the unintended survival of conditional lethal individuals, or the inability to identify them. To target transgene vectors to defined genomic insertion sites having minimal negative effects on gene expression and host fitness, a recombinase-mediated cassette exchange (RMCE) strategy will be developed that. RMCE will also allow for stabilization of the target site, will be tested in tephritid and mosquito species, and will aid to the development of stabilized target-site strains for conditional lethal biocontrol. This will include a molecular and organismal evaluation of an RNAi-based lethality approach. Lethality based on an RNAi mechanism in the proposed insects would increase the species specificity and having multiple targets for lethality versus one target in existing systems. By seeking to improve transgene expressivity and stabilization of transposon-based vector systems, this proposal specifically addresses issues related to new GE insects by reducing their unintended spread after field release, and by limiting the possibilities for transgene introgression.
Research in 'silviculture' and 'forest economics' very often takes place largely independent from each other. While silviculture predominantly focuses on ecological aspects, forest eco-nomics is sometimes very theoretic. The applied bioeconomic models often lack biological realism. Investigating mixed forests this proposal tries to improve bioeconomic modelling and optimisation under uncertainty. The hypothesis is tested whether or not bioeconomic model-ling of interacting tree species and risk integration would implicitly lead to close-to-nature forestry. In a first part, economic consequences of interdependent tree species mixed at the stand level are modelled. This part is based on published literature, an improved model of timber quality and existing data on salvage harvests. A model of survival over age is then to be developed for mixed stands. A second section then builds upon data generated in part one and concentrates on the simultaneous optimisation of species proportions and harvest-ing ages. It starts with a mean-variance optimisation as a reference solution. The obtained results are compared with data from alternative approaches as stochastic dominance, down-side risk and information-gap robustness.
Outbreaks of foodborne illness linked to consumptions of fresh, or partially processed, agricultural products are a growing concern in industrialized and developing countries. The incidence of human pathogens on fresh fruits and vegetables is often related to the use of recycled wastewaster in surface irrigation as well as high amounts of animal manure in agricultural management practice. Thereby the soil inhabiting fauna plays an important role in the transport and dissemination of microorganisms. The focus of the proposed project is on nematodes, well known vectors for bacteria and viruses in soil. The major goals are to: (1) survey human pathogens in soil and on/in free-living and plant parasitic nematodes in agriculture field sites irrigated with recycled wastewater or fertilized with fresh animal manure in Israel and the Palestinian Authority, (2) assess the function of nematodes as vectors in transmitting bacteria from microbial hot spots to plants, and (3) localize bacteria on and/or within the nematode and identify bacterial factors required for survival in the nematode host. Understanding the mechanisms involved in dissemination of human pathogens by nematodes will enhance the ability to develop practical means to minimize contamination of fresh produce and increase safety in food production.
With regard to climate-driven environmental changes in Europe during the next decades (heatwaves and extended drought periods) the understanding of how plants may adapt to these environmental constraints and ensure their survival awaits further attention. Moreover, besides well studied responses of plants to various drought intensities, the capacity of recovery from drought and its velocity and rate will become an important issue for plant species across Europe. As there is a scarcity of studies in the field of recovery from drought, this project is designed to unravel its underlying physiological processes by a systematic analysis of photosynthetic and respiratory traits of several Mediterranean species during recovery from various drought intensities. The time frame of drought within a vegetation period may additionally affect the capacity of drought tolerance and rate of recovery, as well as growth and survival. Main Results and Conclusions The rate of photosynthetic restoration after drought-induced suppression depends on the intensity of drought, as recovery of all examined plant species has always been more rapid after mild or moderate drought (one to three days) than after severe drought (more than three days). Differences appeared among species, as annual species (Nicotiana sylvestris, Glycine max) recovered more rapidly from severe drought than perennial ones (Vitis vinifery, Cistus albidus, Quercus ilex). However, perennials followed a more conservative strategy during drought progression by loosing less water than the annual plants (which reached severe stress more rapidly but recovered also quicker after the short drought period). Limitation of photosynthetic recovery during the re-watering phase was driven by a delayed stomatal opening and impaired internal CO2 diffusion, namely the mesophyll conductance (gm). The gm has been found to be an important factor in limiting photosynthesis during drought and after subsequent re-watering, which further supports the idea of an important role of gm in photosynthetic regulation during stress and the necessity of further studies on its regulation under climatic variables. The impact of other climatic variables than water stress on gm could be assumed by comparing tobacco plants under different growth conditions. Besides the role of gm, the interaction of photosynthesis and respiration during drought and recovery has been shown to be important and highly flexible, as impaired respiratory chain was overcome by enhanced cytochrome pathway activity and hence higher total respiration. This adjustment might help to match the cellular ATP demand and maintain the cell redox balance, thus resulting in a similar response of photosynthesis to drought and re-watering.
Responding to the twin crises of global warming and biodiversity loss requires a deep understanding of how climate affects the processes that generate and destroy biodiversity, primarily through its effects on the ecology and distribution of species. Recent improvements in our ability to reconstruct the history of biodiversity through timed phylogenies, estimate changes in genetic diversity, and predict the potential distribution of selected species with ecological niche models (ENMs) now allow us to infer the evolution of ecological preferences and distributional ranges at different temporal scales. Our two case studies focus on alpine/arctic regions, because they are among those most endangered by global warming. The first study will use, for the first time, a combination of ENM and phylogeny to test the model of hybrid, polyploid speciation by secondary contact in arctic/alpine plants. We selected Primula sect. Aleuritia (simply Aleuritia, from here on), because our previous phylogenetic work provided clear hypotheses for the parental origins of polyploids, yet the distributions of the inferred progenitors do not currently overlap. Did the ranges of the proposed parents overlap at the time of allopolyploid origins, as predicted by the secondary contact model? To answer this question, we will produce a high-resolution, dated phylogeny of Aleuritia, optimize the ecological preferences of the hypothesized progenitors onto the dated phylogeny, and project their past distributional ranges onto the fine-resolution climatic scenarios recently developed for the Pleistocene. In the second case study, we will try to explain how small populations persisted on summits in the past and how they are affected by current and future climate change. Here we selected Saxifraga florulenta, a rare, endemic species of the Maritime Alps, because hypotheses of its phylogenetic relationships are available from our previous work, it occurs exclusively above 2000 m, and has very narrow ecological requirements. Consequently, if current trends of global warming continue, the strict ecological adaptation of S. florulenta to siliceous substrates at the highest altitudes of the Maritime Alps may represent a serious extinction risk. We will investigate whether the phylogeographic history, genetic diversity, climatic niche and dispersal mode of S. florulenta can explain its long persistence in the Maritime Alps, a hot spot of biodiversity, and predict its future survival or extinction on mountain tops. We will use a combination of genetic analysis and niche modeling to reconstruct changes in the niche, geographic distribution, and genetic diversity of this cold-adapted species.
The number one question in ecology is why certain organisms occur where they do, and what the traits are which make them successful. This project aims at arriving at a mechanistic rather than a correlative explanation of the climatic limits of major European broad leaved tree taxa. It will focus on and explore their temperature-related limits and aims at reviving Europe's traditional strength in physiology based ecology by training a group of young scientists to answer such questions. The project builds upon the PIs experience in mechanism-oriented ecology (e.g., synthesis in Körner 2003) and should help trading those rapidly disappearing skills to a next generation of experimental ecologists. The project adopts a three-step approach: (1) Assess the current extreme postions of tree taxa along thermal gradients, using existing data bases and site visits (data mining, biogeography). (2) Associate those patterns with bioclimatic information, both available and newly acquired (climatology). (3) Empirically test hypotheses of causes of growth limitation and stress survival, both in the field and in the laboratory (ecophysiology). The project will account for ecotypic differentiation by using the marginal and central (optimal) positions of taxa and will explore plant establishment as well as adult plant performance. It will use in situ measurements, transplant and common gardens as well as phytotron testing. Genotypic control of phenology, frost hardiness, thermal constraints for shoot and root growth and reproductive system (fitness) will play a central role. The results will, for the first time, offer a mechanistic (rather then correlative) explanation for broad leaf tree species distribution in Europe and thus, will provide a basis for improved parameterization and evaluation of species distribution models in a climate change context. The new European Research Council (ERC) has granted Prof. Körner one of the extremely rare 5 year 'advanced grants', which contrast any previous granting regime by being personal. The 2 Mio Swiss Francs will permit to explore where, why and how major European tree taxa find climatic range limits. A team of two PhD students and two postdocs plus a technician will be established for a period of four years each (overlapping). The project has various tasks, such as - Idendification of tree species range limits as precise as possible based on GIS and archive data, interviews and site visits - Climatology of those limits based on climate stations and climate data bases - Assess local climate by a large data logging programm with backward cross correlating - Assess marginal versus non marginal location dendrological responses - Assess seedling versus adult positions and viability of seeds - Common garden experiments across climatic gradients (recipical transplants) - Assess freezing resistance of key tissues at key phenophases and link with climatic extremes In a first phase starting 1st April 2009, we will focus on GIS and c
This thesis presents studies that describe and explain phenotypic differentiation within several alpine plant species. The key elements that are addressed are threefold: (1) effects of neutral genetic drift, natural selection and phenotypic plasticity on phenotypic differentiation; (2) effects of glacial history, geography and climate on phenotypic differentiation and adaptation; (3) genetic structure and gene flow at small spatial scale. Combining all three elements, the aim of this thesis is to understand how a plant species' evolution towards its current state is affected at different spatial scales by neutral genetic drift and historical (i.e. glaciation-related) as well as more recent (i.e. postglacial) environmental influences. To measure phenotypic differentiation in important plant traits, common garden experiments were performed with several alpine plant species (Campanula thyrsoides, C. barbata, Geum reptans) sampled from populations across the European Alps and Jura Mountains. Phenotypic differentiation was generally mirrored by molecular differentiation into distinct phylogeographic groups, which is explained by long-term survival in isolated glacial refugia. The results therefore suggest that glacial history affected not only the species' neutral genetic structure but also its phenotype. For some traits and in some regions, such differentiation could be explained as adaptation to the regional environment. For instance, the distinct phenology in Campanula thyrsoides, showing delayed flowering in the submediterranean southeastern Alps contrasting with early flowering at higher elevation in the other regions to the west, is clearly an adaptation to season length in the respective environments. Differentiation in various other traits could not be explained as adaptations and may therefore be due to drift alone. Postglacial adaptation was detected when correlating trait values with altitude of origin. For instance, the negative correlation of altitude with plant height in Campanula thyrsoides, achieved without compromising flower production, is probably an adaptation to harsher conditions and to increased investment in roots. Adaptation can also occur through phenotypic plasticity. In an experiment in which Campanula thyrsoides was grown in common gardens at three different altitudes, variability in the functional trait of specific leaf area could be dissected into a constitutive genetic part and a phenotypic plastic part.
Toona ciliata (Australian red cedar) is highly valued for veneer and furniture production and endangered in its natural ecosystems due to exploitation. This work aims to improve the availability of this wood on the market and help reduce pressure on the species in its native environment. An afforestation project cultivating Toona ciliata was introduced to the study site in Misiones, Argentina. The local cultivation faces losses caused by drought and frost, because T. ciliata requires overstory protection when young. Consequently, Grevillea robusta, Pinus elliottii x Pinus caribaea, and Pinus taeda, nurse tree species which also produce sought-after wood were chosen to provide protection. One-year-old T. ciliata seedlings were planted underneath each of the six-year-old nurse species. An inventory after one year indicated that both survival and height increment were highest underneath G. robusta and lowest underneath P. elliottii x P. caribaea. In this study I am examining possible facilitation and competition mechanisms between the overstory and understory T. ciliata. Extensive empirical data collected over the course of 3 years will be utilized to project potential growth scenarios for several rotations using a computer based forest growth model.
Despite the remarkable progress accomplished in water and wastewater treatment over the past decades, viral pathogens in drinking and recreational water continue to pose a threat to public health in both industrialized and developing nations. Some of the most effective treatment methods to enhance microbial water quality (e.g., waste stabilization ponds) rely on naturally occurring disinfection processes typically encountered in surface water. Even though such treatment methods are extensively used, little is known about the factors that govern virus inactivation. In particular, the interaction of viruses with suspended particles may affect inactivation, but the interconnection is complex and not well understood; particles have been shown to both increase and decrease virus inactivation compared to free viruses. An in-depth understanding of the effects of particle association on virus survival is crucial to assess and control the fate of viruses in both natural and engineered surface water systems. The overall goal of this project is to determine how adsorption onto particles influences naturally occurring virus inactivation processes in the dark and under sunlight. The involvement of sunlight is a key component of this project because it is an important contributor to virus inactivation in surface water. A range of iron-based particles with varying surface properties will serve as the model for naturally occurring particles, and a selection of bacteriophages of different sizes and genome types will be used as surrogates for human viruses. Specific objectives are to I) quantify virus adsorption and particle-mediated inactivation in the dark, and establish whether an interrelation between the two processes exists; II) determine if photooxidants produced by the particles upon illumination by sunlight enhance particle-mediated inactivation, and characterize the dominant inactivation mechanisms; and III) assess if infective viruses can be released from particles upon changes in the solution conditions. A combination of photochemical techniques, molecular biological methods, and state-of-the-art surface analyses will be used to address the project objectives. Our findings will significantly augment our current knowledge of the fate of viruses in surface waters. They will improve the assessment of the public health risk posed by viral contamination of water systems, and they will offer insight into better ways to control the discharge of pathogenic viruses into the environment.
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