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Effects of water content, input of roots and dissolved organic matter and spatial inaccessibility on C turnover & determination of the spatial variability of subsoil properties

It is well established that reduced supply of fresh organic matter, interactions of organic matter with mineral phases and spatial inaccessibility affect C stocks in subsoils. However, quantitative information required for a better understanding of the contribution of each of the different processes to C sequestration in subsoils and for improvements of subsoil C models is scarce. The same is true for the main controlling factors of the decomposition rates of soil organic matter in subsoils. Moreover, information on spatial variabilities of different properties in the subsoil is rare. The few studies available which couple near and middle infrared spectroscopy (NIRS/MIRS) with geostatistical approaches indicate a potential for the creation of spatial maps which may show hot spots with increased biological activities in the soil profile and their effects on the distribution of C contents. Objectives are (i) to determine the mean residence time of subsoil C in different fractions by applying fractionation procedures in combination with 14C measurements; (ii) to study the effects of water content, input of 13C-labelled roots and dissolved organic matter and spatial inaccessibility on C turnover in an automatic microcosm system; (iii) to determine general soil properties and soil biological and chemical characteristics using NIRS and MIRS, and (iv) to extrapolate the measured and estimated soil properties to the vertical profiles by using different spatial interpolation techniques. For the NIRS/MIRS applications, sample pretreatment (air-dried vs. freeze-dried samples) and calibration procedures (a modified partial least square (MPLS) approach vs. a genetic algorithm coupled with MPLS or PLS) will be optimized. We hypothesize that the combined application of chemical fractionation in combination with 14C measurements and the results of the incubation experiments will give the pool sizes of passive, intermediate, labile and very labile C and N and the mean residence times of labile and very labile C and N. These results will make it possible to initialize the new quantitative model to be developed by subproject PC. Additionally, we hypothesize that the sample pretreatment 'freeze-drying' will be more useful for the estimation of soil biological characteristics than air-drying. The GA-MPLS and GA-PLS approaches are expected to give better estimates of the soil characteristics than the MPLS and PLS approaches. The spatial maps for the different subsoil characteristics in combination with the spatial maps of temperature and water contents will presumably enable us to explain the spatial heterogeneity of C contents.

Informationssystem Misteln und andere Baumkrankheiten miraculix

Zielsetzung: Streuobst sind hochstämmige Obstbäume, die verstreut und in größeren Abständen in Gärten, an Ortsrändern, entlang von Wegen und Feldern oder auf einer Wiese in der Landschaft stehen. Eine Streuobstwiese erlaubt eine Nutzung auf zwei Etagen: am Boden als Grünland oder Weide und darüber für das Obst. Pflanzenschutzmittel werden nur im geringen Umfang oder gar nicht eingesetzt. Genau das macht Streuobstwiesen zu wertvollen Lebensräumen, die unsere Natur- und Kulturlandschaft mit einer enormen Artenvielfalt bereichern und das Kleinklima fördern. Sie prägen das Landschaftsbild und sind zudem Naherholungsräume für die Menschen. Streuobstwiesen sind allerdings auch extrem bedrohte Lebensräume, die in vielen Bundesländern auf der Roten Liste der Biotoptypen als ‚stark gefährdet’ eingestuft sind. Im Bundesgebiet gibt es nach Schätzungen des NABU nur noch rund 400.000 ha Streuobstwiesen. In Baden-Württemberg gibt es EU-weit die größten zusammenhängenden Streuobstbestände und hier steht fast jeder zweite Streuobstbaum Deutschlands. Baden-Württemberg ist somit als Untersuchungsraum repräsentativ. Laut den jüngsten fachlichen Erhebungen gingen zudem innerhalb von zehn Jahren 17% der Streuobstbestände in Baden-Württemberg verloren. Die verbliebenen Bestände sind in Teilen lückig und vergreist, da bestehende Bestände immer seltener gepflegt werden. Das Projekt "miraculix" fokussiert daher neue Forschungsansätze (u.a. zur Detektion von Misteln) für eine bessere Bewirtschaftung und Bestandssicherung vor allem durch die Mitwirkung von Landkreis, Kommune und Privatpersonen. Durch die Hochschule, die Landkreise und Kommunen können Öffentlichkeitsarbeit, Bildung und Beratung auf diesem Gebiet erweitert werden. Zur Vorbildfunktion gehört auch das verstärkte Engagement der Kommunen durch aktive Mitwirkung am Projekt. Um dies zu erreichen, ist das wesentliche Ziel des Projektes die Konzeption und Implementierung einer innovative App-Lösung, die bei der Bewirtschaftung und der Pflege von Streuobstwiesen unterstützt und damit zum Erhalt der Kulturlandschaft Streuobstwiesen beiträgt. Damit einhergehend werden praxistaugliche und weitestgehend automatisierte Erfassungs- und Monitoringverfahren auf der Basis von UAV-Befliegungen und Bodensichtkontrollen entwickelt und erforscht. miraculix stellt somit eine neue Form der Informations- und Datenbereitstellung für Fachbehörden (bei Kommunen und Landratsämtern), Obstbauberater und Landnutzer unter Beteiligung zivilgesellschaftlicher Akteure (Streuobstvereine und -verbände) zur Verfügung.

Adaptations and counter-adaptations in the coevolutionary arms race of a baculovirus and its insect host

Cydia pomonella granulovirus (CpGV, Baculoviridae) is one of the most important agents for the control of codling moth (CM, Cydia pomonella, L.) in both biological and integrated pest management. The rapid emergence of resistance against CpGV-M, which was observed in about 40 European CM field populations from 2003 on, could be traced back to a single, dominant, sex-linked gene. Since then, resistance management has been based on mixtures of new CpGV isolates (CpGV-I12, -S), which are able to overcome this resistance. Recently, resistance even to these novel isolates was observed in CM field populations. This resistance does not follow the described dominant, sex-linked inheritance trait. At the same time, another isolate CpGV-V15 was identified showing high virulence against these resistant populations. To elucidate this novel resistance mechanism and to identify the resistance gene(s) involved, we propose a comprehensive analysis of this resistance on the cellular and genomic level of codling moth. Because of the lack of previous knowledge of the molecular mechanisms of virus resistance in insects, several different and complementary approaches will be pursued. This study will not only give an in-depth insight into the genetic possibilities for development of baculovirus resistance in CM field populations and how the virus overcomes it, but can also serve as an important model for other baculovirus-host interaction systems.

Modes of vector transmission of Cherry leaf roll virus (CLRV) - molecular basis and potential arthropod vector species

Cherry leaf roll virus (CLRV) is a plant pathogen of economic and ecologic importance. It is globally distributed in a wide range of forest, fruit, and ornamental trees and shrubs. In several areas of cherry and walnut production CLRV causes severe losses in yield and quality. With current reference to the rapid dissemination and strong symptom expression in Finnish birches and the Germany-wide distribution of CLRV in birches and elderberry, we continuously investigate and gradually reveal CLRV transmission pathways as by pollen, seeds or water. However, modes and interactions responsible for the wide intergeneric host transmission as well as for the exceptional CLRV epidemic in Fennoscandia still remain unknown. In this project systematic studies shall investigate biological vectors as a causal agent to finally derive control mechanisms and strategies to avoid new epidemics in different hosts and geographic regions. Detailed monitoring of the invertebrate fauna of birch stands/forests and elderberry plantations in Germany and Finland shall reveal potential vectors to subsequently study them in detail by approved virus detection methods and transmission experiments. Molecular analyses of the CLRV coat protein shall prove its role as a viral determinant for a virus/vector interaction. Consequently, this project essentially will contribute important answers on the CLRV epidemiology, and this will be a key element within the first network of research on plant viral pathogens in forest trees.

Nachhaltige Begrenzung der Ackerkratzdistel (Cirsium arvense Scop (L.)) im Ackerbau unter Nutzung populationsgenetischer Grundlagen

Ziel des Forschungsvorhabens ist es, umweltgerechte Begrenzungsstrategien der Ackerkratzdistel basierend auf Wissen zur genetischen Populationsstruktur, zum Konkurrenzgeschehen in wichtigen landwirtschaftlichen Kulturen und zur Ausbreitung in vorrangig ackerbaulich genutzten Landschaften zu erarbeiten. Dafür müssen zunächst Methoden zur Bestimmung genetischer Diversität in Populationen der Ackerkratzdistel entwickelt werden, die ggf. auch die genetische Identifizierung des Geschlechts ermöglichen. In einem Feldversuch werden Wege der nicht-chemischen Begrenzung mit Hilfe von pflanzenbaulichen Maßnahmen (Fruchtfolge, Stickstoffdüngung, mechanische Pflege von Klee-Gras-Einsaaten) an Distelpopulationen verschiedenen Alters geprüft. In einem begleitenden Semi-Feldversuch wird modellhaft geklärt, wie die Maßnahmen zur Beeinflussung der Konkurrenz durch die Feldfrüchte zusammenwirken. Zwei Landschaftsausschnitte, in denen großflächige Ackerbausystemversuche etabliert sind, dienen zu Prüfung der Zusammenhänge zwischen geographischen und genetischen Distanzen in den Distelpopulationen. Die Erkenntnisse des Forschungsvorhabens würden es ermöglichen, die Bedeutung verschiedener Ausbreitungswege der Ackerkratzdistel besser als bisher einzuschätzen und die Begrenzung der Unkrautart im Ackerbau auf dieser Basis zu planen. Dies ist vor allem für die Produktionsverfahren im Ökologischen Landbau dringend erforderlich. Entsprechendes Wissen käme auch konventionell wirtschaftenden Landwirten zugute, insbesondere wenn Extensivierungs- und landschaftspflegende Maßnahmen einen größeren Stellenwert einnehmen.

Steuerung und Bilanzierung von Kohlenstoffakquisition, Wasserumsatz und Wachstum im Mistel-Wirt-System in Abhängigkeit von Klima, Wasserversorgung und Nährstoffangebot

Im ersten Schritt des Vorhabens sollen die Reaktionsmuster des CO2- und H2O Blattgaswechsels von Mistel-Wirt-Paaren bezüglich Mikroklima und Lebensform des Wirts (immer- oder wechselgrün) im Jahreslauf möglichst kontinuierlich untersucht werden, um diese bis heute offen gebliebenen Informationslücke zu schliessen. Dabei soll die Hypothese überprüft werden, derzufolge Misteln vielfach mehr als ihre Wirte transpirieren, um über den Transpirationsstrom Nährstoffe des Wirtes, insbesondere Stickstoff, an sich zu binden. Es sollen hierzu auch Düngungsversuche an getopften Mistel-Wirt-Paaren durchgeführt und dabei besonderes Augenmerk auf die Nettophotosynthese und Wasserumsatz gelegt werden. Weiterhin wird die unterschiedliche Reaktion der beiden pflanzlichen Komponenten auf Wasserstress untersucht. Im fortgeschrittenen Stadium der Untersuchungen ist es das Ziel, über Kronenphotosynthese und deren Bilanzierung die C-Allokationsmuster des Parasiten zu bestimmen. Aufgrund des hohen Mistelbefalls von Forstbeständen und Obstbäumen, insbesondere im Raum Baden-Württemberg, ist diese Grundlagenforschung unmittelbar vor einem angewandten Hintergrund zu sehen.

DFG Trilateral collaboration Deutschland-Israel-Palestine: Nematodes as potential vectors for human pathogens

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.

Forschergruppe (FOR) 861: Cross-scale Monitoring: Biodiversity and Ecosystem Functions, Quantification of functional hydro-biogeochemical indicators in Ecuadorian ecosystems and their reaction on global change

Water is an intrinsic component of ecosystems acting as a key agent of lateral transport for particulate and dissolved nutrients, forcing energy transfers, triggering erosion, and driving biodiversity patterns. Given the drastic impact of land use and climate change on any of these components and the vulnerability of Ecuadorian ecosystems with regard to this global change, indicators are required that not merely describe the structural condition of ecosystems, but rather capture the functional relations and processes. This project aims at investigating a set of such functional indicators from the fields of hydrology and biogeochemistry. In particular we will investigate (1) flow regime and timing, (2) nutrient cycling and flux rates, and (3) sediment fluxes as likely indicators. For assessing flow regime and timing we will concentrate on studying stable water isotopes to estimate mean transit time distributions that are likely to be impacted by changes in rainfall patterns and land use. Hysteresis loops of nitrate concentrations and calculated flux rates will be used as functional indicators for nutrient fluxes, most likely to be altered by changes in temperature as well as by land use and management. Finally, sediment fluxes will be measured to indicate surface runoff contribution to total discharge, mainly influenced by intensity of rainfall as well as land use. Monitoring of (1) will be based on intensive sampling campaigns of stable water isotopes in stream water and precipitation, while for (2) and (3) we plan to install automatic, high temporal-resolution field analytical instruments. Based on the data obtained by this intensive, bust cost effective monitoring, we will develop the functional indicators. This also provides a solid database for process-based model development. Models that are able to simulate these indicators are needed to enable projections into the future and to investigate the resilience of Ecuadorian landscape to global change. For the intended model set up we will couple the Catchment Modeling Framework, the biogeochemical LandscapeDNDC model and semi-empirical models for aquatic diversity. Global change scenarios will then be analyzed to capture the likely reaction of functional indicators. Finally, we will contribute to the written guidelines for developing a comprehensive monitoring program for biodiversity and ecosystem functions. Right from the beginning we will cooperate with four SENESCYT companion projects and three local non-university partners to ensure that the developed monitoring program will be appreciated by locals and stakeholders. Monitoring and modelling will focus on all three research areas in the Páramo (Cajas National Park), the dry forest (Reserva Laipuna) and the tropical montane cloud forest (Reserva Biologica San Francisco).

Between Path Dependence and Path Creation: The Impact of Farmers' Behavior and Policies on Structural Change in Agriculture

Farm structures are often characterized by regional heterogeneity, agglomeration effects, sub-optimal farm sizes and income disparities. The main objective of this study is to analyze whether this is a result of path dependent structural change, what the determinants of path dependence are, and how it may be overcome. The focus is on the German dairy sector which has been highly regulated and subsidized in the past and faces severe structural deficits. The future of this sector in the process of an ongoing liberalization will be analyzed by applying theoretical concepts of path dependence and path breaking. In these regards, key issues are the actual situation, technological and market trends as well as agricultural policies. The methodology will be based on a participative use of the agent-based model AgriPoliS and participatory laboratory experiments. On the one hand, AgriPoliS will be tested as a tool for stakeholder oriented analysis of mechanisms, trends and policy effects. This part aims to analyze whether and how path dependence of structural change can be overcome on a sector level. In a second part, AgriPoliS will be extended such that human players (farmers, students) can take over the role of agents in the model. This part aims to compare human agents with computer agents in order to overcome single farm path dependence.

Flowering time, development and yield in oilseed rape (Brassica napus): Sequence diversity in regulatory genes

Flowering time (FTi) genes play a key role as regulators of complex gene expression networks, and the influence of these networks on other complex systems means that FTi gene expression triggers a cascade of regulatory effects with a broad global effect on plant development. Hence, allelic and expression differences in FTi genes can play a central role in phenotypic variation throughput the plant lifecycle. A prime example for this is found in Brassica napus, a phenotypically and genetically diverse species with enormous variation in vernalisation requirement and flowering traits. The species includes oilseed rape (canola), one of the most important oilseed crops worldwide. Previously we have identified QTL clusters related to plant development, seed yield and heterosis in winter oilseed rape that seem to be conserved in diverse genetic backgrounds. We suspect that these QTL are controlled by global regulatory genes that influence numerous traits at different developmental stages. Interestingly, many of the QTL clusters for yield and biomass heterosis appear to correspond to the positions of meta-QTL for FTi in spring-type and/or winter-type B. napus. Based on the hypothesis that diversity in FTi genes has a key influence on plant development and yield, the aim of this study is a detailed analysis of DNA sequence variation in regulatory FTi genes in B. napus, combined with an investigation of associations between FTi gene haplotypes, developmental traits, yield components and seed yield.

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