Institut für Landschafts- und Pflanzenökologie

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From alien to native Asteraceae : how effects of climate, functional traits, and biotic interactions on population growth change with residence time
(2023) Brendel, Marco; Sheppard, Christine
Biological invasions pose a major threat to native biodiversity and even drive native species to extinction. It is thus of utmost importance to gain a better understanding of limits to population growth and spread of invasive plants. Invasion success in the introduced area is determined by the combined effects of climatic mismatches between the area of origin and the introduced area as well as biotic resistance of resident native communities. Alien plants can respond to environmental selection via changes in functional traits and thereby adapt to novel abiotic conditions. Native community species are expected to adapt to the presence of the invader by gaining eco-evolutionary experience and build-up biotic resistance over time. The aim of this thesis is to investigate interactions of alien plants with the novel abiotic and biotic environment in their introduced range over eco-evolutionary timescales. To this end, I conducted common garden experiments based on an alien-native species continuum to cover a broad range of residence times in Germany (7 to 12,000 years before present). I followed the population growth of 47 annual Asteraceae (including neophytes, archaeophytes, and natives) over two years and measured their performance in intra- and interspecific competition to answer the following questions: 1) How are effects of climatic distances between the area of origin and the introduced area as well as functional traits on population dynamics of alien plants determined by residence time? 2) How is biotic resistance of native communities towards alien plants related to residence time? 3) How are competitive outcomes between single alien and native plants shaped by residence time and serve as a predictor of range sizes? For the first question, I followed population growth of the Asteraceae in monocultures. I calculated climatic distances between the area of origin and the introduced area and measured functional traits in terms of seed mass, maximum height, and specific leaf area. Firstly, I tested whether negative effects of climatic distances on population growth weaken with residence time. Secondly, I investigated trait-demography relationships and tested if functional traits converge towards values that increase population growth. I found a strong effect of seed mass and no effects climatic distances on population growth. A strong negative relationship between seed mass and population growth resulted in directional selection of seed mass towards low values with increasing residence time. For the second question, I measured population growth of the Asteraceae in a Central European grassland community. I tested if competitive effects of the community on the Asteraceae increase with residence time (i.e. co-existence time with the native community). I used a second community native to North American grasslands that never co-existed with the Asteraceae to disentangle competitive effects related to eco-evolutionary experience of the native community from inherent competitive abilities of the Asteraceae. I compared trait-demography relationships in both community types with monocultures and found very similar competitive effects of both communities on the Asteraceae and thus no evidence for a build-up of competition-induced biotic resistance over time. Instead, invasion success was determined by a strong seed-mass-mediated trade-off between population growth in low- vs. high-competition. For the third question, I tested if the response of biomass and seed production of native targets to competition with alien and native neighbours depends on residence time. I tested if competitive effects differ between invasion status groups and explain species’ range sizes in Germany. I generally did not find a higher tolerance of native Asteraceae to competition of neighbouring aliens and natives with increasing residence time. Both established neophytes and natives showed similar competitive abilities and species’ range sizes were not influenced by competitive effects. The detected trait-demography relationships and related directional selection as a mechanism of adaptation to novel abiotic conditions improve the understanding of constraints on population growth and spread of invaders. The lack of interspecific competitive superiority as a determinant of range sizes might indicate that other mechanisms are more important for invasion success. The functional trade-off between population growth in low vs. high competition reveals that invaders that are likely to escape this trade-off should be of highest management concern. By the combination of experimental macroecology with approaches of functional and community ecology used in my study, I strongly advanced the understanding of mechanisms of limits to population growth and spread of alien plants and provide a fundamental basis for future research in invasion ecology.
The performance of and interactions between multiple co-occurring alien and native plant species
(2023) Ferenc, Viktoria; Sheppard, Christine
This thesis focuses on investigating species interactions in the context of alien species establishment, which poses severe threats to species, communities, and ecosystems due to climate change and globalization. The study emphasizes the need to understand the effects of multiple co-occurring alien species and their potential explanations, such as niche or fitness differences. The outcome of competition can also be influenced by priority effects, where earlier emerging species affect later emerging species in a given environment. Positive interactions, like facilitation, are often overlooked but play a significant role in species interactions. Legumes, known for their ability to fix atmospheric nitrogen, can facilitate alien species, leading to both severe negative effects on natives and reduced resource competition. The research conducted three common garden pot experiments to address various aspects of alien species interactions. The first experiment examined pairwise combinations of 20 alien annual plant species in Germany to identify the mechanisms driving these interactions. It tested the prevalence of competition versus facilitation and assessed the effectiveness of individual traits, hierarchical or absolute trait distances, multivariate trait or phylogenetic distance, and trait plasticity in explaining plant performance. Results indicated that while interspecific competition was more common, interspecific facilitation occurred in 24% of cases. Hierarchical trait distances provided better explanations for interactions than phylogenetic or multivariate trait distances. Accounting for trait plasticity did not necessarily improve plant performance predictions. Notably, taller individuals with lower specific leaf area than their alien neighbours exhibited increased biomass and seed production when growing together. The second experiment focused on interactions between five pairs of alien and native species. It evaluated the impact of growing with one or two alien neighbour species on native plants and manipulated the arrival time of alien or native neighbours. Generally, native species performed worse when surrounded by two alien species compared to one, although the effect varied among species. Both native and alien species experienced significant performance decreases when arriving second in the pot, while alien species tended to benefit more from early arrival. However, further studies are required to generalize these findings across multiple alien and native plants regarding neighbour species and arrival time responses. The third experiment delved into legume facilitation in more detail. It involved growing 30 annual Asteraceae species (neophytes, archaeophytes, and natives) in communities with or without legume presence. The study measured functional traits, fitness, and nitrogen characteristics to understand how legume presence affected Asteraceae fitness and the relationship between traits, nitrogen concentration, and fitness. Using the δ15N natural abundance method, the research explored whether facilitation mechanisms differed among native phytometer, neophyte, and archaeophyte Asteraceae. Specific leaf area negatively affected aboveground biomass and seed production, with a stronger effect in the absence of legumes. Nitrogen concentration was positively correlated with biomass but did not significantly increase seed production. The results suggested direct legume facilitation for the native grass phytometer Festuca rupicola when growing alongside archaeophytes but not neophytes. This indicated varied mechanisms of competition for nitrogen between natives and alien species of different residence times and deepened understanding of altered facilitative leguminous effects in the presence of alien species. Overall, this research demonstrates the application of community ecology concepts and theories to investigate alien species interactions, particularly when multiple co-occurring alien species are involved. As the rate of alien species arrival in new habitats continues to increase, understanding their combined impact on native species, communities, and ecosystems becomes increasingly crucial.
Impacts of temperature increase and change in precipitation pattern on ecophysiology, biomass allocation and yield quality of selected crops
(2023) Drebenstedt, Ireen; Högy, Petra
Climate change poses a challenge for the production of crops in the twenty-first century due to alterations in environmental conditions. In Central Europe, temperature will be increased and precipitation pattern will be altered, thereby influencing soil moisture content, physiological plant processes and crop development in agricultural areas, with impacts on crop yield and the chemical composition of seeds. Warming and drought often occur simultaneously. The combination of multiple abiotic stresses can be synergistic, leading to additive negative effects on crop productivity. To date, little information is available from multi-factor experiments analyzing interactive effects of warming and reduced precipitation in an arable field. In addition, one major issue of studying climate change effects on crop development in the long-term is that weather conditions can vary strongly between years, e.g., with hot and dry summers in comparison to cool and wet ones, which directly affects soil moisture content and indirectly affects crop development. Thus, considering yearly weather conditions seems to be important for the analyses of climate change effects on aboveground biomass and harvestable yield of crops. The aim of the present work was to identify single and combined effects of soil warming (+2.5 °C), reduced summer precipitation amount (-25%), and precipitation frequency (-50%) on crop development, ecophysiology, aboveground biomass and yield as well as on yield quality of wheat, barley, and oilseed rape grown in the Hohenheim Climate Change (HoCC) field experiment. This thesis presents novel results from the HoCC experiment in the long-term perspective. Thus, aboveground biomass and yield data (2009-2018) of the three crops were analyzed with regard to their inter-annual variability, including annual fluctuations in weather conditions.This thesis consists of three publications. In the first and second publication a field experiment within the scope of the HoCC experiment was conducted with spring barley (Hordeum vulgare L. cv. RGT Planet) and winter oilseed rape (Brassica napus L. cv. Mercedes) in 2016 and 2017. The objective was to investigate the impacts of soil warming, altered precipitation pattern and their interactions on biomass production and crop yield. In addition, it was examined, whether the simulated climate changes affecting barley photosynthesis and the seed quality compounds of oilseed rape. In the third publication, long-term plant productivity data of wheat, barley, and oilseed rape were evaluated, including aboveground biomass and yield data from the field experiment in 2018 with winter wheat (Triticum aestivum L. cv. Rebell).
Heavy metals from phosphate fertilizers in maize-based food-feed energy systems
(2023) Niño Savala, Andrea Giovanna; Fangmeier, Andreas
The problem of polluted agricultural lands with heavy metals due to anthropogenic activities, including applying phosphorous (P) fertilizers polluted with cadmium (Cd) and other metal such as uranium, has been extensively studied. Several reviews, including the one in the present dissertation, have elaborated this issue with often the same results: the application of P fertilizers with high Cd levels is strongly correlated to Cd accumulation in arable soil, which could imply environmental risks as well as health risks for humans and animals through the food chain. Therefore, these reviews have often the same conclusion: the application of low Cd-P fertilizers, either mineral, organic or recycled, is diminishing the risks of Cd pollution at the soil, crop and consumption level. However, globalization, trade politics, economy, dependency on Morocco mineral P fertilizers, and the finite stock in the raw material have challenged this possibility, especially in the European Union. Meanwhile, in China, polluted arable soils are related to other anthropogenic activities and type of fertilizers rather than Cd-polluted phosphate rock and mineral P fertilizers. At the farm level, other options to diminish Cd pollution in soil and crops, besides low Cd-P fertilizers, could consist of different fertilizer and crop management. These options were studied in this dissertation. A different P management, including different rate applications and placements, did not influence the total Cd concentration in silage maize grown in Germany, regardless of the developmental stage of the crop and the Cd levels in P fertilizer. Silage maize might take up Cd derived from P fertilizers under unpolluted soils, without high risks due to its high biomass production. However, significant changes in the labile Cd fraction were already visible after applying Cd-polluted P fertilizers at 150% of the required amount to the soil after only two growing seasons. Further research should be done to understand the correlations between the bioavailable metal fraction and the actual Cd uptake by silage maize, especially in unpolluted soils. This recommendation also follows the meta- analysis results presented in the second publication, which indicated a possible bias as most of the studies are performed under polluted conditions. Considering the results of the third and fourth publication, the Cd uptake by silage maize was strongly correlated to labile Zn in the soil and the Zn uptake at the early development stage after two field seasons. Placed P fertilizer had a significant and negative effect on the Zn uptake by young silage maize. Further research is needed to understand the behavior of Cd and Zn in the uptake process by maize under P fertilization in unpolluted soils. According to three of the four publications presented in this dissertation, the soil pH was the main soil characteristic influencing the bioavailability and the plant uptake of Cd under unpolluted conditions, regardless of the P treatment, the development stage, and the maizes intended use. However, the total Cd concentration in the soil was the dominant variable for the Cd concentration in maize grain when the soil was polluted with high Cd levels, which was the case in several experiments analyzed in the second publication. P fertilizers with average Cd contamination might enhance labile Cd accumulation in arable land and crops when applied to low biomass crops, such as wheat and legume crops. In this regard, crop management such as crop rotation in the central field experiment indicated that the wheat rotation induced a lower Cd accumulation in maize-soil systems, owing to wheat likely accumulating Cd at higher levels than other crops. The results presented in the second publication also indicated high Cd accumulation by the wheat crop: the wheat grain accumulated more Cd than the maize grain. Thus, potential hazards related to Cd accumulation in wheat grain should also be considered in wheat-maize systems. In conclusion, suitable crop rotations considering the crop-specific potential of Cd accumulation, efficient P management including soil P levels and nutrient use efficiency, and low Cd-P fertilizers remain the most viable options and the main challenge to avoid Cd accumulation in arable soils.
Fallstudien zu Stickstoffdioxid und Feinstaub - Untersuchung und Vergleich verschiedener Pflanzenarten und Dachflächen im urbanen Raum
(2022) Neher, Philipp; Fangmeier, Andreas
More and more people are living in cities. Therefore, one of the main tasks of municipalities is to ensure a good quality of life for people living in cities. Among many other factors, air quality plays a decisive role, because we all need air to live and consume many litres of it every day. This study therefore deals with the question of whether urban vegetation, especially green roofs, can contribute to an improvement in air quality. In order to answer this question, parameters reflecting air quality were recorded on several roof surfaces. The parameters investigated were primarily particles in the range of 2.5 to 80 micrometres and nitrogen dioxide (NO2). Airborne particles were recorded using Sigma-2-samplers and NO2 using Palmes tubes. On the other hand, morphological leaf characteristics of different plant species were examined microscopically and a statement was made about the "filtering capacities" of the species. In support of this, heavy metal contents in the substrate and wash-out were investigated. Investigations on roof surfaces showed that, due to the height difference, significantly lower pollutant levels were recorded on roof surfaces than at street level. For NO2, about 50 % lower values were recorded. The comparison between greened and ungreened roof surfaces showed slightly significantly lower values for both particulate matter and NO2 on greened roofs. Investigations on the different plant species showed that plants with a structurally rich leaf surface, dense and tall growth, "filter" more particles from the ambient air than low-growing species or species with a smooth leaf surface. In summary, it can be stated that green roofs can lead to a slight improvement in air quality with regard to particulate matter and NO2. The decisive factors here are the choice of plants used in greening systems and ultimately also the distance to the emitters.
Suitability of conventional flowering fields and organic lentil mixed-crops to promote biodiversity on arable land
(2020) Gayer, Christoph; Dieterich, Martin
The rapid agricultural intensification during the last decades is among the main drivers of the dramatic and ongoing biodiversity loss on earth. The decline of species diversity and associated ecosystem services due to highly intensified farming practices and structural simplified agricultural landscapes includes the reduction of species richness and abundance of species. The loss of species and related shifts in species communities can also lead to altered functional traits within species communities. It can also include deteriorated population developments of single species known to be important ecosystem service suppliers for agricultural production. In Europe, billions of euros are spent each year to support farmers for applying environmentally friendly practices, but so far biodiversity continues to decline. This calls for the development of more effective biodiversity conservation measures on agricultural land. Within the framework of agri-environmental measures, agronomically non-productive measures exist such as the establishment of flowering fields, but there are also production integrated measures such as the organic farming of crops. Further, the growing of flowering lentil mixed-crops could be a valuable, but rarely studied option to further increase the biodiversity benefits of organic farming systems. Up to that, little is known about the relative effectiveness of non-productive flowering fields under conventional management and organically farmed mono- as well as lentil mixed-crops for the promotion of biodiversity on arable land. Within the scope of this thesis, i studied biodiversity effects in response to the establishment of annual flowering fields under conventional management, organically managed winter spelt as well as organic lentil mixed-crops. These three crop-use types were compared to conventional winter wheat (control). Besides, I took into account biodiversity effects of the within-field position (field edge versus interior) as well as the surrounding landscape complexity in 500 m around each study field. To get a comprehensive overview about potential biodiversity effects and related ecosystem functions in response to the four crop-use types, I assessed the abundance, species richness and community composition of wild plants (primary producers), carabids and spiders (ground-dwelling predators) as well as butterflies and wild bees (flower-visiting arthropods). I further assessed the functional diversity of carabids as an important species group for biological pest control. To quantify functional diversity in comparison between the four crop-use types, I used the community weighted means and functional divergence of three ecological traits – body size, feeding type, and flight ability. These traits can affect mobility (body size, flight ability) as well as pest and weed seed predation (feeding type, body size) of carabids. Last, I measured the population development of colonies of Bombus terrestris, I observed weight gain, foraging activity, worker body size, queen brood cell number and stored pollen types of colonies exposed at each study field in 2018. I found clear taxon-specific effects of the total abundance and species richness in response to the studied crop-use types. No distinct differences were found for the community composition, which was similar between crop-use types. Arable wild plants benefited most strongly from organic farming, in particular from lentil mixed-crops, but also from field edges. Ground-dwelling arthropods were also mainly promoted by field edges, whereas flower-visiting arthropods solely benefited from conventional flowering fields and organic lentil mixed-crops. Carabid functional diversity was higher at the field edge than the interior irrespectively of crop-use type. Feeding type diversity (carnivorous, ominovorous, herbivorous) of carabid assemblages did also profit from conventional flowering fields and organic winter spelt. Colonies of Bombus terrestries had higher foraging activity and larger body sizes, if exposed at organic winter spelt fields, whereas weight gain and queen brood cell numbers were unaffected by local crop-use type. Pollen stores within the colonies were dominated by Phacelia (Phacelia tanacetifolia) irrespectively of crop-use type. Phacelia was part of the sown seed-mixture in flowering fields, indicating a landscape-wide attraction of flowering fields as pollen source for Bombus terrestris. Over all studies i found only minor effects of the surrounding landscape, except the negative correlation between flower cover and pollen diversity of Bombus terrestris colonies. In summary, this thesis revealed that the establishing of annual flowering fields can be an appropriate measure to enhance biodiversity in conventional farming systems. Organic lentil mixed-crops are appropriate to further increase biodiversity benefits of organic farming systems. Within the conducted studies, different crop-use types promoted specific species groups and thereby different components of biodiversity. Hence, the results of this thesis reveal, that there is no single best measure for the promotion of biodiversity on arable land. Instead, the additive effects of non-productive and productive measures as well as field edge habitats underline, that a mosaic of different types of measures hold the greatest potential to benefit overall biodiversity in agricultural landscapes. Therefore, future agri-environmental schemes should provide particular incentives for individual farmers to apply a diversity of different measures on their farmland and should foster the collaboration and spatially coordinated implementation of complementary biodiversity measures between multiple farmers at the landscape scale.
Performance and governance challenges of a government-funded microcredit program for the handloom weavers in Bangladesh
(2019) Parvin, Mst. Tania; Birner, Regina
Microfinance is an important policy tool for poverty reduction and employment generation in developing countries. The first microfinance institution was developed in Bangladesh in the 1970s. Since its inception, many studies have been conducted on different aspects of microfinance, such as outreach, impact and sustainability. However, these studies have mostly been limited to the performance of microcredit programs operated by non-government organizations (NGOs). Therefore, it is justified to shift the focus from NGOs to microcredit programs operated by the public sector. To fill this knowledge gap, a case study of Bangladesh Handloom Board (BHB)’s microcredit scheme has been conducted, which represents a publicly sponsored credit program targeting handloom weavers. Using a mixed methods approach, this thesis has analyzed three dimensions of the selected credit program: impact assessment, repayment performance, and governance challenges. These three topics are covered by three different papers in the thesis. The first two papers apply quantitative techniques whereas the third one adopts a qualitative approach for assessing the institutional viability. The objective of the first paper is to estimate the impact of BHB’s microcredit scheme on the handloom weaver’s investment behavior in Bangladesh. From a policy perspective, this analysis is relevant for two reasons. First, it fills the gaps in the impact assessment studies of credit which have largely neglected the government-run microcredit programs. Second, the article provides insights for the promotion and continuation of this public credit program. Using an Instrumental Variable (IV) Two-stage Least Squares (2SLS) regression model, the study findings reveal that the government credit program alone is not sufficient to increase the investment in the handloom sector of Bangladesh. The credit received from sources other than BHB was thought to be more relevant with regard to this goal. However, this result also implies that access to multiple sources of credit put borrowers into a debt trap, which makes them economically worse off after repaying loans with interest. As a result, productive investment does not take place through the credit program. This finding, however, does not imply that the credit program should be stopped. It is concluded that the credit amount available under this program for technology adoption in the handloom sector should be increased. Moreover, providing credit for power looms will facilitate a structural change from using handlooms to power looms, which may provide a more sustainable means of future livelihood for current handloom weavers. The second paper analyses the credit repayment of the BHB’s microcredit scheme. Considering that the repayment rate (which is regarded as one of the success factors of the credit program) was only 65% as of June 2015, this study identifies factors that contribute to such low repayment rate, which makes government-sponsored microcredit programs financially unsustainable. This analysis is important to guide the public credit institutions to design a better lending policy by focusing on the factors that require special attention while lending to the eligible borrowers. Using a Probit model, this study reveals that socioeconomic and community-level factors associated with the borrowers played an essential role in determining timely loan repayment. Some of these factors were beyond the control of the credit institution. In conclusion, this study suggests strengthening the loan monitoring system by opening up more branches so that the timely delivery of financial as well as non-financial services to borrowers can be assured. The third paper examines the governance challenges faced by the BHB. The analysis is based on the findings of the previous two papers. As the findings from both papers highlight the challenges of BHB, it is important to understand why such challenges occur when implementing a government-sponsored credit program and from where they exactly originate. This analysis also has implications for policy revision and reformulation of BHB, which should be guided by a better understanding of the organization-specific problems that a government-funded microcredit program is facing. These challenges are assessed by using a qualitative research method called Process Net-map. The use of this method helps to understand how the credit program is implemented in practice, which may deviate from the prescribed implementation plan. Moreover, this study analyzes the challenges that arise from the perspectives of both the supply-side and the demand-side stakeholders of BHB. The major finding of the first paper is supported by the outcome of this paper as it reveals that shortage of funds was the main obstacle for implementing BHB’s microcredit scheme, which failed to meet the clients’ financial needs. Besides this problem, the shortage of adequate staff was responsible for weak field administration, which is amplified by the lack of incentives to motivate them. Political influence and corruption in the system were also identified as central challenges. From the beneficiary-side, high opportunity cost to get loans, lack of non-financial services, inadequacy of funds, and difficulty in group formation were also major problems. A lack of transparency in information flow between groups was also noted as a problem. This paper concludes that a poorly designed program which fails to address the organization-specific challenges of government-run microcredit program will not improve the livelihood of the intended beneficiaries. Hence, the study recognizes the credit program’s need for a better legal and regulatory framework to address the governance challenges that are identified. The focus should be placed on flexible, demand-driven, bottom-up and participatory initiatives. Overall, the study concludes that government-run microcredit programs, affected by problems from large bureaucracies, face specific challenges, which tend to be larger than those faced by NGO-run microcredit programs. One possible solution may be an enhanced collaborative system that involves both public and private credit institutions as it may encourage cross-sector learning.
Analysis of phytosociological composition and spatial structure of the central zone of Lake Baikal Eastern coast vegetation
(2018) Brianskaia, Elena; Schmieder, Klaus
The object of this study is the terrestrial ecosystem of Lake Baikal enlisted by UNESCO as the World Heritage Site. The analysis of spatial and phytosociological structures of the vegetation can reveal important stages of its formation and future dynamics. Today, the present flora and vegetation of the complex Baikal Siberian ecosystem is reflected in studies of many Russian and international phytosociologists. However, despite the huge amount of data, the phytosociological vegetation structure and its spatial distribution of the central zone of Lake Baikal eastern coast has not been studied. By this thesis, we provide the first results about the flora, phytosociological composition of the vegetation and the soil diversity of the central zone of Lake Baikal eastern coast. Selecting the area to study, we hypothesize that this complex territory can be considered as a model biome that adjoins Lake Baikal central zone in the east. The major landscape of the studied area is composed of forests complicated by the bogged valleys of the rivers Cheremshanka, Talovka and Bezymyanka. The Katkovskaya and Chernaya Griva mountains range stretches from the northto the east. 167 relevés were performed by standard methods of the Braun-Blanquet approach. To reveal the phytosociological composition of the vegetation supervised k-means classification was performed in JUICE program. By comparing the vegetation data from the studied area (167 relevés) with data from the adjacent territories of Lake Baikal, Svyatoi Nos Peninsula and the Barguzin mountain range (589 relevés) was obtained the final prodromus of the vegetation. The soil identification was performed according to Russian soil classification. The vegetation mapping was performed in ArcGIS 10.3.1 by the supervised image classification of multispectral panchromatic imagery SPOT 6. The vegetation of the territory under study is represented by four classes. The dominant type of the vegetation is represented by forests which are classified into Vaccinio-Piceetea Br.-Bl. in Br.-Bl. et al. 1939 class. The wetland vegetation includes two classes Scheuchzerio-Caricetea nigrae (Nordh. 1936) Тх. 1937 and Oxycocco-Sphagnetea Br.-Bl et R. Tx. 1943. The vegetation of shifting sands of the coastal line is classified into Brometea korotkyi Hilbig et Korolyuk 2000 class. For all phytosociological vegetation units are identified seven soil types, such as, Lithozems, Brown soil, Soddy Brown Forest soil and Rzhavozems, Fen Peat, and Peat Gleyzem. The soil distribution demonstrates its contingence with an altitudinal gradient; however, transitioning from mountain to plain areas, a hydrological regime becomes crucial. Despite a relatively small territory under study (approx. 500 km2), the vegetation is relatively diverse. Location of the studied area within the zonal forest belt contributes to the leading position of the forest communities. The close ground water occurrence creates suitable conditions for wetland vegetation formation. Lake Baikal coastal line is considered as a refugium of the unique ancient Miocene-Pliocene xerophytic vegetation and flora. Thus, Lake Baikal water body, mountain landform and close ground water occurrence contribute to the formation of diverse vegetation communities. We suggest that the vegetation of this relatively small territory can be considered as a model within the central zone of Lake Baikal eastern coast.
Fernerkundungsgestützte Analyse und Bewertung ökologischer Auswirkungen des Anbaus von Bioenergiepflanzen auf die Agro-Biodiversität anhand der Modellierung der Habitatansprüche der Feldlerche (Alauda arvensis)
(2017) Schlager, Patric; Schmieder, Klaus
For the first time in 2002, the transformation of the conventional energy system into a system based on renewable energies was politically and legally decided in Germany. On the regional level numerous communities and municipalities followed this decision by voicing their own political resolutions, addressing the coverage of energy consumption with renewable energies. Their implementation is accompanied by a spatial expansion of bioenergy crops which lead to a controversial discussion about food safety, biodiversity and landscape change. Framed by the above mentioned discussion, this study assesses potential changes of skylark (Alauda arvensis) occurrence caused by a spatial expansion of bioenergy crops in the municipality of Schwäbisch Hall, Germany. The skylark was selected due to the comprehensive state of research about skylarks, their endangerment (“Red list of German breeding birds”), and the status as umbrella species for open agricultural landscapes (skylarks typically avoid vertical structures like hedges or edges of forests). The latter emphasizes their role as representatives for other species which are potentially affected by an expansion of bioenergy crops. This study is based on a stratified bird monitoring scheme of Baden-Württemberg, which was developed during a project that aimed to set up an indicator for species richness and was financed by the Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV). From the bird monitoring scheme, the stratum, which covers the municipality of Schwäbisch Hall, was extracted and served as a base for the development of a Generalized Linear Habitat Model of the skylark. In order to assess potential habitat changes caused by an expansion of bioenergy crops, Schwäbisch Hall was mapped with an airborne remote sensing technology in 2011. The resulting aerial images were transformed into orthophotos and later classified (focusing on agricultural areas) with an object oriented image analysis approach. Based on the outcomes of the habitat association model and the land use classification, skylark territories were predicted for 1 km² plots covering Schwäbisch Hall. For an in-depth understanding of ecological impacts from expanded bioenergy cropping, a bioenergy scenario was developed considering § 17 BBodSchG (national soil protection act) and regional food security. Based on the scenario, skylark territories were predicted for 1 km² plots covering Schwäbisch Hall. The most reasonable habitat association model resulted in a negative binomial Generalized Linear Model with the predictors winter sown crops and mean patch size per plot. Model performance was assessed by Wald z-statistics with p-values, ANOVA, explained variance, theta, residuals, AIC, and independent field data. Field data was only available for one plot. Therefore, the field data only indicate model performance. The comparison of the model predictions with the field data resulted in an accuracy of 92.21%. The land use classification resulted in the following five classes: 1. winter sown crops (33985.78 ha), 2. maize (9621.36 ha), rapeseed (2952.36 ha), unidentified crops (7244.18 ha), and grassland (30720.88 ha). Grasslands were not mapped by remote sensing techniques, but taken from a digital landscape model. Accuracy assessment showed an overall accuracy of 89.16 % and 0.78 kappa statistics. Prediction of skylark territories based on the land use classification of 2011 resulted in 46269 territories, or a mean density of 8.4 territories per 10 ha on agricultural areas and 5.4 territories per 10 ha on agricultural and grassland combined areas. The scenario assumed a three partite crop rotation (maize, rapeseed, winter sown crops) and a mean value of 0.17 ha per inhabitant for food security. Areas for fodder production were considered in course of the calculation of food security because Schwäbisch Hall is characterized by many livestock farms, which made it necessary to avoid conflicts between potential bioenergy sites and areas for fodder production. Considering the above mentioned assumptions, Schwäbisch Hall has a bioenergy potential of 5955 ha for maize and 15033 ha for rapeseed cropping. The results of the bioenergy scenario were randomly distributed to the land use polygons which resulted from the remote sensing analysis. With that, prediction of skylark territories based on the bioenergy scenario was feasible. Skylark territories for the bioenergy scenario resulted in 36472 territories, or a mean value of 6.8 territories per 10 ha on agricultural areas and 4.3 territories per 10 ha on agricultural and grassland combined areas. Considering both land use options, skylark territories declined by 8797 in total numbers or by 19.43 % in relative numbers. In addition to the land use options described above, landscape structure and territory distribution were analyzed based on six landscape units (Naturräumliche Haupteinheiten) covering the municipality of Schwäbisch Hall. The analysis revealed an agriculturally dominated northwestern part, with high numbers and mean values of skylark territories, and a grassland/forest dominated southeastern part, with lower numbers and mean values of skylark territories. The relative decline of these territories between the two land use options within the landscape units resulted approximately in 22 % in the northwestern and approximately 11-15 % in the southeastern part. The results indicate that an expansion of bioenergy crops will have negative effects on breeding birds in open agricultural landscapes which already suffer from degraded habitat conditions. Based on the assumptions of this study, skylark territories will decline by approximately 20 % in comparison to 2011. Yet, considering the results of the indicator report of the German National Strategy on Biodiversity (BMU 2010) and the European Bird Census Council the baseline of 2011 already represents a degraded situation in terms of habitat quality for agricultural breeding birds.
Spatial and functional determinants of long-term fecundity in serotinous shrub communities
(2016) Nottebrock, Henning; Schurr, Frank
Understanding the dynamics of biological communities is a central aim of ecological research. Contemporary environmental change reinforced this interest: in order to predict how communities will react to environmental change, we have to understand the processes driving their dynamics. Ultimately, the dynamics of a community depends on the reproduction, mortality and dispersal of its component individuals, and on how these demographic processes are altered by environmental factors and biotic interactions. A general understanding of biological communities is unlikely to arise from a species-specific approach that attempts to quantify all pairwise interactions between species. Instead, it seems promising to pursue a trait-based research program that quantifies how variation in the performance of species and individuals is shaped by the interplay of functional traits, biotic interactions and environmental factors. In this thesis, I investigated how functional plant traits determine plant-plant, plant-pollinator and plant-herbivore interactions in space and time, and how these spatiotemporal interactions affect the long-term fecundity of plants. In the South African Fynbos biome (a global biodiversity hotspot), I studied a species-rich, ecologically and economically important group of woody plants (genus Protea) and its interactions with pollinators and seed predators. The objectives of this thesis were: (1) to combine plant traits and high-resolution maps of Protea communities in order to quantify the landscapes of nectar sugar and seed crops that plant communities provide for pollinators and seed predators, (2) to examine how sugar landscapes shape pollinator behaviour, and how pollinator behaviour and pollinator-mediated interactions between plants affect the reproduction of Protea individuals, (3) to study how the spatial structure of plant communities and seed crop landscapes determine direct and predator-mediated interactions between plants, and (4) to understand how the interplay of these biotic interactions shapes the dynamics of plant communities. I addressed these objectives by analysing spatially-explicit data and high-resolution maps from 27 sites of 4 ha each that contained 129,750 plants of 22 Protea species. The results show that Protea plants and their pollinators interact on several spatial and temporal scales, and that these interactions are shaped by sugar landscapes. Within plants, inflorescences compete for pollination. At a neighbourhood scale, Protea reproduction benefits from nectar sugar of conspecific neighbours but not from heterospecific neighbour sugar. Seed set also increases with the amount of nectar sugar at the scale of entire study sites. This corresponds with the finding that the abundance and the visitation rates of key bird pollinators strongly depend on phenological variation of site-scale sugar amounts. Nectar sugar furthermore influences the strength of interactions between Protea species and bird pollinators: Protea species that provide nectar of high sugar concentration depend more strongly on bird pollinators to reproduce. When foraging in sugar landscapes, these bird pollinators show both temporal specialization on single plant species and a preference for common plant species. In addition to these pollinator-mediated interactions, the long-term fecundity of Protea individuals is reduced through both competition and apparent competition mediated by seed predators. Competition is stronger between conspecifics than between heterospecifics, whereas apparent competition shows no such differentiation. The intensity of competition between plants depends on their size and the intensity of apparent competition between plants depends on their seed crops. Moreover, competition has a stronger effect on plant fecundity than apparent competition. These findings have interesting implications for understanding the dynamics of Protea communities and the maintenance of plant diversity in the Fynbos biome. The positive interspecific density-dependence resulting from pollinator-mediated interactions causes community-level Allee effects that may lead to extinction cascades. My analyses also imply that competition stabilizes the coexistence of Protea species (because intraspecific competition is stronger than interspecific competition), whereas apparent competition via seed predators does not have such a stabilizing effect. In summary, this study highlights the benefits of ‘community demography’, the demographic study of multiple interacting species. Community demographic studies have the potential to identify general determinants of biotic interactions that act across species and communities. In this thesis, I identified nectar sugar and seed crops as interaction currencies that determine how multiple plant species interact through shared pollinators and seed predators. In megadiverse systems such as Fynbos, such generalizations are urgently needed to understand and forecast community dynamics. The analysis of community dynamics with respect to such interaction currencies provides an alternative to the classical species-specific approach in community ecology.
Testing vegetation flammability : examining seasonal and local differences in six mediterranean tree species
(2016) Kauf, Zorica; Fangmeier, Andreas
Fire is an important factor controlling vegetation structure, with 40% of terrestrial ecosystems owing their distribution and ecological properties to the accompanying fire regime. In recent decades climate and land use change led to shifts in fire regimes rendering ecosystems more vulnerable to fire. The greatest effects of these changes are expected in the Mediterranean regions. Vegetation is the only factor affecting fire regime which can be directly managed. Promotion of less flammable species is considered to be a valid management option for reducing negative consequences of wildland fires, but reliable information on vegetation flammability and its fluctuations is still lacking. This study strived to bring new insight on the relationship between environmental conditions, fluctuations of morphological characteristics, physiological activity and measured flammability related parameters of Mediterranean tree species. Only a small part of the field study data is included in the final thesis. The field study was conducted from May to October 2010 in the Mediterranean biogeographic region of Croatia, where three sampling locations were positioned along a climate gradient. Selected species included: Aleppo pine (Pinus halepensis Mill.), Holm oak (Quercus ilex L.), olive (Olea europaea L.), carob (Ceratonia siliqua L.), pomegranate (Punica granatum L.), and strawberry tree (Arbutus unedo L.). If possible, all the species were sampled on all the locations during each sampling event. Presented results include: results of the leaf litter flammability method pretesting, regular measurements on leaf litter samples, and monthly measurements on fresh leaf samples. P. granatum samples were not included in the method pretesting, instead laurel (Laurus nobilis L.), mastic (Pistacia lentiscus L.) and Japanese mock orange (Pittosporum tobira Thunb.) were sampled in order to increase the diversity of the materials included. All measured traits of leaf litter) are reported and the relationships between them examined. For fresh leaves only ignition related traits and moisture content results are presented, the relationship between them is examined, and potential effects of the Keetch-Byram drought index on these parameters are explored. Initially, the application of already established epiradiator based methods was intended. Nevertheless, method pretesting identified several flaws of established methods. It revealed that an epiradiator is not a stabile heat source as previously thought, recognising a need for monitoring and stabilizing epiradiator temperature to ensure similar heat exposure at the beginning of each tests. Furthermore, pretesting results demonstrated that materials that rarely flame under certain testing conditions can readily flame if testing conditions are slightly altered, thus challenging the presumption that low ignition frequency always corresponds to low fire danger (flammability) – a basic presumption of the vegetation flammability tests. Results of leaf litter flammability testing showed that properties of the leaf litter particles significantly change within the fire season, and indicated that species specific weathering and decomposition could play an important role in these changes. They demonstrated that a change in a single leaf trait can have opposite effects on different flammability parameters, and that these relationships are dependent on the incoming heat flux. Results of fresh leaves testing identified phenological changes as important factor governing fluctuation of moisture content and ignition related parameters, and showed that the relationship between drought indices and moisture content is not limited to shallow rooting species. They challenged the presumption that increasing leaf thickness is related to “fire retardance” – a relationship found if samples are tested outside their natural moisture content range. Instead, this study, in which fresh leaves were tested within their natural moisture content range, implies that higher sclerophylly is related to higher ignition frequency, indicating an opposite trend and confirming the importance of moisture content as one of the most important factors governing fire behaviour of the materials. All the gathered data indicated that, O. europaea, Q. ilex and P. halepensis exhibit higher tendency to ignite than C. siliqua and P. granatum; A. unedo showed high variation in ignition related parameters. Nevertheless, ignition related parameters reveal only a part of the information on fire behaviour of the material. Overall results demonstrated that the experimental setup can have tremendous impacts on the results of flammability tests, thus data interpretation should be done with caution. Furthermore, instead of attributing single flammability scores based on all measured parameters, interpretation of test results in relation to their influence on fire behaviour is advocated.
Rye (Secale cereale L.) : agronomic performance under drought and methods of crop physiology to determine the drought tolerance of winter rye
(2015) Kottmann, Lorenz; Fangmeier, Andreas
Winter rye (Secale cereale L.) is predominantly cultivated on light and sandy soils with a low water holding capacity and will therefore be especially affected by drought induced yield losses in Central and Eastern Europe in the future. Drought adaption through breeding is therefore an important task in order to adapt this crop to future climate conditions. In this context, the crop physiology methods canopy temperature depression (CTD = Tair - Tcanopy) and carbon isotope discrimination (delta) were examined for their suitability as selection criterion under drought on a small number of genotypes. Two sets of each 16 genotypes were therefore grown under different drought conditions in rain-out shelters and under well-watered conditions in the years 2011, 2012, and 2013. The CTD was determined several times during the growth period using two infrared (IR) thermometers and an IR camera. delta-analyses were performed on mature flag leaves (delta_leaf) and grains (delta_grains). Furthermore, ash content in mature flag leaves and grains, as well as mineral concentrations in mature flag leaves (Ca, K, Mg, and Si) were examined for their use as surrogates for the expensive and time-consuming delta-analyses. In addition to the evaluation of possible selection criterions, the agronomic performance of rye in the different drought regimes was assessed: Grain-, straw-, and total aboveground biomass yields, the grain yield components spikes m-2, kernels spike-1, and thousand kernel weight (TKW), leaf area index (LAI), and phenological characteristics were examined. Drought induced grain yield reductions ranged from 14 to 57%, whereas straw yield was generally lesser affected. The growth period was shortened by up to 12 days under drought conditions compared to optimal water supply. Grain yield was positively associated to straw yield, LAI, spikes m-2, and kernels spike-1 under water deficit. High number of grains per area land seemed to be especially important for high grain yields under drought. Furthermore, the results suggest a strong importance of pre-anthesis reserves for the reallocation of assimilates for grain filling under drought in rye. Regarding the suitability of possible selection criterions, CTD was significantly positively related to grain yield under drought. Significant correlations between CTD and grain yield were, however, only observed when the measurements were carried out on days with optimal weather conditions. Optimal conditions turned out to be days with a clear sky, a solar irradiation >700 W m-2, an air temperature of at least 20°C, as well as wind speeds <3 m s-1. Furthermore, the results showed that also rather inexpensive IR instruments are suitable to assess the CTD. Regarding the carbon isotope discrimination, delta_leaf was significantly positively related to grain yield under water deficit, but the correlation was weaker than between CTD and grain yield. Delta_grains was not related to grain yield at all. Ash content and mineral concentrations were significantly related to grain yield under drought, but the correlations were quite inconsistent between the two experimental years. Because of the weak or missing relationship with grain yield, carbon isotope discrimination and its potential surrogates ash content and mineral concentration cannot be recommended for their use as selection criterions under German climate conditions at present. A general limitation of the preset work was, however, the low genetic variability of the genotypes, which may have reduced the significance of the results. The results should therefore be validated with a more diverse set of genotypes. However, especially the CTD seemed to be a promising selection criterion which may help to develop drought tolerant rye genotypes, if this method can be successfully integrated into the breeding process.
Ecology of alluvial arable land polluted by copper mine tailings : new insights for restoration
(2013) Nikolic, Nina; Böcker, Reinhard
Mining and extraction of metals generates huge amounts of tailings waste (a mixture of water, finely ground ore rock and processing effluents, which remains after removal of mineral concentrate). Unfortunately, accidental release of mine tailings into river systems and their further deposition in floodplains, often over arable land, has been reported from many parts of the world, with environmental implications difficult to predict. Mine tailings from sulphidic metal ores combine high potential for generating soil acidity, and high concentrations of plant available heavy metals, which are the two most intractable issues in restoration of post-mining sites. On the other hand, barren land degraded by mining waste provides an exciting opportunity to reveal some important ecological principles which might not be apparent under ?normal? conditions. Understanding of the process of primary vegetation succession is in particular crucial for the practice of ecological restoration, which is increasingly seen as a preferable alternative to technical reclamation of land degraded by mining. This work addresses the two major issues relevant for ecology and restoration of alluvial arable land polluted by mining waste, which have so far been very poorly understood: Firstly, the long-term fate of contaminants and their actual impact on soil quality and crop production under true field conditions. Secondly, the process of spontaneous revegetation of barren land under the extreme soil conditions and the environmental setup considerably different from the well-studied Central European. The explorative study was undertaken on an exceptional locality created by long-term and large scale-fluvial deposition of sulphidic copper (Cu) tailings over alluvial fields in Eastern Serbia. Comprehensive surveys of spontaneous vegetation, weed assemblages and cereal crops (species cover-abundance; biomass per m2; and foliar mineral analyses), and concomitant surveys of rhizosphere soils (31 physical and chemical parameter) included 297 sampling locations throughout the polluted floodplain (flexible sampling scheme based on visual appearance of vegetation). Data were jointly analysed in a gradient approach framework by different multivariate statistical methods (ordination: NMS, PCA, CCA; classification: agglomerative clustering; group comparisons: MRPP, ISA; habitat modelling: NPMR; and, regression analysis). The results revealed exceptionally strong structure in the vegetation which was highly correlated with the measured soil properties; the regular change of vegetation and soil properties occurred along spatially explicit transects perpendicular to the river channel. The clear gradients observed in this ?field laboratory? research brought forward some new ecological patterns which had not been reported by other relevant studies so far: 1. Severe P deficiency, most likely not amenable by fertilization, is identified as the master limiting soil factor for grains under the multiple abiotic stresses caused by deposition of sulphidic Cu mining waste. Other plausible soil constraints (low pH, excessive concentrations of available Cu and Al, deficiency of N and B; P deficiency-induced increase of As uptake; competition with superior hemicryptophytic weeds), have remained in domain of a ?black-box?. 2. Frequent ploughing accelerates the substitution of high plant available Cu by nutrient deficiency (primarily P and microelements) and excessive exchangeable Al. Thus, agronomic soil quality indicated by crop yield does not improve even when Cu is leached to the background levels. The environmental consequences of intensive land use are however drastic, and increase vulnerability of these soils to further environmental hazards. On the other hand, one type of spontaneously occurring pioneer forests was shown to considerably slow down the oxidative weathering of the tailings deposits and thus prevent Cu leaching via phytostabilization. 3. Although many characteristics of cereal weed assemblages markedly change along the soil pollution gradient, the species? ability to maintain leaf P homeostasis appears to be the key adaptation underlying the observed vegetation structure. The novel associations of unusual species combinations showed a set of functional adaptations which have enabled the leaf N:P homeostasis and thus the uninterrupted survival of weed vegetation along the soil gradient. 4. The proposed conceptual model describes a highly patterned process of spontaneous revegetation of the created barren land under the severe environmental filtering. In this process, the xerothermic surrounding vegetation adapted to calcareous soils has a very limited role. Instead, primary succession relies on novel types of early vegetation which comprise not only novel combinations of species, but also the key role of species which are novel to the affected region, and do not survive outside of the polluted area. We demonstrate for the first time that pollution-induced severe nutrient deficiency can override the well-established importance of both surrounding vegetation and water level gradient for primary succession. Overall, this study implies that severe nutrient deficiency, which is often a neglected issue in studies of metal-polluted sites, can override the effects of Cu toxicity, the role of surrounding vegetation, and even the role of water level gradients, on the process of spontaneous restoration of vegetation cover. It is highly unlikely that spontaneous restoration under the current conditions would allow the reestablishment of the original (or close to original) alluvial vegetation or pre-pollution agricultural land use. Weathering of the substantial residues of sulphides, further acidification and Cu leaching is the major environmental risk; ploughing (or any mechanical soil disturbance with similar effect) of this vast marginalized area should be avoided. Maintenance of the natural flooding regime, which had, bizarrely, caused this vast degradation in the first place, is indicated important for the current spontaneous succession and warrants further research.
Biomonitoring of ammonia deposition by means of higher plants
(2013) Ilogu Chibuzo Franklin; Fangmeier, Andreas
Atmospheric nitrogen deposition emanating from oxidized or reduced nitrogen sources has been influenced immensely by human activities. This is as a result of the need to improve and meet the ever changing demands of an increasing growth in global population. The benefits accrued from such activities however, have not been without some negative effects on several ecosystems, plants, air quality and human health. This is due to the emission of reactive nitrogen species and its contribution to the level of atmospheric nitrogen pollution in the environment as well as nitrogen deposition afterwards. Atmospheric ammonia (NH3) arguably is an important source of nitrogen deposition. Its major source is from agricultural activities involving various aspects of crop production including, fertilizer and manure applications among others and also importantly from livestock management. It is pertinent therefore, to conduct continuous monitoring studies in order to ascertain the prevailing ambient NH3 concentration in an area, so as to identify periods when threshold values are exceeded and also to determine how certain plants would respond when exposed to NH3 pollution. This necessitated the need to investigate in this thesis, through active biomonitoring, the interaction of NH3 pollution on selected indicator species namely, Italian ryegrass (Lolium multiflorum L.), barnyard grass (Echinochloa crus-galli L.), stinging nettle (Urtica dioica L.) and common lambsquarters (Chenopodium album L.). The influence of nitrogen deposition, arising from NH3 pollution on the selected indicator species were examined by the responses of the free amino acids and above ground biomass accumulation of the various plants studied, as an indicator of nitrogen accumulation. In order to execute plant and atmospheric NH3 interactions, two different experiments were conducted. The first experiment was a field study carried out around a livestock farm as a source of NH3 pollution and nitrogen deposition. Plant materials were exposed alongside passive diffusion tube samplers at three selected distances from the stable along a transect of 804m. The three different sites were selected with increasing distance from the stable, in order to enable a comparison between the plants exposed in close proximity to the source NH3 emission and those further away. The ambient NH3 concentration at each site was measured with the passive diffusion tube samplers exposed at each location. This measurement was conducted with a view to determine the ambient NH3 concentration exposed to the plant materials at each site and also to observe the influence of increasing distance on NH3 pollution and its exposure on the plants, from a point source of NH3 pollution. Furthermore, two fumigation experiments were conducted under controlled greenhouse conditions. In the fumigation study, only Lolium multiflorum and Echinochloa crus-galli, plants were used for this experiment and exposed to three treatment levels of gaseous NH3 fumigations in different growth chambers. The plants were exposed to the following treatments, non-filtered air (NFA), non-filtered air with low NH3 concentration (NFA+) and non-filtered air with high NH3 concentration (NFA++) in both fumigation experiments. In the field experiment, the ambient NH3 concentration measured at each location from the stable, decreased with increasing distance from the point of NH3 emission. This decrease in concentration of NH3 clearly demonstrates the impact of livestock management as a source of NH3 pollution. The free amino acid concentrations and compositions investigated in the various plants studied in the field experiments showed a significant response to NH3 exposure. Several fold increases in the free amino acid concentrations and changes in composition were observed in plant materials exposed to increasing NH3 concentrations at closer proximity to the stable. Observations made from this study showed that an increase in NH3 concentration with closer distance to the source of NH3 pollution influenced remarkably, the percentage increases of low carbon to nitrogen compounds such as Glutamine (Gln) in Lolium multiflorum and Chenopodium album, Asparagine (Asn) in Echinochloa crus-galli and Arginine (Arg) in Urtica dioica. The increases and alterations observed in the free amino acid compositions of the plants studied, demonstrates the uptake and sensitivity of the various plants to NH3 pollution and nitrogen deposition by inducing changes in its free amino acid metabolism. The effects of nitrogen deposition on the above ground biomass of the plants in the field study, indicated a significant effect of the ambient NH3 concentrations on Lolium multiflorum, Echinochloa crus-galli and Urtica dioica. These findings demonstrate a positive influence of NH3 pollution as a nitrogen source on growth and biomass accumulation in the plants. Considering the results obtained in this study based on the responses of the plants to atmospheric NH3 pollution in the field and in the fumigation studies, it is obvious NH3 had an influence over the growth and metabolism of the plants studied. This influence indicates the plants were able to detect changes in the ambient NH3 concentrations in the environment and responded by exhibiting changes in biomass production and alterations in free amino acid compositions, thus indicating they have good potentials as biomonitors of ammonia deposition.
Effects of elevated atmospheric CO2 concentrations on insects and pathogens of spring wheat (Triticum aestivum L. cv. Triso) and oilseed rape(Brassica napus cv. Campino)
(2012) Oehme, Viktoriya; Fangmeier, Andreas
It is suggested that plants, herbivore insects and pathogens will be affected by rising atmospheric CO2. The working hypothesis of this study was that elevated CO2 will affect plant composition and will thus exert influence on plant-insect interactions by changing the nutritive value for insects feeding on phloem sap. To test this hypothesis, experiments were carried out on wheat and oilseed rape in two different systems: controlled environment chambers (climate chamber system) and an open field exposure system with natural climatic and soil conditions (Mini FACE system). The abundance of detrimental insects from different feeding guilds and plant damage by parasitic organisms were examined in a Mini FACE system, while the consequences of elevated CO2 on aphid performance and potential correlations to phloem sap composition of host plants were observed in controlled environment chambers. The concentrations of amino acids and carbohydrates in the phloem of host plants were analysed by high?performance liquid chromatography (HPLC), using a fluorescence detector for amino acids and the evaporative light scattering detector for carbohydrates. In a Mini-FACE system, phenological development of spring wheat and OSR was not significantly changed due to CO2 enrichment. However, elevated CO2 induced changes in plant chemistry (increased carbon:nitrogen ratio and defensive compounds), which resulted in changes in population densities of some pest species. In order to monitor alterations in insect population density, two different methods were applied: direct counts (method 1) and using of yellow sticky traps (method 2). These methods showed both increases and decreases of insect numbers due to elevated CO2, depending on species and on the period of observation. Concerning plant pathogens, leaves of spring wheat were only slightly and not significantly damaged by Erysiphe graminis, Puccinia striiformis, Puccinia recondita and Septoria tritici during the 2006/2008 years in all treatments. Also the OSR was not significantly damaged by Peronospora parasitica. The frequency and severity of disease infestation on spring wheat and OSR was not significantly impacted by elevated CO2. In controlled-environment chambers, the phenology, above ground biomass and RGR of OSR were not significantly impacted due to elevated CO2. And although the phenology of spring wheat was not influenced by raised CO2, significant increases were observed for plant above ground biomass and RGR. The aphid presence significantly reduced the aboveground biomass and RGR of spring wheat, while no effects due to aphids were observed in OSR. High-CO2 treatment differently impacted the performance of aphids. Slight and non-significant increases due to elevated atmospheric CO2 conditions were observed for the aphid relative developmental stages and intrinsic rates of increase, while the weight and RGR were significantly increased for Rhopalosiphum padi and decreased for Myzus persicae. In order to clear CO2-impacts on the insect performance, phloem sap from host plants was analysed for the composition and concentration of amino acids and carbohydrates. In summary, although the phenological development of spring wheat and OSR was not affected due to elevated CO2, significant changes were found for the concentration of carbohydrates in the phloem sap of spring wheat and individual amino acids in both host plants. These alterations in plant chemistry affected the performance and abundance of herbivore insects.
Air pollution by particulate matter and ammonia at suburban and rural sites in the North China Plain
(2011) Kopsch, Jenny; Fangmeier, Andreas
The thesis presented here was conducted at the Institute of Landscape and Plant Ecology at the University of Hohenheim within the scope of the first Sino-German International Research Training Group (IRTG) ?Modeling Material Flows and Production Systems for Sustainable Resource Use in Intensified Crop Production in the North China Plain?. The project is jointly performed by the University of Hohenheim and the China Agricultural University (CAU) Beijing and financed by the German Research Foundation and the Chinese Ministry of Education. The present study was performed in the framework of subproject 1.3 of the IRTG which had the major aim to study air pollution and atmospheric nitrogen deposition in the North China Plain (NCP). For that purpose data on concentrations of atmospheric pollutants were required in order to assess the level of exposure to pollution of both population and environment in the NCP. This study represents the initial work in the NCP in 2005 and 2006 in order to monitor air pollution and dry nitrogen deposition and its effects. Within this work experiments were conducted to monitor concentrations of PM2.5, PM10, TSP, NOx and NH3 in the NCP. Ammonia monitoring and biomonitoring were synchronised in order to study the potential effects of nitrogen deposition on Molinia caerulea. Since there was no air monitoring network existing in the NCP at the onset of this study, one major part of the work consisted of setting up and testing of European measuring devices under the special conditions in the NCP. The measurements have been therefore the starting point of field observations in the NCP and especially the PM monitoring operated at the agricultural study site Dongbeiwang (DBW) was a key element of the field campaign in order to study pollutant concentrations in the NCP but also the influences of the nearby megacity Beijing. Sampling with the High Volume Sampler Digitel DHA 80 proved to be suitable for the conditions in the NCP. The levels of daily PM10 measured in this study exceeded European (50 µg m-3) and Chinese (150 µg m-3) thresholds by far. Also the EU standard for the number of tolerated daily exceedances (35 times per year) was not met in the Beijing area. Results of PM10 measurements at DBW showed 126 exceedances of the daily mean European threshold in only 128 days in 2005 and 43 exceedances in 44 days in 2006. The maximum daily mean of 412 µg m-3 also reflects the high PM10 peak concentrations in the study region. Results of daily PM2.5 measurements at DBW in 2005 and in 2006 showed exceedances of the U. S. daily average air quality standard of 35 µg m-3 for 99 % of the data (mean value in 2005: 222 µg m-3 and in 2006: 123 µg m-3). High daily PM2.5 peak concentrations were observed especially during the winter. Overall, only under extreme meteorological conditions such as heavy rainfalls PM levels of less than 50 µg m-3 were detected at DBW. Diurnal and hourly variations of PM levels were demonstrated. Glass fibre filters proved to be suitable for the collection of high PM loads whereas quartz fibre filters are much more suitable for the laboratory analysis of N species. Determination of particulate ammonium and nitrate on glass fibre filters of spring season was tested and showed averaged concentrations of 2.4 and 13.1 µg m-3 (TSP) and 8.0 and 11.6 µg m-3 (PM10), respectively. The mass spectrometric measurements were challenging due to the filter material and δ15N/14N ratios were found to be very heterogeneous ranging from -3.0 ? to 44.3 ?, referring to both filter types. The simple and low-cost passive sampling method used (Radiellos®) also proved to be an appropriate tool for evaluating ammonia exposure in the NCP. The seasonal ammonia levels were in the range from 9 to 43 µg m-3 at DBW, Wuqiao and Quzhou, which indicates intensive agricultural activity in the whole NCP. No relationship was found between atmospheric ammonia levels and plant growth parameters of Molinia caerulea and thus, growth of these test plants was not related to gaseous dry deposition of ammonia. The NOx measurements in NCP did not yield reliable data within given time. Overall, multiple sources are assumed to interplay at the study site namely, local dust (such as harvest), traffic, biomass burning, coal combustion, secondary aerosol and industrial emissions from Beijing area. Long-range transported air pollutants such as pollutants from Hebei and Shandong province or deserts as well as the weather pattern greatly influence the atmospheric pollution at DBW and NCP in general.
Evaluation der Richtlinienkonformität von Verträglichkeitsprüfungen nach Artikel 6 Flora-Fauna-Habitat-Richtlinie in der Planungspraxis
(2011) Matthäus, Gunther; Dieterich, Martin
The dissertation presents findings of a study on the practical implementation of the Habitats Direktive, Art. 6 (3). The formal und methodological quality of 50 appropriate assessments according to the Habitats-Direktive was analysed. Overall, a solid or even high to very high level of quality was found. Only few assessments exhibited serious shortcomings or mistakes with relevant effects on the finding of the assessments. These shortcomings coud be avoided by the introdiktion of binding quality standards.
Development of assessment tools for Lake Sevan (Armenia) by the application of remote sensing data and geographic information systems (GIS) techniques
(2011) Agyemang, Thomas Kwaku; Schmieder, Klaus
Lake Sevan is the biggest source of water in Armenia. Its littoral zone, in addition to being a food source and a substrate for macrophytes, algae and invertebrates, provide refuge and spawning habitats for both young & old organisms especially fishes. Between 1933 and 1960s, the lake level had been lowered by 20 m below the original level by increasing the lake outflow intermittently for irrigation and electricity generation. This evidently had ecological and economical consequences on the lake ecosystem. The importance of assessing the accuracy of spatial data classifications derived from remote sensing methods and used in geographic information system (GIS) analyses has been regarded as a critical component of many projects. In this project, supervised classified QuickBird satellite imageries of both submersed macrophytes and landcover types (emersed vegetation) of the Gavaraget, Tsovazard and Masrik Regions of the study area were validated in a GIS environment. The results of these assessments were represented by error matrices presenting the overall accuracy, the user and producer accuracies in each category, as well as the kappa coefficients. For submersed macrophytes at the vegetation level, the overall accuracy ranging between 77-88% was achieved in all the investigation years. Alga blooms in the different years impacted on the accuracy of the classification. However, even through severe algal blooms user accuracies between 55% and 95% were achieved. On the other hand, at the growth type level, the overall accuracy was as high as over 70% and as low as below 49%. For emersed vegetation types, predominantly high overall accuracies of more than 70% were obtained in 2 of the investigation years. Above all, in 2008, only slight overall accuracy could be obtained. For reeds areas, high user accuracies of more than 78% could be obtained, while for shrubs, trees, no vegetation and grasses in the different years, very different classification accuracies were attained. Two habitat suitability models (one for fishes and one for birds) were built in a GIS environment in this project. While the Crucian Carp (Carassius auratus Gibelio Bloch) was chosen as lead species for the fish habitat, the Common Coot (Fulica atra) and the Great Crested Grebe (Podiceps cristatus) were chosen for the bird habitat models based on expert knowledge on Lake Sevan. Five fish habitat suitability classes were assigned in the model. There was a similar trend in the fish habitat areas in all the landscapes in Gavaraget, Tsovazard and Masrik regions. The habitat areas increased in 2007 and decreased in 2008. The increases in all the regions were the same (around 43%) while the highest reduction occurred in Gavaraget (47%) followed by Masrik (38%) and Tsovazard (25%) respectively. Apart from the reductions in habitat areas in 2008, there were severe decreases in the quality of the habitat areas in all the regions of interests. The increases and decreases were as a result of interannual fluctuations due to water level fluctuations and algal blooms of Lake Sevan. Also, for the bird habitat model, five classes were assigned. Tsovazard and Masrik had a similar trend in habitat areas with an initial increase in 2007 followed by a decrease in 2008. However, Gavaraget had reductions in 2007 and 2008. Again, in addition to the severe reductions in the habitat areas in 2008, there were severe decreases in the quality of the habitat areas in all the regions of interests. The changes in emersed macrophyte vegetations and the lake water level fluctuations effected the different changes in the bird habitat areas.
Biomonitoring von Fluorwasserstoff : neue Ansätze zum Einsatz Höherer Pflanzen als Akkumulationsindikatoren
(2009) Blanckart, Peter; Fangmeier, Andreas
The standardised grass culture as described in VDI guideline 3957 sheet 2 has successfully been used for years to identify pollution related effects and to assess pollution load with hydrogen fluoride. At the moment, two directives are in preparation for the evaluation of the results from the exposure of standardised grass cultures which provide scales for judging and values for orientation on the basis of detailed studies. The directives will be published as VDI 3857 sheet 1 and sheet 2 as green print in 2009. The directive VDI 2310 sheet 3 is being revised as well. Its publication (green print) is also expected for 2009. According to no. 5.3 of the directive VDI 3957 sheet 2, samples with less than 2 g of dry substance have to be rejected. However, the rejection of these samples leads to a time gap for assessing of 14 days or even of 4 weeks. In this context it should be tested how the accumulation of fluoride after exposure with air containing hydrogen fluoride would be affected at lower growth rates. It should also be tested if samples of exposed grass with a minimum weight of less than the required 2 g of dry substance can be used for determining the pollution situation. To evaluate these problems, exposures were performed with standardised grass cultures and with modified methodology in an area ? the city of Ransbach-Baumbach ? which is highly contaminated by fluorides. Parallel to bioindication, the fluoride concentration in the air was assessed with radial symmetric passive samplers as a physicochemical method. By this means a direct comparison of the concentration of air pollutants with the pollutant concentration in the grass could be performed. The tests confirmed that the study area is indeed quite contaminated with fluoride from anthropogenic sources. The area around Ransbach-Baumbach can be considered as a hot-spot for higher fluoride concentrations within Germany. The results confirm that fluoride pollution in Central Europe is still an ongoing problem, even though the pollution is mostly scattered and small scale limited. Therefore, evaluation fundamentals for bioindication methods for fluoride (passive and active) should be worked out for the future, although fluoride accumulations are no longer regularly determined in large scale bioindication monitoring networks. The application of Deschampsia flexuosa (L.) Trin. as an accumulation indicator as a possible alternative to Lolium multiflorum Lam. could not be confirmed in this study; the deviations of fluoride concentrations in Deschampsia flexuosa (L.) Trin. and in Lolium multiflorum Lam. were too large in the spatiotemporal comparison. The measurements performed with radialsymmetric passive samplers did not show a good relationship between the hydrogen fluoride concentration in the air and the fluoride concentration F- [µg g-1 ds] in the Lolium grass cultures. There were only very low correlations between the fluoride concentration and the increase of biomass as raw and dry weight of Lolium multiflorum Lam. (R2 of 0.0258 and 0.0099 at two measurement stations, respectively). Since conventionally an R2 of ≥ 0,6 is required to indicate significant relationships in ecological/ecotoxicological field studies, no link between the increase of biomass and fluoride concentration for the accumulation indicator Lolium multiflorum Lam. is concluded. Therefore, it is recommended to revise the VDI guideline 3957 sheet 2 so that standardised grass culture samples of less than 2 g dry substance are also accounted for in the determination of the accumulation of air pollutants like fluoride in plants.
Pathways of C and N turnover in soil under elevated atmospheric CO2
(2008) Dorodnikov, Maxim; Fangmeier, Andreas
In the present thesis the C and N transformations in soil as influenced by indirect effect of elevated atmospheric CO2, soil physical structure and land use change were studied in four laboratory experiments using stable-C and N isotopes, as well as soil microbiological techniques. To test the interrelations between chemical and biological characteristics of soil organic matter (SOM) as affected by land use change and elevated atmospheric CO2 an approach for SOM partitioning based on its thermal stability was chosen. In the first experiment C isotopic composition of soils subjected to C3-C4 vegetation change (grassland to Miscanthus x gigantheus, respectively) was used for the estimation of C turnover in SOM pools. In the 2nd (Free Air CO2 Enrichment ? FACE ? Hohenheim) and 3rd (FACE Braunschweig) experiments CO2 applied for FACE was strongly depleted in 13C and thus provided an opportunity to study C turnover in SOM based on its δ13C value. Simultaneous use of 15N labeled fertilizers allowed N turnover to be studied (in the 2nd experiment). We hypothesized that the biological availability of SOM pools expressed as the mean residence time (MRT) of C or N is inversely proportional to their thermal stability. Soil samples were analysed by thermogravimetry coupled with differential scanning calorimetry (TG-DSC). According to differential weight losses between 20 and 1000 °C (dTG) and energy release or consumption (DSC), SOM pools (4 to 5 depending on experiment) with increasing thermal stability were distinguished. Soil samples were heated up to the respective temperature and the remaining soil was analyzed for δ13C and δ15N by IRMS. For all three experiments the separation of SOM based on its thermal stability was not sufficient to reveal pools with contrasting turnover rates of C and N. A possible explanation for the inability of thermal oxidation for isolating SOM pools of contrasting turnover times is that the fractionation of SOM pools according to their thermal stability is close to chemical separation. In turn, it was found that chemical separations of SOM failed to isolate the SOM pools of different turnover time because different biochemical plant components (cellulose, lignin) are decomposed in a wide temperature range. Individual components of plant residues may be directly incorporated into, or even mixed with the thermal stable SOM pools and will so mask low turnover rates of these pools. To evaluate the interactions between availability of SOM for decomposition by soil microbial biomass (biological characteristic) under elevated atmospheric CO2 and protection of SOM due to the occlusion within aggregates of different sizes (physical property, responsible for SOM sequestration) we measured the activity of microbial biomass (indicated by enzyme activities) and growth strategies of soil microorganisms (fast- vs. slow growing organisms) in isolated macro- and microaggregates. The contribution of fast (r-strategists) and slowly growing microorganisms (K-strategists) in microbial communities was estimated by the kinetics of the CO2 emission from bulk soil and aggregates amended with glucose and nutrients (Substrate Induced Growth Respiration method). Although Corg and total Cmic were unaffected by elevated CO2, maximal specific growth rates were significantly higher under elevated than ambient CO2 for bulk soil, small macroaggregates, and microaggregates. Thus, we conclude that elevated atmospheric CO2 stimulated the r-selected microorganisms. Such an increase in r-selected microorganisms could increase C turnover in terrestrial ecosystems in a future elevated atmospheric CO2 environment. The activities of β-glucosidase, phosphatase and sulphatase were unaffected in bulk soil and in aggregate-size classes by elevated CO2, however, significant changes were observed in potential enzyme production after substrate amendment. After adding glucose, enzyme activities under elevated CO2 were 1.2-1.9-fold higher than under ambient CO2. This indicates an increased activity of microorganisms, which leads to accelerated C turnover in soil under elevated CO2. Significantly higher chitinase activity in bulk soil and in large macroaggregates under elevated CO2 revealed an increased contribution of fungi to turnover processes. At the same time, less chitinase activity in microaggregates underlined microaggregate stability and the difficulties for fungi hyphae penetrating them. We conclude that quantitative and qualitative changes of C input by plants into the soil at elevated CO2 affect microbial community functioning, but not its total content. Future studies should therefore focus more on the changes of functions and activities, but less on the pools. In conclusion, elevated CO2 concentrations in the atmosphere along with soil physical structure have a pronounced effect on qualitative but not quantitative changes in C and N transformations in soil under agricultural ecosystem. The physical parameters of soil such as aggregation correlate more with biological availability of SOM than the chemical properties of soil organic materials. The increase of soil microbial activity under elevated CO2 detected especially in soil microaggregates, which are supposed to be responsible for SOM preservation, prejudice sequestration of C in agroecosystems affected by elevated atmospheric CO2.

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