@article{LeingaertnerHoissKraussetal.2014,
  author    = {Leing{\"a}rtner, Annette and Hoiss, Bernhard and Krauss, Jochen and Steffan-Dewenter, Ingolf},
  title     = {Combined Effects of Extreme Climatic Events and Elevation on Nutritional Quality and Herbivory of Alpine Plants},
  doi       = {10.1371/journal.pone.0093881},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-112812},
  year      = {2014},
  abstract  = {Climatic extreme events can cause the shift or disruption of plant-insect interactions due to altered plant quality, e.g. leaf carbon to nitrogen ratios, and phenology. However, the response of plant-herbivore interactions to extreme events and climatic gradients has been rarely studied, although climatic extremes will increase in frequency and intensity in the future and insect herbivores represent a highly diverse and functionally important group. We set up a replicated climate change experiment along elevational gradients in the German Alps to study the responses of three plant guilds and their herbivory by insects to extreme events (extreme drought, advanced and delayed snowmelt) versus control plots under different climatic conditions on 15 grassland sites. Our results indicate that elevational shifts in CN (carbon to nitrogen) ratios and herbivory depend on plant guild and season. CN ratios increased with altitude for grasses, but decreased for legumes and other forbs. In contrast to our hypotheses, extreme climatic events did not significantly affect CN ratios and herbivory. Thus, our study indicates that nutritional quality of plants and antagonistic interactions with insect herbivores are robust against seasonal climatic extremes. Across the three functional plant guilds, herbivory increased with nitrogen concentrations. Further, increased CN ratios indicate a reduction in nutritional plant quality with advancing season. Although our results revealed no direct effects of extreme climatic events, the opposing responses of plant guilds along elevation imply that competitive interactions within plant communities might change under future climates, with unknown consequences for plant-herbivore interactions and plant community composition.},
  language  = {en}
}
@phdthesis{Fricke2022,
  author    = {Fricke, Ute},
  title     = {Herbivory, predation and pest control in the context of climate and land use},
  doi       = {10.25972/OPUS-28732},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287328},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Chapter 1 - General introduction Anthropogenic land-use and climate change are the major drivers of the global biodiversity loss. Yet, biodiversity is essential for human well-being, as we depend on the availability of potable water, sufficient food and further benefits obtained from nature. Each species makes a somewhat unique contribution to these ecosystem services. Furthermore, species tolerate environmental stressors, such as climate change, differently. Thus, biodiversity is both the "engine" and the "insurance" for human well-being in a changing climate. Here, I investigate the effects of temperature and land use on herbivory (Chapter 2), predation (Chapter 3) and pest control (Chapter 4), and at the same time identify features of habitats (e.g. plant richness, proximity to different habitat types) and landscapes (e.g. landscape diversity, proportion of oilseed rape area) as potential management targets in an adaptation strategy to climate change. Finally, I discuss the similarities and differences between factors influencing herbivory, predation and pest control, while placing the observations in the context of climate change as a multifaceted phenomenon, and highlighting starting points for sustainable insect pest management (Chapter 5). Chapter 2 - Plant richness, land use and temperature differently shape invertebrate leaf-chewing herbivory on major plant functional groups Invertebrate herbivores are temperature-sensitive. Rising temperatures increase their metabolic rates and thus their demand for carbon-rich relative to protein-rich resources, which can lead to changes in the diets of generalist herbivores. Here, we quantified leaf-area loss to chewing invertebrates among three plant functional groups (legumes, non-leguminous forbs and grasses), which largely differ in C:N (carbon:nitrogen) ratio. This reseach was conducted along spatial temperature and land-use gradients in open herbaceous vegetation adjacent to different habitat types (forest, grassland, arable field, settlement). Herbivory largely differed among plant functional groups and was higher on legumes than forbs and grasses, except in open areas in forests. There, herbivory was similar among plant functional groups and on legumes lower than in grasslands. Also the presence of many plant families lowered herbivory on legumes. This suggests that open areas in forests and diverse vegetation provide certain protection against leaf damage to some plant families (e.g. legumes). This could be used as part of a conservation strategy for protected species. Overall, the effects of the dominant habitat type in the vicinity and diverse vegetation outweighed those of temperature and large-scale land use (e.g. grassland proportion, landscape diversity) on herbivory of legumes, forbs and grasses at the present time. Chapter 3 - Landscape diversity and local temperature, but not climate, affect arthropod predation among habitat types Herbivorous insects underlie top-down regulation by arthropod predators. Thereby, predation rates depend on predator community composition and behaviour, which is shaped by temperature, plant richness and land use. How the interaction of these factors affects the regulatory performance of predators was unknown. Therefore, we assessed arthropod predation rates on artificial caterpillars along temperature, and land-use gradients. On plots with low local mean temperature (≤ 7°C) often not a single caterpillar was attacked, which may be due to the temperature-dependent inactivity of arthropods. However, multi-annual mean temperature, plant richness and the dominant habitat type in the vicinity did not substantially affect arthropod predation rates. Highest arthropod predation rates were observed in diverse landscapes (2-km scale) independently of the locally dominanting habitat type. As landscape diversity, but not multi-annual mean temperature, affected arthropod predation rates, the diversification of landscapes may also support top-down regulation of herbivores independent of moderate increases of multi-annual mean temperature in the near future. Chapter 4 - Pest control and yield of winter oilseed rape depend on spatiotemporal crop-cover dynamics and flowering onset: implications for global warming Winter oilseed rape is an important oilseed crop in Europe, yet its seed yield is diminished through pests such as the pollen beetle and stem weevils. Damage from pollen beetles depends on pest abundances, but also on the timing of infestation relative to crop development as the bud stage is particularly vulnerable. The development of both oilseed rape and pollen beetles is temperature-dependent, while temperature effects on pest abundances are yet unknown, which brings opportunities and dangers to oilseed rape cropping under increased temperatures. We obtained measures of winter oilseed rape (flowering time, seed yield) and two of its major pests (pollen beetle, stem weevils) for the first time along both land-use and temperature gradients. Infestation with stem weevils was not influenced by any temperature or land-use aspect considered, and natural pest regulation of pollen beetles in terms of parasitism rates of pollen beetle larvae was low (< 30\%), except on three out of 29 plots. Nonetheless, we could identify conditions favouring low pollen beetle abundances per plant and high seed yields. Low pollen beetle densities were favoured by a constant oilseed rape area relative to the preceding year (5-km scale), whereas a strong reduction in area (> 40\%) caused high pest densities (concentration effect). This occurred more frequently in warmer regions, due to drought around sowing, which contributed to increased pollen beetle numbers in those regions. Yet, in warmer regions, oilseed rape flowered early, which possibly led to partial escape from pollen beetle infestation in the most vulnerable bud stage. This is also suggested by higher seed yields of early flowering oilseed rape fields, but not per se at higher temperatures. Thus, early flowering (e.g. cultivar selection) and the interannual coordination of oilseed rape area offer opportunities for environmental-friendly pollen beetle management. Chapter 5 - General discussion Anthropogenic land-use and climate change are major threats to biodiversity, and consequently to ecosystem functions, although I could show that ecosystem functions such as herbivory and predation barely responded to temperature along a spatial gradient at present time. Yet, it is important to keep several points in mind: (i) The high rate of climate warming likely reduces the time that species will have to adapt to temperature in the future; (ii) Beyond mean temperatures, many aspects of climate will change; (iii) The compensation of biodiversity loss through functional redundancy in arthropod communities may be depleted at some point; (iv) Measures of ecosystem functions are limited by methodological filters, so that changes may be captured incompletely. Although much uncertainty of the effects of climate and land-use change on ecosystem functions remains, actions to halt biodiversity loss and to interfere with natural processes in an environmentally friendly way, e.g. reduction of herbivory on crops, are urgently needed. With this thesis, I contribute options to the environment-friendly regulation of herbivory, which are at least to some extent climate resilient, and at the same time make a contribution to halt biodiversity loss. Yet, more research and a transformation process is needed to make human action more sustainable. In terms of crop protection, this means that the most common method of treating pests with fast-acting pesticides is not necessarily the most sustainable. To realize sustainable strategies, collective efforts will be needed targeted at crop damage prevention through reducing pest populations and densities in the medium to long term. The sooner we transform human action from environmentally damaging to biodiversity promoting, the higher is our insurance asset that secures human well-being under a changing climate.},
  subject      = {{\"O}kologie},
  language  = {en}
}
@phdthesis{Duque2022,
  author    = {Duque, Laura Maria Ribeiro},
  title     = {Effects of ozone on plants and plant-insect interactions},
  doi       = {10.25972/OPUS-27798},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-277983},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Anthropogenic activities are causing air pollution. Amongst air pollutants, tropospheric ozone is a major threat to human health and ecosystem functioning. In this dissertation, I present three studies that aimed at increasing our knowledge on how plant exposure to ozone affects its reproduction and its interactions with insect herbivores and pollinators. For this purpose, a new fumigation system was built and placed in a greenhouse. The annual plant Sinapis arvensis (wild mustard) was used as the model plant. Plants were exposed to either 0 ppb (control) or 120 ppb of ozone, for variable amounts of time and at different points of their life cycle. After fumigation, plants were exposed to herbivores or pollinators in the greenhouse, or to both groups of insects in the field. My research shows that ozone affected reproductive performance differently, depending on the timing of exposure: plants exposed at earlier ages had their reproductive fitness increased, while plants exposed later in their life cycle showed a tendency for reduced reproductive fitness. Plant phenology was a key factor influencing reproductive fitness: ozone accelerated flowering and increased the number of flowers produced by plants exposed at early ages, while plants exposed to ozone at later ages tended to have fewer flowers. On the other hand, the ozone-mediated changes in plant-insect interactions had little impact on plant reproductive success. The strongest effect of ozone on plant-pollinator interactions was the change in the number of flower visits received per plant, which was strongly linked to the number of open flowers. This means that, as a rule, exposure of plants to ozone early in the life cycle resulted in a higher number of pollinator visits, while exposure later in the life cycle resulted in fewer flower visits by potential pollinators. An exception was observed: the higher number of visits performed by large syrphid flies to young ozone-exposed plants than to the respective control plants went beyond the increase in the number of open flowers in those plants. Also, honeybees spent more time per flower in plants exposed to ozone than on control plants, while other pollinators spent similar amounts of time in control and ozone-exposed plants. This guild-dependent preference for ozone-exposed plants may be due to species-specific preferences related to changes in the quality and quantity of floral rewards. In the field, ozone-exposed plants showed only a tendency for increased colonization by sucking herbivores and slightly more damage by chewing herbivores than control plants. On the other hand, in the greenhouse experiment, Pieris brassicae butterflies preferred control plants over ozone-exposed plants as oviposition sites. Eggs laid on ozone-exposed plants took longer to hatch, but the chances of survival were higher. Caterpillars performed better in control plants than in ozone-exposed plants, particularly when the temperature was high. Most of the described effects were dependent on the duration and timing of the ozone exposure and the observed temperature, with the strongest effects being observed for longer exposures and higher temperatures. Furthermore, the timing of exposure altered the direction of the effects. The expected climate change provides ideal conditions for further increases in tropospheric ozone concentrations, therefore for stronger effects on plants and plant-insect interactions. Acceleration of flowering caused by plant exposure to ozone may put plant-pollinator interactions at risk by promoting desynchronization between plant and pollinator activities. Reduced performance of caterpillars feeding on ozone-exposed plants may weaken herbivore populations. On the other hand, the increased plant reproduction that results from exposing young plants to ozone may be a source of good news in the field of horticulture, when similar results would be achieved in high-value crops. However, plant response to ozone is highly species-specific. In fact, Sinapis arvensis is considered a weed and the advantage conferred by ozone exposure may increase its competitiveness, with negative consequences for crops or plant communities in general. Overall, plant exposure to ozone might constitute a threat for the balance of natural and agro-ecosystems.},
  subject      = {Plant},
  language  = {en}
}