Browsing by Subject "Biological Sciences"

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Long-term trends in yield variance of temperate managed grassland
(2023) Macholdt, Janna; Hadasch, Steffen; Macdonald, Andrew; Perryman, Sarah; Piepho, Hans-Peter; Scott, Tony; Styczen, Merete Elisabeth; Storkey, Jonathan; Macholdt, Janna; Professorship of Agronomy, Institute of Agriculture and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany; Hadasch, Steffen; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Macdonald, Andrew; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK; Perryman, Sarah; Computational and Analytical Sciences Department, Rothamsted Research, Harpenden, UK; Piepho, Hans-Peter; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Scott, Tony; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK; Styczen, Merete Elisabeth; Section of Environmental Chemistry and Physics, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark; Storkey, Jonathan; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK
The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965–2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield variance—with a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems.
Parasites, depredators, and limited resources as potential drivers of winter mortality of feral honeybee colonies in German forests
(2023) Kohl, Patrick L.; Rutschmann, Benjamin; Sikora, Luis G.; Wimmer, Norbert; Zahner, Volker; D’Alvise, Paul; Hasselmann, Martin; Steffan-Dewenter, Ingolf; Kohl, Patrick L.; Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Würzburg, Germany; Rutschmann, Benjamin; Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Würzburg, Germany; Sikora, Luis G.; NaturKonzept, Pfullingen, Germany; Wimmer, Norbert; Bayerische Landesanstalt Für Wald Und Forstwirtschaft, Freising, Germany; Zahner, Volker; Forest Ecology and Management, University of Applied Sciences Weihenstephan-Triesdorf, Freising, Germany; D’Alvise, Paul; Institute for Medical Microbiology and Hygiene, University Hospital Tübingen, Tübingen, Germany; Hasselmann, Martin; Department of Livestock Population Genomics, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany; Steffan-Dewenter, Ingolf; Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Würzburg, Germany
Wild honeybees ( Apis mellifera ) are considered extinct in most parts of Europe. The likely causes of their decline include increased parasite burden, lack of high-quality nesting sites and associated depredation pressure, and food scarcity. In Germany, feral honeybees still colonize managed forests, but their survival rate is too low to maintain viable populations. Based on colony observations collected during a monitoring study, data on parasite prevalence, experiments on nest depredation, and analyses of land cover maps, we explored whether parasite pressure, depredation or expected landscape-level food availability explain feral colony winter mortality. Considering the colony-level occurrence of 18 microparasites in the previous summer, colonies that died did not have a higher parasite burden than colonies that survived. Camera traps installed at cavity trees revealed that four woodpecker species, great tits, and pine martens act as nest depredators. In a depredator exclusion experiment, the winter survival rate of colonies in cavities with protected entrances was 50% higher than that of colonies with unmanipulated entrances. Landscapes surrounding surviving colonies contained on average 6.4 percentage points more cropland than landscapes surrounding dying colonies, with cropland being known to disproportionately provide forage for bees in our study system. We conclude that the lack of spacious but well-protected nesting cavities and the shortage of food are currently more important than parasites in limiting populations of wild-living honeybees in German forests. Increasing the density and diversity of large tree cavities and promoting bee forage plants in forests will probably promote wild-living honeybees despite parasite pressure.