Browsing by Author "Achilles, Sebastian"

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    A Case Study on Fog/Low Stratus Occurrence at Las Lomitas, Atacama Desert (Chile) as a Water Source for Biological Soil Crusts
    (2018) Lehnert, Lukas W.; Thies, Boris; Trachte, Katja; Achilles, Sebastian; Osses, Pablo; Baumann, Karen; Schmidt, Jakob; Samolov, Elena; Jung, Patrick; Leinweber, Peter; Karsten, Ulf; Buedel, Burkhard; Bendix, Joerg
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    Area-Wide Prediction of Vertebrate and Invertebrate Hole Density and Depth across a Climate Gradient in Chile Based on UAV and Machine Learning
    (MDPI, 2021) Grigusova, Paulina; Larsen, Annegret; Achilles, Sebastian; Klug, Alexander; Fischer, Robin; Kraus, Diana; Uebernickel, Kirstin; Paulino, Leandro; Pliscoff, Patricio; Brandl, Roland; Farwig, Nina; Bendix, Joerg
    Burrowing animals are important ecosystem engineers affecting soil properties, as their burrowing activity leads to the redistribution of nutrients and soil carbon sequestration. The magnitude of these effects depends on the spatial density and depth of such burrows, but a method to derive this type of spatially explicit data is still lacking. In this study, we test the potential of using consumer-oriented UAV RGB imagery to determine the density and depth of holes created by burrowing animals at four study sites along a climate gradient in Chile, by combining UAV data with empirical field plot observations and machine learning techniques. To enhance the limited spectral information in RGB imagery, we derived spatial layers representing vegetation type and height and used landscape textures and diversity to predict hole parameters. Across-site models for hole density generally performed better than those for depth, where the best-performing model was for the invertebrate hole density (R-2 = 0.62). The best models at individual study sites were obtained for hole density in the arid climate zone (R-2 = 0.75 and 0.68 for invertebrates and vertebrates, respectively). Hole depth models only showed good to fair performance. Regarding predictor importance, the models heavily relied on vegetation height, texture metrics, and diversity indices.
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    Biological soil crusts along a climatic gradient in Chile: Richness and imprints of phototrophic microorganisms in phosphorus biogeochemical cycling
    (2018) Baumann, Karen; Jung, Patrick; Samolov, Elena; Lehnert, Lukas W.; Buedel, Burkhard; Karsten, Ulf; Bendix, Joerg; Achilles, Sebastian; Schermer, Michael; Matus, Francisco; Oses, Romulo; Osses, Pablo; Morshedizad, Mohsen; Oehlschlaeger, Claudia
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    Higher sediment redistribution rates related to burrowing animals than previously assumed as revealed by time-of-flight-based monitoring
    (Copernicus Publications, 2022) Grigusova, Paulina; Larsen, Annegret; Achilles, Sebastian; Brandl, Roland; Río López, Camilo Del; Farwig, Nina; Kraus, Diana; Paulino, Leandro; Pliscoff Varas, Patricio Andrés; Übernickel, Kirstin; Bendix, Jörg
    Burrowing animals influence surface microtopography and hillslope sediment redistribution, but changes often remain undetected due to a lack of automated high-resolution field monitoring techniques. In this study, we present a new approach to quantify microtopographic variations and surface changes caused by burrowing animals and rainfall-driven erosional processes applied to remote field plots in arid and Mediterranean climate regions in Chile. We compared the mass balance of redistributed sediment between burrow and burrow-embedded area, quantified the cumulative sediment redistribution caused by animals and rainfall, and upscaled the results to a hillslope scale. The newly developed instrument, a time-of-flight camera, showed a very good detection accuracy. The animal-caused cumulative sediment excavation was 14.6 cm3 cm-2 yr-1 in the Mediterranean climate zone and 16.4 cm3 cm-2 yr-1 in the arid climate zone. The rainfall-related cumulative sediment erosion within burrows was higher (10.4 cm3 cm-2 yr-1) in the Mediterranean climate zone than the arid climate zone (1.4 cm3 cm-2 yr-1). Daily sediment redistribution during rainfall within burrow areas was up to 350 %(40 %) higher in the Mediterranean (arid) zone compared to burrow-embedded areas and much higher than previously reported in studies that were not based on continuous microtopographic monitoring. A total of 38 % of the sediment eroding from burrows accumulated within the burrow entrance, while 62 % was incorporated into hillslope sediment flux, which exceeds previous estimations 2-fold. On average, animals burrowed between 1.2-2.3 times a month, and the burrowing intensity increased after rainfall. This revealed a newly detected feedback mechanism between rainfall, erosion, and animal burrowing activity, likely leading to an underestimation of animal-triggered hillslope sediment flux in wetter climates. Our findings hence show that the rate of sediment redistribution due to animal burrowing is dependent on climate and that animal burrowing plays a larger than previously expected role in hillslope sediment redistribution. Subsequently, animal burrowing activity should be incorporated into soil erosion and landscape evolution models that rely on soil processes but do not yet include animal-induced surface processes on microtopographical scales in their algorithms.