Papers by Rebecca Retzlaff
eLife
A major limitation of current reports on insect declines is the lack of standardized, long-term, ... more A major limitation of current reports on insect declines is the lack of standardized, long-term, and taxonomically broad time series. Here, we demonstrate the utility of environmental DNA from archived leaf material to characterize plant-associated arthropod communities. We base our work on several multi-decadal leaf time series from tree canopies in four land use types, which were sampled as part of a long-term environmental monitoring program across Germany. Using these highly standardized and well-preserved samples, we analyze temporal changes in communities of several thousand arthropod species belonging to 23 orders using metabarcoding and quantitative PCR. Our data do not support widespread declines of α-diversity or genetic variation within sites. Instead, we find a gradual community turnover, which results in temporal and spatial biotic homogenization, across all land use types and all arthropod orders. Our results suggest that insect decline is more complex than mere α-dive...
Remote Sensing, 2021
Hyperspectral cameras onboard unmanned aerial vehicles (UAVs) have recently emerged for monitorin... more Hyperspectral cameras onboard unmanned aerial vehicles (UAVs) have recently emerged for monitoring crop traits at the sub-field scale. Different physical, statistical, and hybrid methods for crop trait retrieval have been developed. However, spectra collected from UAVs can be confounded by various issues, including illumination variation throughout the crop growing season, the effect of which on the retrieval performance is not well understood at present. In this study, four retrieval methods are compared, in terms of retrieving the leaf area index (LAI), fractional vegetation cover (fCover), and canopy chlorophyll content (CCC) of potato plants over an agricultural field for six dates during the growing season. We analyzed: (1) The standard look-up table method (LUTstd), (2) an improved (regularized) LUT method that involves variable correlation (LUTreg), (3) hybrid methods, and (4) random forest regression without (RF) and with (RFexp) the exposure time as an additional explanator...
Die Arbeit untersucht das Potential kleiner unbemannter Luftfahrtsysteme (UAS) in Landwirtschaft ... more Die Arbeit untersucht das Potential kleiner unbemannter Luftfahrtsysteme (UAS) in Landwirtschaft und Archäologie. Der Begriff UAS beinhaltet dabei: Fluggerät, Antriebsmechanismus, Sensorik, Bodenstation, Kommunikationsmittel zwischen Bodenstation und Fluggerät und weiteres Equipment. Aufgrund ihrer Flexibilität, fanden UAS seit der Jahrtausendwende eine blühende Entwicklung. Um die wachsende Weltbevölkerung zu ernähren, muss die landwirtschaftliche Produktion sensibel und nachhaltig intensiviert werden, um Nahrungssicherheit für alle zu gewährleisten und weitere Boden- und Landdegradation zu vermeiden. Präzisionslandwirtschaft umfasst technologische Verbesserungen hin zur effizienteren und weniger schädlichen landwirtschaftlichen Praxis. Hierbei ist die Verfügung über zeitnahe, leicht zugängliche hoch aufgelöste räumliche Daten eine Voraussetzung für die Nahrungsmittelproduktion. UAS schließen hier die Lücke zwischen Bodendaten und teuren bemannten Luftfahrtsysteme und selteneren Sa...
PACS. 89.75.Fb – Structures and organization in complex systems. Abstract. – This paper focuses o... more PACS. 89.75.Fb – Structures and organization in complex systems. Abstract. – This paper focuses on the statistical properties of wild-land fires and, in particular, investigates if spread dynamics relates to simple invasion model. The fractal dimension and lacunarity of three fire scars classified from satellite imagery are analysed. Results indicate that the burned clusters behave similarly to percolation clusters on boundaries and look more dense in their core. We show that Dynamical Percolation reproduces this behaviour and can help to describe the fire evolution. By mapping fire dynamics onto the percolation models the strategies for fire control might be improved. In recent times the introduction of satellite imaging facilitated the coarse-scale analysis of wildfires [1]. Being inspired by the self-similar aspect of the fire scars, we want here to provide an explanation for this lack of characteristic length scale. We want to link wildfires spreading with the evolution of diffu...
Handbook of Real-Time Computing, 2020
In this chapter, we introduce the vision of the H2020 project "Precision Farming of Hazelnut Orch... more In this chapter, we introduce the vision of the H2020 project "Precision Farming of Hazelnut Orchards" (PANTHEON), which is to develop the agricultural equivalent of an industrial Supervisory Control And Data Acquisition (SCADA) system to be used for precision farming of orchards. PANTHEONs objective is to design an integrated system where a relatively limited number of heterogeneous unmanned robotic components (including terrestrial and aerial robots) move within the orchard to collect data and perform typical farming operations. In addition, an Internet-of-Things (IoT) agrometeorological solar-powered network is deployed to continuously monitor the environmental conditions of the orchard. The information so collected is then stored in a central operative unit that integrates the data to perform automatic feedback actions (e.g. to regulate the irrigation system) and to support the decisions of the agronomists and farmers in charge of the orchard. The proposed SCADA system will acquire information at the resolution of the individual plant, to drastically increase, compared to current best-practice, the detection of
Remote Sensing, 2019
For grape canopy pixels captured by an unmanned aerial vehicle (UAV) tilt-mounted RedEdge-M multi... more For grape canopy pixels captured by an unmanned aerial vehicle (UAV) tilt-mounted RedEdge-M multispectral sensor in a sloped vineyard, an in situ Walthall model can be established with purely image-based methods. This was derived from RedEdge-M directional reflectance and a vineyard 3D surface model generated from the same imagery. The model was used to correct the angular effects in the reflectance images to form normalized difference vegetation index (NDVI) orthomosaics of different view angles. The results showed that the effect could be corrected to a certain scope, but not completely. There are three drawbacks that might restrict a successful angular model construction and correction: (1) the observable micro shadow variation on the canopy enabled by the high resolution; (2) the complexity of vine canopies that causes an inconsistency between reflectance and canopy geometry, including effects such as micro shadows and near-infrared (NIR) additive effects; and (3) the resolution...
Sensors (Basel, Switzerland), 2017
This paper describes the concept of the hyperspectral Earth-observing thermal infrared (TIR) sate... more This paper describes the concept of the hyperspectral Earth-observing thermal infrared (TIR) satellite mission HiTeSEM (High-resolution Temperature and Spectral Emissivity Mapping). The scientific goal is to measure specific key variables from the biosphere, hydrosphere, pedosphere, and geosphere related to two global problems of significant societal relevance: food security and human health. The key variables comprise land and sea surface radiation temperature and emissivity, surface moisture, thermal inertia, evapotranspiration, soil minerals and grain size components, soil organic carbon, plant physiological variables, and heat fluxes. The retrieval of this information requires a TIR imaging system with adequate spatial and spectral resolutions and with day-night following observation capability. Another challenge is the monitoring of temporally high dynamic features like energy fluxes, which require adequate revisit time. The suggested solution is a sensor pointing concept to al...
International Journal of Remote Sensing, 2000
Euclidean analytical tools for quantifying the patchiness of complex natural patterns such as wil... more Euclidean analytical tools for quantifying the patchiness of complex natural patterns such as wildfires in general do not recognize that measures of object densities over the landscape vary as a function of the size of the spatial elements. Therefore, improved fractal statistical methods are needed to quantify patch structures in ways that capture the spatial variation of the analysed pattern in relation to scale. The aims of this research are to show first, that remotely sensed wildfire scars are fractal objects, and second, how the resulting fractal dimension can be interpreted to give insight into the dynamics of fire spread over the landscape.
E&G Quaternary Science Journal, 2019
The Roman vicus Belginum and the associated Celtic-Roman cemetery have been the subject of system... more The Roman vicus Belginum and the associated Celtic-Roman cemetery have been the subject of systematic archaeological research since 1954. Since 2004, archaeological prospections have been carried out in and around Belginum. Participants included students from the universities of Leipzig, Trier, and Munich as part of study-accompanying field work. This paper deals with the prospections of 2004 and 2016, when nearly 2 ha of land south of the federal road B327 (Hunsrückhöhenstraße) were surveyed. The study area is located on a NW-to-SErunning hillside. All non-local objects present on the surface were collected and three-dimensionally recorded. Previously in 2013, the area was geomagnetically prospected by Posselt & Zickgraf (Marburg). Both surveys revealed a hitherto unknown extent of the vicus about 200 m to the southwest. The findings date back to the late first to third centuries common era. All finds (ceramic, bricks, roof slate, glass, and metal) were recorded and analysed in a QGIS and ArcGIS environment together with lidar scans, the geomagnetic data, and other geographical information. The overall distributions of bricks and pottery were studied in detail. The distribution of bricks is in particular connected to the individual plots, while the pottery is mainly concentrated in the backyards. Regarding surveys in other Roman vici, the brick distribution could be a helpful indicator to identify plots, when no geophysical information is available. Kurzfassung: Der römische vicus Belginum und das zugehörige keltisch-römische Gräberfeld sind seit 1954 Gegenstand systematischer archäologischer Forschungen. Seit 2004 werden archäologische Prospektionen in und um Belginum durchgeführt. Beteiligt waren Studierende der Universitäten Leipzig, Trier und München im Rahmen von Lehrveranstaltungen.
Europhysics Letters (EPL), 2001
This paper focuses on the statistical properties of wild-land fires and, in particular, investiga... more This paper focuses on the statistical properties of wild-land fires and, in particular, investigates if spread dynamics relates to simple invasion model. The fractal dimension and lacunarity of three fire scars classified from satellite imagery are analysed. Results indicate that the burned clusters behave similarly to percolation clusters on boundaries and look denser in their core. We show that Dynamical Percolation reproduces this behaviour and can help to describe the fire evolution. By mapping fire dynamics onto the percolation models, the strategies for fire control might be improved.
Journal International des Sciences de la Vigne et du Vin
Aims: The present investigation in a Luxembourgish vineyard aimed at evaluating the potential of ... more Aims: The present investigation in a Luxembourgish vineyard aimed at evaluating the potential of multispectral, multi-angular UAS (unmanned aerial system) imagery to separate four soil management strategies, to predict physiological variables (chlorophyll, nitrogen, yield etc.) and to follow seasonal changes in grapevine physiology in relation to soil management. Methods and results: Multi-angular (nadir and 45° offnadir) multispectral imageries (530-900 nm) were taken in the years 2011 and 2012. Image grey values and reflectance-derived vegetation indices were computed and canopy and vigour properties were monitored in the field. All four soil management strategies could be significantly discriminated (box-plots, linear discriminant analysis) and vegetation properties estimated (linear regression) in 2011. For 2012, global models predicted chlorophyll contents and nitrogen balance index values with a R²cv of 0.65 and 0.76, respectively. Conclusions: Soil management strategies stron...
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Papers by Rebecca Retzlaff