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Article Reference Octet Stream Sensitivity analysis of the dark spectrum fitting atmospheric correction for metre- and decametre-scale satellite imagery using autonomous hyperspectral radiometry
The performance of the dark spectrum fitting (DSF) atmospheric correction algorithm is evaluated using matchups between metre- and decametre-scale satellite imagery as processed with ACOLITE and measurements from autonomous PANTHYR hyperspectral radiometer systems deployed in the Adriatic and North Sea. Imagery from the operational land imager (OLI) on Landsat 8, the multispectral instrument (MSI) on Sentinel-2 A and B, and the PlanetScope CubeSat constellation was processed for both sites using a fixed atmospheric path reflectance in a small region of interest around the system&\#x2019;s deployment location, using a number of processing settings, including a new sky reflectance correction. The mean absolute relative differences (MARD) between in situ and satellite measured reflectances reach <20&\#x0025; in the Blue and 11&\#x0025; in the Green bands around 490 and 560 nm for the best performing configuration for MSI and OLI. Higher relative errors are found for the shortest Blue bands around 440 nm (30&\#x2013;100&\#x0025; MARD), and in the Red-Edge and near-infrared bands (35&\#x2013;100&\#x0025; MARD), largely influenced by the lower absolute data range in the observations. Root mean squared differences (RMSD) increase from 0.005 in the NIR to about 0.015&\#x2013;0.020 in the Blue band, consistent with increasing atmospheric path reflectance. Validation of the Red-Edge and NIR bands on Sentinel-2 is presented, as well as for the first time, the Panchromatic band (17&\#x2013;26&\#x0025; MARD) on Landsat 8, and the derived Orange contra-band (8&\#x2013;33&\#x0025; MARD for waters in the algorithm domain, and around 40&\#x2013;80&\#x0025; MARD overall). For Sentinel-2, excluding the SWIR bands from the DSF gave better performances, likely due to calibration issues of MSI at longer wavelengths. Excluding the SWIR on Landsat 8 gave good performance as well, indicating robustness of the DSF to the available band set. The DSF performance was found to be rather insensitive to (1) the wavelength spacing in the lookup tables used for the atmospheric correction, (2) the use of default or ancillary information on gas concentration and atmospheric pressure, and (3) the size of the ROI over which the path reflectance is estimated. The performance of the PlanetScope constellation is found to be similar to previously published results, with the standard DSF giving the best results in the visible bands in terms of MARD (24&\#x2013;40&\#x0025; overall, and 18&\#x2013;29&\#x0025; for the turbid site). The new sky reflectance correction gave mixed results, although it reduced the mean biases for certain configurations and improved results for the processing excluding the SWIR bands, giving lower RMSD and MARD especially at longer wavelengths (>600 nm). The results presented in this article should serve as guidelines for general use of ACOLITE and the DSF.
Located in Library / RBINS Staff Publications 2020
Article Reference Sex ratio bias caused by endosymbiont infection in the dwarf spider Oedothorax retusus
Located in Library / RBINS Staff Publications
Article Reference Short-term changes in the structure of ant assemblages in a Guinean savanna under differing fire regimes at Lamto Scientific Reserve, Côte d’Ivoire
To maintain savanna vegetation, mid-seasonal fire has been applied since 1961 in the Lamto Savanna (Côte d’Ivoire). However, this prescribed fire has not impeded tree encroachment during recent years, nor have its effects on insect assemblages been documented. Also the impact of tree intrusion on insect assemblages is poorly studied in savanna. To prevent tree density increasing, a change in fire regime might be a solution. In this study, we examined the effect of different fire regimes (early, mid-seasonal and late fires) on leaf-litter ant assemblages in order to suggest appropriate measures for preventing tree invasion without having an effect on insect communities. Sampling was implemented by combining pitfall trapping and leaf-litter sampling before and after three different fire regimes, early, mid-seasonal and late fires. While the ant species richness declined after the passage of early and mid-seasonal fires, significantly more species were found in the burnt savanna after the late fire. However, the losses or gains of species due to different fire regimes did not cause severe changes in the ant species composition. Of the functional groups identified, only the generalists and specialist predators were respectively strongly affected by the early and mid-seasonal fires, certainly due to micro-habitat modification. Based on the trends observed in the present study, we suggest sampling other invertebrate fauna in similar savanna plots to find out if other insect groups have similar reactions to the applied fire regimes.
Located in Library / RBINS Staff Publications 2018
Webpublished Reference Should local communities be encouraged to develop their own sustainable solutions, such as geothermal energy, to power generation?
Located in Library / RBINS Staff Publications
Inbook Reference Sint-Barbara - Sainte Barbe
Located in Library / RBINS Staff Publications 2022
Article Reference Site Fidelity of Formica rufa: Micro-Scaled and Persistent Despite Disturbance (Hymenoptera: Formicidae)
Long-term site fidelity or Ortstreue is an individual foraging strategy typical of ants exploiting stable and predictable food sources in space and time. Red wood ant workers (Formica s. str.) are central-place foragers feeding on honeydew secreted by stable aphid populations. In this field study, temporal site fidelity of Formica rufa honeydew tenders was investigated on a micro-scaled level for a period of time. Additionally, the effect of exchanging honeydew workers between two trees on site fidelity was examined. Site fidelity of the honeydew tenders was very high and they returned repeatedly to particular micro-sites (branches, set of leaves) on a tree. The transfer to a new feeding site apparently did not influence site fidelity as honeydew tenders mainly return to their initial tree. Small-scale site fidelity decreased with time and was not so rigid as larger-scale fidelity. We discuss how site fidelity on one hand and flexibility in foraging and recruiting on the other hand promote foraging efficiency of the colony.
Located in Library / RBINS Staff Publications
Article Reference Sixteen issid planthopper species in one day in Dong Son-Ky Thuong Nature Reserve in North Vietnam: Eight new species, one new genus and additional new records (Hemiptera: Fulgoromorpha: Issidae)
Located in Library / RBINS Staff Publications 2023
Article Reference Small suspension-feeding amphipods play a pivotal role in carbon dynamics around offshore man-made structures
The establishment of artificial hard substrates (i.e. offshore wind farms and oil and gas platforms) on marine soft sediments increases the available habitat for invertebrate communities that would otherwise be restricted to natural hard bottoms. Suspension feeding invertebrates clear a significant amount of particles from the water column and release organic matter in the form of feces, influencing the basis of marine food webs and affecting surrounding environments. Artificial structures in the southern North Sea are dominated by a suspension-feeding crustacean in terms of abundance and sometimes even biomass: the amphipod Jassa herdmani. Animal densities of this tiny biofouler are known to exceed 1 million individuals per m2. Despite their small body sizes and their simple filter apparatus, we hypothesized that J. herdmani is a highly effective suspension feeder with a significant impact on neighboring communities due to its high abundances. In a feeding experiment, individuals of J. herdmani were provided with either an algal or an animal diet under two different temperature regimes. Clearance rates and fecal-pellet carbon (FPC) were measured. The results revealed high clearance rates and subsequent FPC, which were more pronounced at the higher temperature. Furthermore, clearance rates and FPC varied insignificantly with different food items. We further used the current findings for upscaling calculations to the total number of offshore windfarms and oil and gas platforms in the southern North Sea. Our calculations indicated that J. herdmani alone clears 0.33 – 4.71 km3 water per year in the southern North Sea. At the same time, these amphipods release 255 – 547 tons of carbon per year by means of defecation, thus enriching the surrounding soft sediments with organic matter. Our study highlights that tiny amphipods can mediate indirect effects of man- made structures in the North Sea, which could have a profound impact on pelagic and benthic habitats.
Located in Library / RBINS Staff Publications 2022
Article Reference Sogana cysana sp. nov., a new tropiduchid planthopper from Chu Yang Sin National Park in Vietnam and key to Vietnamese species of the genus (Hemiptera: Fulgoromorpha: Tropiduchidae)
Located in Library / RBINS Staff Publications 2020
Article Reference Soil-litter arthropod communities under pasture land use in southern Rwanda
Land use change caused by human activities is the main driver of biodiversity loss and changes in ecosystem functioning. However, less is known about how the conversion of a natural to pasture land favour the biological diversity of soil-litter arthropods to advance effective conservation plans and management systems. To fill the gap, this study focussed on soil-litter arthropod communities under a pasture land use in southern Rwanda. Data have been collected using pitfall traps and hand collection between April and June 2021. Sampled specimens of soil-litter arthropods have been identified to order and family levels by using dichotomous keys. Further, the species name was given when the identification key was available, while the morphological description was provided in absence of the identification keys. Results indicated a total of 3013 individuals of soil-litter arthropods grouped into 3 classes, 13 orders, 46 families and 87 morpho-species. Coleoptera showed a high number of families, while higher abundance and the number of morpho-species were found for ants (Hymenoptera: Formicidae). Higher abundance of sampled soil-litter arthropods is a sign that the studied area offers suitable habitat for soil-litter arthropods. However, less abundance found for some groups of soil-litter arthropods might be influenced by the used sampling techniques which were not appropriate for them. We recommend surveys using multiple sampling techniques to maximize chances of capturing a wide range of soil-litter arthropods.
Located in Library / RBINS Staff Publications 2022