Feature Relevance Assessment Of Multispectral Airborne Lidar Data For Tree Species Classification

Abstract. The presented experiment investigates the potential of Multispectral Laser Scanning (MLS) point clouds for single tree species classification. The basic idea is to simulate a MLS sensor by combining two different Lidar sensors providing three different wavelngthes. The available data were acquired in the summer 2016 at the same date in a leaf-on condition with an average point density of 37 points/m2. For the purpose of classification, we segmented the combined 3D point clouds consisiting of three different spectral channels into 3D clusters using Normalized Cut segmentation approach. Then, we extracted four group of features from the 3D point cloud space. Once a varity of features has been extracted, we applied forward stepwise feature selection in order to reduce the number of irrelevant or redundant features. For the classification, we used multinomial logestic regression with L1 regularization. Our study is conducted using 586 ground measured single trees from 20 sample plots in the Bavarian Forest National Park, in Germany. Due to lack of reference data for some rare species, we focused on four classes of species. The results show an improvement between 4–10 pp for the tree species classification by using MLS data in comparison to a single wavelength based approach. A cross validated (15-fold) accuracy of 0.75 can be achieved when all feature sets from three different spectral channels are used. Our results cleary indicates that the use of MLS point clouds has great potential to improve detailed forest species mapping. </jats:p

Secular changes in the quiescence of WZ Sge: the development of a cavity in the inner disk

We find a dimming during optical quiescence of the cataclysmic variable WZ Sge by about half a magnitude between superoutbursts. We connect the dimming with the development of a cavity in the inner part of the accretion disk. We suggest that, when the cavity is big enough, accretion of material is governed by the magnetic field of the white dwarf and pulsations from the weakly magnetic white dwarf appear. The time scale of forming the cavity is about a decade, and it persists throughout the whole quiescent phase. Such a cavity can be accommodated well by the proposed magnetic propeller model for WZ Sge, where during quiescence mass is being expelled by the magnetic white dwarf from the inner regions of the accretion disk to larger radii.Comment: 10 pages, 4 figures, accepted for publication in Astronomy and Astrophysics; following referee report, many textual changes, figures improved, more historic data added, conclusions unchange

An examination of in-season external training load in semi-professional soccer players: considerations of one and two match weekly microcycles

The aim of the present study was to firstly, quantify the external training load (TL) of semi-professional soccer players during an annual season and secondly, to examine the influence of one (1MW) and two (2MW) match weekly microcycles. Data were collected from 24 semi-professional outfield soccer players during the 2018-2019 annual season using micro-electromechanical system (MEMS) devices for the following variables: Training duration (min), total distance (TD), Player Load (PL), high speed running (HSR) distance (5.5-7.0 m/s), and acceleration (ACC) efforts (>2 m/s2). Training sessions were defined as days before match day (i.e. MD minus), with match weeks broken down as either 1MW or 2MW. Data revealed higher TD, PL, and HSR distance on MD and MD-5 when compared to all other MD codes. MD-4 displayed significantly higher values compared to MD-1 (mean differences (Mdiff): TD: 785 ± 158 m; PL: 29 ± 9 au; HSR: 192 ± 63 m; ACC: 15 ± 3 #) and MD-2 (Mdiff: TD: 279 ± 137 m; HSR: 127 ± 54 m). During 2MW scenarios, both TD (Mdiff: 685 ± 328 m) and PL (Mdiff: 33 ± 14 au) were higher on MD-1 when compared to 1MW. However, lower values were observed for duration and HSR on MD-2 and MD-4 during 2MW compared to 1MW scenarios. These data suggest that there appears to be a progressive reduction in TD, PL, HSR and ACC leading into competitive matches based on MD- analysis. However, some variability exists in TL prescription as a result of different MW scenarios (i.e. 1MW vs. 2MW)

Forest top canopy bacterial communities are influenced by elevation and host tree traits

Background: The phyllosphere microbiome is crucial for plant health and ecosystem functioning. While host species play a determining role in shaping the phyllosphere microbiome, host trees of the same species that are subjected to different environmental conditions can still exhibit large degrees of variation in their microbiome diversity and composition. Whether these intra-specific variations in phyllosphere microbiome diversity and composition can be observed over the broader expanse of forest landscapes remains unclear. In this study, we aim to assess the variation in the top canopy phyllosphere bacterial communities between and within host tree species in the temperate European forests, focusing on Fagus sylvatica (European beech) and Picea abies (Norway spruce).Results: We profiled the bacterial diversity, composition, driving factors, and discriminant taxa in the top canopy phyllosphere of 211 trees in two temperate forests, Veluwe National Parks, the Netherlands and Bavarian Forest National Park, Germany. We found the bacterial communities were primarily shaped by host species, and large variation existed within beech and spruce. While we showed that there was a core microbiome in all tree species examined, community composition varied with elevation, tree diameter at breast height, and leaf-specific traits (e.g., chlorophyll and P content). These driving factors of bacterial community composition also correlated with the relative abundance of specific bacterial families.Conclusions: While our results underscored the importance of host species, we demonstrated a substantial range of variation in phyllosphere bacterial diversity and composition within a host species. Drivers of these variations have implications at both the individual host tree level, where the bacterial communities differed based on tree traits, and at the broader forest landscape level, where drivers like certain highly plastic leaf traits can potentially link forest canopy bacterial community variations to forest ecosystem processes. We eventually showed close associations between forest canopy phyllosphere bacterial communities and host trees exist, and the consistent patterns emerging from these associations are critical for host plant functioning

Witnessing and re-enacting in Cambodia: reflection on shifting testimonies

Thirty years after the collapse of the Khmer Rouge regime (1975-1979) how do Cambodians cope with the traumatic legacy of Pol Pot's reign of terror? What forms does witnessing take on in post-socialist and transitional Cambodia as senior Khmer Rouge leaders await prosecution at the Cambodian Tribunal? The paper examines aspects of witnessing in today's Cambodia, expressing each in its own way the idea of the 'shifting' of witnessing: the transformation of testimonies due to time passing and contrasted systems of justice through a comparison of testimonies in the trial of the 'Pol Pot/Ieng Sary clique' (1979) and the current Cambodian Tribunal; the complex forms of witnessing emerging from participatory projects developed with Western authors in 'We want (u) to know' (documentary movie made by an international film crew with the inhabitants of the village of Thnol Lok in 2009) and 'Breaking the silence' (theatre play realised by the Dutch dramaturge Annemarie Prins that premiered in Phnom Penh in 2009 and toured Cambodia in the following years); the relationship between documentary and legal forms of witnessing through the example of Vann Nath, a survivor of S-21/Tuol Sleng, the prison where the Khmer Rouge tortured and killed thousands of their fellow countrymen. The paper analyses the difficulty Western organisers of participatory projects experienced in applying the hybrid model of transitional justice to sociocultural contexts of witnessing. Nevertheless it points out their contribution to processes of 'recognition beyond recognition' in which cultural differences in coming to terms with historical trauma are expressed and recorded

Selection of HyspIRI optimal band positions for the earth compositional mapping using HyTES data

The National Aeronautics and Space Administration (NASA) has proposed the launch of a new space-borne sensor called HyspIRI (Hyperspectral and Infrared Imager) which will cover the spectral range from 0.4–12 μm. Two instruments will be mounted on HyspIRI platform: 1) a hyperspectral instrument which can sense earth surface between 0.4 and 2.5 μm at 10 nm intervals and 2) a multispectral infrared sensor will acquire images between 3 and 12 μm in eight spectral bands (one in Mid infrared (MIR) and seven in Thermal Infrared (TIR)). The TIR spectral wavebands will be positioned based on their importance in various applications. This study aimed to identify HyspIRI optimal TIR wavebands position for earth compositional mapping. A Genetic Algorithm coupled with the Spectral Angle Mapper (GA-SAM) was used as a spectral bands selector. High dimensional HyTES (Hyperspectral Thermal Emission Spectrometer) emissivity spectra comprised of 202 spectral bands of Cuprite and Death Valley regions were used to select meaningful subsets of bands for earth compositional mapping. The GA-SAM was trained for fifteen mineral classes and the algorithms were run iteratively 50 times. High calibration (> 95%) and validation (> 90%) accuracies were achieved with a limited number (seven) of spectral bands selected by GA-SAM. The knowledge of important band positions will help the scientists of the HyspIRI group to place spectral bands in regions where accuracies of earth compositional mapping can be enhanced

Bioarchaeological and Climatological Evidence for the Fate of Norse Farmers in Medieval Greenland

Greenland, far north land of the Atlantic, has often been beyond the limit of European farming settlement. One of its Norse settlements, colonized just before AD 1000, is — astonishingly — not even at the southern tip, but a way up the west coast, the \u27Western Settlement\u27. Environmental studies show why its occupation came to an end within five centuries, leaving Greenland once more a place of Arctic-adapted hunters