deadtrees.earth — An open-access and interactive database for centimeter-scale aerial imagery to uncover global tree mortality dynamics

Excessive tree mortality is a global concern and remains poorly understood as it is a complex phenomenon. We lack global and temporally continuous coverage on tree mortality data. Ground-based observations on tree mortality, e.g., derived from national inventories, are very sparse, and may not be standardized or spatially explicit. Earth observation data, combined with supervised machine learning, offer a promising approach to map overstory tree mortality in a consistent manner over space and time. However, global-scale machine learning requires broad training data covering a wide range of environmental settings and forest types. Low altitude observation platforms (e.g., drones or airplanes) provide a cost-effective source of training data by capturing high-resolution orthophotos of overstory tree mortality events at centimeter-scale resolution. Here, we introduce deadtrees.earth, an open-access platform hosting more than two thousand centimeter-resolution orthophotos, covering more than 1,000,000 ha, of which more than 58,000 ha are manually annotated with live/dead tree classifications. This community-sourced and rigorously curated dataset can serve as a comprehensive reference dataset to uncover tree mortality patterns from local to global scales using space-based Earth observation data and machine learning models. This will provide the basis to attribute tree mortality patterns to environmental changes or project tree mortality dynamics to the future. The open nature of deadtrees.earth, together with its curation of high-quality, spatially representative, and ecologically diverse data will continuously increase our capacity to uncover and understand tree mortality dynamics

Lake-Related Cloud Dynamics on the Tibetan Plateau: Spatial Patterns and Interannual Variability

Abstract The scarcity of meteorological observations has hitherto prevented spatially comprehensive and complete assessments on regional and local-scale atmospheric processes such as breeze systems on the Tibetan Plateau (TiP). Because of the high abundance of lakes, the steep topography, and the intense insolation of the TiP, lake breeze and land breeze systems might, however, contribute substantially to the local climatic and hydrological variability. The presented study aims at unveiling the influence of the lake effect over the whole TiP by using a novel high-mountain satellite cloud product, based on Meteosat Indian Ocean Data Coverage (IODC) data from 1999 to 2012, focusing on 70 lake systems larger than 72 km2. Of particular interest are the spatial and interannual variability of lake-related cloud dynamics during boreal summer and autumn. For both seasons, a significant effect of lakes on cloudiness is shown during the early morning. Its mean strength is mainly determined by each basin’s temperature difference between lake and surroundings. For boreal summer the large-scale influences of tropical and extratropical circulation pattern on the interannual variability of the lake effect are also investigated. The results show that the Arctic and North Atlantic Oscillations (AO and NAO) inhibit convective activity above lakes in the northern and central-eastern domain. A positive polarity of the Southern Oscillation index (SOI), in contrast, is in phase with enhanced convective activity. The variability of the Indian summer monsoon circulation does not affect cloud dynamics at more than two locations. Case studies are employed to illustrate interactions between cloud activity and the SOI and NAO. For this purpose satellite data are combined with the modeled 10 km × 10 km High Asia Refined Analysis dataset on a daily basis.</jats:p

Data_files_-_ECOG03137_Pinkert_et_al_2017

Here we provide the environmental, distributional and trait data used in Pinkert et al. 2017 (ECOG-03137), at both the species-level (for habitat preferences, i.e. lentic/lotic) and aggregated at the assemblage-level. We also provide the breakpoints from segmented regressions of the relationship between latitude and four different measures of the diversity of European dragonfly assemblages (species richness, corrected weighted endemism, the residuals of total taxonomic distinctiveness against species richness and standardized effect sizes of mean pairwise distances). For further information and a more detailed description see the manuscript or contact the first author via email ([email protected])

Data from: Evolutionary processes, dispersal limitation and climatic history shape current diversity patterns of European dragonflies

We investigated the effects of contemporary and historical factors on the spatial variation of European dragonfly diversity. Specifically, we tested to what extent patterns of endemism and phylogenetic diversity of European dragonfly assemblages are structured by (i) phylogenetic conservatism of thermal adaptations and (ii) differences in the ability of post-glacial recolonization by species adapted to running waters (lotic) and still waters (lentic). We investigated patterns of dragonfly diversity using digital distribution maps and a phylogeny of 122 European dragonfly species, which we constructed by combining taxonomic and molecular data. We calculated total taxonomic distinctiveness and mean pairwise distances across 4,192 50 km × 50 km equal-area grid cells as measures of phylogenetic diversity. We compared species richness with corrected weighted endemism and standardized effect sizes of mean pairwise distances or residuals of total taxonomic distinctiveness to identify areas with higher or lower phylogenetic diversity than expected by chance. Broken-line regression was used to detect breakpoints in diversity–latitude relationships. Dragonfly species richness peaked in central Europe, whereas endemism and phylogenetic diversity decreased from warm areas in the south-west to cold areas in the north-east and with an increasing proportion of lentic species. Except for species richness, all measures of diversity were consistently higher in formerly unglaciated areas south of the 0°C isotherm during the Last Glacial Maximum than in formerly glaciated areas. These results indicate that the distributions of dragonfly species in Europe were shaped by both phylogenetic conservatism of thermal adaptations and differences between lentic and lotic species in the ability of post-glacial recolonization/dispersal in concert with the climatic history of the continent. The complex diversity patterns of European dragonflies provide an example of how integrating climatic and evolutionary history with contemporary ecological data can improve our understanding of the processes driving the geographical variation of biological diversity