Bavarian Forest National Park Research Articles

Remote Sensing of Forests in Bavaria: A Review

In recent decades, climatic pressures have altered the forested landscape of Bavaria. Widespread loss of trees has unevenly impacted the entire state, of which 37% is covered by forests (5% more than the national average). In 2018 and 2019—due in large part to drought and subsequent insect infestations—more tree-covered areas were lost in Bavaria than in any other German state. Moreover, the annual crown condition survey of Bavaria has revealed a decreasing trend in tree vitality since 1998. We conducted a systematic literature review regarding the remote sensing of forests in Bavaria. In total, 146 scientific articles were published between 2008 and 2023. While 88 studies took place in the Bavarian Forest National Park, only five publications covered the whole of Bavaria. Outside of the national park, the remaining 2.5 million hectares of forest in Bavaria are understudied. The most commonly studied topics were related to bark beetle infestations (24 papers); however, few papers focused on the drivers of infestations. The majority of studies utilized airborne data, while publications utilizing spaceborne data focused on multispectral; other data types were under-utilized- particularly thermal, lidar, and hyperspectral. We recommend future studies to both spatially broaden investigations to the state or national scale and to increase temporal data acquisitions together with contemporaneous in situ data. Especially in understudied topics regarding forest response to climate, catastrophic disturbances, regrowth and species composition, phenological timing, and in the sector of forest management. The utilization of remote sensing data in the forestry sector and the uptake of scientific results among stakeholders remains a challenge compared to other heavily forested European countries. An integral part of the Bavarian economy and the tourism sector, forests are also vital for climate regulation via atmospheric carbon reduction and land surface cooling. Therefore, forest monitoring remains centrally important to attaining more resilient and productive forests.

A taste of wilderness: supplementary feeding of red deer (Cervus elaphus) increases individual bacterial microbiota diversity but lowers abundance of important gut symbionts

The gut microbiome plays a crucial role in the health and well-being of animals. It is especially critical for ruminants that depend on this bacterial community for digesting their food. In this study, we investigated the effects of management conditions and supplemental feeding on the gut bacterial microbiota of red deer (Cervus elaphus) in the Bavarian Forest National Park, Germany. Fecal samples were collected from free-ranging deer, deer within winter enclosures, and deer in permanent enclosures. The samples were analyzed by high-throughput sequencing of the 16 S rRNA gene. The results showed that the gut bacterial microbiota differed in diversity, abundance, and heterogeneity within and between the various management groups. Free-ranging deer exhibited lower alpha diversity compared with deer in enclosures, probably because of the food supplementation available to the animals within the enclosures. Free-living individuals also showed the highest beta diversity, indicating greater variability in foraging grounds and plant species selection. Moreover, free-ranging deer had the lowest abundance of potentially pathogenic bacterial taxa, suggesting a healthier gut microbiome. Winter-gated deer, which spent some time in enclosures, exhibited intermediate characteristics between free-ranging and all-year-gated deer. These findings suggest that the winter enclosure management strategy, including supplementary feeding with processed plants and crops, has a significant impact on the gut microbiome composition of red deer. Overall, this study provides important insights into the effects of management conditions, particularly winter enclosure practices, on the gut microbiome of red deer. Understanding these effects is crucial for assessing the potential health implications of management strategies and highlights the value of microbiota investigations as health marker.

Genetic variation of English yew (Taxus baccata L.) in the Bavarian Forest National Park, Germany

AbstractTaxus baccata L. is a highly valuable species with wide distribution but scattered and locally rare occurrence. Human intervention, including forest management practices and fragmentation, can significantly impact the species’ genetic diversity, structure, and dynamics. In this study, we investigated these factors within T. baccata populations in the Bavarian Forest National Park (NP) in Germany and their implications for conservation. We used 13 EST-SSRs to assess the genetic diversity and structure of the population. Our analysis revealed a scarcity of small-diameter trees, indicating limited natural regeneration over time. However, conservation efforts, like selectively removing competitor species and using protective fencing, have improved growth conditions and promoted seedling emergence. The NP’s natural zone has no active management, which is confined to the development and management zones. Genetic diversity assessments revealed high genetic diversity (He: 0.612 and 0.614 for seedlings and adults, respectively) compared to other studies in Taxus baccata, dispelling concerns of significant inbreeding and showcasing a stable genetic structure. However, significant spatial clustering of related individuals (family structures) in both cohorts and low effective population size in the progeny hints at restricted gene flow, necessitating conservation efforts prioritizing safeguarding and promoting natural regeneration in development and management zones. Limited natural regeneration and the recent decrease in effective population size in the NP populations indicate habitat fragmentation and human interventions. Effective population size estimates emphasize the need for diverse conservation strategies. Conservation efforts should prioritize protecting natural regeneration and enhancing gene flow by actively promoting European yew, e.g., by shelterwood cutting, to ensure the long-term viability of T. baccata in the region outside the NP.

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

BackgroundThe 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).ResultsWe 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.ConclusionsWhile 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.

Red fox cannibalism in a temperate forest ecosystem

Scavengers benefit from carrion and simultaneously provide essential ecosystem services. To assess benefits and risks that carrion might bring, it is crucial to understand ecosystem-specific scavenger communities. Carrion research has mostly focussed on ungulate carcasses and has rarely explored the effects of carnivore carcasses, which can be critical to understanding disease transmission pathways. Therefore, using red fox, roe deer and red deer carcasses, we investigated factors that affect facultative vertebrate scavenger assemblages visiting carnivore and herbivore carcasses in a temperate forest ecosystem. Due to potentially increased disease transmission risk associated with carnivore carrion, we predicted that carnivore carcasses would be visited less and have a reduced visiting species composition compared to herbivore carcasses. Further, we expected red foxes to exhibit less consumption behavior of conspecific carcasses. We placed 22 red fox and 22 herbivore carcasses in a temperate montane protected area in Central Europe, the Bavarian Forest National Park, and analyzed the visits of all species and the consumption behavior of red fox at carcasses to understand whether these depended on carcass type. We found no significant effects of carcass type on visitation rates, visiting species composition, or red fox behavior. Cannibalism of foxes was common and, when controlling for confounding factors, e.g., elevation, temperature, and scavenging seasonality, the predicted consumption rate of red fox at conspecifics was higher than at herbivore carrion. Foxes appeared to consume conspecifics earlier than herbivore carrion, but the difference was not significant. At the very least, our results show that carnivore carcasses and fox behavior, including cannibalism, could provide a pathway for disease transmission. We thereby provide a first impression of the patterns of vertebrate scavenger assemblages at different carcass types in a temperate ecosystem and show that red fox behavior might precipitate a disease transmission pathway.

Response times as explanatory variable for export of dissolved organic carbon (DOC) from small forested catchments

Rising trends in the concentrations of dissolved organic carbon (DOC) are observed in many inland waters, including the headwater catchment of the Große Ohe river in the Bavarian Forest National Park (Germany). During flood events, DOC is mobilized via different hydrological pathways, affecting the hydrochemistry of aquatic ecosystems and the viability of drinking water supply. In our field experiments we observed different phases of DOC mobilization during six intensively studied rainfall-runoff events with contrasting antecedent wetness conditions. We propose response time diagrams to link the different phases of DOC mobilization to different response times along a hillslope-riparian-zone-transect. Depending on the antecedent wetness conditions, the hillslope and riparian zone participated differently to phases of the runoff event and shaped the flow hydrograph and DOC export at the catchment outlet. The hillslope always responded with little time delay to precipitation events regardless of the antecedent wetness condition. In contrast, response times in the riparian zone varied. For wet antecedent conditions we observed little delay between the hillslope- and riparian zone peak response, which caused high peak discharge, fast DOC mobilization and high DOC export from the catchment. In contrast, for dry antecedent conditions, the riparian zone response was significantly lower and much delayed. This led not only to attenuated peak discharge but also to larger time lags between the flow hydrograph- and the DOC concentration peak. The combination of low runoff rates and delayed DOC concentration peaks resulted into lower DOC export from the catchment. Thus, the antecedent wetness condition and response times of the hillslope and riparian zone are important indicators for DOC export in the catchment.

An Open Benchmark Dataset for Forest Characterization from Sentinel-1 and -2 Time Series

Earth observation satellites offer vast opportunities for quantifying landscapes and regional land cover composition and changes. The integration of artificial intelligence in remote sensing is essential for monitoring significant land cover types like forests, demanding a substantial volume of labeled data for effective AI model development and validation. The Wald5Dplus project introduces a distinctive open benchmark dataset for mid-European forests, labeling Sentinel-1/2 time series using data from airborne laser scanning and multi-spectral imagery. The freely accessible satellite images are fused in polarimetric, spectral, and temporal domains, resulting in analysis-ready data cubes with 512 channels per year on a 10 m UTM grid. The dataset encompasses labels, including tree count, crown area, tree types (deciduous, coniferous, dead), mean crown volume, base height, tree height, and forested area proportion per pixel. The labels are based on an individual tree characterization from high-resolution airborne LiDAR data using a specialized segmentation algorithm. Covering three test sites (Bavarian Forest National Park, Steigerwald, and Kranzberg Forest) and encompassing around six million trees, it generates over two million labeled samples. Comprehensive validation, including metrics like mean absolute error, median deviation, and standard deviation, in the random forest regression confirms the high quality of this dataset, which is made freely available.

Habitat visibility affects the behavioral response of a large herbivore to human disturbance in forest landscapes

Wildlife can perceive humans as predators and human disturbance, whether lethal (e.g., hunting) or non-lethal (e.g., hiking, biking, and skiing), triggers antipredator behavior among prey. Visibility is the property that relates habitat structure to accessibility of visual information that allows animals to detect predators and evaluate predation risk. Thus, the visibility of a habitat (hereafter referred to as habitat visibility) for prey species alters the perceived risk of predation and therefore has a strong influence on their antipredator behavior. Yet, knowledge of how habitat visibility affects the response of animals to different types of human disturbance is limited, partly, because it is challenging to measure habitat visibility for animals at a fine spatial scale over a landscape, particularly in highly heterogeneous landscapes (e.g., forests). In this study, we employed a newly described approach that combines terrestrial and airborne LiDAR to contiguously measure fine-scale habitat visibility in a forested landscape. We applied the LiDAR-derived habitat visibility to examine how habitat visibility in forests affects the summer space use of 20 GPS-collared female red deer (Cervus elaphus) modeled with integrated step-selection functions in the Bavarian Forest National Park, Germany when exposed to various types of human disturbance including recreational activities, forest roads, hiking trails, and hunting. We found that red deer in our study area avoided areas with higher all types of human disturbance, especially during daylight hours. Furthermore, habitat visibility significantly modified the use of space by red deer in response to human recreational activities, forest roads, and hiking trails, but not to the hunting area. Red deer tended to tolerate a higher intensity of human recreational activities and to use areas closer to forest roads or hiking trails when they have lower habitat visibility (i.e., more cover). Our findings highlight the importance of considering visual perception when studying the response of wild animals to human disturbance. We emphasize the potential to mitigate negative consequences of human disturbance on wildlife, through measures such as maintaining vegetative buffers around recreational infrastructure (e.g., roads and skiing tracks) in order to reduce habitat visibility around areas frequented by humans.

The Relationship between Measured Visitor Density and Perceived Crowding Revisited: Predicting Perceived Crowding in Outdoor Recreation

Protected areas around the globe face increasing visitation numbers and crowding, a situation exacerbated by the COVID-19 pandemic. Although measured visitor density and perceived crowding are strongly related, analyses of this relationship are lacking. We argue that measured visitor density serves as a reliable and objective indicator of perceived crowding. This study therefore examined the effects of visitation numbers, perceived encounters, and expectations on perceived crowding in the Bavarian Forest National Park (Germany). Automated visitor counts at six park locations were linked to data from an on-site crowding survey conducted in 2021. A predictive model and visitation thresholds were calculated using a logistic regression, which showed that visitation numbers are a well-suited predictor of crowding. The results indicated a strong association between measured visitor density and perceived crowding, moderated by site-specific conditions. The calculated thresholds provide a valuable instrument that can be used to inform the public in advance about peak visiting times.

Assessing Combinations of Landsat, Sentinel-2 and Sentinel-1 Time series for Detecting Bark Beetle Infestations

ABSTRACT Bark beetle infestations are among the most substantial forest disturbance agents worldwide. Moreover, as a consequence of global climate change, they have increased in frequency and in the size and number of affected areas. Controlling bark beetle outbreaks requires consistent operational monitoring, as is possible using satellite data. However, while many satellite-based approaches have been developed, the full potential of dense, multi-sensor time series has yet to be fully explored. Here, for the first time, we used all available multispectral data from Landsat and Sentinel-2, Sentinel-1 SAR data, and combinations thereof to detect bark beetle infestations in the Bavarian Forest National Park. Based on a multi-year reference dataset of annual infested areas, we assessed the separability between healthy and infested forests for various vegetation indices calculated from the satellite data. We used two approaches to compute infestation probability time series from the different datasets: Bayesian conditional probabilities, based on the best-separating index from each satellite type, and random forest regression, based on all indices from each satellite type. Five different sensor configurations were tested for their detection capabilities: Landsat alone, Sentinel-1 alone, Sentinel-2 alone, Landsat and Sentinel-2 combined, and data from all satellite types combined. The best overall results in terms of spatial accuracy were achieved with Sentinel-2 (max. overall accuracy: 0.93). The detections of Sentinel-2 also were the closest to the onset of infestation estimated for each year. Sentinel-2 detected infested areas in larger contiguous patches with higher reliability compared to smaller patches. The results achieved with Landsat were somewhat inferior to those of Sentinel-2 (max. accuracy: 0.89). While yielding similar results, the combination of Landsat and Sentinel-2 did not provide any advantages over using Landsat or Sentinel-2 alone (max. accuracy: 0.87), while Sentinel-1 was unable to detect infested areas (max. accuracy: 0.62). The combined data of all three satellite types did not achieve satisfactory results either (max. accuracy: 0.67). Spatial accuracies were typically higher for Bayesian conditional probabilities than for random forest-derived probabilities, but the latter resulted in earlier detections. The approach presented herein provides a flexible disturbance detection pipeline well-suited for the monitoring of bark beetle outbreaks. Furthermore, it can also be applied to other disturbance types.

Evaluation of GNSS-based Volunteered Geographic Information for assessing visitor spatial distribution within protected areas: A case study of the Bavarian Forest National Park, Germany

Systematic monitoring of recreational use in vulnerable ecosystems is crucial to balance human needs and site capacities. Recently, publicly available digital data, including Global Navigation Satellite System-based Volunteered Geographic Information, gained attention as a potential resource depicting visitor movement. However, there is a need to critically assess its reliability for visitor monitoring across countries, regions and available databases. Our research evaluates the usability of GNSS-based VGI-data obtained from three common platforms: GPSies, Outdooractive, and Komoot for assessing the spatial distribution of hikers in the Bavarian Forest National Park. A total sample of 1742 GNSS-tracks uploaded between 2013 and 2018 were compared across data platforms. Additionally, available systematic field counts, carried out between 2013 and 2014 (11 Eco-Counter sensors), were compared to GNSS-based VGI data uploaded within the corresponding period. The comparisons at individual and collective levels (route lengths, kernel density, optimized hotspot analysis along with fishnet-based counts of GNSS-tracks) showed similarities between VGI data platforms. Data obtained from GPSies and Outdooractive displayed a higher correlation with each other than with those obtained from Komoot. Also, for GPSies, there was a significant positive correlation between VGI-data and field count data. Data sample of Outdooractive and Komoot within the specified spatio-temporal frame was too small to compare with available field count data. We highlight the necessity of systematic validation of GNSS-based VGI data resources, being complementary rather than the primary data source in visitor monitoring and recreation planning. Also, systematic long-term visitor monitoring using other methods is crucial to assess the validity of novel data resources, such as GNSS-based VGI.

Forest–atmosphere exchange of reactive nitrogen in a remote region – Part II: Modeling annual budgets

Abstract. To monitor the effect of current nitrogen emissions and mitigation strategies, total (wet + dry) atmospheric nitrogen deposition to forests is commonly estimated using chemical transport models or canopy budget models in combination with throughfall measurements. Since flux measurements of reactive nitrogen (Nr) compounds are scarce, dry deposition process descriptions as well as the calculated flux estimates and annual budgets are subject to considerable uncertainties. In this study, we compared four different approaches to quantify annual dry deposition budgets of total reactive nitrogen (ΣNr) at a mixed forest site situated in the Bavarian Forest National Park, Germany. Dry deposition budgets were quantified based on (I) 2.5 years of eddy covariance flux measurements with the Total Reactive Atmospheric Nitrogen Converter (TRANC); (II) an in situ application of the bidirectional inferential flux model DEPAC (Deposition of Acidifying Compounds), here called DEPAC-1D; (III) a simulation with the chemical transport model LOTOS-EUROS (Long-Term Ozone Simulation – European Operational Smog) v2.0, using DEPAC as dry deposition module; and (IV) a canopy budget technique (CBT). Averaged annual ΣNr dry deposition estimates determined from TRANC measurements were 4.7 ± 0.2 and 4.3 ± 0.4 kg N ha−1 a−1, depending on the gap-filling approach. DEPAC-1D-modeled dry deposition, using concentrations and meteorological drivers measured at the site, was 5.8 ± 0.1 kg N ha−1 a−1. In comparison to TRANC fluxes, DEPAC-1D estimates were systematically higher during summer and in close agreement in winter. Modeled ΣNr deposition velocities (vd) of DEPAC-1D were found to increase with lower temperatures and higher relative humidity and in the presence of wet leaf surfaces, particularly from May to September. This observation was contrary to TRANC-observed fluxes. LOTOS-EUROS-modeled annual dry deposition was 6.5 ± 0.3 kg N ha−1 a−1 for the site-specific weighting of land-use classes within the site's grid cell. LOTOS-EUROS showed substantial discrepancies to measured ΣNr deposition during spring and autumn, which was related to an overestimation of ammonia (NH3) concentrations by a factor of 2 to 3 compared to measured values as a consequence of a mismatch between gridded input NH3 emissions and the site's actual (rather low) pollution climate. According to LOTOS-EUROS predictions, ammonia contributed most to modeled input ΣNr concentrations, whereas measurements showed NOx as the prevailing compound in ΣNr concentrations. Annual deposition estimates from measurements and modeling were in the range of minimum and maximum estimates determined from CBT being at 3.8 ± 0.5 and 6.7 ± 0.3 kg N ha−1 a−1, respectively. By adding locally measured wet-only deposition, we estimated an annual total nitrogen deposition input between 11.5 and 14.8 kg N ha−1 a−1, which is within the critical load ranges proposed for deciduous and coniferous forests.

From the Serengeti to the Bavarian Forest, and back again: Bernhard Grzimek, Celebrity Conservation, and the Transnational Politics of National Parks

This short piece focuses on the work of the German “celebrity conservationist,” Bernhard Grzimek, situating it in the context of historical and contemporary debates about the political and ecological importance of national parks. Grzimek’s role in the creation of Bavarian Forest National Park may not be as well-known as his public ministrations on behalf of the wild animals of the Serengeti, but in several ways his work in and for these two national parks, engaging with the fraught politics of the period, was intertwined. The essay looks at some of these overlaps, using them to make the case for national parks as complex geopolitical formations in which human and animal interests alternately collide and converge. The essay also makes the case for national parks as multi-scalar entities that need to be understood – politically and ecologically – in both local and global, both national and transnational terms. Finally, the essay cites the multiple roles of Grzimek to re-examine the ambivalent role of the celebrity conservationist as a media spokesperson and publicity-conscious advocate for the world’s wildlife.

Fascioloides magna and other liver parasites in cloven-hoofed game from northeastern Bavaria, Germany: occurrence and pathological findings with special emphasis on red deer (Cervus elaphus)

The first detection of Fascioloides (F.) magna in northeastern Bavaria in 2011 was presumably correlated to natural migration movements of free ranging wild ruminants originating from the neighboring Czech Republic, where high infection rates have been reported frequently. To gain more data on the continuing spreading and current occurrence of the giant liver fluke in surrounding regions, 700 livers of cloven-hoofed game originating from eleven different northeastern Bavarian counties were investigated for the presence of F. magna and accompanying liver parasites in the hunting season 2019–2020. Macroscopically altered liver tissue was further investigated by pathohistological and parasitological examination. F. magna was detected in 5.9% (38/640) of livers from red deer (0.7% < 1 year, 9.8% > 1 year; p < 0.05) whereas none of the investigated livers of wild boar, roe, and fallow deer was infected (n=60). Mild pathological alterations of the liver tissue were documented in 15, moderate in 14, and major in 9 of all F. magna-positive cases. Histologically, the fluke-specific pigment haematin, large trematode eggs, and periportal fibrosis were detected in the liver tissue of infected animals. In 9% of all investigated livers, parasitic stages of other parasites, i.e., Dicrocoelium dendriticum (6.0%), Fasciola hepatica (0.3%), Taenia spp. (1.7%), and Echinococcus multilocularis (1.0%), were found. According to the results of this study, F. magna is not restricted to formerly known affected regions of Upper Franconia, but is also present in the military training ground Grafenwöhr, Upper Palatinate, and the Bavarian Forest National Park, Lower Bavaria, with estimated prevalences of 3.6 and 16.4%, respectively, and thus seems to spread in suitable habitats in northeastern Bavaria.

Using Springs as Sentinels of Climate Change in Nature Parks North and South of the Alps: A Critical Evaluation of Methodological Aspects and Recommendations for Long-Term Monitoring

Spring ecosystems are diverse transition zones between ground- and surface-water habitats. Due to their characteristics and vulnerable species assemblages, springs are considered indicator systems for monitoring environmental change. In particular, climate change is expected to alter spring-ecosystem features, such as water temperature and discharge, affecting otherwise typically stable biotic and abiotic conditions. However, reliable trend-development recognition and analysis require a uniform methodology and comparable data series over long periods of time. Spring research findings in the Berchtesgaden National Park and the Adamello-Brenta Nature Park have been consolidated to develop methodological recommendations to create lasting societal-added value. The successful transfer of the methodology to the Bavarian Forest National Park and the experienced contribution of the Bavarian Association for the Protection of Nature (Bavarian Climate Alliance) strongly improved method validations. Our resulting, newly developed recommendations for long-term spring monitoring have a focus on climate change impacts and aim at providing a decision-making basis for establishing programs in similar ecological and climatic zones. Uniform site-selection criteria and selected climate-sensitive parameters are indicated. This includes documenting the spring’s environment and structure, measuring abiotic parameters, and determining selected floristic and faunistic groups. We recommend measurement and sampling-survey intervals ranging from 3(4) times yearly to every 5 years, depending on the parameter. We further suggest a database system that integrates all monitoring parameters to ensure consistent data management and storage. Analysing the data resulting from our new holistic spring monitoring methodology should provide critical knowledge about putatively changing ecosystems that can then be used as evidence of climate-change impact on spring ecosystems.

Classification of Tree Species and Standing Dead Trees with Lidar Point Clouds Using Two Deep Neural Networks: PointCNN and 3DmFV-Net

Knowledge about tree species distribution is important for forest management and for modeling and protecting biodiversity in forests. Methods based on images are inherently limited to the forest canopy. Airborne lidar data provide information about the trees’ geometric structure, as well as trees beneath the upper canopy layer. In this paper, the potential of two deep learning architectures (PointCNN, 3DmFV-Net) for classification of four different tree classes is evaluated using a lidar dataset acquired at the Bavarian Forest National Park (BFNP) in a leaf-on situation with a maximum point density of about 80 pts/m^{2}. Especially in the case of BFNP, dead wood plays a key role in forest biodiversity. Thus, the presented approaches are applied to the combined classification of living and dead trees. A total of 2721 single trees were delineated in advance using a normalized cut segmentation. The trees were manually labeled into four tree classes (coniferous, deciduous, standing dead tree with crown, and snag). Moreover, a multispectral orthophoto provided additional features, namely the Normalized Difference Vegetation Index. PointCNN with 3D points, laser intensity, and multispectral features resulted in a test accuracy of up to 87.0%. This highlights the potential of deep learning on point clouds in forestry. In contrast, 3DmFV-Net achieved a test accuracy of 73.2% for the same dataset using only the 3D coordinates of the laser points. The results show that the data fusion of lidar and multispectral data is invaluable for differentiation of the tree classes. Classification accuracy increases by up to 16.3% points when adding features generated from the multispectral orthophoto.

Forest–atmosphere exchange of reactive nitrogen in a remote region – Part I: Measuring temporal dynamics

Abstract. Long-term dry deposition flux measurements of reactive nitrogen based on the eddy covariance or the aerodynamic gradient method are scarce. Due to the large diversity of reactive nitrogen compounds and high technical requirements for the measuring devices, simultaneous measurements of individual reactive nitrogen compounds are not affordable. Hence, we examined the exchange patterns of total reactive nitrogen (ΣNr) and determined annual dry deposition budgets based on measured data at a mixed forest exposed to low air pollution levels located in the Bavarian Forest National Park (NPBW), Germany. Flux measurements of ΣNr were carried out with the Total Reactive Atmospheric Nitrogen Converter (TRANC) coupled to a chemiluminescence detector (CLD) for 2.5 years. The average ΣNr concentration was 3.1 µg N m−3. Denuder measurements with DELTA samplers and chemiluminescence measurements of nitrogen oxides (NOx) have shown that NOx has the highest contribution to ΣNr (∼51.4 %), followed by ammonia (NH3) (∼20.0 %), ammonium (NH4+) (∼15.3 %), nitrate NO3- (∼7.0 %), and nitric acid (HNO3) (∼6.3 %). Only slight seasonal changes were found in the ΣNr concentration level, whereas a seasonal pattern was observed for the contribution of NH3 and NOx. NH3 showed highest contributions to ΣNr in spring and summer, NOx in autumn and winter. We observed deposition fluxes at the measurement site with median fluxes ranging from −15 to −5 ngNm-2s-1 (negative fluxes indicate deposition). Median deposition velocities ranged from 0.2 to 0.5 cm s−1. In general, highest deposition velocities were recorded during high solar radiation, in particular from May to September. Our results suggest that seasonal changes in composition of ΣNr, global radiation (Rg), and other drivers correlated with Rg were most likely influencing the deposition velocity (vd). We found that from May to September higher temperatures, lower relative humidity, and dry leaf surfaces increase vd of ΣNr. At the measurement site, ΣNr concentration did not emerge as a driver for the ΣNrvd. No significant influence of temperature, humidity, friction velocity, or wind speed on ΣNr fluxes when using the mean-diurnal-variation (MDV) approach for filling gaps of up to 5 days was found. Remaining gaps were replaced by a monthly average of the specific half-hourly value. From June 2016 to May 2017 and June 2017 to May 2018, we estimated dry deposition sums of 3.8 and 4.0 kgNha-1a-1, respectively. Adding results from the wet deposition measurements, we determined 12.2 and 10.9 kgNha-1a-1 as total nitrogen deposition in the 2 years of observation. This work encompasses (one of) the first long-term flux measurements of ΣNr using novel measurements techniques for estimating annual nitrogen dry deposition to a remote forest ecosystem.

Population genetic structure and connectivity in three montane freshwater invertebrate species (Ephemeroptera, Plecoptera, Amphipoda) with differing life cycles and dispersal capabilities

Abstract Dispersal abilities and the resulting levels of connectivity between streams influence population structure in aquatic organisms. We investigated how different dispersal and life‐history traits affect gene flow and population structure in three aquatic invertebrate species in a central European mountain range. We used microsatellite markers and mitochondrial cytochrome oxidase I barcode data to assess small‐scale population structure and connectivity of the mayfly Baetis alpinus, the stonefly Brachyptera seticornis, and the amphipod Gammarus fossarum in seven streams within Bavarian Forest National Park, Germany. Significant population structure within the study area was detected in B. alpinus and G. fossarum, whereas B. seticornis had signatures of panmixia. In G. fossarum, that structure corresponded to stream topography, while in B. alpinus it did not. The Bavarian Forest range appears to be a contact zone for different mitochondrial lineages of B. alpinus and G. fossarum. Limited geneflow between sample sites in B. alpinus can be explained by the species’ short adult lifespans, which restricts dispersal between sites. Since imagines are able to disperse via adult flight population structure is, however, decoupled from stream topology. Longer‐lived B. seticornis is better able to maintain geneflow between sample sites. In flightless G. fossarum, population structure corresponding to stream topology can be explained by limited dispersal capabilities between streams. Dispersal ability alone is insufficient to predict or explain patterns of gene flow and connectivity for individual species, and should be examined together with life‐history traits when assessing population and community structure.

Spatial risk assessment of radiocesium contamination of edible mushrooms – Lessons from a highly frequented recreational area

The radioactive contamination of edible mushrooms increases human health hazards, especially in high mushroom collection intensity areas. Today only coarse-scale data with low spatial resolution are available, which prevents us from predicting human risk. To reduce the risk for human health, we need spatially explicit recommendations at landscape-scale. We used the Bavarian Forest National Park, a famous mushroom hunting location in Europe, as a model system. We aimed to increase the predictability of the contamination of the two most prominent mushroom species, bay boletus (Imleria badia) and ceps (Boletus edulis), and provide an efficient evidence-based risk assessment at landscape-scale. We revealed a high and a low 137Cs-activity impact area based on soil samples, which is also reflected by the mushroom species. 137Cs-activity of Imleria badia is about five times higher than the contamination of Boletus edulis; with one-third of the Imleria badia samples being over the statutory limit. The difference of contamination between species is more pronounced in the high-impact area. Elevation is a strong predictor in contrast to orientation of slopes. In high-impact areas, mushrooms showed higher 137Cs-activities at lower elevations. Soil analysis revealed that the maximum of the 137Cs-activity is still in the organic layers, indicating further mushroom contamination. We recommend using only Boletus edulis in the low-impact area for diet. We suggest that Boletus edulis bear a lower health risk than Imleria badia due to lower 137Cs-activities. Nevertheless, we need more landscape-scale studies to assess the 137Cs contamination risk for humans. Studies are primarily important in high-impact areas, which can be roughly identified by using soil contamination maps. The focus should be on high accumulating mushroom species like Imleria badia. Our study can serve as a blueprint to rapidly assess human health risks caused by radioactive contamination in landscapes intensively used by mushroom collectors.

Holling meets habitat selection: functional response of large herbivores revisited

BackgroundHolling (Can Entomol 91(5):293–320, 1959) was the first to describe a functional response between a predator’s consumption-rate and the density of its prey. The same concept can be applied to the habitat selection of herbivores, specifically, the change in relative habitat use with the change in habitat availability. Functional responses in habitat selection at a home-range scale have been reported for several large herbivores. However, a link to Holling’s original functional response types has never been drawn, although it could replace the current phenomenological view with a more mechanistically based understanding of functional responses.MethodsIn this study, discrete choice models were implemented as mixed-effects baseline-category logit models to analyze the variation in habitat selection of a large herbivore at seasonal and diurnal scales. Thus, changes in the use of land cover types with respect to their availability were investigated by monitoring 11 land cover types commonly used by roe deer (Capreolus capreolus) in the Bavarian Forest National Park, Germany. Functional response curves were then fitted using Holling’s formulas.ResultsStrong evidence of non-linear functional responses was obtained for almost all of the examined land cover types. The shape of the functional response curves varied depending on the season, the time of day, and in some cases between sexes. These responses could be referenced to Holling’s types, with a predominance of type II.ConclusionsOur results indicate that Holling’s types can be applied to describe general patterns of the habitat selection behavior of herbivores. Functional responses in habitat selection may occur in situations requiring a trade-off in the selection of land cover types offering different resources, such as due to the temporally varying physiological needs of herbivores. Moreover, two associated parameters defining the curves (prey density and predation rate) can aid in the identification of temporal variations and in determinations of the strength of the cost-benefit ratio for a specific land cover type. Application of our novel approach, using Holling’s equations to describe functional responses in the habitat selection of herbivores, will allow the assignment of general land cover attraction values, independent of availability, thus facilitating the identification of suitable habitats.