Third ERTS Symposium: Abstracts

Abstracts are provided for the 112 papers presented at the Earth Resources Program Symposium held at Washington, D.C., 10-14 December, 1973

Remote sensing technology applications in forestry and REDD+

Advances in close-range and remote sensing technologies are driving innovations in forest resource assessments and monitoring on varying scales. Data acquired with airborne and spaceborne platforms provide high(er) spatial resolution, more frequent coverage, and more spectral information. Recent developments in ground-based sensors have advanced 3D measurements, low-cost permanent systems, and community-based monitoring of forests. The UNFCCC REDD+ mechanism has advanced the remote sensing community and the development of forest geospatial products that can be used by countries for the international reporting and national forest monitoring. However, an urgent need remains to better understand the options and limitations of remote and close-range sensing techniques in the field of forest degradation and forest change. Therefore, we invite scientists working on remote sensing technologies, close-range sensing, and field data to contribute to this Special Issue. Topics of interest include: (1) novel remote sensing applications that can meet the needs of forest resource information and REDD+ MRV, (2) case studies of applying remote sensing data for REDD+ MRV, (3) timeseries algorithms and methodologies for forest resource assessment on different spatial scales varying from the tree to the national level, and (4) novel close-range sensing applications that can support sustainable forestry and REDD+ MRV. We particularly welcome submissions on data fusion

Insects

In this thematic series, engineers and scientists come together to address two interesting interdisciplinary questions in functional morphology and biomechanics: How do the structure and material determine the function of insect body parts? How can insects inspire engineering innovations

Responses of a Locust Looming Sensitive Neuron, Flight Muscle Activity and Body Orientation to Changes in Object Trajectory, Background Complexity, and Flight Condition

Survival is one of the highest priorities of any animal. Interaction in the environment with conspecifics, predators, or objects, is driven by evolution of systems that can efficiently and rapidly respond to potential collision with these stimuli. Flight introduces further complexity for a collision avoidance system, requiring an animal to compute air speed, wind speed, ground speed, as well as transverse and longitudinal image flow, all within the context of detecting an approaching object. Understanding the mechanisms underlying neural control and coordination of motor systems to produce behaviours in response to the natural environment is a main goal of neuroethology. Locusts have a tractable nervous system, and a robust, reproducible collision avoidance response to looming stimuli. This tractable system allows recording from the nerve cord and flight muscles with precision and reliability, allowing us to answer important questions regarding the neuronal control of muscle coordination and, in turn, collision avoidance behaviour during flight. In flight, a collision avoidance behaviour will most often be a turn away from the approaching stimulus. I tested the hypothesis that during loosely tethered flight, synchrony between flight muscles increases just prior to the initiation of a turn and that muscle synchronization would correlate with body orientation changes during flight steering. I found that hind and forewing flight muscle synchronization events correlated strongly with forewing flight muscle latency changes, and to pitch and roll body orientation changes in response to a lateral looming visual stimulus. These findings led me to investigate further the role of the looming-sensitive descending contralateral movement detector (DCMD) neuron in flight muscle coordination and the initiation of forewing asymmetry in rigidly tethered locusts that generate a flight-like rhythm. By conducting simultaneous recordings from the nerve cord, forewing flight muscles, and visually recording the wing positions within the same flying animal, I hypothesized that DCMD burst properties would correlate with flight muscle activity changes and the initiation of wing asymmetry associated with turning behaviour. Furthermore, I accessed the effect of manipulating background complexity of the locust’s visual environment, looming object trajectory, and the putative effect of mechanosensory feedback during flight, on DCMD burst firing rate properties. DCMD burst properties were affected by changes in background complexity and object trajectory, and most interestingly during flight. This suggests that reafferent feedback from the flight motor system modulates the DCMD signal, and therefore represents a more naturalistic representation of collision avoidance behaviour. A pivotal discovery in my study was the temporal role of bursting in collision avoidance behaviour. I found that the first burst in a DCMD spike train represents the earliest detectable neuronal event correlated with muscle activity changes and the creation of wing asymmetry. I found strong correlations across all object trajectories and background complexities, between the timing of the first bursts, flight muscle activity changes and the initiation of wing asymmetry. These findings reinforce the importance of the temporal properties of DCMD bursting in collision avoidance behaviour

Development of a software in the loop simulation approach for risk mitigation in unmanned aerial system development

A common method to reduce risk during the development of new designs is simulation and estimation. The extent to which these simulation and estimation techniques can be relied upon for small Unmanned Aerial Systems (sUAS) is unknown. Combining the autopilot together with a simulator for Software in the Loop (SITL) allows designers to tune and observe autopilot behavior before the design is finished. This thesis extends the tools provided through SITL to present methodology that can both provide early insight to the handling qualities of the aircraft and validation of the simulator.ArduPilot and X-Plane 11 are used as the autopilot and simulator. New features were developed to extend the functionality of ArduPilot. Additional software was developed to assist in both identification of aircraft modes and validation of simulation. With mixed results from validation of X-Plane, the need to perform flight testing of real aircraft is still more desirable for precision tuning of sUAS for more desirable handling qualities. What can be gained from SITL is risk mitigation from unconventional additions to sUAS and detailed analysis of failsafe behavior of the autopilot

Processing of Polarization Patterns and Visual Self-Motion in the Locust Central Complex for Spatial Orientation

Despite their relatively small brains with comparatively low neuron counts, insects show complex navigation behavior such as seasonal long-range migration, path integration, and precise straight-line movement. Spatial navigation requires a sense of current heading, which must be tethered to prominent external cues and updated by internal cues that result from movement. Global external cues such as the position of the sun may provide a reference frame for orientation. Sunlight is polarized by scattering in the atmosphere, which results in a sky-spanning polarization pattern that directly depends on the current solar position and makes polarization information, like the sun itself, useful as an external reference cue. Internally, moving through the environment generates optic flow---the motion of the viewed scenery on the retina---, which may inform about turning maneuvers, movement speed, and covered distance. Many insects use these external and internal cues for orientation, and the neuronal center for spatial navigation likely is the central complex, a higher-order brain structure where sensory information is integrated to form an internal compass representation of the current heading. This thesis addresses the question how celestial compass cues, specifically the polarization pattern, and optic flow are processed in the central complex of the desert locust, a long-range migratory insect. All chapters except the last one are electrophysiological studies in which single central-complex neurons were intracellularly recorded while presenting visual stimuli. The neurons' anatomy was histologically determined by dye injection in order to infer their role in the neural network. The studies in Chapters 1 and 2 show that the central complex contains a neuronal compass that robustly signals the sun direction based on direct sunlight and the integration of the whole solar polarization pattern. This shows that the locust brain uses all available skylight cues in order to form a unified compass signal, enabling robust navigation under different environmental conditions. The study in Chapter 3 further examines how neurons at the input stage of the central complex process skylight cues. Already at this stage, single neurons integrate visual information from large areas of the sky and have receptive fields suitable to build the skylight compass. Chapter 4 sheds light on the detection sensitivity for the angle of polarization, finding that central-complex neurons are highly sensitive in this regard, adapted to analyze the skylight polarization pattern almost in its entirety and under unfavorable environmental conditions. In Chapter 5 the locust central complex was scanned for neurons that receive optic flow information. Neurons at virtually all network stages are sensitive to optic flow, mainly uncoupled from skylight-cue sensitivity. This highlights that sensory information is flexibly processed in the central complex, presumably depending on the animal's current behavioral demands. Further, the study hypothesizes how horizontal turning motion is processed in order to update the internal heading representation, backed up by a computational model that adheres to brain anatomy and physiological data. Altogether, these studies advance the understanding of how external and internal cues are processed in the central-complex network in order to establish a sense of orientation in the insect brain. Finally, I contributed with data sets and programming code to the development of the InsectBrainDatabase (www.insectbraindb.org), a free online database tool designed to manage, share and publish anatomical and functional research data (Chapter 6)

The role of the femoral chordotonal organ in motor control, interleg coordination, and leg kinematics in Drosophila melanogaster

Legged locomotion in terrestrial animals is often essential for mating and survival, and locomotor behavior must be robust and adaptable in order to be successful. The behavioral plasticity demonstrated by animals’ ability to locomote across diverse types of terrains and to change their locomotion in a task-dependent manner highlights the flexible and modular nature of locomotor networks. The six legs of insects are under the multi-level control of local networks for each limb and limb joint in addition to over-arching central control of the local networks. These networks, consisting of pattern-generating groups of interneurons, motor neurons, and muscles, receive modifying and reinforcing feedback from sensory structures that encode motor output. Proprioceptors in the limbs monitoring their position and movement provide information to these networks that is essential for the adaptability and robustness of locomotor behavior. In insects, proprioceptors are highly diverse, and the exact role of each type in motor control has yet to be determined. Chordotonal organs, analogous to vertebrate muscle spindles, are proprioceptive stretch receptors that span joints and encode specific parameters of relative movement between body segments. In insects, when leg chordotonal organs are disabled or manipulated, interleg coordination and walking are affected, but the simple behavior of straight walking on a flat surface can still be performed. The femoral chordotonal organ (fCO) is the largest leg proprioceptor and monitors the position and movements of the tibia relative to the femur. It has long been studied for its importance in locomotor and postural control. In Drosophila melanogaster, an ideal model organism due its genetic tractability, investigations into the composition, connectivity, and function of the fCO are still in their infancy. The fCO in Drosophila contains anatomical subgroups, and the neurons within a subgroup demonstrate similar responses to movements about the femur-tibia joint. Collectively, the experiments laid out in this dissertation provide a multi-faceted analysis of the anatomy, connectivity, and functional importance of subgroups of fCO neurons in D. melanogaster. The dissertation is divided into four chapters, representing different aspects of this complex and intriguing system. First, I present a detailed analysis of the composition of the fCO and its connectivity within the peripheral and central nervous systems. I demonstrate that the fCO is made up of anatomically distinct groups of neurons, each with their own unique features in the legs and ventral nerve cord. Second, I investigated the neuropeptide profile of the fCO and demonstrate that some fCO neurons express a susbtance that is known to act as a neuromodulator. Third, I demonstrate the sufficiency of subsets of fCO neurons to elicit reflex responses, highlighting the role of the Drosophila fCO in postural control. Lastly, I take this a step further and look into the functional necessity of these neuronal subsets for intra- and interleg coordination during walking. The importance of the fCO in motor control in D. melanogaster has been considered rather minor, though research into the topic is very limited. In the work laid out herein, I highlight the complexity of the Drosophila fCO and its role in the determination of locomotor behavior

Investigation of visual pathways in honeybees (Apis mellifera) and desert locusts (Schistocerca gregaria): anatomical, ultrastructural, and physiological approaches

Many insect species demonstrate sophisticated abilities regarding spatial orientation and navigation, despite their small brain size. The behaviors that are based on spatial orientation differ dramatically between individual insect species according to their lifestyle and habitat. Central place foragers like bees and ants, for example, orient themselves in their surrounding and navigate back to the nest after foraging for food or water. Insects like some locust and butterfly species, on the other hand, use spatial orientation during migratory phases to keep a stable heading into a certain direction over a long period of time. In both scenarios, homing and long-distance migration, vision is the primary source for orientation cues even though additional features like wind direction, the earth’s magnetic field, and olfactory cues can be taken into account as well. Visual cues that are used for orientational purposes range from landmarks and the panorama to celestial cues. The latter consists in diurnal insects of the position of the sun itself, the sun-based polarization pattern and intensity and spectral gradient, and is summarized as sky-compass system. For a reliable sky-compass orientation, the animal needs, in addition to the perception of celestial cues, to compensate for the daily movement of the sun across the sky. It is likely that a connection from the circadian pacemaker system to the sky-compass network could provide the necessary circuitry for this time compensation. The present thesis focuses on the sky-compass system of honeybees and locusts. There is a large body of work on the navigational abilities of honeybees from a behavioral perspective but the underlying neuronal anatomy and physiology has received less attention so far. Therefore, the first two chapters of this thesis reveals a large part of the anatomy of the anterior sky-compass pathway in the bee brain. To this end, dye injections, immunohistochemical stainings, and ultrastructural examinations were conducted. The third chapter describes a novel methodical protocol for physiological investigations of neurons involved in the sky-compass system using calcium imaging in behaving animals. The fourth chapter of this thesis deals with the anatomical basis of time compensation in the sky-compass system of locusts. Therefore, the ultrastructure of synaptic connections in a brain region of the desert locust where the contact of both systems could be feasible has been investigated

Forests for a Better Future Sustainability, Innovation and Interdisciplinarity

This book highlights the role of research in innovation and sustainability in the forest sector. The contributions included fall within the broad thematic areas of forest science and cover crucial topics such as biocontrol, forest fire risk, harvesting and logging practices, quantitative and qualitative assessments of forest products, urban forests, and wood treatments—topics that have also been addressed from an interdisciplinary perspective. The contributions also have practical applications, as they deal with the ecological and economic importance of forests and new technologies for the conservation, monitoring, and improvement of services and forest value