Understanding forest functioning is limited by the scalability of monitoring solutions and difficulty of access. Manual sensor placement can reach most locations but lacks scalability. Micro‐aerial vehicles (MAVs) allow for scalable sensor delivery, but current solutions are limited to attaching sensors to the trunk or large branches with spines or adhesives. The thinner branches of the outer canopy remain inaccessible, despite being of particular interest due to the important physiological processes occurring in the foliage. Herein, a MAV‐deployable bistable helically coiling origami gripper is developed. The unfurled state allows for transport with a MAV, and when pushed against a branch triggers the second helically coiled state, which permits secure attachment to branches. Origami manufacturing keeps the weight of the gripper below 5 g, despite holding up to 280 g, and gripping diameters from 8 mm to 38 mm inclined up to 30°. The holding force, activation force, and resistance to tilt and rotation offsets are experimentally characterized. The deployment and retrieval of the gripper and sensor are demonstrated outside, where sensor data are collected from previously inaccessible branches in the outer canopy. Enabling robust sensor attachment in the outer canopy marks a step toward scalable environmental monitoring of forest ecosystems.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aisy.202200087

Bistable Helical Origami Gripper for Sensor Placement on Branches

Diagnostic testing to detect forest pathogens requires the collection of physical samples from affected trees, which can be challenging in remote or rugged environments. As an alternative to traditional ground-based sampling at breast height by field crews, we examined the feasibility of aerially sampling and testing material collected from upper canopy branches using a small unoccupied aerial system (sUAS). The pathogen of interest in this study is Ceratocystis lukuohia, the fungal pathogen responsible for Ceratocystis wilt of ‘ōhi‘a, a vascular wilt disease which has caused widespread mortality to ‘ōhi‘ain native forests across the state of Hawai‘i. To characterize the minimum branch diameter needed to successfully detect the pathogen of interest in infected trees, we tested 63 branch samples (0.8–9.6 cm in diameter) collected from felled trees inoculated with C. lukuohia on Hawai‘i Island. Subsequently, we aerially sampled branches from ten symptomatic ‘ōhi‘a (Metrosideros polymorpha) trees using two different branch sampling systems, the Flying Tree Top Sampler from ETH Zurich and the new Kūkūau branch sampler system introduced in this work, producing 29 branch samples with a maximum diameter of 4.2 cm and length of >2 m. We successfully detected the target fungal pathogen from the collected branches and found that branch diameter, leaf presence and condition, as well as wood moisture content are important factors in pathogen detection in sampled branches. None of the smallest branch samples (those <1 cm in diameter) tested positive for C. lukuohia, while 77% of the largest diameter branch samples (5–10 cm) produced positive results. The Kūkūau branch sampler system is capable of retrieving branches up to 7 cm diameter, providing important capacity for pathogenic research requiring larger diameter samples for successful diagnostic testing. Inconclusive and/or non-detection laboratory results were obtained from sample materials that were either too desiccated or from a branch with asymptomatic leaves, suggesting there is an optimal temporal window for sampling.

/pdf/aerial-branch-sampling-to-detect-forest-pathogens-114ao7u9.pdf

Aerial Branch Sampling to Detect Forest Pathogens

The protection and restoration of the biosphere is crucial for human resilience and well-being, but the scarcity of data on the status and distribution of biodiversity puts these efforts at risk. DNA released into the environment by organisms, i.e., environmental DNA (eDNA), can be used to monitor biodiversity in a scalable manner if equipped with the appropriate tool. However, the collection of eDNA in terrestrial environments remains a challenge because of the many potential surfaces and sources that need to be surveyed and their limited accessibility. Here, we propose to survey biodiversity by sampling eDNA on the outer branches of tree canopies with an aerial robot. The drone combines a force-sensing cage with a haptic-based control strategy to establish and maintain contact with the upper surface of the branches. Surface eDNA is then collected using an adhesive surface integrated in the cage of the drone. We show that the drone can autonomously land on a variety of branches with stiffnesses between 1 and 103 newton/meter without prior knowledge of their structural stiffness and with robustness to linear and angular misalignments. Validation in the natural environment demonstrates that our method is successful in detecting animal species, including arthropods and vertebrates. Combining robotics with eDNA sampling from a variety of unreachable aboveground substrates can offer a solution for broad-scale monitoring of biodiversity. Description A drone incorporating a force-sensing cage with adhesive surfaces enables environmental DNA to be collected from tree branches.

/pdf/drone-assisted-collection-of-environmental-dna-from-tree-2pe1p42o.pdf

Drone-assisted collection of environmental DNA from tree branches for biodiversity monitoring

Labour and resource intensive data collection methods drive the use of unmanned aerial vehicles in the field of environmental monitoring. UAV supported sensor deployment in forests can improve localized and continuous monitoring. To advance this field, we present a two fingered gripper with spines integrated on three phalanxes. The softness of the fingers combined with compliantly-supported microspines integrated into adjustable microspine-clusters allow the gripper to wrap and adhere to tree branches. With a differential drive actuation, microspine cluster adjustability as well as load-sharing between spine clusters is achieved. We characterize the bending behaviour of the soft fingers that adapt to curved and irregular objects. We show that the implementation of compliantly-supported and adjustable microspine-clusters increase holding force and that load-sharing between spine clusters is achieved with the differential drive actuation. The demonstration of UAV perching on a tree branch with the gripper shows that sensor deployment in these environments can be achieved. 

/pdf/soft-gripper-with-adjustable-microspines-for-adhering-to-s0cr1urq.pdf

Soft Gripper with Adjustable Microspines for Adhering to Tree Branches

A cost‐effective method to passively sample communities at the forest canopy–aerosphere interface

The arboreal ecosystem is vitally important to global and local biogeochemical processes, the maintenance of biodiversity in natural systems, and human health in urban environments. The ability to collect samples, observations, and data to conduct meaningful scientific research is similarly vital. The primary methods and modes of access remain limited and difficult. In an online survey, canopy researchers (n=219) reported a range of challenges in obtaining adequate samples, including ~10% who found it impossible to procure what they needed. Currently, these samples are collected using a combination of four primary methods: 1) sampling from the ground; 2) tree climbing; 3) constructing fixed infrastructure; and 4) using mobile aerial platforms, primarily rotorcraft drones. An important distinction between instantaneous and continuous sampling was identified, allowing more targeted engineering and development strategies. The combination of methods for sampling the arboreal ecosystem provides a range of possibilities and opportunities, particularly in the context of the rapid development of robotics and other engineering advances. In this study, we aim to identify the strategies that would provide the benefits to a broad range of scientists, arborists, and professional climbers and facilitate basic discovery and applied management. Priorities for advancing these efforts are 1) to expand participation, both geographically and professionally; 2) to define 2-3 common needs across the community; 3) to form and motivate focal teams of biologists, tree professionals, and engineers in the development of solutions to these needs; and 4) to establish multidisciplinary communication platforms to share information about innovations and opportunities for studying arboreal ecosystems.

Ethan Abercrombie

Papers

Extending Our Scientific Reach in Arboreal Ecosystems for Research and Management