land Article Beaver-Driven Peatland Ecotone Dynamics: Impoundment Detection Using Lidar and Geomorphon Analysis Troy P. Swift * and Lisa M. Kennedy   Citation: Swift, T.P.; Kennedy,L.M. Beaver-Driven Peatland Ecotone Dynamics: Impoundment Detection Using Lidar and Geomorphon Analysis. Land 2021, 10, 1333. https://doi.org/10.3390/land10 121333 Academic Editors: Elena D. Lapshina, Tatiana Minayeva and Eeva-Stiina Tuittila Received: 30 September 2021 Accepted: 26 November 2021 Published: 3 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Geography Department, Virginia Tech, Blacksburg, VA 24060, USA; likenne1@vt.edu * Correspondence: swift66@vt.edu Abstract: This investigation focused on remotely detecting beaver impoundments and dams along the boreal-like peatland ecotones enmeshing Cranberry Glades Botanical Area, a National Natural Landmark in mountainous West Virginia, USA. Beaver (Castor spp.) are renowned for their role as ecosystem engineers. They can alter local hydrology, change the ratios of meadow to woodland, act as buffers against drought and wildfire, and influence important climate parameters such as carbon retention and methanogenesis. The Cranberry Glades (~1000 m a.s.l.) occupy ~300 ha, including ~40 ha of regionally rare, open peatlands. Given the likely historical role of beaver activity in the formation and maintenance of peatland conditions at Cranberry Glades, monitoring of recent activity may be useful in predicting future changes. We analyzed remotely sensed data to identify and reconstruct shifting patterns of surface hydrology associated with beaver ponds and dams and developed a novel application of geomorphons to detect them, aided by exploitation of absences and errors in Lidar data. We also quantified decadal-timescale dynamics of beaver activity by tallying detectable active impoundments between 1990–2020, revealing active/fallow cycles and changing numbers of impoundments per unit area of suitable riparian habitat. This research presents both a practical approach to monitoring beaver activity through analysis of publicly available data and a spatiotemporal reconstruction of three decades of beaver activity at this rare and imperiled “Arctic Island” of the southern High Alleghenies. Keywords: geomorphon; Lidar; beaver; remote sensing; peatland; ecotone; Cranberry Glades; hydrology 1. Introduction Beavers (Castor spp.) are ecosystem engineers that often have profound impacts on their terrestrial and riverine environments, especially peatlands [1]. The two extant species, North American (Figure 1a) and Eurasian beaver (C. canadensis and C. fiber, respectively), are quite similar in both appearance [2] and even building behavior when confronting similar circumstances [3]; thus, in this paper we cite relevant literature pertaining to either species. Beaver impoundments enhance floodplain connectivity and geomorphic dynamism [4,5], wetland diversity [6], and local resilience to drought and fire [7]. Beaver ponds and vegetation consumption can greatly alter local hydrology and ratios of meadow to woodland; moreover, they influence important climate parameters such as carbon retention and methanogenesis [8]. Beaver can be important drivers of biomass carbon retention, with an impact comparable to old-growth forest, when impounding streams in unconfined segments of mountain valleys; conversely, abandonment of their dams and meadows by beavers can reduce carbon storage within living and dead biomass [9]. Humans (Homo sapiens) and beavers often come into conflict, especially along the upper reaches of stream courses where habitat alterations are most pronounced [10–14], and C. canadensis has become naturalized as an exotic invasive species in places such as southern Patagonia and much of Europe [15]. Both C. canadensis and C. fiber are ranked as of “least concern” by the International Union for Conservation of Nature [16]. Beaver activity Land 2021, 10, 1333. https://doi.org/10.3390/land10121333 https://www.mdpi.com/journal/land