Imperiled Ecosystems in a Shifting Climate
2016 Atlantic White Cedar Symposium
May 24-26, 2016

Hotel 1620, 180 Water St., Plymouth, MA

Application of UAS technology to monitor Atlantic White-Cedar (AWC) seed dispersal and regeneration success on Hofmann Forest, North Carolina
Travis Howell and Glenn Catts

North Carolina State University, College of Natural Resources, Department of Forestry and Environmental Resources, Raleigh, NC.

Abstract
Hofmann Forest is an 32,375 hectare forest centered on a pocosin having some of the oldest planted Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.] (AWC) in coastal North Carolina. The earliest AWC plantations in HF were established in 1965 as several hectares in species trials at the intersection of Quaker Bridge and Pocosin roads near the center of the pocosin. The 1965 planted AWC was never fostered in any way, but was able to slowly reproduce immediately adjacent to the original planting. The dense shrubby nature of the natural pocosin vegetation precluded significant spread of AWC in the area. In 2010, a 32 hectare block across the road from the original 1965 planting was cleared and site prepared to plant longleaf pine. Work in wetland mitigation banking on Hofmann Forest has shown that longleaf pine grows well on the deep organic histosols (Croatan muck) found in the block. Normal site preparation involves herbicide followed by strip-shearing and bedding.  Immediately after exposing the bare organic soil in the block, the AWC that seeded the site from across the road took a thriving foothold. There is no other potential nearby AWC seed source, so this is an excellent place to examine the natural seeding pattern and spread of AWC after site disturbance.

The objective of this study is to count young AWC regeneration, map its spatial spread in the recently cleared site and measure AWC tree heights using inexpensively acquired UAS aerial imagery, publically available LIDAR and Open Source spatial software to maximize data collection efficiency while minimizing cost. Complete overlapping aerial coverage was obtained by use of the “Drones Made Easy Map Pilot” software in the field at the time of flight. Photos acquired at low/high nadir (up to 122 meters) were utilized in conjunction with Agisoft Photoscan Pro to create a 3D model of the site. LAS files having a resolution of 2 postings per square meter (with as many as 5 returns per posting) were downloaded from the recently created beta website hosting the 2014 LIDAR flown in coastal North Carolina. Bare earth points were exported using Open Source LIDAR software (Fugro Viewer and /or USFS Fusion toolkit). GRASS GIS was used to calculate the difference between a bare earth surface created from LIDAR ground terrain data and the canopy surface (generated from UAS imagery by Agisoft) to estimate AWC tree heights. Recognition of AWC seedlings was done ocularly using color differences observed on UAS imagery.  Results include a map of spatial spread of seedlings in relation to 1965 AWC plantings. In addition, an array of fixed-area field plots coincident with UAS imagery were used to develop regression relationships between estimates of AWC seedlings per acre and AWC seedling heights for both methods. Costs of UAS & field methods and a hybrid approach are compared.

Travis Howell is a second year Master's of Science student at North Carolina State University researching the applications of unmanned aerial systems within Natural Resources and Forestry. His background includes a B.S in Forest Management as well as experience in the timber procurement industry.