Comparison of densiometer and inexpensive hemispherical photography to assess streamside canopy
June 2016 - December 2018
- US Fish and Wildlife Service
The spherical densiometer is a common field tool that measures the overstory density, commonly known as canopy cover, of forested areas. This tool has been used in several fish habitat studies, stream surveys, and sampling protocols when assessing coverage of riparian vegetation over streams. Although densiometers are very effective they cannot visually document an ever-changing canopy. Hemispherical photography is another tool that has been developed to evaluate the forest canopy. Photographs are taken in an upward direction using a wide-angle lens and post processed with image-analyzing software. However, hemispherical photography systems are typically expensive (~$2,000-$8,000), time consuming, and highly susceptible to damage when used in aquatic environments. The purpose of this study was to develop an inexpensive, fast, and rugged hemispherical photography system that can be used in aquatic ecosystems without fear of damage of equipment. We obtained paired densiometer readings and hemispherical photographs using GoPro Hero 4 action camera at sites in the Verde River in central Arizona. We post-processed the photos using two different image editing software programs. The inexpensive hemispherical photography method we developed provided cover measurements which were correlated (r = 0.8546, P < 0.05) with densitometer measurements, but could also provide a visual record of the overstory (different plant species, and amounts). Hemispherical photography, with further development, will be a useful addition or alternative to densitometer measurements for measuring stream canopy. Results are now being prepared for a thesis and a publication. Partners include USFS and USFWS.