Abstract Detail

Ecology

Sterner, Sarah [1], Palmquist, Emily [2], Ralston, Barbara [3].

Comparison of vegetation cover sampling methods for riparian vegetation.

Vegetation cover is a basic metric used in monitoring programs across ecosystems to assess change. The line-point intercept (LPI) and meter-square plot ocular estimates (plots) are two commonly used methods, and they are both used in long-term monitoring for riparian habitats in the southwest U.S. In some ecosystems, the LPI method has been found to have less error between observers and be more time efficient. Ocular estimate plots tend to record more species and among observer error, identified as a downfall of this method, can be reduced by initiating calibration plots among observers. We compared methods at four sample sites along the Colorado River downstream from Glen Canyon Dam to determine how cover values varied by method and by observer in a particularly dense, multi-layered ecosystem. We determined that LPI measurements among observers were as variable, and in some cases, more variable than plot measurements. Taking into account all indicators, we showed that LPI plots had a higher coefficient of variation among observers than ocular plot samples in 59% (151 of 254) of all instances. PERMANOVA analysis indicated that both methods identified significant differences in cover estimates among sample sites (p < 0.05), but not among observers (p > 0.05). Among observers, cover values did not differ within each site for the combined indicators (multivariate) and four individual indicators (total live cover and three species) (PERMANOVA, p > 0.05), with only one exception (total foliar cover at one site for plots). Additionally, plot measurements recorded more species than LPI, regardless of the amount of experience of the observer. For the three observers in our study that sampled all four of the sites, on average each observer recorded nine additional species in the ocular plot samples than in the LPI samples. For riparian habitats that are known for high species diversity and high numbers of infrequent species, these results suggest that meter square plot ocular estimates may be more informative and provide robust long-term trend data for monitoring in this riparian ecosystem.

1 - U.S. Geological Survey; Southwest Biological Science Center, Grand Canyon Monitoring and Research Center , 2255 N. Gemini Drive, Flagstaff, AZ, 86001, USA
2 - USGS, Grand Canyon Monitoring and Research Center, 2255 N Gemini Dr, Flagstaff, AZ, 86001, USA
3 - U.S. Geological Survey , Office of Science Quality and Integrity , 2255 N. Gemini Drive, Flagstaff, AZ, 86001, USA

Keywords:
Riparian vegetation
Line Point Intercept sampling method
Ocular plot samplng method
Landscape-scale vegetation change
Vegetation survey methods comparison.

Presentation Type: Poster
Session: P, Ecology
Location: Exhibit Hall/Omni Hotel
Date: Monday, June 26th, 2017
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEC001
Abstract ID:61
Candidate for Awards:None