Assessing Sampling Methodologies Used to Monitor Riparian Plant Communities
Hisham Al-Waer1, Aziz Syammach2*, Kelly Tobin3, Giovana Davison4, Olivia Larson5, Anna Vogt6, Anna Sher7
1University of Tripoli, Tripoli, Libya
2University of Denver, Denver, Colorado, United States
3University of Denver, Denver, Colorado, United States
4University of Denver, Denver, Colorado, United States
5University of Denver, Denver, Colorado, United States
6University of Denver, Denver, Colorado, United States
7University of Denver, Denver, Colorado, United States
To effectively monitor restoration projects, long term data collection is needed to inform adaptive management plans and produce accurate recommendations for future projects. Such long-term monitoring relies on frequent sampling of sites and so methods used need to be cost effective (i.e. time efficient) while accurately capturing community abundance and richness. A range of sampling methods are used to monitor restoration outcomes. These include point intercept, line transect, nearest neighbor, meter-square quadrats, densitometer, and nested Whittaker plots. No study has compared the time use efficiency of these methods nor their accuracy in estimating species cover and richness. Additionally, the ability of these six methods to sample riparian plant communities accurately and efficiently in the Western US has not been evaluated either. Therefore, there is no science-based guidance that can help restoration practitioners choose which method is most appropriate for monitoring their projects. To fill this gap in the literature, we used the six sampling methods listed above to monitor a total of 25 riparian plant communities two times a year for two years. Sites are in Eastern and Western Colorado. Overall, we found that time use efficiency (time needed to sample sites) did not significantly vary with the exception that nested Whitiker plots were significantly quicker. In terms of species cover, nested Whittaker plots captured more understory cover although there was no difference in methods used to capture overstory cover or species richness. Due to this, we recommend that if the goal is to monitor both understory and overstory responses to restoration, then the line-point intercept method should be used as it is the only method that captures both ecosystem components simultaneously and is therefore the most efficient to implement in the field. However, if the goal is to monitor the understory, then, nested Whittaker plots should be used due to the increased accuracy and high time use efficiency of this method. Therefore, these findings provide insights into what sampling methods should be used to monitor restoration outcomes depending on the ecosystem component that is being targeted for recovery.