Abstract
Cover data are used to assess vegetative response to a variety of ecological factors. Estimating cover in the herbaceous layer of forests presents a problem because the communities are structurally complex and rich in species. The currently employed techniques for estimating cover are less than optimal for measuring such rich understories because they are inaccurate, slow, or impracticable. A reference-based approach to estimating cover is presented that compares the area of foliar surfaces to the area of an observer’s hand. While this technique has been used to estimate cover in prior studies, its accuracy has not been tested. We tested this hand-area method at the individual plant, population, and community scales in a deciduous forest herbaceous layer, and in a separate farm experiment. The precision, accuracy, observer bias, and species bias of the method were tested by comparing the hand-estimated leaf area index values with actual leaf area index, measured using a leaf area meter. The hand-area method was very precise when regressed against actual leaf area index at the plant, population, and community scales (R 2 of 0.97, 0.93, and 0.87). Among the deciduous sites, the hand-area method overestimated leaf area index consistently by 39.1 % at all scales. There was no observer bias detected at any scale, but plant overestimation bias was detected in one species at the population scale. The hand-area method is a rapid and reliable technique for estimating leaf area index or cover in the forest herbaceous layer and should be useful to field ecologists interested in answering questions at the plant, population, or community level.
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Acknowledgments
We thank John Weems and Zach Fowler for permission to sample at the Core Arboretum and Barton Baker and Bobby Clemer at the West Virginia University Agronomy Farm. Also thanks to Phil Crim, Justin Mathias, and Sarah Nunley for their help measuring plant cover and to Donna Ford-Werntz for assistance in the West Virginia University Herbarium. We are grateful to Jennifer Chandler, Mike Elza, Jim McGraw, and Jessi Brie Turner for insightful feedback while writing this manuscript. Funding for this research was provided by the National Science Foundation from their Long Term Research in Environmental Biology (LTREB) program (grant nos. DEB-0417678 and DEB-1019522) and by the West Virginia University Eberly College of Arts and Sciences.
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Walter, C.A., Burnham, M.B., Gilliam, F.S. et al. A reference-based approach for estimating leaf area and cover in the forest herbaceous layer. Environ Monit Assess 187, 657 (2015). https://doi.org/10.1007/s10661-015-4878-7
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DOI: https://doi.org/10.1007/s10661-015-4878-7