Digitized images provide more accuracy and efficiency to estimate bryophyte cover

Abstract

Bryophytes constitute important components of many ecosystems. However, the methods used to measure their dominance have remained unchanged during the last 25 years. Herein we compare accuracy, efficiency and objectivity among three methods used to estimate bryophyte cover: Braun-Blanquet cover classes, grid percentage and digital image processing. Using these methods, two observers determined bryophyte cover on 30 clay tiles planted with Neckeropsis disticha. Accuracy among methods was estimated by relating the cover values with the dry weight. Efficiency was estimated using the relation between time and data variability. Objectivity was estimated by comparing the variability between observers. The digital method resulted in less time in the field (F = 272, p < 0.001) and lower variation among data (F = 0.55, p = 0.02) than from the other two methods. Our results showed that the digital processing method was more reliable as it minimized observer effect in the cover values while providing higher efficiency in the field. The method is especially useful in monitoring studies that use repeated measurements because it helps to detect small variations in bryophyte cover. This method is particularly useful to improve the analysis in communities with low bryophyte cover, such as tropical epiphylls.