How reliable is the monitoring of permanent vegetation plots? A test with multiple observers

Abstract

Abstract Questions: A multiple plot design was developed for permanent vegetation plots. How reliable are the different methods used in this design and which changes can we measure ? Location: Alpine meadows (2430 m a.s.l.) in the Swiss Alps. Methods: Four inventories were obtained from 40 m2 plots: four subplots (0.4 m2) with a list of species, two 10m transects with the point method (50 points on each), one subplot (4m2) with a list of species and visual cover estimates as a percentage and the complete plot (40 m2) with a list of species and visual estimates in classes. This design was tested by five to seven experienced botanists in three plots. Results: Whatever the sampling size, only 45–63% of the species were seen by all the observers. However, the majority of the overlooked species had cover < 0.1%. Pairs of observers overlooked 10–20% less species than single observers. The point method was the best method for cover estimate, but it took much longer than visual cover estimates, and 100 points all...