Presence-absence sampling for estimating plant density using survey data with variable plot size

1. Presence-absence sampling is an important method for monitoring state and change of both individual plant species and communities. With this method only the presence or absence of the target species is recorded on plots and thus the method is straightforward to apply and less prone to surveyor judgment compared to other vegetation monitoring methods. However, in the basic setting all plots must be equally large or otherwise it is unclear how data should be analyzed. In this study we propose and evaluate five different methods for estimating plant density based on presence-absence registrations from surveys with variable plot sizes.
2. Using artificial plant population data as well as empirical data from the Swedish National Forest Inventory we evaluated the performance of the proposed methods. The main analysis was conducted through sampling simulation in the artificial populations, whereby bias and variance of density estimators for the different methods were quantified and compared...