Estimating plant abundance in irregular polygons: plot-based sampling with a conditional spatial configuration

When estimating plant species abundance using plot-based methods in irregular polygons, there are some constraints to the spatial configuration of the sampling plots: i) the sample plots must be positioned within the polygon, ii) the sample plots may not overlap, iii) due to the spatial variation in abundance often found in natural plant communities, the spatial coverage must be relatively large in order to decrease the sampling variance, iv) due to a possible mosaic structure of the vegetation, systematic designs should be avoided due to the possibility of biased estimates. Here, we suggest a protocol using simulations of the possible random spatial configurations to select a conditional spatial configuration that meets these constraints.