Simulating Forest Stands By Resampling One-Acre Stem Maps: Spatial Characteristics of Results

Abstract

The purpose of this research is to generate forest stands for sampling simulations on anoperational level. In this research, a simulated forest stand consists of x and y coordinates ofstems and their attributes. One-acre stem maps are mapped stem locations and attributes from thefield. The simulation procedure is a two step process. The first step is to create discrete samplesfrom a one-acre stem map. Secondly, the discrete samples are selected randomly withreplacement and placed adjacently until a simulated forest stand of desired size and shape is built. The simulated forest stands are then compared with the one-acre stem map from which they werecreated by their respective average clump size, spatial point pattern, and spatial variability of stemdiameter. Average clump size is estimated using stem counts from grids of contiguous quadrats(Greig-Smith, 1952). Spatial point pattern is classified based on the mean and variance of first,second, third, and fourth nearest neighbor distances (Smith, 1977). The spatial variability of stemdiameter is assessed using the robust semi-variogram estimator (Cressie et al., 1980) The abilityof the simulation procedure to reproduce the above mentioned spatial characteristics is related tothe second order stationarity of stem diameter in the one-acre stem map. In this case, secondorder stationarity is the premise that the mean stem diameter is constant in the one-acre stem mapand the variance is only dependant on stem separation distance. Stem locations, the speciespercentages, and the coefficient of variation of stem diameter should be assessed to determine theapplicability of this simulation procedure for a particular one-acre stem map.