Street Tree Inventory: A Case Study Comparing Systematic Sampling vs. Stratified Systematic Sampling in Piracicaba City, Brazil

Abstract Background The inventory of street tree populations has acquired new importance due to interest in the provision of ecosystem services. That said, this paper aims to compare systematic sampling with stratified systematic sampling using different sizes of sampling units to estimate the variables of interest: number of trees per kilometer of sidewalk ( D F ), basal area per kilometer of sidewalk ( D g ), mean total height , volume per kilometer of sidewalk ( D V ), and number of species per kilometer of sidewalk ( D E ). An innovative contribution here is testing new alternative density variables. Methods In the densely urbanized area of Piracicaba (Sao Paulo State, Brazil), 90 sets of 4 blocks were systematically sampled. They were used to compose sampling units of 1, 2, 3, and 4 blocks. Stratification was based on the percentage of street tree cover obtained with geoprocessing tools. Only public trees with a circumference at breast height greater than or equal to 12 cm and planted on sidewalks or avenue medians were included. Results The effect of sampling unit size and stratification on estimate accuracy, sample size, and sampling intensity were analyzed. The results show that stratified systematic sampling was the more accurate process, especially for D F , D g , and D V . Conclusions Reductions in sample size were more significant when stratified systematic sampling of 2-block sampling units were used.