Simple Street Tree Sampling
David J. Nowak, Jeffrey T. Walton, James Baldwin, and Jerry Bond
Abstract: Information on street trees is critical for management of this important resource. Sampling of street tree populations provides an efficient means to obtain street tree population information. Long-term repeat measures of street tree samples supply additional information on street tree changes and can be used to report damages from catastrophic events. Analyses of several street tree populations reveal that a 2%–3% sample of block segments with known length within a city will likely produce estimates on the total number of trees with a standard error around 10% of the total population estimate (relative standard error of 10%). Ratio estimates of number trees per length of street sampled reduced the number of block segments needed to attain a 10% relative standard error. Communities with a small tree population, or analyses of specific subsets of the population (e.g., individual species information), will likely need a higher proportion of block segments sampled to attain the same relative precision. This paper presents a simple means to sample street tree populations to aid in street tree management and presents information on how many block segments need to be sampled to achieve a desired sampling precision. Results can be used to develop simple, cost-efficient, and accurate means to sample street tree populations.
Keywords: Block Sampling; Ratio Estimates; Sample Size; Street Trees.