Analysis of ecosystem service assessment and estimation accuracy of street trees using i-Tree Eco

This study evaluated the ecosystem services provided by street trees and examined the relationship between sample size and estimation accuracy using the i-Tree Eco model. A complete inventory of 249 Zelkova serrata trees along Oike Street in Kyoto, Japan, was conducted to obtain detailed tree structural data. Ecosystem services were assessed based on six key indicators: tree replacement value, carbon storage, carbon sequestration, air pollutant removal, stormwater runoff reduction, and total annual benefits. To examine the influence of sample size, a bootstrap resampling simulation (n = 10,000) was conducted using R. The results showed that a sample of 10 to 15 trees (4.0% - 6.0% of the total population) yielded estimation errors below 10% for all indicators, while a sample of 40 to 60 trees (16.1% - 24.1%) reduced errors to below 5%. Across the three confidence interval methods, interval widths were comparable, and given simplicity and cost, percentile and standard error methods are practical. These findings indicate that reliable estimates of street tree ecosystem services can be obtained with smaller sample sizes, enhancing the efficiency and feasibility of applying i-Tree Eco in urban tree management. This study offers practical insights for designing effective survey strategies and promoting sustainable green infrastructure planning.