Knowledge about individual tree species health and growth in the urban environment can provide urban forest managers with useful decision making tools for planning and managing successful afforestation projects. Urban environmental conditions are often different from conditions found in rural ecosystems. Anthropogenic influences can result in an environment which includes high levels of atmospheric pollutants, soils that contain chemical contamination and construction debris, higher temperatures and exotic invasive plant species in addition to vandalism and other ongoing human disturbances. The NYC Afforestation Project in Kissena Park, Queens, NY was designed to explore the performance of an assemblage of six native species under various treatments: tree species diversity (two/ six), shrubs/ no shrubs, and compost/ no compost. We conducted an annual assessment on the health and growth of approximately 1,300 trees across 54 experimental plots (2011 – 2015) following planting of 3-5year-old seedlings. We measured caliper and height and assessed each tree for signs of stress which included vigor, drought, pest and leaf discoloration ratings. These ratings were standardized and combined into one stress index score for each tree. We examined differences in tree health between individual treatments and examined whether the stress index was related to the following year’s tree size.
Results/Conclusions
Previously published analysis of growth data three years post planting showed that the one-time addition of compost and the presence of shrubs had a positive effect on tree growth at the species level. This analysis, five years post planting, shows the same trends that existed after three years except that the addition of compost was not a significant factor for growth of Celtis occidentalis or Prunus serotina. In addition, species-level analyses identified that tree stress is negatively correlated with caliper, height, and volume in all species. Also, the stress index is a significant predictor of the following year’s caliper, height, and volume for all six species. Including the stress index improved model fit (AIC) for all six species’ models. These results show that amending soils with compost at the time of planting and the inclusion of shrubs in planting have a long-lasting and increasing impact on the health performance of young trees. In addition, rapid tree health assessment methods can be a valuable tool for managers as they assess the current status of young trees and help pinpoint areas of concern in time to prevent mortality.