Young Urban Tree Growth Curves for Two NYC Tree Species

Summary

This presentation will compare growth of three tree species established in a mown grass tree lawn with the same species established in sidewalk using a designed soil installed across the street.  Over the past 16 years, tree dimensions have been recorded in a field study in New York City a total of 8 times.  Analysis and interpretation has been challenging due to early losses and a series of replacements in the tree lawn, reducing replication from which to directly compare growth and dimension (Grabosky et al.  2002, Grabosky and Bassuk 2008).    With the population in the tree lawn becoming stable over several years, individual growth curves for each tree can now be used to compare growth between the trees in the pavement and those in the tree lawn.   Consistent with previous research notes in A&UF, there is still no noticeable difference in mean height or DBH between the two sides of the street in the annual census of the tree population.  Comparing only the dimensions of the remaining original trees in a non-parametric analysis of median dimensions, it appears that while there is still no difference between treatments, although the trees in the lawn now no longer lag behind those in the street.   This is partially due to imbalance and low replication in the tree lawn due to higher mortality in the original cohort.  We correct for the smaller dimensions of the replacement trees and track each tree as an individual over multiple measurement visits, and then develop a species/treatment generalized growth curve for comparison.  Quadratic curves adequately describe growth curves of trunk diameter versus time post-transplant for two oak species (R2 of .86 -.94 in sidewalks as an example).   The growth curve analysis and growth trajectory will be discussed.  Analysis is on-going and there may be an influence of major reconstruction around the tree lawn for a public park renovation effort adjacent to the planting zone. 

Grabosky J and Bassuk N.  2008.  Growth of three tree species in designed stone-soil blend under pavement and non-paved lawn in a Brooklyn, New York Streetscape: tenth year data.  Arboriculture & Urban Forestry 34(4):265-266.

Grabosky J, Bassuk N, Marranca B.  2002.  Preliminary findings from measuring street tree shoot growth in two skeletal soil installations compared to tree lawn plantings.  Journal of Arboriculture 28(2):106-108.