Compared to their natural counterparts, trees in urban ecosystems experience distinctive environmental conditions that can be beneficial (e.g., reduced resource competition) and harmful (e.g., higher ozone levels) to tree functions and fitness. Thus, the phenological and physiological functions of trees in urban ecosystems can be unique, and might not be predictable from patterns identified in natural forests, where most research on tree ecology has occurred. To better understand how different tree species contribute to ecosystem services in urban environments, including canopy shading, stormwater retention, and carbon sequestration, we characterized interspecific variation in leaf phenology, the timing and rate of stem (bole) growth, and other plant traits.
We monitored 220 individual trees, including 50 species, at an arboretum and cemetery in northeast Ohio. Stem (bole) growth of each individual was measured weekly from April to December using dendrometer bands. Leaf phenology was assessed weekly during leaf development (April to May) and senescence (August-December). We hypothesized that leaf phenology and bole growth would vary substantially among species, that the timing and rate of wood growth would be constrained by leaf phenology, and that both leaf phenology and wood growth would be constrained by other plant traits, including wood anatomy and leaf morphology.
Results/Conclusions
Results from 2017 indicate there is substantial interspecific variation with respect to bole growth and leaf phenology. Species identity was highly predictive of the timing of leaf out, leaf senescence, and the duration of canopy greenness (R2>0.7, p<0.0001). Bole growth varied less significantly and predictably among species (R2=0.49, p=0.001) and, although the timing of bole growth varied substantially among individuals and species, we did not detect a significant effect of species identity. Regression analyses suggest that species with shorter periods of canopy greenness and earlier leaf senescence can have high or low rates of bole growth, but species with longer periods of canopy greenness and later leaf senescence had low rates of bole growth. This suggests there might be a tradeoff among species between traits that maximize shade production and stormwater retention (late leaf senescence) and traits that maximize carbon sequestration in wood (bole growth). Species with late leaf senescence also tended to have bole growth extend later into the growing-season, suggesting leaf phenology is predictive of bole growth phenology. We will expand this analysis with growth and phenological data from a second growing-season, and with data on additional functional traits, including leaf economic traits and wood anatomy.