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 radial growth, and other plant traits.
We monitored 40 individual trees, including 9 species, at an arboretum in northeast Ohio. Radial growth of each individual was measured weekly from April to December using dendrometer bands. Canopy (i.e. leaf) phenology was assessed weekly during leaf development (April to May) and senescence (August-December). Annual carbon storage was estimated using allometric equations and radial growth data. We hypothesized that canopy phenology and annual carbon storage would vary substantially among species, that the timing and rate of carbon storage would be constrained by canopy and wood phenology, and that both canopy phenology and carbon storage would be constrained by other plant traits, including wood anatomy and leaf morphology.
Results/Conclusions
Preliminary results from 2018 indicate substantial interspecific variation in the rate of carbon storage (F=12.1, p<0.001), timing of carbon storage (F=12.44, p<0.001), and the duration of canopy greenness (F=5.39, p<0.001). While neither the timing nor the rate of carbon storage appears to be constrained by canopy phenology, the rate of carbon storage was strongly constrained by its timing. Specifically, we found that species which initiate storage earlier in the season accumulate more carbon than those that do so later (R2=0.35, p<0.001), and that the ‘early’ species generally cease to accumulate carbon earlier in the season than the ‘late’ species (R2=0.23, p<0.01). Furthermore, we found that carbon storage was strongly constrained by wood anatomy (t=-6.91, p<0.001), with ring porous species accumulating significantly more carbon than diffuse porous species. This suggests that ‘fast’ species (i.e. early growing species with ring porous vessels) are good candidates for maximizing carbon sequestration, although these same species may also be vulnerable to early season droughts. We will expand this analysis by measuring an additional subset of traits related to carbon storage and phenology, including foliage density, canopy volume, and drought tolerance.