Red oaks (Quercus rubra) and white oaks (Quercus alba) co-occur throughout eastern US forests, but possess different functional traits that allow them to occupy separate ecological niches. Both oaks are ring porous and contain easily-distinguishable earlywood vessels that are used to transport water vertically through the tree stem. However, the characteristics of the earlywood vessels differ between the two species, with white oaks vessels containing tyloses that occlude earlywood vessels and reduce the risk of embolism. The different vessel characteristics between the two species indicate potential tradeoffs in the hydraulic strategies. We sought to characterize these tradeoffs and how they influence tree response to climate variability and forest management of co-occurring trees at an oak-dominated deciduous forest at The Morton Arboretum in northern Illinois. We quantified the average vessel area, vessel density, and total conductive area of earlywood vessels in tree cores taken from oaks in four management units that receive different levels of prescribed fire at The Morton Arboretum.
Results/Conclusions
Vessel characteristic measurements were compared between red and white oaks to see if any significant differences were present and we used 1980-1985 as a pre-management reference period to provide a baseline for climate-driven growing strategies and focus on effects of management in 2000-2017. Prior to intensive management (1980-1985), red and white oaks had similar total conductive area in their annuals rings, but red oaks had 23% higher vessel density compared to white oaks (p=0.01), but 36% smaller vessels (p<0.01). Differences in vessel size and density among red and white oaks are indicative of alternate strategies for minimizing risk of embolism. The different hydraulic strategies for embolism avoidance may impact plant water use during drought stress and may impact tree growth responses to interannual climate variability and forest management.