Urban development is expanding rapidly, leaving a patchwork of small, isolated forests in its wake. Urban areas tend to have more paved surfaces that retain heat leading to an urban heat island effect. Nearby, forests are subjected to higher temperatures leading to higher evaporative demand from leaf surfaces while soil compaction and altered water flow can lead to limited soil water availability. This may be particularly detrimental for young seedlings that are vulnerable to desiccation.
Our understanding of how the urban heat island impacts the physiology and survival of native tree seedlings is limited. There is evidence that mature trees can acclimate to the urban heat island by adjusting their leaf biochemistry. Research has also shown that the seedlings of mature trees that have been subjected drought over several years can tolerate drought better than seedlings from naïve trees. The question is, does this happen in our urban forests? Are the seedlings from urban trees “prepped” for the urban heat? If the stress (e.g. heat, low soil moisture) of urban sites in the Cleveland areas is strong enough, then the parent trees should confer drought tolerance to their offspring via water-use changes. In turn, this should lead to higher survival in urban tree seedlings.
Using a common greenhouse approach, my research will compare the ability of Red Maple and Red Oak seedlings originating from urban and rural locations to tolerate drought conditions. Along with student intern, Miranda Shetzer, I will be measuring photosynthetic rates, water status, and survival of the plants throughout the drought treatments. We hope our project will shed light on the key ecological processes that may allow remnant urban forests to regenerate, as well as identify physiological traits that allow tree seedlings to persist in urban forests. This ecological information on the trajectory of urban remnant forests can help practitioners make critical decisions regarding conservation of these areas and the potential benefits of using native seed source for plantings.