Oak sapling recruitment is a major concern in the Midwest including the Chicago area based on the predicted longer summer droughts driven by climate change. Mature oak (Quercus alba L.) trees can perform hydraulic redistribution and thus specifically benefit the overall soil health and ecosystem function; oak tap roots draw deep soil water to the upper drier soil layers with specific benefit during droughts. This research tests whether mature white oaks in three locations within Mary-Mix McDonald Woods Forest Preserve in the Chicago Botanic Garden (CBG) demonstrate a positive effect on saplings through hydraulic lift and redistribution of deep soil water during summer drought, and concurrently assesses the shallow lateral hydrological redistribution of water to nearby saplings via mycorrhizal networks that persist during summer drought. These associations also work as an extension of the oak’s root system by allowing for the sharing of water and nutrients with nearby saplings and saplings through common mycorrhizal networks. We investigated the soil moisture dynamic, sapling height as a biomass growth metric, isotopic distribution of deuterium (δD) and oxygen-18 (ẟ18O) from leaf and aqueous source (lake, rainwater and surface runoff) water, mycorrhizal functional type distribution, and light intensity (photosynthetic photon flux density or PPDF) and ambient / subsurface soil temperature. The mean soil moisture, sapling height and mycorrhizal types differed between the three subsite locations. Notably, in Area-2 – the central area – sapling height was 12 cm shorter than in the other two areas, and this area had the lowest mean soil moisture and the fastest rate of decline in soil moisture after rain events. Light intensity differed between the three sites quantitatively but not qualitatively. Suggesting that soil moisture in this location has a greater influence in sapling growth patterns than light availability. We do not find evidence that hydraulic lift occurs in mature oaks in the woods based on the isotopic signatures. We also do not find that water is shared between saplings and mature trees. This study provides insight that can assist in understanding hydrologic patterns in fragmented suburban forests in the northeastern portion of Illinois.

Last modified

• 08/12/2022

Creator

• Ry'yan Clark

Contributors

• Magdalena Osburn
• William Miller
• Patricia Beddows
• Louise Egerton-Warburton

DOI

• https://doi.org/10.21985/n2-e7nc-zm90

Keyword

• hydrogeology
• oak
• hydraulic lift
• recruitment
• stable isotopes
• hyphae morphological type
• sapling
• photosynthetic photon flux density
• common mycorrhizal networks

Date created

• 2022-08-09

Rights statement

• No Known Copyright