Responses of Red Oak Species Differing in their Flood Tolerance to Extreme Climatic Events

Project Information

Principal Investigator: Marco Yáñez (University of Arkansas at Monticello)
Project Start: August 2024
Proposed Project Completion: July 2026
Implements Science Plan Theme:  At-Risk Species
Co-Investigators:
Hamdi Zurqani (University of Arkansas at Monticello)
Benjamin Babst (University of Arkansas at Monticello)

Overview:

Bottomland Hardwood Forests (BHF) in the Lower Mississippi Alluvial Valley (LMAV) are considered a biodiversity hotspot in North America. However, because of the historical anthropogenic degradation and fragmentation, these forests are currently one of the most vulnerable ecosystems to climate change. In BHF, specially adapted oak species are a major component of the vegetation and have high economic, environmental, and social value for the communities along the Mississippi River. Oak species are spatially distributed within the floodplain according to their flood tolerance and are classified according to this attribute. Nonetheless, the higher fluctuations in precipitation and drought events predicted for this century, combined with higher temperatures, are expected to increase the physiological stress on oak trees, consequently threatening their growth and persistence in their current ecological niche. Because flooding is generally assumed to be the major stress to trees in bottomlands, drought stress in BHF has received very little consideration. This study aims to assess the vulnerability of red oak species differing in their flood tolerance to extreme climatic events.

The objectives of this study are:

1. To generate a vulnerability map in BHF based on the dryness potential using elevation and spectral canopy index, such as the normalized difference vegetation index (NDVI)
2. to evaluate the impact of past instances of flooding and drought events on the growth and physiological performance of mature trees of red oak species differing in flood tolerance, and relate tree performance to expected future climate.

In selected areas with BHF in Arkansas, elevation maps and spectral canopy indices will be integrated using machine learning algorithms to identify areas prone to both flooding and drought. Additionally, using historical climatic data, we will identify dry and wet years in the study area. Then, satellite images of those years will be obtained and used to calculate spectral indices associated with the canopy vigor and vegetation greenness, which will be used as the spectral signal for water stress. This information will be used to identify sampling sites, where two red oak species differing in flood tolerance will be marked and cored at DBH. Wood cores will be submitted for dendrochronological analysis. In parallel, we will extract the associated tree rings associated with wet and dry years to estimate water use efficiency through carbon isotope discrimination. Analyses will be focused on the differential response of the species to contrasting climatic events (wet versus dry years), which will allow us to have a better understanding of their potential vulnerability under the climate change scenario. The results of this project will be disseminated to scientific audiences (scientific journals and conferences) as well as forestry practitioners (fact sheet production and workshops). New datasets collected within the project and maps of vulnerability zones for the impact study area will be publicly available. The intended beneficiaries of the project are different nongovernmental organizations and government agency stakeholders involved with the conservation and management of this ecosystem.