Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
(N/A)
Non Technical Summary
Georgia produces an average of 100 million lb pf pecans annually, accounting for 1/3 of all U.S. pean production. In the past five years, southern Georgia was devastated by two major hurricanes. In late August of 2023, Hurricane Idalia made landfall in the Florida panhandle as a Category 3 hurricane and continued northeast, affecting pecan orchards in Valdosta and surrounding areas. Only five years earlier in October 2018, Hurricane Michael made landfall as a category 5 storm in the Florida panhandle and continued toward Albany, GA causing an estimated $560 million in lost pecan production in the southwestern part of the state.Pecan orchards are a major category of land use in rural Georgia andinfluence the economic and environmental footprint of the region.Existing guidelines to help pecan growers with hurricane mitigation are fairly sparse, providing advice on which varieties and soil types may be most susceptible to hurricanes, but these guidelines rely on anecdotal observations. The primary focus of this research is to estimate how wind risk varies with tree size and orchard placement.The study will determine the relationship between tree size and wind risk, enabling growers to implement preventative measures.We will also employ state-of-the-art satellite and computing technology to assess how landscape factors such as soil type, topography, and even orientation of orchard rows lead to different interactions with hurricane winds. We will work closely with pecan growers in the state and ensure the study's findings are directly applicable to local practices.This comprehensive approach will result in more precise recommendations for hurricane mitigation strategies.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The long-term goal of this research is to develop evidenced-based strategies to promote climate resilience in pecan orchards of the U.S. The overall objective is to use new information on wind risk to inform the development of hurricane mitigation guidelines for pecan growers. Bothtree properties and site factors influence susceptibility of pecan orchards to wind. Preliminary data suggeststhat wind susceptibility is sensitive to tree size. We propose three specific objectives:Objective 1: Identify tree-level factors that determine wind susceptibility in pecan. Our working hypothesis is that wind susceptibility first decreases, then increases with tree size. This is based on findings in natural forests and our aforementioned data in young pecan orchards demonstrating that wind risk is reduced at diameters >15 cm.Objective 2: Identify how site selection influences wind susceptibility. Our working hypothesis is that wind susceptibility will be highest in heavier soils, poorly-drained landscape positions, and more exposed sites, and adjacent to open fields.Objective 3: Connect pecan growers with updated wind mitigation guidelines. In collaboration with stakeholders, we will produce an outreach video on wind mitigation strategies based on the findings from Obj. 1-2. To maximize reach, we will produce blogs and briefs distributed through the Georgia and Southeastern Pecan Growers Associations.
Project Methods
Objective 1: Identify tree-level factors that determine wind susceptibility in pecan.To determine how stem size affects wind vulnerability, we will assess how hurricane mortality varies across a range of tree sizes. We will conduct immediate ground surveys from ~10 orchards that experienced damage from Hurricane Idalia. Because tree and stump removal is occurring rapidly, these measurements must be conducted immediately in coordination with growers whom we have already contacted. We will identify hurricane-impacted orchards containing a range of tree sizes concentrated in a relatively small area (~2 acres). At each orchard we will survey 100-200 trees across a range of sizes.We will measure diameter at root collar (drc) for dead trees, and measure both drc and dbh for surviving trees, and predict the dbh of stump. Our preliminary data suggests that dbh and stump diameter are strongly correlated.The final dataset will result in mortality and size measurements on up to ~1,500 trees from 10 orchards. To test the hypothesis that tree size influences susceptibility, we will model tree survival as a function of tree size using generalized linear mixedeffects models that incorporate a random effect for each site.Objective 2: Identify how site selection influences wind susceptibility.We will assess how hurricane severity in pecan orchards varies with wind intensity, soil type, topographic exposure, and landscape configuration. We will estimate hurricane damage severity to pecan orchards from Hurricanes Idalia and Michael by measuring changes in satellite-derived vegetation indexes that capture major changes in vegetation structure. After calibrating remotely measured hurricane damage with ground surveys of orchards we will relate damage patterns to landscape-scale factors. To measure mortality, we will compile pre- and post-hurricane imagery using Google Earth Engine. We will generate cloudless summer composite imagery by using multiple scenes from the summer months, and calculate the normalized difference vegetation index (NDVI), masking portions of imagery not classified as pecan cover. To calibrate changes in NDVI to damage severity, we will conduct ground surveys at ~200 points stratified across 20 orchards in the paths of Hurricanes Idalia and Michael. At each plot, we will collect standard tree inventory measurements to estimate aboveground biomass (AGB). We will relate ground-based measures of AGB to satellite-derived NDVI to estimate changes in AGB through time within the study area. We will compile landscape-scale data on maximum sustained hurricane wind speed, topography, soil type, and landscape configuration. Lastly, we will use generalized linear models that predict damage based on landscape variables.Objective 3: Connect pecan growers with updated wind mitigation guidelines.Our objective is to develop and deliver a communication strategy to deliver climate-smart wind buffering strategies to pecan growers. The strategy will emphasize the adoption of practical tactics and guide growers in site selection, cultivar selection, and canopy pruning practices. Our approach will be to develop recommendations based on outcomes from Objectives 1-2 and disseminate them through targeted meetings that attended by growers and industry professionals, and use written and video formats to reach a broader audience.