Browsing by Author "Fallon, Beth"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Leaf and canopy spectra, symptom progression, and physiological data from experimental detection of oak wilt in oak seedlings
    (2019-04-26) Fallon, Beth; Yang, Anna; Nguyen, Cathleen; Armour, Isabella; Juzwik, Jennifer; Montgomery, Rebecca A.; Cavender-Bares, Jeannine; eafallon@gmail.com; Fallon, Beth; University of Minnesota, Department of Ecology, Evolution, and Behavior; University of Minnesota, Department of Forestry; US Forest Service Northern Research Station
    These data were collected as part of an experimental effort to accurately detect oak wilt infections in oak seedlings using remote sensing tools and to differentiate that disease stress from other mechanisms of tree decline. Oak wilt disease causes rapid mortality in oaks in the central and eastern United States. Management of the disease requires early diagnosis and tree removal to prevent fungal spread. Hyperspectral tools provide a potential method of early remote diagnosis, but accurately differentiating oak wilt from other agents of oak decline is integral to effective management. We conducted experiments (2017 and 2018) on two year old seedlings of Quercus ellipsoidalis and Q. macrocarpa in which treatments were 1) maintained as healthy individuals, 2) subjected to chronic drought, or inoculated 3) stems with oak wilt fungus (Bretziella fagacearum, a fungal vascular wilt) or 4) leaves with bur oak blight fungus (Tubakia iowensis, a fungal leaf pathogen). We measured leaf and whole plant hyperspectral reflectance (350 to 2400nm, Spectra Vista HR 1024i spectroradiometer (Spectra Vista Corporation, New York, USA)), gas exchange (LI-6440XT with a leaf chamber fluorometer attachment (LI-COR Environmental, Nebraska, USA)), and tracked symptom development in repeated measures of seedlings over the course of each experiment. In 2018, we explicitly measured spectral reflectance and gas exchange on both symptomatic and green leaves, as available and we also measured collected thermal images of leaves twice during the experiment (2018 only).
  • Thumbnail Image
    Item
    Leaf-level trade-offs between drought avoidance and desiccation recovery drive elevation stratification in arid oaks: site environmental data, individual tree stem and leaf physiological data, and analyses
    (2018-02-14) Fallon, Beth; Cavender-Bares, Jeannine; eafallon@umn.edu; Fallon, Beth
    This dataset and RStudio project includes all processed data, most raw data, and R scripts needed for analysis and figure construction included in the manuscript Fallon and J. Cavender-Bares 2018 (Fallon B. and J. Cavender-Bares. 2018. Leaf-level trade-offs between drought avoidance and desiccation recovery drive elevation stratification in arid oaks. Ecosphere. in press). We investigated whether oak species in the Chiricahua Mountains were 1) elevationally stratified, 2) whether that stratification was correlated with temperature minima, maxima, and water availability, 3) if physiological tolerances to freezing or drought stress correlated with elevation ranges, and 4) if traits important to local (elevation) distributions were correlated with climatic values of the wider species ranges. Data were collected at field sites from wild, adult trees in the Chiricahua Mountains, Arizona, USA from 2014-2015.This research was done with funding to B. Fallon from the Southwestern Research Station (SWRS, American Museum of Natural History), the University of Minnesota Charles J. Brand, Carolyn Crosby, and Dayton Bell Fellowships, and the Department of Plant and Microbial Biology. Additional funding was provided by NSF Award 1146380 (J. Cavender-Bares PI). We performed all data collection under permit with the Coronado National Forest, Douglas Ranger District, managed by the United States Forest Service (USDA).
  • Thumbnail Image
    Item
    Physiological evidence for climate limitations of oak distributions at local and regional scales
    (2017-11) Fallon, Beth
    Understanding the extent to which physiological tolerances of climate may limit plant distributions is critical to predicting the effects of a changing climate. This dissertation research focuses on how responses to drought and cooling influence species ranges among oaks (Quercus L.), a globally-distributed woody genus that is highly diverse within the Americas. I used functional and physiological traits to investigate correlations between cold and drought resistances and climate at two scales: 1) local species elevation limits in a semi-arid montane system and 2) regional range limits among North and Central American oaks. In Chapter 1, I found that a trade-off between the leaf-level drought resistance traits of avoidance (leaf abscission) and desiccation recovery (leaf capacitance), and not stem freezing tolerance, influenced species sorting by elevation in a semi-arid mountain system in the southwestern US. In Chapter 2, I found that stem drought tolerance (xylem vulnerability) is correlated with aridity of climate of origin among oaks from across the Americas, but that the seasonality of precipitation best predicted leaf level drought avoidance (leaf habit and stomatal closure). Finally, in Chapter 3, I found that oak species in the Americas have different leaf level cooling responses (chlorophyll fluorescence measurements of photosynthetic stress and yield) that were correlated with minimum temperatures in their climate of origin, but that ability to acclimate to cold temperatures was best predicted by leaf phenology, not climate of origin. I also found that we could predict chlorophyll fluorescence measurements with models created from hyperspectral reflectance data measured on the same leaves. These models included regions of important biological significance, including wavelengths corresponding with reflectance of photosynthetic and protective pigments. Overall, there I found significant evidence that species distributions are strongly influenced by climate. Oak species have suites of traits as mechanisms of drought resistance, and these strategies are correlated with not only overall aridity in their current habitats, but with the seasonality of precipitation. Oak species may also be able to acclimate to cooler temperatures outside of those commonly experienced in their current range. Oak species within the Americas and the mountainous, arid southwest US, may be vulnerable to range shifts as global temperatures continue to rise and precipitation regimes change.