Browsing by Subject "Quercus"

Now showing 1 - 6 of 6
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    Fire Affects Ecophysiology and Community Dynamics of Central Wisconsin Oak Forest Regeneration
    (1990) Reich, Peter B; Abrams, Marc D; Ellsworth, David S; Kruger, Eric L; Tabone, Tom J
    In order to understand better the ecophysiological differences among competing species that might influence competitive interactions after, or in the absence of, fire, we examined the response to fire of four sympatric woody species found in intermediatesized gaps in a 30-yr-old mixed-oak forest in central Wisconsin. Selected blocks in the forest were burned in April 1987 by a low-intensity controlled surface fire. The fire had significant effects during the following growing season on community structure, foliar nutrient concentrations, and photosynthesis. Acer rubrum seedling density declined by 70% following the fire, while percent cover increased several-fold in Rubus allegheniensis. In general, leaf concentrations of N, P, and K were increased by the fire in all species, although the relative enhancement decreased as the growing season progressed. Daily maximum photosynthetic rates were 30-50% higher in burned than unburned sites for Prunus serotina, Quercus ellipsoidalis, and R. allegheniensis, but did not differ between treatments for A. rubrum. Mean sunlit photosynthetic rates and leaf conductances were stimulated by the burn for all species, with the greatest enhancement in photosynthesis measured in Q. ellipsoidalis. Leaf gas exchange in R. allegheniensis was most sensitive to declining leaf water potential and elevated vapor pressure gradient, with Q. ellipsoidalis the least sensitive. Fire had no discernable effect on water status of these plants during a year of relatively high rainfall. In comparison with other species, A. rubrum seedlings responded negatively after fire-both in terms of survival/reproduction (decline in the number of individuals) and relative leaf physiological performance. Fire enhanced the abundance of R. allegheniensis and the potential photosynthetic performance of R. allegheniensis, P. serotina, and particularly Q. ellipsoidalis. We conclude that post-fire stimulation of net photosynthesis and conductance was largely the result of enhanced leaf N concentrations in these species.
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    Functional leaf and stem traits of the Oaks of the Americas
    (2020-06-26) Kaproth, Matthew A; Hahn, Marlene; Manos, Paul S; Hipp, Andrew L; González-Rodríguez, Antonio; Cavender-Bares, Jeannine; cavender@umn.edu; Cavender-Bares, Jeannine; Oaks of the Americas Group
    Leaf and stem trait data: Measured interspecific variation of Quercus (L.) - totaling 15+ functional traits for 135* American oak species. Our goal was to hand-measure/characterize as many North American species as possible. Measurements include: (1) specific leaf area (SLA, mm2 mg), an important leaf economic spectrum (LES) trait associated with leaf lifespan, resource acquisition, and nutrient use (Wright et al., 2004; Reich, 2014), (2) perimeter per unit leaf area (PLA, cm−1), a leaf trait that increases with degree of lobing and decreases with leaf size and is associated with hydraulic conductance and boundary layer resistance for all species (Sack et al., 2003; Kaproth and Cavender‐Bares, 2016), (3) total length of major veins per area (cm−1), associated with leaf hydraulic function (Sack and Scoffoni, 2013), (4) leaf length (mm), (5) petiole length (mm), and (6) stem specific density (g·cm−3), associated with mechanical strength and drought tolerance (Cornelissen et al., 2003; Kunstler et al., 2015). Specimens from sunlit branches were pressed and dried alongside samples collected for herbarium specimens as part of the Oaks of the Americas Project (Hipp et al., 2018).
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    Mapping oak wilt disease from space using land surface phenology
    (Remote Sensing of Environment, 2023-12-01) Guzmán, Jose A; Pinto-Ledezma, Jesús N; Frantz, David; Townsend, Philip A; Juzwik, Jennifer; Cavender-Bares, Jeannine
    Protecting the future of forests relies on our ability to observe changes in forest health. Thus, developing tools for sensing diseases in a timely fashion is critical for managing threats at broad scales. Oak wilt —a disease caused by a pathogenic fungus (Bretziella fagacearum)— is threatening oaks, killing thousands yearly while negatively impacting the ecosystem services they provide. Here we propose a novel workflow for mapping oak wilt by targeting temporal disease progression through symptoms using land surface phenology (LSP) from spaceborne observations. By doing so, we hypothesize that phenological changes in pigments and photosynthetic activity of trees affected by oak wilt can be tracked using LSP metrics derived from the Chlorophyll/Carotenoid Index (CCI). We used dense time-series observations from Sentinel-2 to create Analysis Ready Data across Minnesota and Wisconsin and to derive three LSP metrics: the value of CCI at the start and end of the growing season, and the coefficient of variation of the CCI during the growing season. We integrate high-resolution airborne imagery in multiple locations to select pixels (n = 3872) from the most common oak tree health conditions: healthy, symptomatic for oak wilt, and dead. These pixels were used to train an iterative Partial Least Square Discriminant (PLSD) model and derive the probability of an oak tree (i.e., pixel) in one of these conditions and the associated uncertainty. We assessed these models spatially and temporally on testing datasets revealing that it is feasible to discriminate among the three health conditions with overall accuracy between 80 and 82%. Within conditions, our models suggest that spatial variations among three CCI-derived LSP metrics can identify healthy (Area Under the Curve (AUC) = 0.98), symptomatic (AUC = 0.89), and dead (AUC = 0.94) oak trees with low false positive rates. The model performance was robust across different years as well. The predictive maps were used to guide local stakeholders to locate disease hotspots for ground verification and subsequent decision-making for treatment. Our results highlight the capabilities of LSP metrics from dense spaceborne observations to map diseases and to monitor large-scale change in biodiversity.
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    Natural selection and neutral evolutionary processes contribute to genetic divergence in leaf traits across a precipitation gradient in the tropical oak Quercus oleoides
    (2018-02-28) Ramírez-Valiente, José A.; Deacon, Nicholas J.; Etterson, Julie; Center, Alyson; Sparks, Jed P.; Sparks, Kimberlee L.; Longwell, Timothy; Pilz, George; Cavender-Bares, Jeannine; cavender@umn.edu; Cavender-Bares, Jeannine; LOARD: Live Oak Adaptation and Response to Drought project
    The impacts of drought are expanding worldwide as a consequence of climate change. However, there is still little knowledge of how species respond to long-term selection in seasonally-dry ecosystems. In this study, we used QST-FST comparisons to investigate (i) the role of natural selection on population genetic differentiation for a set of functional traits related to drought resistance in the seasonally-dry tropical oak Quercus oleoides and (ii) the influence of water availability at the site of population origin and in experimental treatments on patterns of trait divergence. We conducted a thorough phenotypic characterization of 1896 seedlings from ten populations growing in field and greenhouse common gardens under replicated watering treatments. We also genotyped 222 individuals from the same set of populations using eleven nuclear microsatellites. The data sets include all of the raw data used in the analyses include nuclear microsatellites from populations examined in the field common garden, phenotypic data from a field common garden, nuclear microsatellites from populations examined in a greenhouse experiment, and phenotypic data from a field common garden.
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    Physiological and fitness consequences of seasonal rainfall variation in neotropical live oak seedlings (Quercus oleoides): implications for global change
    (2015-06) Center, Alyson
    Broadly distributed species often span a large range of environmental conditions, which pose contrasting physiological challenges. Such species are thought to persist across this heterogeneity, either by locally adapting or by evolving wide environmental tolerances via phenotypic plasticity or maintaining high genetic variation. The extent to which populations display local adaptation, phenotypic plasticity, and high within-population genetic variation will have large impacts on species responses to climate change. Large- scale habitat fragmentation impedes migration making plasticity and adaptation important mechanisms for in situ persistence. Using common gardens with reciprocal plantings we investigated the consequences of changes in water availability in the broadly distributed tropical live oak, Quercus oleoides. Chapter 1 examines the relationship among seed production timing, germination and seedling fitness at the local scale in dry forests of NW Costa Rica. In chapter 2, I investigate the extent to which four populations of Q. oleoides from regions with contrasting rainfall patterns exhibit local adaptation and the role of changes in water availability on seedlings fitness. In chapter 3, I examine the extent that populations exhibit differentiation in traits related to carbon and water use. Chapter 3 also investigates the role of trait plasticity in seedling responses to changes in seasonal water availability and the patterns of phenotypic selection on traits. Results from these studies show that local-scale differences in seed production timing have significant consequences for germination and seedling fitness. At a larger spatial scale, results of this work indicate that the broadly distributed Q. oleoides does not consist of a series of locally adapted populations, but rather, of populations with wide environmental tolerances. Seedlings from all populations show similar physiological and morphological responses to changes in water availability and differences among garden sites. Trait plasticity contributes more to phenotypic trait variation than within-population genetic differences. Overall, populations of Q. oleoides lineage represent a lineage well-adapted to drought. Populations are able to maintain fitness with changes in water availability in the short-term through plasticity but may be limited in their long-term adaptive capacity to future changes in rainfall patterns due to low within-population genetic variation for physiological traits.