Browsing by Subject "Quercus rubra"

Now showing 1 - 5 of 5
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    Are shade tolerance, survival, and growth linked? Low light and nitrogen effects on hardwood seedlings
    (1996) Walters, Michael B; Reich, Peter B
    Variation in shade tolerance is a primary mechanism driving succession in northern deciduous forests. However, little is known about interspecific differences in the traits responsible for shade tolerance. Is shade tolerance due to the ability to grow or survive in deep shade, or both? How do plant morphology and photosynthesis relate to growth in shade? Is low light the sole critical stress determining differences in "shade tolerance" or do below ground resources interact with low light to affect growth and survival? In this study we address these questions for seedlings of Betula papyrifera Marsh., Betula alleghaniensis Britton, Ostrya virginiana (Mill.) K. Koch, Acer saccharum Marsh., and Quercus rubra L. grown for 2 yr in outdoor shade houses in a complete factorial of low light (2 and 8% open sky) and nitrogen (forest soil and forest soil plus 200 kg N.ha-'.yr-'). For these seedlings we examined effects of light and nitrogen on the interrelationships among survival, growth, and shade tolerance and explored the physiological bases of shade tolerance by examining the relationship of plant morphology and photosynthesis to growth. Nitrogen amendments did not have a significant effect on any plant trait at either light level. In 8% light, growth and survival were highest for shade-intolerant Betula papyrifera and mid-tolerant Betula alleghaniensis, lower for shade-tolerant Ostrya and Acer, and lowest for disturbance-adapted Quercus. In 2% light, species rankings reversed as Ostrya and Acer had higher growth and survival than the other species. Second-year survival was strongly related to 1st-yr growth (P < 0.001), whereas relationships with 1st-yr plant mass and 1styr absolute growth rates were weak. Therefore, survival of shade-tolerant species at 2% light was related to their maintenance of positive growth, whereas intolerant species had growth near zero and high rates of mortality. In both 2 and 8% light photosynthetic rates on mass (but not area) bases and the proportion of the plant in leaves (leaf area ratio and leaf mass ratio) were positively related to growth. Greater rates of growth and survival for shade-tolerant species in very low light, and for intolerant species in higher light, suggest that there is a species-based trade-off between maximizing growth in high light and minimizing the light compensation point for growth. This trade-off may be an important mechanism driving forest community dynamics in northern hardwood forests.
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    Coordination of Phloem Function and Anthocyanin Accumulation in Senescing Leaves of Quercus rubra
    (2023-11) Rooney, Rebecca
    Autumnal senescence is an important annual occurrence for many deciduous temperate species, as it is the final period for plants to regain limiting nutrients from leaf tissue. Effective remobilization requires efficient breakdown of cellular components and translocation into perennating tissues via the phloem, a vascular tissue primarily responsible for the transport of photoassimilates. Anthocyanins are a pigment that accumulate in some species during senescence and are hypothesized to confer a photoprotective role in senescing leaves. Anthocyanin biosynthesis is regulated, in part, by sugar signaling, and girdling studies have linked phloem to anthocyanin accumulation to the augmentation of sugar concentrations in leaf tissue. While these studies show that halted translocation is associated with anthocyanin biosynthesis, natural changes in the phloem during autumnal senescence have yet to be examined with respect to anthocyanin. Here I elucidate how changes in phloem function (e.g., leaf carbon export and callose deposition) corresponds to soluble sugars and anthocyanin buildup in leaf tissue during senescence. I found that while phloem function declined throughout senescence, soluble sugars did not accumulate in leaf tissue. Despite this, anthocyanin content did significantly increase by the end of the season. Carbon export did not correlate to anthocyanin buildup or callose deposition. Instead, carbon export corresponded to changes in the proportions of leaf soluble sugars, while anthocyanic leaves were associated with higher fructose concentrations. My results indicate that soluble sugars are involved in multiple processes in senescing leaves and their relationship to anthocyanin and phloem is nuanced. This study provides insight into how phloem function declines during senescence, while prompting further studies into the regulation of phloem transport and how changes in this system may impact other leaf functions during autumnal senescence.
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    Phenotypic And Molecular Insight Into Genetic Differentiation, Introgression And Selection In Quercus Rubra At A Fine Spatial Scale
    (2021-07) Gomez Quijano, Maria Jose
    The massive scale and cold temperature of Lake Superior creates unique microclimates in coastal terrestrial environments resulting in cooler summers, an extended fall season, warmer winters, and a reduced risk of spring frost. This gives rise to a steep climate gradient from coastal to inland regions that could lead to genetic differentiation among populations. To test this hypothesis, we studied Northern red oak (Quercus rubra L.) to examine phenotypic and molecular differentiation among populations ranging from 1–160 km from the lake shore. In a common garden experiment, we found 30% of germination and juvenile traits differed significantly from expectation. We also used restriction site associated DNA sequencing (RAD-seq) to examine population structure and genomic signatures of selection in these populations. Our results suggest that, in contrast to quantitative traits, Q. rubra populations are not differentiated at neutral genetic markers according to their distance from Lake Superior. However, unexpectedly, we also found evidence of increasing levels of introgression from the closely related species Quercus ellipsoidalis E.J. Hill into Q. rubra as species overlap and population distance from the lake increased. Our scan for selection and environmental association analysis identified one outlier locus in common, and this locus is associated with the precipitation of the wettest month. Overall, despite the lack of molecular population structure, the common garden experiment revealed that Q. rubra populations differ for key phenotypic traits. This, in combination with the genomic scans for selection, suggests the influence of natural selection driven by climate heterogeneity with increasing distance from the lake. Moreover, this is the first study that has jointly leveraged quantitative and molecular genetics to dissect signatures of selection in Q. rubra across a fine geographical scale.
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    Water relations: Soil fertility, and plant nutrient composition of a pygmy oak ecosystem
    (1980) Reich, Peter B; Hinckley, Thomas M
    The water and nutrient relations of Buzzard's Roost, an unusual pygmy oak ecosystem in southwest Missouri, USA, were studied in 1976 and 1977 in an attempt both to characterize the ecophysiology of the individuals and find the causative agents for the existence of the pygmy forest. The stunted trees were mostly blackjack oak (Quercus marilandica) with some northern red oak (Q. rubra) and a few black oak (Q. velutina). In addition to being stunted, the trees were gnarled and twisted and had miniature leaves and acorns. Results of soil analysis showed the pygmy forest soil to be very acidic (pHw = 4.6), with very low levels of Ca and Mg (0.25 and 0.12 meq/100 g, respectively) and very high levels of Al (600 ppm). Adjacent non-pygmy forest soils did not display these characteristics. Foliar analysis of blackjack, northern red, and black oak showed Ca and Mg to be much lower in pygmy foliage than in non-pygmy foliage, at three times during the growing season. Diurnal and seasonal patterns of xylem pressure potential, leaf conductance, and soil moisture content illustrated the development of very severe tree water deficits at Buzzard's Roost. Predawn and midday xylem pressure potentials declined to as low as -3610 and -4200 kPa, respectively, accompanied by complete daytime stomatal closure. However, water stresses in nearby non-pygmy oaks were greater than at two of three pygmy oak sites, implying that water stress was not the major factor or causative agent in the stunting process. The evidence suggests that the very low nutrient levels in the soil, especially of Ca and Mg, plus the very high levels of Al, may be deficient (and/or toxic) for normal tree growth and development, and possibly responsible for the existence of the pygmy oak forest. Also, the xeric site characteristics add another severe stress to this ecosystem.
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    Why do coastal seeds fail? Evidence of local adaptation of northern red oak ( Quercus rubra ) in Minnesota coastal forests - Genomics and Geospatial Data
    (2020-04-30) Gomez Quijano, Maria Jose; Gross, Briana, L.; Etterson, Julie, R.; gomez312@d.umn.edu; Gomez Quijano, Maria Jose; University of Minnesota Duluth Gross Lab; University of Minnesota Duluth Etterson Lab
    Genomic and Geospatial data for 30 northern red oak (Quercus rubra) used in a study to identify population structure and investigate poor performance of coastal seeds. We used restriction site associated DNA sequencing (RADseq) of 358 northern red oak (Quercus rubra) leaf tissue samples from trees across the state of Minnesota and 45 northern pin oak (Quercus ellipsoidalis) leaf tissue samples used as outgroups. We used the Minnesota Department of Natural Resources releve data, to identify populations across the state of Minnesota that had presence of Q. rubra trees.