Browsing by Subject "growth rate"

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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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    Hirsch Lab UAV Commercial Maize Phenotyping Project at UMN SROC Waseca: 2020, 2021, and 2022
    (2024-04-22) Sweet, Dorothy D; Hirsch, Candice N; Hirsch, Cory D; cnhirsch@umn.edu; Hirsch, Candice N; Candice Hirsch Lab; Cory Hirsch Lab
    This dataset provides a valuable resource for evaluating the ability of unoccupied aerial vehicles to collect plant height information from commercial agricultural fields and predict within field variation in yield using temporal traits including plant height, growth rate, and vegetative indices. Many flights were conducted over commercial maize fields using an UAV equipped with an RGB camera and this dataset includes orthomosaics and digital elevation models generated from those flights as well as plot boundary shape files used for extraction of data from those flights. Data in this repository includes extracted plant height, extracted RGB vegetative indices, manual height measurements, weather data, soil data, and grain yield. This experiment consisted of three commercial fields containing single maize hybrids and is therefore useful in assessing the ability of UAV extracted values in identifying within field variation for prediction of yield. It can also be used to test different methods of extracting plant height values from commercial fields as it includes manual measurements of height to be used in evaluation.