Tyler Volk
New York University, Biology, Faculty Member
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A modified CROPGRO model is applied to phasic temperature and photoperiod control in order to optimize soybean production for NASA's program in Advanced Life Support. Baseline model simulations were established using data from soybean... more
A modified CROPGRO model is applied to phasic temperature and photoperiod control in order to optimize soybean production for NASA's program in Advanced Life Support. Baseline model simulations were established using data from soybean temperature experiments conducted at elevated CO2 levels (1100 micromol mol-1) at Utah State University (USU). The model simulations show little advantage in using phasic temperature control alone to increase average seed yield rate over the USU experimental values. However, simulations that combine phasic control of temperature (two phases) and photoperiod (two phases) do indicate the potential to improve seed yield (in g m-2 day-1) by approximately 15% over those currently obtained experimentally at USU for soybean cultivar Hoyt. This temperature and photoperiod phasing is experimentally practical. The simulations suggest extending photoperiods over those typically used experimentally during later phases of the crop life cycle, which would length...
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A modified CROPGRO model is applied to phasic temperature and photoperiod control in order to optimize soybean production for NASA's program in Advanced Life Support. Baseline model simulations were established using data from soybean... more
A modified CROPGRO model is applied to phasic temperature and photoperiod control in order to optimize soybean production for NASA's program in Advanced Life Support. Baseline model simulations were established using data from soybean temperature experiments conducted at elevated CO2 levels (1100 micromol mol-1) at Utah State University (USU). The model simulations show little advantage in using phasic temperature control alone to increase average seed yield rate over the USU experimental values. However, simulations that combine phasic control of temperature (two phases) and photoperiod (two phases) do indicate the potential to improve seed yield (in g m-2 day-1) by approximately 15% over those currently obtained experimentally at USU for soybean cultivar Hoyt. This temperature and photoperiod phasing is experimentally practical. The simulations suggest extending photoperiods over those typically used experimentally during later phases of the crop life cycle, which would length...
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Journal o f Big History, Volume IV , Number 3 Introduction: Patterns and Metapatterns Patterns are fundamental to big history. A focus on patterns allows us to formulate a unified field of study, linking things as disparate as protons,... more
Journal o f Big History, Volume IV , Number 3 Introduction: Patterns and Metapatterns Patterns are fundamental to big history. A focus on patterns allows us to formulate a unified field of study, linking things as disparate as protons, stars, oceans, amoebas, trees, ancient cities of Mesopotamia, and democracies. Toward this end, David Christian’s (2011, 505) words are spot on: “Of all the patterns that occur at many different scales, the most fundamental is the existence of pattern itself.” We patternologists are concerned not only with patterns of things. Things have relations (affordances, capabilities). Thus, relations are an important type of pattern for big history. Jack The Metapattern of General Evolutionary Dynamics and the Three Dynamical Realms of Big History
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Radiation-use efficiency (dry matter produced per unit absorbed radiation) of a spring wheat (Triticum aestivum L., cv. Veery-10) was 40% higher in controlled growth chamber experiments than under optimal field conditions. Simulations... more
Radiation-use efficiency (dry matter produced per unit absorbed radiation) of a spring wheat (Triticum aestivum L., cv. Veery-10) was 40% higher in controlled growth chamber experiments than under optimal field conditions. Simulations with CERES-Wheat, a field model modified to account for growth chamber conditions, suggest that the observed increase in radiation-use efficiency was due to the large fraction of diffuse light in the experimental chamber. Under optimal conditions in the field, the highest crop growth rates occur when the daily photosynthetic photon flux (PPF) is at its highest levels (50-60 mol m-2 d-1). However, these high growth rates do not appear to be associated with the highest radiation-use efficiency. High PPF levels in the field occur on clear days when the fraction of direct radiation is high and the diffuse fraction is low. In controlled environments with reflective walls, high PPF levels with a large fraction of diffuse radiation can be obtained. Diffuse radiation penetrates to the lower leaves of a canopy better than direct radiation, with the result that the upper leaves are less light saturated and the lower leaves receive more light, increasing radiation-use efficiency, and thus growth rates. The data and model simulations presented here suggest that when diffuse light is a high fraction of the total PPF crop productivity can exceed the highest values attainable in the field under optimal conditions.
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Page 1. Thinking of Biology Gaia and evolutionary biology T he Gaia concept has achieved some prominence in the dis-course of earth-system science. ... Although many biologists have been hostile to the Gaia concept, the debate may lead to... more
Page 1. Thinking of Biology Gaia and evolutionary biology T he Gaia concept has achieved some prominence in the dis-course of earth-system science. ... Although many biologists have been hostile to the Gaia concept, the debate may lead to fruitful inquiry ...
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The carbonate, soft tissue, and solubility 'pump' processes by which the steady state distribution of CO2 at the ocean surface is depleted relative to that at depth are treated. While the first two result from the biological flux... more
The carbonate, soft tissue, and solubility 'pump' processes by which the steady state distribution of CO2 at the ocean surface is depleted relative to that at depth are treated. While the first two result from the biological flux of organic and CaCO3 detritus at the ocean's surface, the third is due to the increased CO2 solubility in downwelling cold water.
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Use of plants in advanced life support requires models of crop growth to analyze data, to evaluate areas for improvement, and, for design and engineering, to predict the gas exchanges of crops. We used data from experiments at Utah State... more
Use of plants in advanced life support requires models of crop growth to analyze data, to evaluate areas for improvement, and, for design and engineering, to predict the gas exchanges of crops. We used data from experiments at Utah State University and the Kennedy Space Center for wheat (Triticum aestivum L.) and examined it for time dependence of the major three components in the energy cascade: photosynthetic photon absorption, canopy quantum yield, and carbon use efficiency. From the Utah State data, we developed a model with a total of five trends: absorption increasing until canopy closure, then constant; quantum yield as constant, then decreasing during senescence; carbon use as constant. This system probably is the lower limit of simplicity to which a model can be reduced and yet provide substantial utility. We demonstrated this utility by using the model to predict photosynthesis and respiration for experiments at Kennedy Space Center. The most uncertainty arose in predictin...
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Phasic control refers to the specification of a series of different environmental conditions during a crop's life cycle, with the goal of optimizing some aspect of productivity. Because of the enormous number of possible scenarios,... more
Phasic control refers to the specification of a series of different environmental conditions during a crop's life cycle, with the goal of optimizing some aspect of productivity. Because of the enormous number of possible scenarios, phasic control is an ideal situation for modeling to provide guidance prior to experiments. Here we use the Ceres-Wheat model, modified for hydroponic growth chambers, to examine temperature effects. We first establish a baseline by running the model at constant temperatures from 10 degrees C to 30 degrees C. Grain yield per day peaks at 15 degrees C at a value that is 25% higher than the yield at the commonly used 23 degrees C. We then show results for phasic control limited to a single shift in temperature and, finally, we examine scenarios that allow each of the five phases of the life cycle to have a different temperature. Results indicate that grain yield might be increased by 15-20% over the best yield at constant temperature, primarily from a b...
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Research Interests: Biochemistry, Bioinformatics, Evolutionary Biology, Environmental Science, Developmental Biology, and 15 moreClimate Change, Computational Biology, Biotechnology, Cancer, Biology, Cell Cycle, Ecology, Drug Discovery, Evolution, Astrophysics, Functional Genomics, Astronomy, DNA, Cell Signalling, and Earth Science
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An analysis developed by Westgate et al. for the digestible energy of edible and inedible biomass, including hydrolysis and fermentation, is reexamined with state-of-the-art values for the harvest index of hydroponic crops.
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Phenological development affects canopy structure, radiation interception, and dry matter production; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate... more
Phenological development affects canopy structure, radiation interception, and dry matter production; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate as a function of temperature and daylength among wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) cultivars. Leaf emergence rate and phyllochron were modeled as functions of temperature alone, daylength alone, and the interaction between temperature and daylength. The resulting equations contained an unwieldy number of constants. Here we simplify by reducing the constants by > 70%, and show leaf emergence rate as a single response surface with temperature and daylength. In addition, we incorporate the effect of photosynthetic photon flux into the model. Generic fits for wheat and barley show cultivar differences less than +/- 5% for wheat and less than +/- 10% for barley. Barley is more sensitive to daylength changes than wheat for common environmental values of daylength, which may be related to the difference in sensitivity to daylength between spring and winter cultivars. Differences in leaf emergence rate between cultivars can be incorporated into the model by means of a single, nondimensional factor for each cultivar.
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The scientists supported by the NASA sponsored Controlled Ecological Life Support Systems (CELSS) program have played a major role in creating a Committee on Space Research (COSPAR) section devoted to the development of bioregenerative... more
The scientists supported by the NASA sponsored Controlled Ecological Life Support Systems (CELSS) program have played a major role in creating a Committee on Space Research (COSPAR) section devoted to the development of bioregenerative life support ...
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Page 1. Thinking of Biology Gaia and evolutionary biology T he Gaia concept has achieved some prominence in the dis-course of earth-system science. ... Although many biologists have been hostile to the Gaia concept, the debate may lead to... more
Page 1. Thinking of Biology Gaia and evolutionary biology T he Gaia concept has achieved some prominence in the dis-course of earth-system science. ... Although many biologists have been hostile to the Gaia concept, the debate may lead to fruitful inquiry ...
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We use a previously-developed model of wheat growth, which was designed for convenient incorporation into system-level models of advanced space life support systems. We apply the model to data from an experiment that grew wheat under... more
We use a previously-developed model of wheat growth, which was designed for convenient incorporation into system-level models of advanced space life support systems. We apply the model to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. We examine the adequacy of modeling the transpiration as proportional to the inedible biomass and an age factor, which varies during the life cycle. Results indicate that during the main phase of vegetative growth in the first half of the life cycle, the rate of transpiration per unit mass of inedible biomass is more than double the rate during the phase of grain development and maturation during latter half of the life cycle.
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Design/methodology/approach The authors review examples of Bateson's great pattern of combination, which the authors call the binary. Bateson showed that binary is the minimal solution to the problem of gaining new... more
Design/methodology/approach The authors review examples of Bateson's great pattern of combination, which the authors call the binary. Bateson showed that binary is the minimal solution to the problem of gaining new characteristics by combining parts into a larger whole. ...
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We explore the implications of indicating the biosphere's self-organization by the trend over time of the net entropic flow from the Earth's surface, the actual physical boundary of virtually all biotic mass. This flow, derived from the... more
We explore the implications of indicating the biosphere's self-organization by the trend over time of the net entropic flow from the Earth's surface, the actual physical boundary of virtually all biotic mass. This flow, derived from the radiative surface entropy budget, is approximately inversely related to the surface temperature when the solar incident flux remains constant. In the geophysiological (‘gaian’) interpretation, biospheric self-organization has increased with the progressive colonization of the continents and evolutionary developments in the land biota, as a result of surface cooling arising from biotic enhancement of weathering. The key site for this self-organization is at the interface between land and atmosphere, the soil, where carbon is sequestered by its reaction (as carbonic and organic acids) with calcium magnesium silicates. Along with disequilibrium (steady-state) levels of carbon dioxide in the atmosphere, the occurrence of differentiated soil is the critical material evidence for biospheric self-organization, whether it be geophysiological or geochemical (ie., purely result of inorganic reactions). The computed equilibrium levels of carbon dioxide and corresponding equilibrium temperatures in the past are dramatically different from the steady-state levels. With future solar luminosity increase, the biospheric capacity for climatic regulation will decrease, leading to the ending of self-organization some two billion years from now. The Earth's surface will then approach chemical equilibrium with respect to the carbonate-silicate cycle.
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By Late Cretaceous or early Tertiary time, the diversification and proliferation of angiosperm-deciduous ecosystems resulted in higher rates of mineral weathering. This increase in the global average weathering rate would have caused a... more
By Late Cretaceous or early Tertiary time, the diversification and proliferation of angiosperm-deciduous ecosystems resulted in higher rates of mineral weathering. This increase in the global average weathering rate would have caused a decrease in atmospheric carbon dioxide and, hence, global cooling. The magnitude of this decrease is quantitatively explored here by developing a formulation for global weathering which combines ecosystems that differ in their fractional global coverage and intrinsic rates of weathering. Incorporating this formulation into models—specifically, several previously developed global steady-state models of the geochemical cycle of carbon between the atmosphere and carbonate rocks—gives results that show signifi-cant global cooling from the evolution of the angiosperm-deciduous ecosystems. This cooling may vary from a few degrees up to 10°C. In this way, deciduous ecosystems with high rates of mineral weathering could have contributed to the evolution during the past 100 m.y. of a cooler Earth and thus were a factor in producing conditions that enhanced their global proliferation.
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[Amerscan Journal of Science, Vol. 287, October, S987, P. 763-779) FEEDBACKS BETWEEN WEATHERING AND ATMOSPHERIC C02 OVER THE LAST 100 MILLION YEARS TYLER VOLK Department of Applied Science, New York University, New York, New York 10003 ...
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A model of the carbonate-silicate geochemical cycle is presented that distinguishes carbonate masses produced by shallow-ocean and deep-ocean carbonate burial and shows that reasonable increases in deep-ocean burial could produce... more
A model of the carbonate-silicate geochemical cycle is presented that distinguishes carbonate masses produced by shallow-ocean and deep-ocean carbonate burial and shows that reasonable increases in deep-ocean burial could produce substantial warmings over a few hundred million years. The model includes exchanges between crust and mantle; transients from burial shifts are found to be sensitive to the fraction of nondegassed carbonates subducted into the mantle. Without the habitation of the open ocean by plankton such as foraminifera and coccolithophores, today's climate would be substantially colder.
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A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance.... more
A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photo...