Kevin A Simonin

Kevin A Simonin
San Francisco State University | SFSU · Department of Biology

31.73
 · 
Ph. D. Integrative Biology, UC Berkeley

About

48
Publications
9,553
Reads
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1,564
Citations
Research Experience
August 2014 - September 2020
San Francisco State University
Position
  • Associate Professor
January 2011 - July 2014
The University of Sydney
Position
  • Teaching and Research Fellow
January 2010 - December 2010
University of California, Berkeley
Position
  • PostDoc Position
Education
August 2003 - December 2009
August 2000 - December 2003

Publications

Publications (48)
Article
Full-text available
The abrupt origin and rapid diversification of the flowering plants during the Cretaceous has long been considered an “abominable mystery.” While the cause of their high diversity has been attributed largely to coevolution with pollinators and herbivores, their ability to outcompete the previously dominant ferns and gymnosperms has been the subject...
Article
Full-text available
For most angiosperms, producing and maintaining flowers is critical to sexual reproduction, yet little is known about the physiological processes involved in maintaining flowers throughout anthesis. Among extant species, flowers of the genus Calycanthus have the highest hydraulic conductance and vein densities of species measured to date, yet they...
Article
Full-text available
Maintaining water balance has been a critical constraint shaping the evolution of leaf form and function. However, flowers, which are heterotrophic and relatively short‐lived, may not be constrained by the same physiological and developmental factors. We measured physiological parameters derived from pressure‐volume curves for leaves and flowers of...
Preprint
Full-text available
A central challenge in plant ecology is to define the major axes of plant functional variation with direct consequences for fitness. Central to the three main components of plant fitness (growth, survival, and reproduction) is the rate of metabolic conversion of CO2 into carbon that can be allocated to various structures and functions. Here we (1)...
Preprint
Full-text available
Maintaining high rates of photosynthesis in leaves requires efficient movement of CO 2 from the atmosphere to the chloroplasts inside the leaf where it is converted into sugar. Throughout the evolution of vascular plants, CO 2 diffusion across the leaf surface was maximized by reducing the sizes of the guard cells that form stomatal pores in the le...
Preprint
Full-text available
The need to maintain water balance has been a critical constraints shaping the evolution of leaf form and function. Vein and stomatal traits have undergone coordinated evolution to maintain water supply and prevent water loss. However, flowers, which are heterotrophic and relatively short-lived, may not be constrained by the same physiological and...
Article
Full-text available
Many efforts to improve science teaching in higher education focus on a few faculty members at an institution at a time, with limited published evidence on attempts to engage faculty across entire departments. We created a long-term, department-wide collaborative professional development program, Biology Faculty Explorations in Scientific Teaching...
Article
Full-text available
The abrupt origin and rapid diversification of the flowering plants during the Cretaceous has long been considered an “abominable mystery.” While the cause of their high diversity has been attributed largely to coevolution with pollinators and herbivores, their ability to outcompete the previously dominant ferns and gymnosperms has been the subject...
Article
Full-text available
During the Cretaceous (145-66 Ma), early angiosperms rapidly diversified, eventually outcompeting the ferns and gymnosperms previously dominating most ecosystems. While the cause of their high diversity has been attributed largely to coevolution with pollinators and herbivores, their ability to outcompete the previously dominant ferns and gymnosper...
Data
Fossil data of anatomical traits plotted with limits of trait values reconstructed from extant species (curves from Fig 4). Data can be found in S1 Data. (TIF)
Data
Bootstrapping analyses of the lower limit of genome size modeled from ancestral state reconstructions based on 35%, 52%, and 78% of angiosperm species in our entire dataset. Heavy black lines are the modeled limit from the entire dataset, and the light grey, red, and blue lines are the modeled limits from each of 100 replicate runs at each level of...
Data
Trait and PGLS regressions for all species and for only the angiosperms. Trait regressions are in the upper triangle and PGLS regressions are in the lower triangle. Values are regression slopes. Asterisks indicate significance level: *p < 0.05; **p < 0.01; ***p < 0.001. PGLS, phylogenetic generalized least squares. (DOCX)
Data
The distributions of genome size among angiosperms in the Kew plant DNA C-values database, which includes over 7,000 species, and of species sampled in the present study are not significantly different (t = 1.69, p = 0.1). (a) Untransformed distributions and (b) Log-transformed distributions. In both figures, the number of species for the Kew datab...
Data
lg, Ds, and Dv for species used in the analysis. Ds, stomatal density; Dv, vein density; lg, guard cell length. (DOCX)
Data
lg, Ds, and Dv for species used in the analysis. Ds, stomatal density; Dv, vein density; lg, guard cell length. (XLSX)
Data
The number of currently accepted species for 20 named clades in our phylogeny is strongly correlated with the number of species representing those clades in our dataset (r = 0.69, p < 0.001). (TIFF)
Article
Understanding how major food crops respond to environmental stress will expand our capacity to improve food production with growing populations and a changing climate. This study uses chemical and physiological adaptations to heat, water deficit and elevated light stresses in Phaseolus vulgaris L. to identify changes in carbon (C) allocation that,...
Article
Stomata represent one resistor in a series of resistances for carbon and water exchange between the leaf and the atmosphere; the remaining resistors occurring within the leaf, commonly represented as mesophyll conductance to CO2, gm, and leaf hydraulic conductance, kLeaf. Recent studies have proposed that gm and kLeaf may be coordinated across spec...
Article
Full-text available
The use of carbon isotope abundance (δ13C) to assess plant carbon acquisition and water use has significant potential for use in crop management and plant improvement programs. Utilising Phaseolus vulgaris L. as a model system, this study demonstrates the occurrence and sensitivity of carbon isotope fractionation during the onset of abiotic stresse...
Article
Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C4 plants. An online oxygen isotope technique was developed to allow quantification of mesophyll conductance in C4 plants and to provide an alternative estimate in C3 plants. The technique is compared to an establishe...
Article
Full-text available
Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals inco...
Article
Full-text available
The combined use of a gas-exchange system and laser-based isotope measurement is a tool of growing interest in plant ecophysiological studies, owing to its relevance for assessing isotopic variability in leaf water and/or transpiration under non-steady state (NSS) conditions. However, the current Farquhar & Cernusak (F&C) NSS leaf water model, orig...
Article
The two-pool and Péclet effect models represent two theories describing mechanistic controls underlying leaf water oxygen isotope composition at the whole-leaf level (δ18OL).To test these models, we used a laser spectrometer coupled to a gas-exchange cuvette to make online measurements of δ18O of transpiration (δ18Otrans) and transpiration rate (E)...
Article
Full-text available
Stable oxygen isotope techniques may be a useful tool to investigate the pathways of water movement within leaves. However, implementation of such methods is limited due to uncertainty in the effective path length (L) for the Péclet effect in leaf water enrichment models. Previous studies have found relationships between L and physiological paramet...
Article
Full-text available
Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between s...
Article
Obtaining the d-excess parameter from oxygen and hydrogen stable isotope composition of meteoric waters has the potential power to reconstruct changes in atmospheric water pools (e,g. sources, origins and overall balance) and the climatic conditions that prevail during surface evaporation. Recently, plant and ecosystem scientists turned their atten...
Article
In Mediterranean climates, the season of water availability (winter) is out of phase with the season of light availability and atmospheric moisture demand (summer). We investigate the seasonality of evergreen tree transpiration in a Mediterranean climate, using observations from a small (4000 m2), forested, steep (32°) hillslope, in the northern Ca...
Article
Full-text available
During daylight hours the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange syste...
Article
Full-text available
Previous research suggests that the lifetime carbon gain of a leaf is constrained by a tradeoff between metabolism and longevity. The biophysical reasons underlying this tradeoff are not fully understood. We used a photosynthesis-leaf water balance model to evaluate biophysical constraints on carbon gain. Leaf hydraulic conductance (K(Leaf)), carbo...
Article
Transpiration varies with the availability of sunlight and water as well as with tree species. We present high frequency observations of sap flow in a small, steep (>30 degree) watershed in the northern California coastal range, where there is a distinct summer dry season and winter wet season. We investigate how heterogeneous patterns of atmospher...
Conference Paper
Background/Question/Methods Many tropical forests experience one or more dry seasons annually. There is growing recognition that seasonal variation in water availability is a strong environmental force that shapes tropical plant species diversity, distribution, and functional biology. Research on tropical plant response to seasonal changes in wat...
Chapter
Forests cover approximately one third of the terrestrial land surfaces (Hansen et al. 2000) and are arguably the most important biome type on Earth for acquiring, transforming, and recycling major and limiting biogeochemical resources such as water, carbon, and many mineral elements such as nitrogen or phosphorous; well-documented drivers of global...
Article
Field studies and models generally presume that the transition from the soil mantle to the underlying bedrock is a major hydrologic boundary: plants rely on soil moisture, shallow subsurface flow develops along the soil/rock boundary, and water that enters the bedrock takes a slow path, recharging deep groundwater. Three intensive field studies in...
Article
Determining the contribution of the soil and biotic surfaces to water cycling on Earth has been best accomplished using H and O stable isotope information, including one key variable called the ``d-excess''. The d-excess or the y-intercept of the Global Meteoric Water Line (GMWL) was first given explicit consideration by Dansgaard (1964) and furthe...
Article
The regulation of Earth's climate and its ability to sustain life are critically linked to water as it exists in all three of its phases (gas, liquid, and solid). Earth's water cycle, its movement between the hydrosphere, biosphere, and the atmosphere, and how it undergoes phase changes, is incredibly complex. While we continue to gain insight into...
Article
Stable isotope analysis of water is a proven tool for gaining insight into the processes that govern the hydrologic cycle. One of the most challenging aspects of characterizing the movement of water between the biosphere, hydrosphere, and the atmosphere has been capturing shifts in the isotope value of ambient water vapor. Traditional methods of cr...
Article
Hilly and mountainous landscapes are often capped by relatively thin soil that mantles a thicker, but nonetheless relatively shallow fractured bedrock zone. The few studies that have quantitatively explored this near-surface zone have demonstrated that subsurface runoff, saturation overland flow, and pore pressure development are dominated by pathw...
Article
Full-text available
The stable oxygen isotope ratio (delta(18)O) of plant material has been shown to contain essential information on water and carbon fluxes at the plant and ecosystem scales. However, the effective path length (L(m)), a parameter introduced to leaf-water models still requires a comprehensive biological characterization to allow interpretation of delt...
Article
Full-text available
Evaluations of plant water use in ecosystems around the world reveal a shared capacity by many different species to absorb rain, dew, or fog water directly into their leaves or plant crowns. This mode of water uptake provides an important water subsidy that relieves foliar water stress. Our study provides the first comparative evaluation of foliar...
Article
Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indi...
Article
Stable oxygen isotope ratios (delta18O) have become a valuable tool in the plant and ecosystem sciences. The interpretation of delta18O values in plant material is, however, still complicated owing to the complex interactions among factors that influence leaf water enrichment. This study investigated the interplay among environmental parameters, le...
Article
Full-text available
It is commonly assumed that transpiration does not occur at night because leaf stomata are closed in the dark. We tested this assumption across a diversity of ecosystems and woody plant species by various methods to explore the circumstances when this assumption is false. Our primary goals were: (1) to evaluate the nature and magnitude of nighttime...
Article
Full-text available
To understand the effect of restoration thinning on the water balance of upland semi-arid ponderosa pine (Pinus ponderosa) forests of the southwestern US, we compared the components of forest water balance between an unthinned plot and a thinned plot using a paired water balance approach. Forest overstory transpiration (EO) was estimated from tree...
Article
Full-text available
Ponderosa pine (Pinus ponderosa Dougl. ex P. Laws) forest stand density has increased significantly over the last century (Covington et al. 1997). To understand the effect of increased intraspecific competition, tree size (height and diameter at breast height (DBH)) and leaf area to sapwood area ratio (AL:AS) on water relations, we compared hydraul...

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