David Williams

David Williams
University of Wyoming | UW · Department of Botany

PhD

About

212
Publications
37,986
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13,959
Citations
Additional affiliations
August 2003 - November 2019
University of Wyoming
Position
  • Professor

Publications

Publications (212)
Article
Full-text available
Columnar cacti occur naturally in many habitats and environments in the Americas but are conspicuously dominant in very dry desert regions. These majestic plants are widely regarded for their cultural, economic, and ecological value and, in many ecosystems, support highly diverse communities of pollinators, seed dispersers, and frugivores. Massive...
Preprint
Full-text available
Isotopic exchange with atmospheric vapor can strongly influence the isotopic values of evaporating surface water bodies (e.g., lakes), influencing our understanding of hydrological processes across aquatic and terrestrial environments. Rather than measure the isotopic values of the atmosphere directly, it is much more common to estimate values by a...
Article
Full-text available
The plant family Cactaceae is considered among the most threatened groups of organisms on the planet. The threatened status of the cacti family has created a renewed interest in the highly evolved physiological and morphological traits that underpin their persistence in some of the harshest sub-tropical environments in the Americas. Among the most...
Article
As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the capacity of soils to accumulate or retain carbon is uncertain. Free-air CO2 enrichment (FACE) experiments have been conducted to better understand the plant, soil and ecosystem response to elevated [CO2], frequently employing commercial CO2 that imparts a...
Article
Full-text available
The isotopic composition of xylem water is frequently measured to identify sources of plant water uptake and evaluate the ecosystem water budget. The most common approach to sample xylem water is cryogenic vacuum distillation (CVD). However, the water recovered by CVD is total xylem water from the complex xylem tissue, including living xylem parenc...
Article
Carbon (C) allocation strategy plays a critical role in plant adaptability, which are also important to assess the productivity stability under environmental change. Based on optimal partitioning theory we asked two questions: (1) How is plant C allocation within tissues affected by nutrient enrichment (N addition)? And (2) does long‐term N additio...
Article
Full-text available
Microbes in snow and ice ecosystems in polar regions contribute substantially to C, N, and P cycling, but few studies have explored microbial activity in seasonal snow. The purpose of this study was to explore the relative importance of snow microbial processing of C, N, and P compounds in atmospheric deposition and litter and detect elemental limi...
Article
Nitrogen (N) oligotrophication is increasing globally across terrestrial ecosystems and manifested in decreasing nitrogen concentration ([N]) and changes in the stable nitrogen isotope composition (δ¹⁵N) of foliage. Heterogeneity in plant nitrogen sources makes it challenging to detect the effects of N oligotrophication at a small catchment scale....
Article
Predicting plant growth from functional traits has been a long-term goal of experimental botany. Early studies considered that resource traits align across a single axis, from high to low growth rates. The drivers of nocturnal and cuticular leaf conductances have received much recent attention, but how they align with other functional traits along...
Article
The utility of a particular tracer to perform hydrograph separations depends on the dominant watershed properties combined with meteorological patterns; therefore, drawing conclusions from one tracer can be misleading. Combining information from multiple tracers can reveal complimentary insights that advance our knowledge of runoff generating proce...
Article
Full-text available
The tall (>4 m), charismatic and threatened columnar cacti, pasacana [Echinopsis atacamensis (Vaupel) Friedrich & G.D. Rowley)], grows on the Bolivian Altiplano and provides environmental and economic value to these extremely cold, arid and high-elevation (~4000 m) ecosystems. Yet very little is known about their growth rates, ages, demography and...
Article
Full-text available
Terrestrial paleoclimate records are rare in the South Atlantic, limiting opportunities to provide a prehistoric context for current global changes. The tussock grass, Poa flabellata, grows abundantly along the coasts of the Falkland Islands and other subantarctic islands. It forms extensive peat records, providing a promising opportunity to recons...
Article
Full-text available
Premise: The impact of elevated CO2 concentration ([CO2 ]) and climate warming on plant productivity in dryland ecosystems is influenced strongly by soil moisture availability. We predicted that the influence of warming on the stimulation of photosynthesis by elevated [CO2 ] in prairie plants would operate primarily through direct and indirect eff...
Article
Full-text available
Measurements of the isotopic composition of separate and potentially interacting pools of soil water provide a powerful means to precisely resolve plant water sources and quantify water residence time and connectivity among soil water regions during recharge events. Here we present an approach for quantifying the time-dependent isotopic mixing of w...
Article
Full-text available
Resprouting is an ancestral trait in angiosperms that confers resilience after perturbations. As climate change increases stress, resprouting vigor is declining in many forest regions, but the underlying mechanism is poorly understood. Resprouting in woody plants is thought to be primarily limited by the availability of non‐structural carbohydrate...
Preprint
Full-text available
Terrestrial paleoclimate records are rare in the South Atlantic, limiting opportunities to provide a prehistoric context for current global changes. The tussock grass, Poa flabellata, grows abundantly along the coasts of the Falkland Islands and other sub-Antarctic islands. It forms extensive peat records, providing a promising opportunity to recon...
Preprint
Full-text available
Abstract. Measurements of the isotopic composition of water recovered from soil at different tensions provide a powerful means to identify potential plant water sources and quantify heterogeneity in residence time and connectivity among soil water regions. Yet incomplete understanding of mechanisms affecting isotopic composition of different soil w...
Article
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Crassulacean acid metabolism (CAM) photosynthesis is one of the principle carbon-concentrating mechanisms in terrestrial plants. A primary feature of the CAM photosynthetic pathway revolves around the night-time uptake of CO2 and its subsequent storage as organic acids for later daytime fixation into sugars. This unique, water-saving, and carbon-co...
Article
Full-text available
Aims Our goal was to better understand tree growth and photosynthetic responses to variations in plant available water and elucidate the role of the inverse texture effect in snow dominated montane forests. Methods We measured tree ring carbon isotope composition and annual growth over a 31-year record for lodgepole pine (Pinus contorta Douglas ex...
Article
Over the past century, atmospheric nitrogen deposition (Ndep) has increased across the western United States due to agricultural and urban development, resulting in degraded ecosystem quality. Regional patterns of Ndep are often estimated by coupling direct measurements from large-scale monitoring networks and atmospheric chemistry models, but such...
Article
Full-text available
Sublimation is an important hydrological flux in cold, snow-dominated ecosystems. In high-elevation spruce-fir forests of western North America, spruce beetle outbreaks have killed trees, reduced the canopy, and altered processes that control sublimation. We evaluated two hypotheses related to effects of disturbance on sublimation in this ecosystem...
Article
Full-text available
Global changes that alter soil water availability may have profound effects on semiarid ecosystems. Although both elevated CO2 (eCO2) and warming can alter water availability, often in opposite ways, few studies have measured their combined influence on the amount, timing, and temporal variability of soil water. Here, we ask how free air CO2 enrich...
Article
Full-text available
Giant saguaro (Carnegiea gigantea) is one of the longest‐lived and massive cacti species in the Americas. They occur throughout the Sonoran Desert region with a distribution spanning a five‐fold gradient in mean annual precipitation. Relationships between fitness traits, including stem growth, and spatio‐temporal climate patterns are still poorly u...
Article
Full-text available
Premise of the Study Giant cacti species possess long cylindrical stems that store massive amounts of water and other resources to draw on for photosynthesis, growth, and reproduction during hot and dry conditions. Across all giant cacti taxa, stem photosynthetic surface area to volume ratio (S:V) varies by several fold. This broad morphological di...
Article
Aim Within C3 plants, photosynthesis is a balance between CO2 supply from the atmosphere via stomata and demand by enzymes within chloroplasts. This process is dynamic and a complex but crucial aspect of photosynthesis. We sought to understand the spatial pattern in CO2 supply–demand balance on a global scale, via analysis of stable isotopes of car...
Article
Temporal variation in soil nitrogen (N) availability affects growth of grassland communities that differ in their use and reuse of N. In a 7-year-long climate change experiment in a semi-arid grassland, the temporal stability of plant biomass production varied with plant N turnover (reliance on externally acquired N relative to internally recycled...
Poster
Full-text available
Mountain peatlands are susceptible to a changing climate via changes in the water cycle. Understanding the impacts of such changes requires knowledge of the hydrological processes within these peatlands and in the upland forests that supply them with water. We investigated hydrological processes in peatland catchments in the Rocky Mountains by deve...
Poster
A modern proof-of-concept study has determined how modern living P. flabellata records temperature, relative humidity, and precipitation using carbon (δ13C) and oxygen (δ18O) stable isotopes of leaf and root cellulose.
Article
Grassland soils are significant carbon (C) sinks as more than half of grassland plant biomass is belowground and roots are the main source of soil C. It is uncertain if grassland soils will continue as C sinks in the future because climate change may affect the dynamic, belowground relationships among crown and root biomass, root chemistry and morp...
Article
Global climate change is expected to alter seasonal patterns and rates of evapotranspiration in dry regions. While climate change will involve elevated CO2 and increased temperatures, independently these factors may have different impacts on actual evapotranspiration (AET) due to their opposing effects on transpiration. We used canopy gas exchange...
Article
Full-text available
Increased anthropogenic nitrogen (N) deposition can lead to N saturation of ecosystems, altering water quality, biogeochemical cycling and biodiversity. Although some N deposition (Ndep) is natural, there has been an increase of Ndep in the Greater Yellowstone Ecosystem (GYE), largely due to local and regional intensification of agricultural activi...
Article
Full-text available
Volume-to-surface area ratio (V:S) across stem succulent taxa varies by almost two orders of magnitude. The broad range in V:S of cacti and other succulent species likely has considerable importance for adaptation since stem volume determines the storage capacity of water, carbon and nutrients and stem surface area is directly related to whole-stem...
Article
Full-text available
It is unclear how elevated CO2 (eCO2 ) and the corresponding shifts in temperature and precipitation will interact to impact ecosystems over time. During a 7-year experiment in a semi-arid grassland, the response of plant biomass to eCO2 and warming was largely regulated by interannual precipitation, while the response of plant community compositio...
Article
Full-text available
Human impacts on biogeochemical cycles are evident around the world, from changes to forest structure and function due to atmospheric deposition, to eutrophication of surface waters from agricultural effluent, and increasing concentrations of carbon dioxide (CO2) in the atmosphere. The National Ecological Observatory Network (NEON) will contribute...
Article
Full-text available
Free amino acids (FAAs) in soil are an important N source for plants, and abundances are predicted to shift under altered atmospheric conditions such as elevated CO2. Composition, plant uptake capacity, and plant and microbial use of FAAs relative to inorganic N forms were investigated in a temperate semiarid grassland exposed to experimental warmi...
Article
Vegetation greenness, detected using digital photography, is useful for monitoring phenology of plant growth, carbon uptake, and water loss at the ecosystem level. Assessing ecosystem phenology by greenness is especially useful in spatially extensive, water-limited ecosystems such as the grasslands of the western United States, where productivity i...
Article
Full-text available
Terrestrial plant and soil respiration, or ecosystem respiration (Reco), represents a major CO2 flux in the global carbon cycle. However, there is disagreement in how Reco will respond to future global changes, such as elevated atmosphere CO2 and warming. To address this, we synthesized six years (2007-2012) of Reco data from the Prairie Heating An...
Article
Full-text available
Soil amino acids are often an important source of nitrogen (N) for plants, and anticipated global changes, including climate warming and rising atmospheric CO2 levels, have the potential to alter plant and microbial production and consumption of this N source in soils. We determined soil amino acid composition over a 1-year period at diurnal and se...
Conference Paper
Full-text available
We established a large-scale manipulative experiment in a semidesert grassland on the Santa Rita Experimental Range to determine how the recruitment and physiology of woody plants (Prosopis velutina Woot.) are affected by invasive grasses, seasonal precipitation regimes, and underlying soil characteristics. We established 72 2.8-m2 plots beneath si...
Conference Paper
This report describes accomplishments for the two-year project investigating temporal dynamics of glacial ice and snow meltwater, rainfall and base flow contributions to stream flow of Dinwoody Creek in the Wind River Range of western Wyoming. The primary objectives were to 1) characterize diurnal, seasonal and interannual variation in the isotopic...
Article
Full-text available
Deep snow in sub-alpine ecosystems may reduce or eliminate soil freezing, thus contributing to the potential for winter soil respiration to account for a significant fraction of annual CO2 efflux to the atmosphere. Quantification of carbon loss from soils requires separation of respiration produced by roots and rhizosphere organisms from that produ...
Article
Full-text available
Climate controls vegetation distribution across the globe, and some vegetation types are more vulnerable to climate change, whereas others are more resistant. Because resistance and resilience can influence ecosystem stability and determine how communities and ecosystems respond to climate change, we need to evaluate the potential for resistance as...
Conference Paper
Background/Question/Methods In grassland ecosystems, roots play a key role in carbon sequestration and root decomposition is a notable, though often not quantified, source of CO2 to the atmosphere. Within a large field manipulation experiment in a mixed-grass prairie, we sought to 1) understand the impact of elevated CO2 and temperature on fine ro...
Conference Paper
Background/Question/Methods The interaction between soil conditions and climate variability plays a central role in the functioning of montane conifer forests. Although soil moisture availability to trees is largely dependent on climate, the depth and texture of soil exerts a key secondary influence. I hypothesize that soil texture plays a more p...
Article
Full-text available
This paper summarizes results obtained from an FAO/IAEA Coordinated Research Project (CRP) on "Managing Irrigation Water to Enhance Crop Productrvrty under Water-Limiting Conditions: A Role for Isotopic Techniques", Implemented from 2007 to 2012. Its objective was to Identify approaches to Improve crop water productivity (production per unit of wat...
Article
Full-text available
The fraction of evapotranspiration (ET) attributed to plant transpiration (T) is an important source of uncertainty in terrestrial water fluxes and land surface modeling (Lawrence et al. 2007, Miralles et al. 2011). Jasechko et al. (2013) used stable oxygen and hydrogen isotope ratios from 73 large lakes to investigate the relative roles of evapora...
Article
Woody plant encroachment into former grasslands currently represents a major physiognomic shift globally. Seedling establishment is a critical demographic bottleneck and is considered to be alleviated by increases in water availability and negatively impacted by interactions with grasses, particularly when water stress increases. However, interacti...
Article
Full-text available
Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of this study was to characterize the effect of antece...
Article
Full-text available
As global changes reorganize plant communities, invasive plants may benefit. We hypothesized that elevated CO2 and warming would strongly influence invasive species success in a semi-arid grassland, as a result of both direct and water-mediated indirect effects. To test this hypothesis, we transplanted the invasive forb Linaria dalmatica into mixed...
Article
Full-text available
The flux of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere may ameliorate or exacerbate climate change, depending on the relative responses of ecosystem photosynthesis and respiration to warming temperatures, rising atmospheric CO2, and altered precipitation. The combined effect of these global change factors is especially u...
Data
Relationship between midday and daily measurements of ecosystem respiration. Individual data points reflect pairs of midday measurements and daily sums for a given treatment during diurnal field campaigns conducted in 2007–2010. (TIF)
Data
Relationship between midday and daily measurements of ecosystem photosynthesis. Individual data points reflect pairs of midday measurements and daily sums for a given treatment during diurnal field campaigns conducted in 2007–2010. (TIF)
Conference Paper
Background/Question/Methods Grasslands cover 30-40% of the Earth’s terrestrial surface and constitute the largest intact biome in the conterminous US. Semi-arid grasslands are expected to be particularly sensitive to climate change because of the overriding control of soil moisture on virtually all ecological processes in these ecosystems. Over 7...
Conference Paper
Background/Question/Methods In the western great plains of North America, cheatgrass (Bromus tectorum) is a common and often troublesome species, but does not commonly dominate landscapes as it does in many parts of the intermountain west. Global change, however, could make great plains grasslands more susceptible to cheatgrass invasion. A variet...
Article
Full-text available
Eucalyptus species are grown widely outside of their native ranges in plantations on all vegetated continents of the world. We predicted that such a plantation species would show high potential for acclimation of photosynthetic traits across a wide range of growth conditions, including elevated [CO2 ] and climate warming. To test this prediction, w...