Richard Gill, Biology
Background and Importance
The National Research Council, in its report on how people learn, identified key differences between novices and experts (Bransford et al. 2000; Donovan and Bransford 2005). One of the grand challenges of education is to shepherd students through the process of becoming experts. Mentored research experiences are a critical component of this process as students “grow in skills and increase in responsibility” (Mentoring Principle #3) and participate in projects that “extend well beyond the routine” and “[develop] of new concepts of learning” (Mentoring Principle #5). Bransford et al. (2000) emphasized that developing into an expert requires, among other things, (1) using initial understanding to frame new concepts and (2) the ability to transfer knowledge from one realm into another. This two step process—gain new knowledge and transfer it to a new realm—is a key element of this mentoring proposal.
The time and effort required to produce expertise in students represents one of the primary commitments in academia. In laboratories with large undergraduate populations producing institutional expertise is challenging because of high turnover and student inexperience with specific techniques. Initiating a new laboratory with new students makes this even more difficult because there is a lack of expertise other than the supervising faculty member. For complex, interdisciplinary projects students need intensive, multi-‐ technique training. One way to accomplish this is to invest in creating expertise through short-‐courses and internships. Once individual students become experts they can transfer their understanding to broad research teams. A benefit of this approach is that investments in single students enrich the experience of many students.
The long-‐term educational goal of my laboratory is to “[prepare] students who can make a difference in the world, who can draw on their academic preparation to participate more effectively in the arenas of daily life. They are parents, Church leaders, citizens, and compassionate human beings who are able to improve the . . . ecological environment in which they and their families live” (AIM of a BYU Education). One of the long-‐term research goals in my laboratory is to understand the impacts of hydrological variability on western ecosystems. The goal of this application, which is a step toward attaining my education and research goals, is to fund short-‐course experiences for three students who will become “student-‐experts” and serve as instructors and mentors for an additional students in my laboratory. As part of this project, student-‐experts will transfer their understanding to others during a 3-‐day workshop. The specific expertise that they will gain and then share is (1) the use of stable isotopes to partition water sources and measure water stress, (2) the use of Infrared Gas Analyzers (IRGAs) and fluorometers to measure plant gas exchange and instantaneous water use efficiency, and (3) the use of tracers and mass flux to measure ecosystem water budgets. The central educational hypothesis is that intensive, short-‐term experiences will allow students to move from novices to experts and serve as mentors for other students.
The rationale for this approach is that real learning occurs when (1) students transfer specific knowledge from one realm to another (Donovan and Bransford 2005) and (2) as learners gain sufficient expertise that they can become teachers of others. This approach is consistent with BYU’s 5 Principles of Mentoring:
- Students should have access to faculty (or mentoring teams) for sufficient time to allow development of personal and professional relationships.
In this project I will provide pre-‐short course training for the students and work closely with student-‐experts in the design and delivery of the workshop presentations. Students will interact frequently with me as they use their new skills in the design of individual mentored experiences. The proposed framework will allow me to spend more time mentoring on science questions than on training in specific methods.
- Students should be involved in programs and processes wherein scholarship and central academic activities in its several forms constitutes the core of their experiences.
The core experience for both the student-‐experts and the additional students in the laboratory will reflect rigorous academic activities, including professional training, federally funded research, and presentations at regional and national meetings.
- Students should be given the opportunity to grow in skills and increase in responsibility in the project or experience in which they are involved.
This approach is the fundamental guiding principle of this application. Students will be tasked with developing expertise in specific skills and made responsible for the application of these skills in a rigorous research setting.
- Students should be taught integration of spiritual and secular understanding.
While this is not explicitly an element of this application, it is consistent with the culture that currently exists within my laboratory. Several individuals in the lab have been involved in my Religion and the Environment (BIO 347) and Our Place on Earth (Honors 265) courses.
- Mentored experiences should be pertinent to the students’ future discipline.
The skills developed as part of this proposal are among the most important for hydroecologists and plant physiological ecologists. Students going on to graduate studies will be at a distinct advantage relative to their colleagues because of their experiences with this project. In addition, the process of intensive learning and transferring knowledge is pertinent to the future careers of our preprofessional students.
Our lab is well suited to accomplish this work because we have sufficient funding from other sources to support >10 undergraduate students, allowing this funding to leaven the lab by providing training beyond what is available at BYU. Students will be able to apply their additional training to projects spanning from the drought and El Nino impacts on Great Basin/Mojave Desert ecology, timing of snow melt on subalpine ecosystems, and the influence of mycorrhizae on mineral weathering and nutrient mass fluxes. The timing of this grant is critical as we work to build a critical mass of technical expertise within the lab. This is my third year at BYU and I have now built enough human resource infrastructure that the next rate-‐limiting step is technical understanding among lab members. The expertise developed in this proposal will make the lab less dependent on a single faculty member and more dynamic.
As a result of the work outlined here, coupled with existing funding, we anticipate training 12 students, producing 3-‐5 peer reviewed publications with equal numbers of meeting presentations, and having 8-‐12 student coauthors. In addition, this work will provide pilot data for future funding applications to NSF and USDA.
Hydroecology is the discipline focused on the impacts of water on ecological systems (Huxman et al. 2004; Jackson et al. 2005; Katul et al. 2007; Wilcox et al. 2008). In Western ecosystems, hydroecology is critical because much of the west is water limited and is highly sensitive to the timing and amount of precipitation (Huxman et al. 2004; Knapp et al. 2006; Knapp et al. 2008). In addition, snow dynamics influence our montane systems, with earlier snowmelt altering plant phenology and species-‐interactions (Steltzer et al. 2009).
Fluctuations in precipitation on inter-‐annual to multi-‐decadal time scales in the Western US are strongly influenced by several climate patterns including the Pacific Decadal Oscillation (PDO), the Atlantic multidecadal oscillation (AMO) and El Nino Southern Oscillation (ENSO) (Mo 2010; Mo et al. 2009). Western precipitation is highly variable but with natural periodicity that is linked to Pacific sea surface temperature with distinct multi-‐year wet and dry cycles (Mo et al. 2009). Understanding the impacts of hydrology on western ecosystems represent a complex problem. However, now human activities have resulted in well-‐documented increases in atmospheric carbon dioxide (CO2) concentration and mean annual temperature, with forecast future increases of between 1.1 and 6.4 oC (IPCC 2007). These increased temperatures will alter patterns of atmospheric circulation and influence hydrologic processes. This has already been seen in the Western U.S. where snowpacks and streamflows have decreased in the past decades (Kalra et al. 2008; Mote et al. 2005)
In addition to historical variation and global change factors, understanding hydrological processes requires an understanding of novel regional influences. In the Western US we have begun to recognize the influence of dust generated in basins on snow hydrology. Painter et al. (2007) found that in the San Juan Mountains of southwestern Colorado snow cover duration was shortened by 18-‐35 days due to desert dust. This dust increased the absorption of shortwave radiation, increasing radiative forcing and snow melt. Interestingly, Painter et al. (2007) and Neff et al. (2008) found that humans were the cause of increased dust production in the desert southwest and therefore directly impact the hydrology of a distant ecosystem.
As a consequence of the pace and magnitude of these changes, it will become increasingly challenging for scientists and managers to understand the natural systems that society depends upon without diverse tools that span traditional disciplines of geology, hydrology, and biology. These tools will be used to understand the sources, transport, and fate of water within an ecosystem. The use of sophisticated tools such as stable isotopic analysis, plant gas exchange systems, and hydrological tracers will enable scientists to better understand human influences on hydrology and forecast their impacts on ecological systems (Figure 1).
Where the hydrosphere and biosphere intersect there are a number of critical processes (Newman 2006), (Figure 1). These include plant rooting profiles and their connection to seasonal water availability (Casper et al. 2003; Jackson et al. 1996; Schenk and Jackson 2002), water use efficiency (plant production/water loss), plant water stress, and ecosystem scale water partitioning to evaporation, transpiration, and water yield (Oki and Kanae 2006; Wilcox et al. 2008). These processes influence plant productivity, patterns of invasions, and water yield to streams—key elements of sustainability in the Western US.
These processes are complex and dynamic and require diverse techniques to quantify. These methods include stable isotopes, plant gas exchange, and ecosystem water balance (see below).
Short Course Background
I am proposing to send students to three short courses that are focused on developing specific instrumentation/skills that are necessary to understand hydroecology. These three courses are the Stable Isotopes in Ecology Research course at the University of Utah, the LiCOR LI-‐6400XT Training Course, and the Washington State University NSPIRE Hydrology & Tracers course.
Stable Isotopes in Ecology Research
The stable isotope course is offered at the University of Utah, which is home to the preeminent isotope ecologist (Jim Ehleringer) with a host of other instructors from around the country. This course teaches the application of stable isotopes in natural abundances to address ecological questions. The course is from June 13-‐24. Tuition for the course is $2500, with an additional $400 for housing.
This course is highly regarded among ecologists, with short course alumni found throughout the stable isotope community. The course is comprehensive in its instruction concerning the application of stable isotopes to ecology and includes daily laboratory experiences along with classroom instruction. Instruction and labs include courses directly related to our research goals:
- Meteoric water and plant and soil water, taught by Todd Dawson (UC Berkeley). Dr. Dawson has published widely on the use of stable isotopes to identify the meteoric source of water used by plants, allowing researchers to partition the seasonal water use of plants between snow melt, summer rain, and fog (Burgess and Dawson 2008; Corbin et al. 2005; Dawson et al. 2007; Gaudinski et al. 2005; Johnstone and Dawson 2010; Lee et al. 2007; Limm et al. 2009).
- Plant Carbon and Carbon in Terrestrial Ecosystems, taught by Jim Ehleringer (University of Utah). Dr. Ehleringer pioneered the use of carbon isotopes to measure water stress in plants and has developed additional methods for using stable isotopes of C, N, O, and H to reconstruct food webs and for forensic applications (Ehleringer et al. 2008; Hultine et al. 2010; O’Grady et al. 2010; Schwinning et al. 2008; West et al. 2007)
- Additional related courses include Tree Rings, Carbon Isotopes, and Climate taught by Steve Leavitt of the University of Arizona, Leaf Water, Organic Oxygen, and Climate taught by John Roden of Southern Oregon University, and Water at Landscape and Regional Scales by Gabe Bowen of Purdue University.
This course is has a highly competitive admission policy and is only open to graduate students. I propose to send Lafe Conner, a second year PhD student in my lab to this course. Since arriving at BYU I have worked closely with Drs. Bowling and Ehleringer to promote cross-‐university collaborations and I anticipate no problem with Lafe being admitted to the course. During 10 days he will work toward becoming an isotope expert. His expertise will then be applied to the research projects described below and will be used to support the efforts of several undergraduates who will be mentored by me. After the course he will provide a one-‐day workshop for the lab to demonstrate the specific applications of his new understanding to our research efforts. An ancillary benefit is increased use of BYU’s stable isotope facility by researchers in the College of Life Sciences.
LI-‐6400XT Training Course
One of the most important and temperamental instruments in our laboratory is the LiCor LI-‐6400 portable photosynthesis system. This instrument allows us to produce high-‐ precision, real time measurements of plant gas exchange. For a hydroecologist this instrument is vital because it allows an investigator to quickly assess rates of photosynthesis and water loss on plants in the laboratory and in the field. However, its operation requires substantial expertise. It is possible to train individual students to make a few simple measurements, but to take full advantage of the sophistication of this instrument requires intensive training. The manufacturer of this instrument provides three-‐day short courses to train investigators on the fundamentals of gas exchange measurements, the protocol for making survey and response curve measurements, instrument maintenance, calibration, and troubleshooting. In addition, this course provides an introduction to fluorescence theory and measurements.
This course is available for $500, plus travel and housing for the three-‐day course in Lincoln, NE. I propose to send Beau Walker, a senior majoring in Biology. Beau has experience making survey measurements on the Li-‐6400 and would benefit from this additional training. We anticipate that Beau will begin a master’s project with me beginning in Fall 2011 and he will therefore be able to act as a student-‐master on projects requiring gas exchange expertise. He will be an undergraduate at the time of the training in May 2011.
WSU NSPIRE Hydrology and Tracer Course
This course is part of an NSF funded IGERT proposal to Washington State University. I served as co-‐PI on the project prior to my move to BYU and I helped design this short course. This course, taught in mid-‐May by a hydrogeologist, teaches how to conduct mass balance calculations for water yield and ecosystem water balance. In addition, it teaches the use of ionic tracers in mass balance calculations. These skills are vital for understanding watershed hydrology and are also used in much smaller scale projects, including our recently funded project Weathering Under Cover: Role of Biofilms in Mineral Weathering and Nutrient Uptake in the Mycorrhizosphere.
The cost for this course is $1200 plus travel expenses to Pullman, WA. I propose to send Tatyana Isupov, a junior Conservation Biology major to this course. Tatyana has worked in my lab for one year and shows great promise as a research scientist interested in hydroecology.
Gill Lab Workshop
A key component of this proposal is providing an opportunity for the student-‐ experts to transfer their training to additional students in the lab. The format that we will use is a three-‐day workshop with morning instruction from the students and afternoon laboratory experiences designed by the student-‐experts and me. I propose to hold this workshop June 28-‐30, 2011. All of the undergraduates working in my lab will attend the workshop. These attendees will include two students funded on my biofilm project, four students working on a forest ecology project, and four students working on our precipitation variability project. We are proposing to pay all ten student’s salaries for this workshop at a cost of approximately $2250. In addition, we are requesting funds for sample analysis as part of the training.
The ultimate goal of this project is to produce experts who have been mentored in conducting independent research and who have the skills necessary to accomplish relevant research projects. One measure of success in this is presentations at national meetings. I propose to take 4-‐5 students to the American Geophysical Union meeting in Fall 2011 as part of this research. This is a national venue where hydroecologists frequently present their research within the Hydrology or Biogeoscience Sections.
This proposal is not designed to support research. Rather, it is to augment existing research that is being conducted in my lab. Students from a variety of projects will benefit from the skills developed in the above short courses and workshop. Within each of the projects described below there will opportunities for undergraduate students to conduct independent research. I am requesting a modest amount for isotopic and tracer analyses so that students will be able to experiment with their new skills.
Project 1: Climate driven invasive grass-‐fire cycles: understanding ecosystem responses for effective pre-‐ and post-‐fire management of Great Basin and Mojave rangelands (PI: Sam St. Clair, R. Gill Co-‐PI). USDA Rangelands Program (Funded 2010-‐2012) (2-‐4 Undergraduate Students)
The goal of this project is to identify critical processes that will allow land managers to minimize the negative impacts from invasion-‐fire cycles. This is a large, multi-investigator project that includes elements of social science, community ecology, environmental biophysics, and hydrology. My responsibility in the project includes the construction and monitoring of rainout shelters (Figure 2) that will simulate drought conditions at sites in the Mojave and Great Basin. At each of our two sites we will have a large factorial experiment that includes (1) burned/unburned treatments; (2) small mammals/small mammal exclusion; (3) -‐50%/+50%/Control precipitation treatments.
The skills developed in the short courses and workshop will allow students to quantitatively measure the impacts of the precipitation treatments on plant water status and discriminate between the impacts of precipitation variability on native and non-‐native plants. This information is crucial if we are to understand the mechanisms responsible for non-‐native grass invasions into native rangelands. Stable isotope analyses will allow us to measure season water stress and water use efficiencies while gas exchange measurements will provide instantaneous measures of water loss and water use efficiency between species.
Project 2: Utah EPSCoR RII Track-‐1: iUTAH – Urban Transitions and Aridregion Hydro-‐ sustainability (PI-‐Jim Ehleringer; Gill-‐Collaborator) (Submitted NSF Proposal $25M; 5 year project) (if funded 3-‐6 undergraduate students)
This recently submitted project represents a statewide effort to understand the sources and fate of dust within Utah and its influence on water sustainability. My portion of the project examines the feedbacks between dust on snow, snow melt, and subalpine plant ecology.
Snow accumulation, sublimation and melt are important hydrologic processes that impact the quantity and timing of runoff as well as recharge of mountain block aquifers, both of which are critical to Utah’s water supply. In this proposal we hypothesize that dust accumulation and vegetation cover influence the partitioning of snow into sublimation (a local loss of water) or melt (water flux into soils, aquifers, and mountain streams). Previous work in Colorado’s San Juan Mountains, dust accumulation resulted in accelerated snowmelt due to increased shortwave radiative forcing (Neff et al. 2008; Painter 2007). Little is known about the effect of desert dust and anthropogenic particulates on snow dynamics in the Wasatch Front, but preliminary data suggest local forests are responsive to dust (Dave Bowling, U of U, preliminary data).
While this project is not yet funded, we are initiating dust trials on the Wasatch Plateau in central Utah. This project will examine the questions of how melt dynamics associated with dust deposition vary in different montane forests and how does summer soil moisture depend on timing of melt. Lafe Conner, my PhD student, will begin dust treatments this spring during the period of snow melting. He has instrument his research plots to measure soil moisture fluxes. The short courses and workshop will prepare him and additional students to examine the impacts of earlier snow melt on hydroecology in this region. Initial data indicate that oxygen and hydrogen isotopes are valuable in understanding the source of water used by the dominant vegetation (Figure 3). With isotopic tools we will be able to directly assess the influence of dust on water use and availability. In addition, tracer application will allow us to develop a water balance model for these systems to address the broader question related to water sustainability in the Western US.
Project 3: Weathering Under Cover: Role of Biofilms in Mineral Weathering and Nutrient Uptake in the Mycorrhizosphere. (PI: C.K. Keller, Washington State University; R. Gill co-‐PI). NSF Emerging Topics in Biogeochemical Cycles (2010-‐2012) (2 undergraduate students)
The goal of this project is to produce a mechanistic understanding of plant-‐fungi-‐ mineral associations in primary successional environments. This is an extension of other work that we have done exploring plant uptake of ions directly from mineral surfaces or in primary successional soils (Balogh-‐Brunstad et al. 2008; Gill et al. 2006). Our premise is that a key adaptation of many plants to these conditions is development of mycorrhizospheric biofilms, which attach the root system to mineral surfaces and micro-‐localize the biology, chemistry, and hydrology of weathering and nutrient uptake at the root system-‐mineral interface. At this micron scale, dissolution and biological mass transfers occur over very small distances and in relative isolation from bulk soil water, thereby increasing macroscopic nutrient acquisition efficiency and decreasing nutrient loss in drainage. Our central hypothesis is that varying degrees of nutrient limitation (need to extract base cations from mineral sources) influence biofilm development and weathering/uptake function. To address this hypothesis, we will use replicated ectomycorrhizal seedling systems in a growth experiment, and vary the availability of Ca and K in bulk soil water and primary minerals by manipulating irrigation solutions and initial mineral composition.
To interpret the results from this research we will employ water balance models to understand the partitioning of water and ions between bulk soil water and plant water. In earlier experiments similar to those we will use in this project we employed isotopic analyses and gas exchange to relate mineral uptake to plant physiological status. This project is ideal for undergraduate students because the research is conducted in plant growth chambers and can be done during the academic year.
Project 4: Forest Ecology and Stand Structure in Ephraim Canyon, UT. US Forest Service (PI: R. Gill) Funded 2010 (4 undergraduate students)
This project has been funded to survey forest structure at the Great Basin Experimental Range in Ephraim, UT. Students will spend the summer measuring the distribution of species and biophysical conditions for plots throughout the forest. Their work will compliment an ongoing experiment that I am conducting within Ephraim Canyon to examine the influence of precipitation timing and amount on forest species. These students will be able to use the workshop training to develop independent research projects to better understand tree physiology and forest community structure. Figure 3: Isotopic analysis of stem water for the dominant functional groups on the Wasatch Plateau. These pilot data indicate that aspen primarily depend on snow-derived water while grasses are far more dependent on monsoonal rains.
Anticipated Outcomes Related to Mentoring
As mentioned above, this project is designed around BYU’s principles of mentoring. Principle 1 states “students should have access to faculty (or mentoring teams) for sufficient time to allow development of personal and professional relationships.” The design of this mentoring environment will allow me to spend more time mentoring and focusing on principles of science while I use outside courses to develop a broader mentoring team. I will provide initial training prior to the short courses, help prepare workshop presentations, and then provide substantial scientific oversight and mentoring on individual student research project tied to existing projects. I anticipate mentoring >10 students, with the structure of this proposal allowing my mentoring to focus on the process of science while others in the lab serve as technical advisors.
Mentoring Principle 2 says, “Students should be involved in programs and processes wherein scholarship and central academic activities in its several forms constitutes the core of their experiences.” I anticipate that this project will allow for the development of rich knowledge in specific research techniques and the structure models the key intellectual process of novices becoming experts that can then mentor novices.
Mentoring Principle 3 says that, “students should be given the opportunity to grow in skills and increase in responsibility in the project or experience in which they are involved.” As a result of this work >10 students will be exposed to diverse hydroecological skills, while three students will gain deep knowledge of specific techniques and develop responsibility to teach and mentor others.
Mentoring Principle 5 states, “Mentored experiences should be pertinent to the students’ future discipline.” The end result of this work will be a community of students who have gained skills related to research and have been mentored in individual research projects. Those students who pursue future graduate studies will be well equipped with technical skills and with an understanding of the intellectual process involved in developing personal expertise. One key metric of the development of disciplinary skills is scientific presentations and publications. I anticipate 5 presentations at the 2011 AGU meeting and 3-5 publications that involve undergraduate coauthors using the skills acquired as part of this proposal.
Qualifications; Experiences/Successes Related to Mentoring
Since arriving at BYU in 2008 I have received two MEG awards. The primary focus of these awards was a rainfall manipulation experiment in Ephraim Canyon, UT. The MEG funding provided initial expertise that helped produce the successful USDA Rangeland proposal (see above). The mentoring philosophy for those two proposals was to bring together students from diverse majors including Conservation Biology, Biology, Environmental Science, Chemical Engineering, and Mechanical Engineering to create interdisciplinary research teams. From these two awards I have employed 12 undergraduate students. Successes related to mentoring can be evaluated by the mentoring principles. I have developed good professional relationships with my students through weekly lab meetings (currently attended by 6 students) and through the desire of two of these students applying to graduate school in my lab. Students have demonstrated that the core of their experiences was academic through the development of independent research projects (four students will submit ORCA proposals this year; four were submitted last year). Students have shown their development and independence with a number of demonstrable skills. Sarah McQueen, a sophomore engineering student, learned skills in simulation modeling and used the CENTURY model to generate the hypotheses that we tested this summer in the field. Five students (Lisa Jensen, Beau Walker, Tatyana Isupov, Sarah McQueen, and David Robinson) learned to program dataloggers and collectively they have programmed, maintained, and monitored a network of dataloggers for two years. Six students (Allison Orgill, Marissa Laflin, Beau Walker, Rachel Hill, Brad Chandler, David Robinson) learned simple gas exchange protocols and measured light response and CO2 response curves as part of a seedling physiology study. When a Vice President from Decagon Devices, an instrument manufacturer, visited our research site this summer he noted how professional our crew was and offered one student an internship next summer. Finally, one measure of pertinence in science is professional meetings, publications, and commitment to science. Of the twelve students supported on these MEG grants, five have been coauthors on abstracts to meetings, including two first authored poster presentations. Because of the nature of the research (field based, multi-‐year project) we are only now beginning to submit papers. Currently there are three publications from student work in draft form (Sarah McQueen— Hydrology of the Wasatch Plateau; Tatyana Isupov—Nitrogen responses to rainfall variability; Allison Orgill—Physiological responses of Engelmann Spruce to changes in nighttime temperature). Five other students will be coauthors on these papers. Of the twelve students that have worked with me, three will be graduating and applying for graduate school, four continue to work in the lab, two have moved to other labs, and one is on a mission. The two engineering students now have internships where they are using some of the skills developed in the lab.
- Balogh-‐Brunstad Z, Keller CK, Gill RA, Bormann BT, Li CY (2008) The effect of bacteria and fungi on chemical weathering and chemical denudation fluxes in pine growth experiments. Biogeochemistry 88:153-‐167
- Bransford JD, Brown AL, Cocking RR (2000) How people learn: brain, mind, experience, and school. National Academy Press, Washington, D.C.
- Burgess SSO, Dawson TE (2008) Using branch and basal trunk sap flow measurements to estimate whole-‐plant water capacitance: a caution. Plant and Soil 305:5-‐13
- Casper BB, Schenk HJ, Jackson RB (2003) Defining a plant’s belowground zone of influence. Ecology 84:2313-‐2321
- Corbin JD, Thomsen MA, Dawson TE, D’Antonio CM (2005) Summer water use by California coastal prairie grasses: fog, drought, and community composition. Oecologia 145:511-‐521
- Dawson TE et al. (2007) Nighttime transpiration in woody plants from contrasting ecosystems. Tree Physiology 27:561-‐575
- Donovan MS, Bransford JD (2005) How students learn: Science in the classroom. National Academies Press, Washington, D.C.
- Ehleringer JR, Bowen GJ, Chesson LA, West AG, Podlesak DW, Cerling TE (2008) Hydrogen and oxygen isotope ratios in human hair are related to geography. Proceedings of the National Academy of Sciences of the United States of America 105:2788-‐2793
- Gaudinski JB et al. (2005) Comparative analysis of cellulose preparation techniques for use with C-‐13, C-‐14, and O-‐18 isotopic measurements. Analytical Chemistry 77:7212-‐ 7224
- Gill RA, Boie JA, Bishop JG, Larsen L, Apple JL, Evans RD (2006) Linking community and ecosystem development on Mount St. Helens. Oecologia 148:312-‐324
- Hultine KR, Bush SE, Ehleringer JR (2010) Ecophysiology of riparian cottonwood and willow before, during, and after two years of soil water removal. Ecological Applications 20:347-‐361
- Huxman TE et al. (2004) Convergence across biomes to a common rain-‐use efficiency. Nature 429:651-‐654
- IPCC (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, New York
- Jackson RB, Canadell J, Ehleringer JR, Mooney HA, Sala OE, Schulze ED (1996) A global analysis of root distributions for terrestrial biomes. Oecologia 108:389-‐411
- Jackson RB et al. (2005) Trading Water for Carbon with Biological Carbon Sequestration. Science 310:1944-‐1947
- Johnstone JA, Dawson TE (2010) Climatic context and ecological implications of summer fog decline in the coast redwood region. Proceedings of the National Academy of Sciences of the United States of America 107:4533-‐4538
- Kalra A, Piechota TC, Davies SR, Tootle SA (2008) Changes in US streamflow and western US snowpack. J Hydrol Engineering 13:156-‐163
- Katul G, Porporato A, Oren R (2007) Stochastic Dynamics of Plant-‐Water Interactions. Annual Review of Ecology, Evolution, and Systematics 38:767-‐791
- Knapp A, Burns C, Fynn R, Kirkman K, Morris C, Smith M (2006) Convergence and contingency in production–precipitation relationships in North American and South African C4 grasslands. Oecologia 149:456-‐464
- Knapp AK et al. (2008) Consequences of more extreme precipitation regimes for terrestrial ecosystems. BioScience 58:811-‐821
- Lee JE, Oliveira RS, Dawson TE, Fung I (2007) Root functioning modifies seasonal climate (vol 102, pg 17576, 2005). Proceedings of the National Academy of Sciences of the United States of America 104:13531-‐13531
- Limm EB, Simonin KA, Bothman AG, Dawson TE (2009) Foliar water uptake: a common water acquisition strategy for plants of the redwood forest. Oecologia 161:449-‐459
- Mo KC (2010) Interdecadal Modulation of the Impact of ENSO on Precipitation and Temperature over the United States. Journal of Climate 23:3639-‐3656
- Mo KC, Schemm JKE, Yoo SH (2009) Influence of ENSO and the Atlantic Multidecadal Oscillation on Drought over the United States. Journal of Climate 22:5962-‐5982
- Mote PW, Hamlet AF, Clark MP, Lettenmaier DT (2005) Declining mountain snow pack in Western North America. Bull Amer Meteor Soc 86:39-‐49
- Neff JC et al. (2008) Increasing eolian dust deposition in the western United States linked to human activity. Nature Geoscience 1:189-‐195
- Newman BDW, Bradford P.; Archer, Steven R.; Breshears, David D.; Dahm, Clifford N.; Duffy, Christopher J.; McDowell, Nate G.; Phillips, Fred M.; Scanlon, Bridget R.; Vivoni, Enrique R. (2006) Ecohydrology of water-‐limited environments: A scientific vision. WATER RESOURCES RESEARCH 42:6302
- O’Grady SP et al. (2010) Aberrant Water Homeostasis Detected by Stable Isotope Analysis. Plos One 5
Oki T, Kanae S (2006) Global Hydrological Cycles and World Water Resources. Science 313:1068-‐1072
- Painter TH, A. P. Barrett, C. C. Landry, J. C. Neff, M. P. Cassidy, C. R. Lawrence, K. E. McBride, and G. L. Farmer (2007) Impact of disturbed desert soils on duration of mountain snow cover . GEOPHYSICAL RESEARCH LETTERS 34
- Schenk HJ, Jackson RB (2002) The global biogeography of roots. Ecological Monographs 72:311-‐328
- Schwinning S, Belnap J, Bowling DR, Ehleringer JR (2008) Sensitivity of the Colorado Plateau to Change: Climate, Ecosystems, and Society. Ecology and Society 13
- Steltzer H, Landry C, Painter TH, Anderson J, Ayres E (2009) Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes. Proceedings of the National Academy of Sciences 106:11629-‐11634
West AG, Hultine KR, Jackson TL, Ehleringer JR (2007) Differential summer water use by Pinus edulis and Juniperus osteosperma reflects contrasting hydraulic characteristics. Tree Physiology 27:1711-‐1720
Wilcox BP, Huang Y, Walker JW (2008) Long-‐term trends in streamflow from semiarid rangelands: uncovering drivers of change. Global Change Biology 14:1676-‐1689 i.