William K. Smith, Ph.D. - US grants

If current projections of climate warming are accurate, future global change will include the disappearance of a significant portion of the Earth's biodiversity during the 21st century, e.g. alpine tundra ecosystems in temperate and subtropical latitudes may be replaced by the subalpine forest below. Despite these predictions, mechanistic explanations for the upper elevational limits of subalpine forests across the globe have been pondered for over a century, and are still controversial today. The stability of this alpine treeline will be evaluated based on the ecophysiology of tree seedling establishment away from the forest edge and into the subalpine-alpine ecotone by the two dominant conifers, Abies lasiocarpa (subalpine fir) and Picea engelmannii (Engelmann spruce). Paradoxically, sunlight exposure during the day and leaf warming can enhance photosynthesis and growth in most plant species, while prior exposure to a clear, cold night sky (longwave thermal radiation sink) leads to lower minimum leaf temperatures, a major limiting factor at high elevation. In combination, low leaf temperatures at night followed by high sunlight the following morning can result in potentially severe low temperature photoinhibition of photosynthesis (LTP) and substantial reductions in carbon assimilation. It is hypothesized that this decrease in carbon assimilation is due primarily to excessive sky exposure and LTP, resulting in inadequate carbon gain to support the root growth necessary to survive rapidly drying soils following spring runoff. In addition, the timing and degree of mycorrhizal infection of fine roots may also play a vital role in preventing lethal water stress. Three primary venues for adaptation are proposed for seedling establishment under such a multiple stress regime: (i) microsite facilitation, (ii) seedling architecture, and (iii) photosynthetic physiology. The relative effectiveness of each of these adaptive venues for seedling establishment will be evaluated quantitatively from field measurements on photosynthesis, growth, and survival. If the hypotheses linking greater sky exposure to lower minimums in leaf temperature, greater LTP, less carbon gain and root growth, and lower seedling survival (desiccation death) are correct, conifer tree seedling establishment in this treeline ecotone could flourish under current scenarios of global warming and, thus, lead to the encroachment of subalpine forest and the potential loss of alpine tundra ecosystems.

Workshop: Scaling photosynthesis from the chloroplast to the landscape

Understanding the interactions of plant form and photosynthetic function among different species will be critical to the success of future management of both native and agricultural species, especially under current scenarios of global change. The purpose of this workshop is to evaluate photosynthetic limitations and adaptive solutions that emerge at the higher levels of structural organization found in the plant kingdom. The workshop will be held in conjunction with the 12th International Congress on Photosynthesis in Brisbane, Australia (August 18-23, 2001) and will be divided into sessions dealing with the chloroplast, cell, cell layers inside a leaf, the leaf, crown, canopy, and landscape. Across this broad structural/spatial hierarchy, chloroplasts are packaged progressively into more and more complex levels of organization (e.g. cells, leaves, branches, and crowns), generating new limitations to light and CO2 capture for photosynthesis.

This award supports purchase of a research-grade, epifluorescence stereomicroscope together with a digital camera, image analysis system and a vibration-isolation table. The equipment will allow users to view and capture images of large, intact structures with the magnification permitted by a stereomicroscope, and to combine fluorescence with low magnification imaging. The equipment will be housed and maintained in the Microscopy Core Facility, where it will be accessible to all members of the Biology department and to members of other departments. The equipment will be used in diverse research programs that span four major focus groupings: Ecology, Evolution, and Systematics; Comparative Physiology and Behavior; Cellular and Molecular Biology; and Integrative Plant Biology. Within these broad groupings, faculty pursue research at the level of the intact organism by examining the structure and function of intact, often living organisms. The research uses include, among others, the study of in vivo responses to changing physiological conditions, the time-lapse imaging of animal behavior, and determination of gene expression and protein localization at the level of the whole organism. In addition to its role in research, the stereoscopic imaging system imaging will be used to expand the types of microscopy used in the training of significant numbers of undergraduate and graduate students, including use in formal coursework and individual projects.

This international doctoral dissertation enhancement project will provide a U.S. graduate student and an undergraduate research assistant an opportunity to work in the Republic of Georgia. The general focus of their research is on environmental factors determining the upper elevation limit observed for forest trees. The principal investigators are William K. Smith from Wake Forest University and Maia Akhalkatski from the Institute of Botany in Tbilsi, Georgia.

Most previous research on the ecological or physiological factors responsible for maintaining tree lines has focused on older saplings or mature trees. Recent studies have shown that young, newly emerged seedlings may suffer the greatest mortality, by far, of all life stages. High mountain plants have always received special attention at the Institute of Botany in Georgia because mountainous regions dominate the country. The Department of Ecology of the Institute of Botany has recently been re-oriented to emphasize the reproductive ecology of plants in extreme environments. This research specifically focuses on seedling establishment in Betula litwinowii, with and without association with Rhododendron caucasicum in the Greater Caucasus mountain range of Georgia.

This project in environmental biology will provide a U.S. graduate student and an undergraduate research assistant access to unique research specialties that are not available in the U.S. - as much of the research on tree line questions originated in Europe and Eurasia. This project also fulfills the program objectives of bringing together leading experts in the U.S. and Central Europe and Eurasia to combine complementary efforts and capabilities in areas of strong mutual interest and competence on the basis of equality, reciprocity, and mutuality of benefit.

Barrier islands are unique island ecosystems that border coastal shorelines and separate the offshore oceanic province with the inshore sounds and estuaries. As their name implies, they provide a physical barrier that protects continental shorelines from often powerful wave action originating offshore, occurring along all major continents worldwide. Importantly, these ecosystems have an abundance of highly adapted endemic and indigenous species that survive in a uniquely stressful environment within the ecotonal transition from land to sea. The relatively unique physiochemical features of barrier islands also create a diverse spatial and temporal environment, supporting a diversity of plant species that may be highly specialized in their adaptive modes. However, these same communities often appear limited in species richness, due most likely to the stressful nature of this abiotic regime. In addition, these island ecosystems may be particularly vulnerable to global change impacts, including sea level rise and the prediction that the intensity and duration of severe oceanic storms such as hurricanes will increase with continued global warming. There may be few ecosystems that demonstrate so vividly the tight coupling between ecosystem stability, episodic extreme disturbances, and global change effects. The objective of this proposed workshop will be to consider, from a broad spectrum of expertise, the sustainability of barrier island ecosystems under current global change scenarios (more frequent and intense storms), including the likelihood of increasing anthropogenic disturbance. Solution of this future sustainability question for barrier islands could serve as a model system whereby biology, geology, economics, and remote sensing can be effectively integrated for the purpose of sustaining healthy ecosystems .

Coastal barrier islands are found along many continental shorelines worldwide, including the heavily populated eastern seaboard and Gulf Coast of the United States. Coastal barrier islands are very popular areas for residential development but also provide critical protection for adjacent shorelines from high-energy oceanic waves. They create a variety of shoreline and wetland habitats that support diverse plant and animal assemblages, including migratory birds and commercially important fish species. Despite the large number of engineering, natural, and social science researchers who conduct research on these ecosystems, no organization currently exists for fostering communication among these researchers and evaluating the future sustainability of these important ecosystems. The focus of the current project is to develop an interdisciplinary network that will address the effective management of U.S. barrier island ecosystems under the pressures of global climate change (e.g., sea level rise and increased hurricane activity) and continued urbanization. Through the formation of the Coastal Barrier Island Network (CBIN), scientists and municipal planners will interact through workshops, summer courses for students, a newsletter, and an interactive web site that will emphasize public and educational outreach activities.

Climate change may have potentially devastating impacts on barrier island ecosystems and the associated socioeconomic and cultural infrastructures of these heavily populated areas. Predicted increases in sea level and the frequency of intense storms will particularly impact barrier island ecosystems due to their extreme vulnerability to both. By facilitating communication among barrier island researchers from multiple disciplines, as well as with managers, this project will lead to better understanding and more effective management strategies for protecting barrier islands. Educational and outreach activities will lead to improved public understanding of the value of barrier islands.

Potential changes in cloud patterns due to global warming are of critical importance because of their strong influence on sunlight, temperature, and precipitation experienced by plant communities. Plants are especially sensitive to changes in cloud cover because sunlight, temperature, and water availability are important factors driving photosynthetic carbon gain, growth, reproduction, and spatial distribution patterns. The most dramatic response to changes in cloud patterns are projected for plant communities currently characterized by frequent cloud cover (e.g. mountain cloud forests, temperate and tropical rainforests). The purpose of this project is to use field measurements of photosynthesis, water stress, leaf temperature, and growth of native tree species in the Southern Appalachians Mountains (eastern US) and the Rocky Mountains (western US) under a range of naturally-occurring cloud regimes. From these data, a model will be developed that predicts long term effects of changing cloud-cover patterns on future growth and survival. These forest ecosystems represent two common types of mountain cloud regimes found across the globe?morning cloud-immersion and afternoon broken clouds, respectively. These forest tree species are physiologically adapted to their current climactic conditions, and it is anticipated that predicted changes in cloud cover may result in increased water, sunlight, and leaf temperature stress, leading ultimately to geographic and altitudinal migration, and/or extinction. Loss or decline of these high-mountain forests would have major impacts on such important features as timber production, snow accumulation, and corresponding water supply for agricultural and municipal use. This project will involve a collaborative effort between a university with a strong graduate program (Wake Forest University) and a local liberal arts college lacking the facilities and equipment to facilitate undergraduate research (High Point University). Three undergraduates from HPU (from underrepresented groups in science) have committed to the project and are highly motivated to become graduate students.

Mountains cover a major portion of the Earth's land area (approximately 24%), house approximately 20% of the world's population, provide critical ecosystem services to nearly half of the world population, and often form the boundaries between countries. Most of these mountain ecosystems are covered with tree forests that are key to important, often critical, services such as water storage and supply, commercial building and heating products, recreation and tourism, all of which dictate an important need for understanding their future sustainability under future global changes. This workshop will bring together experts from around the globe in an attempt to synthesize the mechanistic causes of observed forest boundaries. Specifically, emphasis at the meeting will be placed on ecophysiological adaptations and their linkages to genetic mechanisms. The meeting will be held at a facility that offers summer experiences to high school students interested in science but underrepresented in the fields of science, technology, engineering, and mathematics. The workshop will allow direct access by students attending summer classes at the field station. The intellectual approach of the meeting will be to generate predictive capabilities about potential future shifts in the elevational distributions of mountain forests. The upper and lower treeline boundaries define this distribution pattern, and future shifts have been projected based on current scenarios of rising atmospheric carbon dioxide and global warming. Such shifts in the boundaries and, thus, size of these forests could dramatically alter a host of ecosystem services, including snowpack accumulation and water supply to agriculture and municipalities. Moreover, future forest management policies could benefit significantly from early estimates of the anticipated changes in the future size and distribution of these mountain forests.

The workshop will bring together global researchers with recognized expertise for understanding how the abiotic and biotic environment influences mechanistically the elevation of the lower and upper boundaries (treelines) of mountain forests and, thus, a method for estimating future changes in the total breadth of the zonal forest bands found on mountains across the globe. Mountain forest boundaries have been recognized previously as a bellwether of climate change impacts on global ecosystems. Yet, little consensus exists regarding the specific mechanisms driving the elevations currently observed for treelines across the globe. Conflicting ideas currently exist concerning physiological constraints, including fundamental metabolic processes such as the photosynthetic capture versus the metabolic processing of carbon, plus the abiotic/biotic factors that may be limiting either. Moreover, most of the evidence for mechanisms driving treeline elevations comes from measurements on mature trees, rather than the early establishment stages when mortality is often the highest of all life stages. More specifically forest tree reproduction at treelines has been a neglected area of focus, including the idea that new seedling establishment is a critical, bottleneck life stage. Also, workshop participants will address the idea that carbon processing (sink) instead of carbon acquisition (source) limitations should be included as a missing, yet crucial, component for understanding new seedling establishment at treeline. The ultimate objective will be the formulation of a synthesis manuscript to be submitted for publication in an internationally-refereed journal with a broad readership. Another primary objective will be to involve the interaction of as many external workshop participants as possible via the K-12 program at the workshop venue (McCall Field Station, Univ Idaho), participating graduate students and Assistant Professors, and major social media outlets.