Current Projects

Influence of Disturbance and Seasonality on Regional Carbon Flux Upscaling
NASA ROSES 2010, Carbon Cycle Science, $ 883,605

Integration of disturbance patterns into carbon (C) flux estimates to improve terrestrial-atmosphere C exchange is a critical priority for the North American Carbon Program.  This project is built upon previous finding from The
Chequamegon Ecosystem Atmospheric Study and aims to
quantify uncertainty in C flux upscaling, evaluate multiple disturbance stressors, and develop two-way communication channels between federal agencies and scientists.  This project asks three main questions: (1) does incorporation of variation in physiological model parameters improve seasonal and interannual CO2 flux hindcasts from eddy flux towers? (2) does incorporation of stand-replacement and partial disturbance processes from remotely sensed observations improve yearly to decadal CO2 flux hindcasts from eddy flux towers? and (3) To what degree does model-data integration aid regional and landscape decision-making for forest C storage management?  The finding from this project will directly contribute to national efforts to constrain uncertainty in terrestrial-atmospheric C exchange in several important ways.  First, it will utilize new disturbance algorithms using Landsat imagery to test whether inclusion of partial and stand-replacing disturbance reduces uncertainty in C flux upscaling.  Second, it will use a computationally tractable but responsive photosynthetic model to evaluate whether a more sophisticated parameterization of plant physiology aids temporal diagnosis of C flux estimates.  Third, by collaborating with regional and national Forest Service personnel, this project aims to partially address the ‘end-to-end’ problem of C cycle science by helping managers to diagnose adaptive capacity of forested landscapes, target locations, and prioritize C management activities.

Co-I(s): Erica A.H. Smithwick (PI)– Penn State University

Kenneth J. Davis Penn State University

Klaus Keller – Penn State University

Kusum J. Naithani – Penn State University

Robert Kennedy – Oregon State University

Jeff Masek – NASA Goddard

Collaborators: Robert B. Cook – ORNL

Linda Parker - Forest Service

Nathan Urban - Princeton University

Climate, Fire and Carbon: Tipping Points and Landscape Vulnerability in the Greater Yellowstone Ecosystem

USDI/ Joint Fire Science Program, $ 140,653

Current model projections suggest that, by the end of the 21st C, climate conditions like those of 1988 (the year of the well-known Yellowstone Fires) will represent close to the average year rather than an extreme year. The consequences of a climate shift of this magnitude for the fire regime, post-fire succession and carbon (C) balance of western forest ecosystems are well beyond what scientists have explored to date, and may fundamentally change the potential of western forests to sequester atmospheric C.  In this project, we hypothesize that vegetation communities will contribute differentially to future landscape C flux because of different sensitivities to future climate and fire combinations, and the net result could qualitatively change the C dynamics of western forests. To explore this idea, we are focusing on the Greater Yellowstone Ecosystem (GYE) to address three overarching questions that are broadly relevant for many Rocky Mountain forests: (1) How great a change in climate and fire regime would be required to shift each of the dominant vegetation communities in the GYE from a net C sink to a net C source? (2) Do current projections indicate that changes of this magnitude are likely to occur in the next century, and if so, where in the GYE do they occur? (3) What are the integrated effects of changing climate, vegetation, and fire on spatial patterns of carbon flux across the GYE landscape as a whole?  To answer these questions, we are using observed relationships between climate and fire occurrence and downscaled climate data from general circulation models (GCMs) to determine future climate and fire regimes and develop spatially explicit maps of landscape C flux based on individual contributions of vegetation types to future climate and fire – determined from the CENTURY ecosystem model.  


Monica G. Turner – University of Wisconsin, Madison

Anthony Westerling - Sierra Nevada Research Institute and UC-Merced

William H. Romme, Colorado State University

Michael G. Ryan, USDA Forest Service RMRS

Consequences of Novel Disturbance Regimes on Climate-Induced Biogeographic Shifts along the Appalachian Trail

Department of Energy, National Institute of Climatic Change Research, $ 125,000

Northward biogeographical shifts are expected in the Eastern US with more southerly species (e.g., oak, hickory, pine) replacing northern hardwoods (e.g., maple, beech, birch).  The Appalachian Trail (AT) MEGA-Transect, an ecological monitoring program along this vector, provides an exceptional opportunity to test scientific hypotheses of disturbance-vegetation-climate interactions between southeast and northeast regions.  Fire is an extensive disturbance agent in the southeastern US but has a disputed historical role in the northeast. In this project, we hypothesize that under future climate, fire risk may be enhanced, resulting in positive feedbacks and sustaining northward migration of fire-prone vegetation.  Alternatively, in the absence of these fire-climate conditions, niche-based projections of northerly migration of fire-prone habitat may be overestimated.  This research will clarify how climate-induced shifts in species may interact with or produce novel disturbance regimes.  To explore this, we are developing a multi-scaled modeling approach that links a biogeographical model (MC1) with a species-specific model of potential suitable habitat called DISTRIB (Iverson et al., 2008). Model simulations will test fire-climate-vegetation feedbacks, allowing the dynamically generated fires of MC1 to influence the species composition predictions of DISTRIB and the species composition predictions of DISTRIB to influence the fuel load in MC1.  Models will be driven with new downscaled 4 km2 resolution climate datasets (historical PRISM
baseline, 3 GCMs, 3 emission scenarios) to test fine-scale fire-climate-vegetation interactions along the AT.

Dominique Bachelet - Oregon State University
Louis Iverson - USDA Forest Service Northern Research Station
Anantha Prasad - USDA Forest Service Northern Research Station

Spatial patterns of nutrient limitation and carbon storage in South African coastal lowland landscapes

National Science Foundation: EAGER, $150,000
George H. Deike, Jr. Research Grant, College of Earth and Mineral Sciences, $50,000

Geographically, Africa is one of the weakest links in the understanding of land-atmosphere carbon exchange.   The objectives of this research are to (1) employ a novel experimental design to determine how variation in nutrient availability determines spatial patterns in grassland carbon productivity and (2) provide the first-ever quantification of carbon storage in coastal and dune forests within two priority nature reserves in the southeastern coast of South Africa.  Contrasting fire and vegetation patterns within each reserve will allow for the development of new pyrogeographic perspectives on African carbon storage at landscape scales.  By studying carbon storage in priority conservation areas in coastal South Africa, this research will establish a deeper understanding of the role of African landscapes in conservation management and global ecosystem science. 

A current lack of understanding of complex interactions among fire, climate, and nutrient cycling hinders broad-scale modeling of ecosystem response to climate change.  This issue is particularly acute for Africa, which represents the largest source of fire-derived carbon emissions and for which carbon storage estimates are scarce. Direct measurement of carbon storage in new locations and identification of its limiting factors across multiple scales, as explored in this project, is critical for the development of future diagnostic modeling efforts. Understanding how fire and soil nutrients govern these patterns will contribute to landscape and conservation management in the region and globally.

As one facet of this ongoing research, undergraduate Arianna Simpson cataloged and digitally archived a manual of tree and shrub species present in the Cwebe and Dwesa national reserves on South Africa's Wild Coast.

This research is run in parallel with an education abroad program at Penn State, Parks and People, focused on interdisciplinary training of undergraduate students in collaborative international science.  Those interested in the study abroad program should visit: for further information.


Climatic Extremes, Mining, and Mycobacterium ulcerans: A Coupled Systems Approach

NSF-Coupled Natural Human Systems, $1,421,997


In this project, we are working in Ghana to explore the emergence of Buruli ulcer (BU) at multiple temporal and spatial scales.  Our project considers BU emergence as a function of climatic changes that interact with human-modified landscapes, resulting in increases in flooding and stagnant water.

We expect that human knowledge and behavior, which differ by occupation, age, location, and the degree of marginality people occupy in society, govern the resultant exposure to stagnant water bodies that may house the bacterium causing BU. We believe that the transmission of BU is due to previously unidentified thresholds in these coupled human-natural patterns that interact across spatial and temporal scales. We aim to make concrete recommendations about the conditions under which landscape rehabilitation would enhance human-ecosystem health and resilience. In addition, a key element of our project is the development of a sister-school approach, linking elementary, intermediate, and high schools from Penns Valley Area School District with partner schools in Tarkwa, Asankragwa, Deaso, and Dunkwa. Through collaborative activities, the students and teachers aim to understand human-modified landscapes and disease patterns in Pennsylvania and in Africa.


Petra Tschakert (PI) Penn State University, USA, Joseph Oppong - University of North Texas, USA, Richard Amankwah- University of Mines and Technology, Ghana, Edith Parker - University of Iowa, USA, Simon Gawu, KNUST, Ghana, Kamini Singha - Penn State University, USA, Heidi Hausermann - Penn State University, USA, Erasmus Klutse Ghana Health Directorate, Ghana, Ray Voegborlo KNUST, Ghana,Frank Nyame - University of Ghana, Ghana, Annmarie Ward-Penn State University, USA.

GK-12: Carbon Education and Research Together for Humanity (CarbonEARTH)

NSF-GK12, $3,000,000

CarbonEARTH uses the interdisciplinary theme of carbon, broadly construed, as a unifying platform for investigation, discovery, training and education. Carbon is a ubiquitous element in our world, featured highly in a broad spectrum of basic and applied research areas, including materials science, energy science, geosciences, and life sciences.  Many challenges facing society today involve carbon, including global warming, waste disposal, renewable energy, and nanoelectronics and these issues are frequently addressed in the media, with varying degrees of scientific accuracy.  The majority of K-12 student achievement standards for science relate to these issues.  CarbonEARTH will provide teachers and students from a wide range of disciplines with science learning experiences that not only teach the concepts, but also develop the skills with scientific inquiry for approaching these problems scientifically.  Specifically, CarbonEARTH teams STEM graduate students with upper elementary and middle school science teachers from rural and urban school districts to teach PA standards-based science topics related to the themes of Energy, Matter & Materials, Earth Processes, and Ecosystems, focusing on inquiry-based teaching strategies. Recent government reports describe the severity of our nation’s need to increase the STEM pipeline and the multitude of underlying problems, such as lack of interest and retention in STEM by women, minorities, and low socioeconomic populations.  CarbonEARTH aims to increase representation of women, minorities, and low-socioeconomic populations by promoting STEM education and careers of underrepresented groups at all levels; enhancing graduate students’ research and other non-research skills needed for successful careers,  working with upper elementary and middle school teachers and students to promote deeper understanding of STEM concepts and skills in scientific inquiry, and providing experiences for upper elementary and middle school students that reflect the excitement and importance of STEM careers through interactions with graduate student role models.


PI and Co-PI(s)
Renee Diehl - Physics (PI)
Angela Lueking - Energy and Mineral Engineering
Erica Smithwick - Geography
Elizabeth Boyer - Forest Hydrology
Annmarie Ward - Education (CoPIs)
Faculty and Departments:  Rachel Brennan (Environmental Engineering); Nicole Brown (Wood Chem); Craig Cameron (Biochem and Molecular Bio); Kristen Fichthorn (Chem Engineering); Katherine Freeman (Geosciences); Heather Karsten (Crop Production and Ecology); Margot Kaye, (Forest Ecology); Jennifer Macalady (Geosciences); Erin Sheets (Chem); Jorge Sofo (Physics); Jun Zhu (Physics)

Past Projects


Pacific Northwest

Erica Smithwick, Ph.D.

I have developed (with Mark Harmon, Jimm Domingo) a model to predict how carbon storage changes under altered disturbance regimes (Smithwick et al. Landscape Ecology 2006). I also modeled how non-linear interactions across forest edges result in emergent behavior at broad scales, contributing to a greater understanding of scaling issues (Smithwick et al. Landscape Ecology 2003). Leading to a better valuation of ecosystem services, I also calculated that future carbon sequestration potential in the Pacific Northwest could be worth billions of dollars (Smithwick et al. Ecological Applications 2001).



The Effect of Wildfire Severity on Short-Term Post-Fire Boreal Vegetation Recovery in Interior Alaska

Jared Oyler

Wildfire is the dominant disturbance in the interior boreal region of Alaska and is predicted to increase with climate change.  However, due to limited fine-scale studies, it is not known how increased fire severity (i.e.—amount of organic material consumed) alters post-fire recovery of vegetation productivity and biomass, nor how the relationship between severity and post-fire recovery varies across heterogeneous landscapes.  Using remotely sensed data, this study will analyze the effect of fire severity (Normalized Burn Ratio) and related landscape variables (land cover, elevation, slope, aspect, etc.) on post-fire productivity and biomass recovery (MODIS NDVI/EVI) and determine how recovery varies within and among all fires that burned in Alaska in 2004.  A stand-scale analysis of field-based measures of fire severity, pre-fire stand variables, and succession vegetation biomass and productivity at a subset of the 2004 fire sites will augment the remote sensing analysis.  Understanding how increased fire severity alters boreal vegetation recovery and succession is critical in predicting associated feedbacks and effects on climate and global biogeochemical cycles.



Nitrogen Availability Along a Condition Gradient in Headwater Wetlands in the Upper Juniata Watershed, Pennsylvania

Misha Williams-Tober

Human activities have led to a large inc
rease in nitrogen inputs to terrestrial and aquatic ecosystems.  Elevated nitrogen levels in water are deleterious to both aquatic biota and h umans.  The reduction of nitrogen inputs to streams can be achieved through the protection and restoration of riparian zones, including he adwater wetlands.  Management of riparian zones for the function of nitrogen removal requires understanding the factors that control the process.  In non-wetland riparian zones, vegetation uptake might be the primary source of nitrogen removal, while nitrogen removal in headwater wetlands might depend more upon oxic/anoxic conditions and denitrification.  Through collaboration with the Penn State Cooperative Wetland Center, 12 headwater wetland sites within the Upper Juniata watershed were selected.  Four condition categories were established, ranging from 0 (extremely poor condition) to 100 (excellent condition), and each category includes three sites.  Readily available nitrogen at each site will be collected with free ion exchange resin bags and analyzed with a Lachat autoanalyzer for dissolved organic nitrogen, ammonium, and nitrate.  Regression will be used to characterize the relationship between these nitrogen pools and soil moisture, condition category, pH, vegetation type, percent vegetation, and biomass of trees (by species).  This will reveal the controls over nitrogen removal in headwater wetlands.  Knowledge of these controls can be used to properly manage headwater wetlands for the function of nitrogen removal.