Research focus areas:
Elemental sources and cycling - role of nutrients and metals |
Studies that address the long-term fate of such metals are critical to the long-term health of
agricultural ecosystems. The effect of societal activities on the burden of toxic trace metals is
another facet of ongoing research. The extent to which these metals may affect major nutrient cycling
is unknown. This interdisciplinary nature of the Biogeochemistry and Environmental Biocomplexity
program allows us to bring together the strengths of individuals whom have traditionally studied
major nutrient cycling in managed ecosystems with those studying trace metal biogeochemistry.
The bioavailability and mobility of metals is often strongly controlled by the presence of organic
and inorganic complexing agents. While the importance of microbially mediated reactions is well
recognized in the geochemical cycling
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of some elements, such as carbon and nitrogen, it is just
being established and/or is poorly understood in others. The influence of bacteria on the global
cycling of manganese serves as an example. Another example related to metal biogeochemistry comes
from the complex interactions that occur at plant roots. Although the importance of adherent
symbiotic bacteria has received considerable attention in the area of N fixation, the understanding
of how microbial associations (both bacterial and fungal) affect nutrient or toxic element uptake
and bioavailability is just beginning to emerge. Research also focuses on the development of new
techniques and tracers for the study of elemental cycling; and importants aspect to furthering
knowledge in the field of trace metal boigeochemistry.
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Biogeochemistry and Biocomplexity: the Microbial Connection |
Microorganisms are the primary agents of geochemical change. Their small size, ubiquitous distribution,
and astounding metabolic diversity and genetic plasticity cast microorganisms in the role of recycling
agents for the biosphere. Microorganisms drive the geochemical cycling of the elements, detoxify many
contaminant organic compounds, make essential nutrients available to themselves and other organisms, and
maintain the conditions required by other inhabitants of the biosphere. Examples of the microbial
processes investigated by participants in the BEB program include:
- Methanogenic microbial communities in wetland soils-
Molecular biological, microbiological, and biogeochemical approaches are used to study microbial
community structure and carbon flow to methane in three upstate New York wetlands. |
- Biogeochemisty of aromatic hydrocarbon degradation-
Stable isotopic values of carbon pools, as well as cloning of community-derived 16S rRNA genes are
used to investigate the amount of carbon and electron flow at the site is channeled through
anaerobic food chains.
- Anaerobic biodegradation of chlorinated solvents-
Studies of the reductive dechlorination of the chlorinated solvents and groundwater pollutants
tetrachloroethene (PCE) and trichloroethene (TCE) have led to the isolation of Dehalococcoides
ethenogenes (De), the first organism known that can reduce PCE completely to ethene using an
anaerobic respiratory process. Efforts continue to make use of genomic array technology to study
De gene expression at contaminated sites.
- Microbial community structure in the plant rhizosphere-
Researchers seek to use microbiological and molecular approaches to study how land management processes
affect the rhizosphere microbial communities.
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Nitrogen in the terrestrial environment |
Despite great advances in recent decades, the need to improve our understanding of the biogeochemical
cycling of nitrogen remains one of the principal challenges facing terrestrial and aquatic
ecologists, both because of the complexity of the nitrogen cycle and because fixed nitrogen can be a
limiting plant nutrient as well as an environmental pollutant. The leaching of nitrate from forests
to surface water has serious consequences both to forest soils and to the receiving waters. Nitrate
can cause acidification of streams and lakes as well as eutrophication of estuaries and coastal waters.
In addition, the loss of nitrate from forests can cause the leaching of nutrient base cations from
soils and may lead to nutritional imbalances as the ratio of N to base cations changes.
Microbially-mediated reduction of nitrate to gaseous products plays a crucial role in the cycle and
budget of
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N in both terrestrial and aquatic ecosystems. Environmental controls of denitrification
rate at the community level are dominated by the interactions of nitrate availability, organic matter
substrate availability, oxygen diffusion, and environmental redox potential. Quantifying and
predicting the dependence of these environmental factors on ecological processes (e.g., natural
disturbances) and human influences (e.g. agricultural activity) as well as its variation at small
spatial and temporal scales remains an important challenge to biogeochemists. Students are able to
take advantage of the large-scale (regional, landscape, ecosystem) context of the ongoing studies of
nitrogen budgets, ecosystem-scale work on specific plant and microbial processes and apply the
state-of-the-art microbial and molecular methods available in Cornell laboratories. |
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The effects of variation in genotype and phenotype on ecosystem functioning |
Phenotypic variation, particularly in physiology, among organisms can lead to important differences
in ecosystem functioning. Rapid microevolution can lead to changes in community and ecosystem
functioning over short time intervals. At a larger spatial scale, the functioning of similar
ecosystems in different locations can vary depending upon the particular genotypes (and phenotypes)
present. Phylogenetic methods
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provide powerful tools for studying the macroevolutionary origins of
trait associations. Research in this area focuses on the effects of genotypic and phenotypic variation
on nutrient cycling and trophic dynamics while fully acknowledging the importance of the effects of
ecosystem variation on the distributions of phenotypes and genotypes. |
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Complex behavior from the coupling of simple mechanisms |
The collective behavior of a whole ecosystem results from an intricate network of interactions
between many individual biological and chemical components, each of which is dynamic in space and
time. A number of phenomena arise in biogeochemical systems that have a reasonably well-understood
basis in non-linear dynamics, including bifurcations and limit cycles. Although real examples of
each are now recognized, it is almost without question that we have seen only the tip of the iceberg
so far. The following research themes are examples of complex of behaviors that occur quite widely
in natural systems:
- Ecosystem-level effects of changes in species composition and abundance in tropical streams, such
as effects of fish grazing on primary productivity.
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- The effects of plant root exudates on the chemical speciation and soil/water phase distribution
of toxic metals in the rhizosphere, and their effects on bioavailability of toxic metals to plants;
effect of bacterial colonization of roots on rates of ligand release.
- Effects of community composition on nutrient cycling in aquatic ecosystems; links between natural
selection on organisms and ecosystem processes, e.g. how rapid zooplankton evolution affects
ecosystem responses to nutrient enrichment.
- Interactions of nutrient inputs and food webs to determine the relative abundance of various
groups of organisms and their productivity. Projects in lakes, estuarine mesocosms, and the Hudson
River, illustrate how particular species can modify trophic interactions and have enormous influence
on the structure and function of ecosystems.
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Outreach Activities
Science at the convergence
of disciplines provides both challenges and opportunities for the scientists involved. A common
perception is that there is a dichotomy between thorough study in a discipline and investigating
issues broadly across fields. Interactions between students and faculty across core disciplines
significantly enhance research efforts across both Cornell and our field of environmental science.
The ongoing formal activities of the program create a sense of cohesiveness among the participants
based upon frequent shared experiences and collaborative efforts, while allowing the educational
program to remain flexible; accommodating each individual’s goals, interests, strengths and needs. |
Workshops
Much of the formal classroom learning will be done through a variety of short courses or workshops,
giving us the flexibility to utilize the full spectrum of our faculty's talents, and giving the
students the opportunity to develop a program that best suits their individual needs and interests.
Workshops fit in to the broad categories of collaborative problem solving, professional development,
science-policy interaction, ethics in research, and modern methods in biogeochemistry and
biocomplexity. A specific list of previous topics can be found on the workshops page.
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Non-academic Internships
Issues in biogeochemistry and biocomplexity are at the forefront of management questions facing
government agencies, non-governmental organizations, private industry, and major consulting
firms. We enjoy close relations with the U.S. Environmental Protection Agency, the Environmental
Defense Fund, Chevron Production and Research Corporation, The Nature Conservancy, the Boyce
Thompson Institute for Plant Research, the U.S. Geological Survey, the Institute of Ecosystem
Studies, CIMMYT Mexico, and CRPG, Nancy, France. Students have the opportunity to
intern at these and other non-academic centers of research or policy formation and implementation as
a means to broaden their perspectives on both science and careers. |
Seminar series
The biogeochemistry seminar series plays a key role in bringing together students, researchers, and
faculty from across campus in a lively and interactive format. The seminar series reflects the
interdisciplinary nature of the larger biogeochemistry program.
Speaker suggestions come from students and faculty in a wide array of departments. Special attention
is made to include speakers from disparate backgrounds including industry, non-profit organizations,
and government agencies as a way to reinforce cross-linkages among academia and the outside world.
Invited speakers spend at least a full day on campus, providing numerous opportunities for all
interested students and faculty to meet with the speaker, both one-on-one and in a group setting.
It is considered one of the most successful aspects of our biogeochemistry program. This semester’s
list of speakers is available on the seminar page. |
Small Grants for Integrative Research and Travel
One of the more important aspects of professional development for students is learning how to fund
one’s own research. Students should have experience in applying for their own competitive grants in a
supportive environment where they can learn from detailed feedback and participate in the process as
reviewers. The Small Grants Program will be open to any graduate student interested in the program,
not just those currently receiving fellowship support from BEB. This makes for a rich mix from which
new interactions and synergisms can arise to further build the program. A list of proposals
which have recieved Small Grant awards is available on the Small Grants page. |
