Hydrologic and Biogeochemical Fluxes in Land-Water Mosaics
Steve Carpenter, Monica Turner, Jon Foley
Project Overview
Funded by the Andrew W. Mellon Foundation
August 2002-August 2006
Our overarching goal is to understand carbon and nutrient cycles for a landscape
on which terrestrial and freshwater systems are intimately connected in multiple and
reciprocal ways. In the Northern Highlands region of Wisconsin, we are studying a
spatially complex landscape in which the dominant land covers are diverse types of
forests and shrublands (81% of land surface) and lakes (13%) (see attached file,
NHLD_maps.doc). We hypothesize that reciprocal interactions of terrestrial vegetation
and lakes, through flows of water, organic carbon, and nutrients, are more complex than
previously thought. Improved understanding of these interactions demands a
combination of terrestrial and aquatic expertise, in an appropriately integrated research
plan. This need for collaboration prompts our inquiry to the Mellon Foundation.
Terrestrial ecologists have made great strides in understanding the geophysical
template, climate, disturbance regimes, and vegetation dynamics that control
groundwater, surface water, carbon and nutrient fluxes in the Northern Highlands and
other landscapes. Despite these advances, there are considerable gaps in
understanding the magnitude and spatial patterns of biogeochemical fluxes. For
example, terrestrial ecologists have found important imbalances in the carbon cycle.
These gaps may be closed by studies that consider the complete landscape – that is,
the integrated behavior of terrestrial vegetation and surface waters.
Aquatic ecologists have made considerable progress toward understanding inlake processes, and documented extensive chemical transformations of water that
passes through lakes. The connections between terrestrial vegetation and lake
dynamics, however, are not well understood. Furthermore, the reciprocal exchanges of
water, carbon and nutrients between lakes and terrestrial vegetation have not been
explored. These include not only the hydraulic fluxes from land to lakes, but also the
effects of lakes on terrestrial vegetation through processes such as flows of
groundwater and floodwater, transformation of the chemical composition of water, and
activities of animals (for example, emergence of insects or activities of beavers).
These connections suggest that an integrated approach to complex landscapes
of terrestrial vegetation and lakes is needed. Many specific questions require such an
integration of terrestrial and freshwater understanding, such as:

How do the geology, soils, and climate of the region interact with disturbance
regimes (windthrow, fire) to create a dynamic spatial pattern of forests, lakes,
and other land covers?
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
How does this dynamic pattern of terrestrial vegetation and surface waters
influence the spatial flows of water, organic carbon, and nutrients at the scale of
the complete, integrated landscape?

How does the presence of significant amounts of surface water change the
dynamics of the terrestrial vegetation and the flows of water, organic carbon, and
nutrients at the scale of the complete, integrated landscape?

Does the presence of lakes create unique spatial patterns of terrestrial
vegetation?

Does the presence of lakes create unique spatial patterns of organic carbon
decomposition or nutrient cycling?

What are the implications for terrestrial vegetation of lake-driven changes in
biogeochemistry of groundwater and surface water?

What are the implications for terrestrial ecosystems of lake-driven release of
trace gases and emerging insects, and of lake-centered activities of beavers1?

How have past changes in climate (e.g. end of the Little Ice Age, 1930s drought,
late 1980s drought) affected the spatial pattern of land cover and flows of water,
organic carbon, and nutrients?

Did these changes in climate induce a linear (proportional) response across the
landscape, or are there sharp changes in certain subsets of the landscape? If
such thresholds are present, what controls them? What are their implications for
water, organic carbon, and nutrient flows at the scale of the complete landscape?
Our primary approach will involve spatially-explicit simulation models of the
complete landscape (terrestrial and aquatic components) at regional spatial scales. We
have already developed several key components of these models, although integration
of these components will require a significant amount of new modeling work. We will
develop and calibrate these models using long-term and spatially-extensive data bases
available for the Northern Highlands Lake District, many of which have been
constructed through our past research.
This proposed project on Land-Water Mosaics (LWM) will benefit from synergistic
interactions with ongoing work funded by the National Science Foundation, NASA,
USGS, and EPA. The key projects are as follows.

1
The North Temperate Lakes Long-Term Ecological Research program (directed
by Carpenter, with Foley and Turner as co-Principal Investigators) is based at
We anticipate that any work on beavers will be covered by our NSF funding.
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Trout Lake Station near the center of the NHLD. LTER’s extensive data bases
on climate, land use and cover, regional hydrology, and limnology will be
available to the proposed LWM project (see http://lter.limnology.wisc.edu). We
also have access to the expertise of other LTER researchers, including
hydrologists and biogeochemists.

Our LTER site is a primary site for the USGS Water, Energy, and
Biogeochemical Budget (WEBB) program, and we collaborate regularly with
USGS researchers.

Carpenter and Turner are Principal Investigators of a NSF BioComplexity project
which is focused specifically on ecological interactions at the land-water interface
in the NHLD (http://biocomplexity.limnology.wisc.edu/). Data on riparian
vegetation and limnology collected under the BioComplexity award will be made
available for the proposed LWM project.

With NASA support, Foley’s group is developing detailed models of terrestrial
ecosystem processes (including water, carbon and nutrient budgets) that can be
used across a variety of scales (from field-sized to regions). Foley’s group is
also developing landscape-scale hydrological models, which simulate the flow of
water and solutes within groundwater and surface-water systems. These models
will be a foundation for our proposed LWM research.

Turner is leading an EPA-funded project on ecological dynamics and vegetation
change in the floodplain of the Wisconsin River, which rises from Lac Vieux
Desert on the east side of the NHLD. While the field sites for the Wisconsin
River Floodplain project are downstream of the NHLD, the concepts and models
are similar and intellectual exchange between the projects will be productive.

Carpenter is involved in whole-ecosystem experiments in the NHLD, funded by
the NSF Ecosystems Program, which will provide weather, gas flux, and carbon
cycle data to the proposed LWM project.
In summary, the strong funding base already present in the NHLD provides tremendous
leverage for the funding we are requesting from the Mellon Foundation. This proposed
project build on literally millions of dollars spent to build data bases and scientific
understanding in the NHLD. All of these projects will benefit from exchange of ideas,
data, and models.
As a trio, the three of us are already collaborating on exploratory research that is
related to this new proposed project. We are team-teaching a course on large-scale
biogeochemical modeling, and co-fund several graduate students already. We have the
necessary skills in large-scale modeling and analysis of vegetation dynamics,
hydrology, organic carbon and nutrient flows, and lake ecosystems. We are
enthusiastic about collaborating on this work. We believe that it will provide new
insights into complete landscapes – integrated mosaics of terrestrial and freshwater
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ecosystems – that will fundamentally change our understanding of water, carbon and
nutrient flows at extensive spatial scales.