FORT COLLINS SCIENCE CENTER 

Ecosystem Dynamics Branch

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2008–3100

December 2008

Capabilities

Complex natural resource issues require 

understanding a web of interactions among ecosystem 

components that are (1) interdisciplinary, encompassing 

physical, chemical, and biological processes; (2) spatially 

complex, involving movements of animals, water, and 

airborne materials across a range of landscapes and 

jurisdictions; and (3) temporally complex, occurring over 

days, weeks, or years, sometimes involving response 

lags to alteration or exhibiting large natural variation. 

Scientists in the Ecosystem Dynamics Branch of the U.S. 

Geological Survey, Fort Collins Science Center (FORT), 

investigate a diversity of these complex natural resource 

questions at the landscape and systems levels, with a 

focus on the following areas:

•	 Energy and Land Use

 Applied research and integrated regional assessments emphasize spatially explicit analyses of ecosystem components affected by energy development and 

land-use change in the western United States. Topics 

include sagebrush-steppe ecology; sagebrush habitat 

assessments; the effects of human activities (including 

energy development, transportation, and recreation) on 

habitat health and wildlife behavior; habitat fragmentation and disrupted migration corridors; and tool development for managers and decision makers. 

•	 Climate Change and Long-term Integrated 

Assessments

 Research on Federal trust lands, especially in 

the mountains of western national parks and forests, 

addresses long-term ecosystem dynamics associated 

with climate change. Studies include ecosystem biogeochemistry, atmospheric deposition, forest dieback, and 

assessment of forest biomes ranging from the Arctic to 

the desert Southwest. FORT scientists are collaborating with researchers from around the world to describe 

and document global patterns of climate-induced forest 

dieback.

•	 Herbivore-Ecosystem Interactions

 Data from these studies help inform ungulate management decisions on public lands, typically in large, 

jurisdictionally complex landscapes. Recent work 

involves investigations on the impacts of herd size and 

movements of elk, bison, and wild horses on various 

ecosystem components. Specifically, scientific efforts 

include (1) quantifying interactions among carnivores, 

herbivores, plants, and soils; (2) determining the 

effects of ungulate herbivory on ecosystem processes 

and vegetation communities; (3) testing survey techniques for more accurate population estimates; and (4) 

evaluating contraceptive methods for managing wild 

horse populations.

Sky Pond in Loch Vale watershed, Rocky Mountain National Park. 

Photo: Jill Baron, USGS.
•	 Fire and Post-Fire Restoration

 This research examines the effects of fire on 

plant and animal communities at various spatial and 

temporal scales. Using interdisciplinary approaches, 

scientists investigate post-fire rehabilitation (including 

community education), interactions between post-fire 

biotic (plant establishment, including invasive species) 

and abiotic (runoff and erosion) processes, and public 

responses during fire emergency situations. 

•	 Environmental Flows and River Restoration

 Anthropogenic alteration of watersheds impacts 

the quantity and quality of surface and ground waters. 

Land-use changes and development have long-lasting 

and often permanent adverse effects on the plants and 

animals that share these environments with human 

populations. Current research in regulated and unregulated river basins integrates hydrology and hydraulics, 

fluvial geomorphology, river and riparian ecology, and 

aquatic habitat modeling to explain and predict patterns 

and variation in ecological responses to perturbations. 

Research addresses management issues such as water 

supply, restoration of aquatic and riparian habitats, and 

the effects of instream flow on native riparian vegetation, invasive plants, and endangered wildlife. 

Selected Projects

Energy and Land-Use Research and Technical 

Assistance

Exploration and development of domestic oil and 

gas resources have become a national priority, yet our 

understanding of the direct and indirect effects of energy 

development on surrounding ecosystems remains limited. 

This poses a challenge for natural resource managers, who 

are balancing priorities that include maintaining healthy 

rangelands and wildlife habitats while providing for 

resource development and multiple public uses. Scientists 

at FORT and several other USGS science centers, along 

with Federal, State, and local partners, are jointly conducting interdisciplinary research focusing on these issues at a 

regional landscape level in the western United States. This 

interdisciplinary work contributes directly to the Wyoming Landscape Conservation Initiative (WLCI), a longterm, landscape-scale science collaboration to ensure full 

consideration and adaptive management of Wyoming’s 

wildlife and habitats in the face of increasing land-use 

pressures. Scientists are investigating diverse energy and 

land-use issues by using a multidisciplinary approach 

to assess sagebrush habitat condition; employ targeted 

research and monitoring plans; identify and evaluate the 

ecological impacts of fire, grazing, roads, and energy 

development on sagebrush ecosystems and species; 

refine scientific understanding of sage-grouse population 

dynamics and genetics; and develop predictive models and 

maps that address management priorities. 

Western Mountain Ecosystem Responses to 

Climate Change

FORT is participating in the Western Mountain 

Initiative, a cooperative effort to understand and predict 

the sensitivities, thresholds, resistance, and resilience 

of western mountain ecosystems to climatic variability 

and change. FORT scientists helped develop vulnerability indices of select mountain regions in Colorado, New 

Mexico, Montana, Washington, and California to current climate variability and future climate changes. They 

also are (1) continuing long-term ecological research and 

monitoring of the Loch Vale watershed in Rocky Mountain National Park, Colo., and Bandelier National Monument, N.M.; (2) clarifying centennial- to millennial-length 

shifts in past vegetation and fire regimes; (3) elucidating 

responses of fire to short-term climatic variation; (4) 

determining long- and short-term climatic controls of tree 

mortality, including thresholds for dieback; (5) documenting rapid and extensive climate-induced vegetation mortality, including global patterns of massive forest dieback; 

and (6) determining the effects of climatic variability, fire, 

and land use on watershed runoff and erosion processes. 

A FORT scientist also was lead author for the chapter 

on national parks in Preliminary Review of Adaptation 

Options for Climate-Sensitive Ecosystems and Resources, 

a report to Congress by the U.S. Climate Change Science 

Program and Subcommittee on Global Change Research, 

and a national collaboration among scientists from numerous agencies, universities, and nonprofit organizations.

Riparian Exotic Species

In the arid and semi-arid interior of western North 

America, riparian cottonwood, willow, and other native 

species are being replaced by exotic shrubs and trees. The 

most abundant of these, saltcedar (or tamarisk), now covers about 500,000 hectares and is the dominant riparian 

woody species in much of the southwestern United States. 

Russian olive and Siberian elm are other invasive species 

prevalent in the West. These great changes in species composition of riparian woody plants have been associated 

with loss of plant diversity, degradation of habitat for 

Tamarisk-dominated vegetation along the lower Colorado River, 

California-Arizona. Photo: Pat Shafroth, USGS.
vertebrate animals, decreased channel conveyance, 

increased water loss from evapotranspiration, and loss 

of aesthetic and recreational opportunities. Scientists are 

examining how environmental factors, including climate 

change, latitude, livestock grazing, substrate composition, 

flood regimes, and the upstream presence of dams influence the susceptibility of a river to invasion, especially by 

saltcedar and Russian olive. This information is being provided to land managers who need to know which systems 

are most susceptible to invasion by exotics and which are 

most likely to respond positively to restoration efforts.

Elk and Bison Grazing Ecology in Great Sand Dunes 

National Park and Preserve

FORT scientists are conducting studies on bison and 

elk in the Great Sand Dunes National Park and Preserve 

to determine population status and movements, the effects 

of herbivory, and suitable habitat and population potential in the park and surrounding lands. Scientists will use 

these data to develop an elk and bison grazing model 

that includes grazing as a significant natural ecological 

process and incorporates protection of sensitive nativeplant communities. Scientists are applying study results to 

development of a predictive management-planning model 

that will make predictions based on several management 

scenarios. These tools will directly support park managers 

in developing and evaluating management alternatives for 

elk and bison.

River and River Basin Modeling

Resource management agencies continually face the 

need to reach defensible conclusions and prepare documents describing the processes and reasoning behind 

management decisions. The complexity of water resource 

management requires interdisciplinary conversations 

about such diverse issues as physical parameters, habitat, 

water flow, chemistry, biology, and social needs. Decision 

support systems provide interactive, flexible, and adaptable computer-based information systems for quantifying 

tradeoffs and multiple resource impacts related to changes 

in water management. FORT scientists are developing 

customized model components for use in interactive 

decision-support systems that evaluate changes in hydrologic, hydraulic, and instream flow values.

American bison grazing at Great Sand Dunes National Park and Preserve. 

Photo: Richard Madole, USGS.

Yakima River geospatial information system. Example shows spawning/

incubation habitat persistence map for Coho salmon (top) and associated 

habitat time-series analysis (bottom). Images: Ken Bovee, USGS.

Greater sage-grouse chick

 with radio transmitter. 

Photo: Cameron Aldridge, 

Colorado State University.
Staff

Ecosystem Dynamics research staff possess extensive education and experience in ecology, wildlife biology, 

population ecology and dynamics, hydrology, river-systems modeling, biogeochemistry, fire science, climate 

change, riparian systems, natural and human-caused perturbations, and physical science. For a complete list, visit 

http://www.fort.usgs.gov/ED/Staff.asp

Zack Bowen 

 Branch Chief 

 Ecosystem Dynamics

 U.S. Geological Survey 

 Fort Collins Science Center

 2150 Centre Avenue, Building C 

 Fort Collins, Colorado 80526-8118

 Tel. 970.226.9218 Fax 970.226.9230 

 bowenz@usgs.gov

Learn more about FORT science, products, and 

resources at http://www.fort.usgs.gov

Learn more about the Ecosystem Dynamics Branch 

at http://www.fort.usgs.gov/ED/

Contact Information

Soil sampling on Thatchtop Mountain, Rocky Mountain National Park. 

Photo: Melannie D. Hartman, Colorado State University.

Front page photo: Sparse willow along portions of the Illinois River, Arapaho National Wildlife Refuge, Walden, Colorado. Photo: Gregor Auble, USGS.

Inside photo: Sagebrush biome, Wyoming. Photo: Cameron Aldridge, Colorado State University.

Back page photo: Drought and climate change are causing extensive forest dieback in the U.S. West as well as worldwide. These dead ponderosa pines in the 

Jemez Mountains of New Mexico were killed by a combination of drought stress and attacks by bark beetles on weakened trees. Photo: Craig D. Allen, USGS.

Wildlands Restoration Volunteers 

construct temporary fencing and plant 

willow poles in a relict channel of the 

Illinois River, Arapahoe NWR. 

Photo: Gregor Auble, USGS.