Overview of Research in the Aridlands Ecology Laboratory

I am currently asking questions related to the role of past climate and land use as drivers of regional vegetation change. Furthermore, I am examining how these vegetation changes impact ecosystem scale C and N cycling. In my research program, I employ a variety of techniques in the fields of terrestrial plant ecology, soil biogeochemistry, and dendrochronology to address questions that not only further our knowledge of the structure and function of dryland ecosystems, but also address contemporary issues in management of these systems.

Funded Projects

Achieving Dryland Restoration Through the Deployment of Enhanced Biocrusts to Improve Soil Stability, Fertility and Native Plant Recruitment

PI: Nichole Barger, University of Colorado
Co-PI: Ferran Garcia-Pichel (ASU), Matthew Bowker (NAU), Jayne Belnap (USGS)
Co-PI: Mike Duniway (USGS), and Sasha Reed (USGS)
Funding Source: SERDP, Strategic Environmental Research and Development
Time Period: 3/1/13 - 2/29/18

        Biological soil crusts ('biocrusts') are communities of microorganisms that develop on soil surfaces and are a critically important functional component of dryland systems of the globe. They are often associated with increased soil nutrient and water retention—resources that are highly limiting to plant productivity in these ecosystems. But most importantly, biocrusts stabilize soil surfaces against wind and water erosion. While resilient to wind and water erosion, biocrusts are highly susceptible to compressional forces, such as those generated from foot and vehicle traffic associated with ground-based military training activities. Due to the functional importance of biocrust communities to the ecological functioning of dryland ecosystems there is keen interest in restoring these communities. Thus our overarching research objective in this project is to facilitate the recovery of degraded arid and semi-arid Department of Defense (DoD) lands by restoring biocrust communities. In this project we will: 1) establish a biocrust nursery as an inoculum testing and supply center for biocrust restoration 2) identify successful field application methods of biocrust inoculum in a series offield trials 3) evaluate soil and plant responses to biocrust restoration in multi-factorial field experiments and 4) share knowledge of biocrust restoration success and challenges with DoD and federal land managers.


Nitrogen Inputs and Cycling in Ecosystems of the Western Cape Province of South Africa

United States PI:
Dr. Jason Neff, Geosciences Department, CU Boulder
Dr. Nichole Barger, Ecology and Evolutionary Biology, CU Boulder
South Africa Collaborating Scientist:
Dr. John Stockton, Department of Geological Sciences, University of Cape Town
Funding Source:Mellon Foundation
Time Period: 8/2008 - 10/2013

        In this project we outline a study of nitrogen (N) cycling across the diverse flora of the Western Cape province of South Africa.  This region of South Africa has a remarkable diversity of floral assemblages that are arrayed across (and associated with) an equally diverse collection of geologic settings.  We propose a study of nitrogen inputs and cycling that will be closely tied to an ongoing NRF funded study led by John Stockton of the University of Cape Town that is focused on understanding the role of geologic and geochemical variation in the control of floral composition in this region. This current project is oriented around the study of the inputs and cycling of macro and micronutrients (excluding N) in ecosystems that range from the Strandveld coastal ecosystems to the mountain Fynbos ecosystems of Table Mountain National Park.  This existing set of sites and studies offers a remarkable opportunity to not only examine N cycling across a range of settings, but also to better understand the interaction between the N cycle and the cycling of other P and the micronutrients.  In this project we will specifically focus on the response of N fixation to variation in soil nutrient status and marine aerosol N input into Western Cape Ecosystems.  We expect to find increasing reliance on N fixation derived N in the Fynbos ecosystems compared to the coastal settings where marine aerosol inputs are higher.  However, the extraordinary diversity of geochemical settings in this area (and the corresponding variation in vegetation cover) suggests the possibility that micronutrient and P availability may interact with, and potentially control, the biological fixation of N to these ecosystems.  The combination of the proposed N studies and the ongoing geochemical and floristic opportunities offer a unique opportunity to examine the interactions between the major biogeochemical cycles and the role that these interactions play in structural biological communities.


Development of a Science-Based Decision Making Model for Restoration of Pinyon-Juniper Woodlands

PI: Nichole Barger, University of Colorado
Co-PI: Mark Miller, US Geological Survey Southwest Biological Science Center, Kanab, UT
Co-PI: Jeff Herrick, USDA ARS. Las Cruces, NM
Funding Source: USDA Cooperative State Research Extension and Education Services (CSREES)-Managed Ecosystems program
Time Period: 6/1/08-5/31/2012

        The focus of this integrated research program is the development of approaches and tools for restoration and long-term sustainable management of pinyon-juniper (P-J) ecosystems that are based on principles of adaptive ecosystem management. Our research objectives are 1) to identify the P-J treatment strategies that are most effective in overcoming constraints to understory restoration and 2) evaluate the impacts of P-J treatment strategies on  important ecosystem attributes and functions. By understanding the important constraints to restoring understory vegetation and the potential risks associated with different treatment strategies, we expect that the long-term outcome of this research will be more effective restoration of understory vegetation communities in combination with improved ecosystem conditions. Building on the research program, our extension objectives are 1) to use the results of our research to develop a series of science-based decision making models and 2) to provide training to land managers and other stakeholders in using these models to plan and implement future projects. Training land managers to use science-based decision making models that are grounded in fundamental principles of ecology should lead to increased awareness of ecological processes and how these processes function across managed landscapes.  Following this, application of such models to managing P-J woodlands should lead to more scientifically defensible management plans and protection from litigation, which is always a management concern when working with a range of stakeholders that differ in how they believe these landscapes should be managed. Our educational objectives are to provide both classroom and field-based training to undergraduate and graduate students in methods of adaptive ecosystem management. This will be accomplished by developing an Ecosystem Management course for undergraduates, directing a summer undergraduate research and management internship program and training graduate students to direct their research to address the needs of land management goals. Our goal in providing these educational opportunities to students is to forge stronger ties between future ecologists and land managers with the outcome of bridging the knowledge gap between academic science and applied management issues.


Regional Carbon Storage Responses to Woody Encroachment in Western Pinyon-Juniper Systems

PI: Greg Asner, Department of Global Ecology, Carnegie Institution of Washington, Stanford University
Co-PI: Jason Neff, Department of Geological Sciences and Environmental Studies, University of Colorado
Co-PI: Nichole Barger, University of Colorado
Funding Source: NASA North American Carbon Program
Time Period: 2/2004-5/2008

        Arid and semi-arid ecosystems cover about 3.4 million square kilometers of North America.  The spatial patterns and abundance of herbaceous and woody plants throughout these regions are determined by bio-climatic conditions, topography, soil properties, and disturbance regimes.  During the past century, the balance between woody and herbaceous plants has shifted in many U.S. dryland ecosystems to favor trees and shrubs.  Recent syntheses suggest that woody plant encroachment contributes significantly to a North American carbon sink.  However, current estimates of gross or net rates of woody cover change in the western U.S. are crude and have not been linked to changes in C storage, thus the potential contribution of woody encroachment to the U.S. carbon budget remains elusive.
        While our regional knowledge of current woody cover distributions, woody vegetation changes over time, and ecosystem C responses is very crude, what we do know has largely come from studies in “lowland” arid and semi-arid regions.  Pinyon-juniper (P-J) woodlands are among the least understood systems in terms of woody encroachment and thickening.  We do not know: (1) the current distribution, cover and carbon stocks of P-J ecosystems in a ~ 500,000 km2 portion of the Southwest; (2) regional rates of P-J cover and carbon change in relation to soils and grazing history; (3) soil organic carbon responses to changes in P-J cover; and (4) how to model current and future distributions of carbon stores in the P-J region.
        The broad goal of this project is to quantify and understand regional effects woody encroachment on carbon storage in pinyon-juniper ecosystems of the Southwest U.S.  We will quantify the contribution of woody encroachment in these systems to a proposed U.S. carbon sink and the interaction of aboveground changes in carbon with direct grazing impacts on soil carbon.  We will combine multi-platform remote sensing, field biogeochemical and dendrochronology studies, and spatio-temporal carbon modeling to achieve this goal.