Projects
Current and recent research
projects
Recent NSF dissertation improvement
awards
Current postdoc fellowships
Dissertations and theses
completed through the lab
CURRENT AND RECENT RESEARCH
PROJECTS
Climatic drivers of forest dynamics.
Sponsor: U.S. Geological Survey. 2007-08
Under this project we are re-measuring permanent forest plots installed in the early 1980s in the subalpine zone of the Colorado Front Range to study the effects of climatic variation on the demography of the tree populations. The focus of the research is on the role of drought and warming in the mortality of conifer populations. The 25-year record of tree mortality from the permanent plots is being supplemented by tree-ring dating of tree mortality patterns over a time span of more than a century.
This work is in support of USGS-Biological Resources Discipline’s Western Mountain Initiative (WMI) global change research project.
Fire Risk and Ecological Integrity in the Wildland Urban Interface of the Colorado Front Range.
Sponsor: National Science Foundation, Ecological Studies Program. 2006-2009.
In the western U.S. resource managers are increasingly concerned with the objectives of restoring ecosystems to their pre-settlement conditions while also mitigating the risks of fires to property and resource values. The dual management goals of ecological restoration and fire risk mitigation are not always compatible, especially where natural fire regimes consisted of large, severe fires. This research explores the relationship between forest management, land use change, fire risk and ecological integrity in the wildland-urban interface (WUI) spanning four counties of the Colorado Front Range. This research will develop spatially explicit baseline studies that evaluate how fire exclusion and land use patterns have affected wildfire behavior and the spatial extent of fire risk to people and property across the WUI landscape. Building upon these baseline assessments, the study will consider which spatial combination of land use and forest management scenarios would significantly reduce fire risk while also protecting ecological integrity across a heterogeneous wildland-urban interface. This work integrates natural and human dimensions of resilience and landscape change in the WUI of the Colorado Front Range.
Scientific and communication products will be generated through this project, which will have application to societal questions of how resilient human and natural communities can be sustained in a fire-prone, ever-expanding WUI. These include significant baseline studies of (1) historical fire regimes and forest stand structures across the Colorado Front Range WUI, (2) historical exurban development patterns and effects on the degree and distribution of wildfire risk across the WUI, (3) analysis of departure from historical ecological conditions and an improved wildfire risk map, and (4) spatially explicit evaluation of key fire mitigation and forest restoration options.
This project is integrated with Tania Schoennagel’s David H. Smith Conservation Fellowship on “Fire risk and forest restoration in the wildland urban interface of the Colorado Front Range.”
Climatic variation and disturbance interactions in subalpine
Rocky Mountain forests.
Sponsor: National Science Foundation, Ecological Studies
Program. 2003-2006.
Much is known in a general sense about how weather conditions
at time scales of days to months, affect the potential for
fire occurrence and the population dynamics of disturbance-causing
insects. However, research is needed on how climatic influences
on disturbances vary in relation to broad environmental gradients
(i.e. elevation, topography and regional climate) and with
the temporal scale of the climatic variation. Although climate
may interact with environmental gradients in influencing the
spatial and temporal configuration of disturbance events,
disturbance interactions (e.g. the influence of a severe insect
outbreak on subsequent fire occurrence or vice versa) also
act as a source of the spatial heterogeneity in vegetation
attributes that influence disturbance processes and subsequent
landscape patterns. Disturbance legacies may alter stand susceptibility
to climatically sensitive disturbances such as fire and insect
outbreaks through the alteration of stand structures (tree
ages and sizes) and species composition.
In this context, this project addresses the following three
key research questions in southern Rocky Mountain forest ecosystems:
1) What are the climatic conditions, including temporal scale
of variability, that are conducive to fire and lethal insect
outbreaks across topographic and broad climatic gradients?
How are these climatic conditions related to broad-scale drivers
of climatic variation such as the El Niño-Southern
Oscillation, the Pacific Decadal Oscillation
and the Atlantic Multi-decadal Oscillation?
2) How does topographic variability, through its influence
on the nature and rate of forest recovery following previous
fire and insect outbreaks, affect future susceptibility to
disturbance?
3) How do legacies of stand structure resulting from major
preceding disturbance by fire and insect outbreaks affect
the subsequent frequency, spread, and/or severity of disturbances?
We are examining disturbance processes and forest stand attributes
across a range of spatial scales from the regional- to the
stand-scale. At the broader regional scale we identify general
constraints, primarily regional climatic variation and secondarily
broad differences in topography, on the disturbance processes
observed at the landscape scale. At the landscape scale we
observe where and why disturbances interact in the context
of variation in topography, stand structures, and composition
(i.e. cover type). Analyses of intra-stand and tree-level
variations should reveal evidence of mechanisms that may explain
the observed disturbance interactions at the landscape scale,
if in fact, mechanisms operating at this scale are causative.
This project is integrated with Tania Schoennagel’s
NSF postdoc fellowship on modeling climatic influences on
disturbance and forest dynamics in the subalpine zone of the
southern Rockies. This involves the use of empirical relationships
derived from the research described above to construct climatically
driven, probabilistic models of fire spread to compare the
potential responses of fire regimes and successional patterns
within the subalpine zones of different regions to plausible
climate change scenarios. The objective of this research is
to utilize fire history maps to tease apart the relative influence
of regional vs. local heterogeneity on climatically sensitive
fire disturbances, and to consider what effects these altered
fire regimes may have on age class and species distributions
across heterogeneous landscapes.
Forest decline in Chilean temperate rainforests: a multiscale approach.
Sponsor: National Geographic Society. 2006-2007.
This study is examining fire and regeneration patterns in the long-lived conifer Pilgerodendron uviferum in temperate rainforests of southern South America. The project is examining historical fire patterns in relation to climatic variation and human activities as well as spatial variation in fire occurrence in relation to vegetation type and abiotic environmental factors. One of the goals is to assess the role of fire in the historical dynamics of these forests and to address the question of why post-fire regeneration of this species is sometimes inadequate. Methodologically, the work is based age-structure sampling of post-fire stands, tree-ring dating of fires, and remote sensing documentation of the recent fire record. GIS methods are used to relate fire occurrence to biotic and abiotic variables and create spatially-explicit models of habitat susceptibility to fire and prediction of post-fire regeneration success.
Many of the Pilgerodendron forests affected by fire are in National Parks, and presently park managers lack information on the historic fire regimes and post-fire regeneration in these forests. We expect our findings, including the GIS-layers created in this project, to inform management decisions and policy discussions. This is a one-year seed project integrated with Andres Holz’s NSF Dissertation Award that will allow us to write a larger proposal to support multi-year work of a broader scope on the role of fire in the Patagonian rainforest district of southern Chile mainly at latitudes 43 to 48 degrees S.
Effects of blowdown, beetle outbreak, and fire history
on the behavior and effects of the 2002 fires in western Colorado.
Sponsor: The Inter-Agency Joint Fire Science Program.
2003-2006.
Research is needed on the relationships between pre-fire
forest conditions and the behavior and effects of the 2002
fires in Colorado. We have high-quality and unique pre-fire
data on the extent and severity of fires, blowdown, and spruce
beetle outbreak in areas of Routt and White River National
Forests that were affected by the 2002 fires. The objectives
of this research are to analyze and describe the influences
of the pre-fire disturbance history, stand structures, and
landscape patterns on the extent and severity of the 2002
fires and ensuing forest recovery in subalpine forests of
western Colorado.
Regional and landscape analysis of our existing data and
recent Forest Service spatial data sets of the 2002 fires
are being conducted in a Geographic Information System (GIS).
The focus of this analysis is on the spatial interactions
between pre-2002 disturbance events (fire, blowdown, and beetle
outbreak) and the spread and severity of the 2002 fires. In
the field, finer scale (intra-stand) analysis are being conducted
on disturbance interactions and post-fire recovery (i.e. tree
regeneration), and permanent plots have been installed to
study post-fire patterns of vegetation recovery.
Assessment of current conditions and long-term trends
in Colorado’s aspen forests.
Sponsor: U.S.D.A. Forest Service. 2003-2005.
This assessment will provide managers, law-makers, and the
public with an initial assessment on (i) where in the State
aspen is declining and where it is thriving, and (ii) the
specific environmental conditions associated with aspen decline,
e.g., the role of local climate, soils, topography, browsing
pressure, fire history, logging history, and other factors.
The specific questions addressed in this study will be: (1)
What is the relative proportion of seral versus persistent
aspen stands in different regions of Colorado and how does
this vary across the State? (2) How do topography, elevation,
soil and disturbance history influence aspen’s persistence?
And, (3) What are the inter-stand dynamics associated with
persistent versus seral aspen stands? During the first year
of what is expected to be a multi-year project, we have focused
on Grand Mesa and White River National Forests.
Historic Range of Variability Assessments for Pike, San
Isabel, Arapaho, Roosevelt, Grand Mesa, Routt, and White River
National Forests.
Sponsor: U.S.D.A. Forest Service. 1999-2006.
Since 1999, under a series of Cooperative Agreements with
Region 2 (Colorado and Wyoming) of the USDA Forest Service,
we have been producing reports on “Historic Range of
Variability of Forest Ecosystems” for each National Forest
in central and northern Colorado. These reports examine changes
in forest conditions in relation to fire history, insect pest
outbreaks, land use and climatic variation over the past c.
400 years. The aim of each report is to synthesize scientific
knowledge, both published literature and unpublished data,
that can inform resource planning and forest policy
discussions from the perspective of how and why these forest ecosystems have changed in recent centuries. Each draft report is peer reviewed by a panel appointed by the Ecological Society of America and is published by the Colorado Forest Research Institute under an agreement with the Regional Office of the USDA Forest Service. Reports have been published for Pike-San Isabel and Arapaho-Roosevelt National Forests, and drafts are under review for Grand Mesa and Routt-White River National Forests.
Fire and landscape change in Northern Patagonia, Argentina:
Integrating landscape heterogeneity, land use and climatic
variability.
Sponsor: National Science Foundation, Geography Program.
2001-2005.
In the context of global climate change and increased impacts
of humans on natural landscapes, increased fire occurrence
is likely to be a major cause of widespread change in forested
ecosystems. Although much is known about how short-term weather
conditions affect the probability of fire occurrence and its
intensity, much less is known about how the history of land
use and the heterogeneity of the landscape affect the potential
for both fire spread and ecosystem response to fire. In Northern
Patagonia, Argentina, this project addresses the following
key questions: 1) How does landscape heterogeneity resulting
from recent (i.e. past c. 200 years) disturbance history (mainly
fires) affect the spread of fire and subsequent post-fire
vegetation and fuel changes? 2) What are the effects of climatic
conditions on post-fire vegetation recovery, especially tree
regeneration? 3) What are the effects of livestock (i.e. land
use) on the critical, early phases of post-fire vegetation
and fuels recovery? These three questions are being examined
through an integrated multi-scale approach to vegetation dynamics
and landscape change across a range of ecosystem types from
dry shrublands to wet forests. The methodology integrates
broad-scale spatial analyses of vegetation and fire patterns
derived from historical aerial photographs and satellite images
with detailed field studies of disturbance history based on
tree-ring samples. These methods are combined with plot-scale
experimental manipulation of moisture availability and herbivory
by livestock to simulate the effects of climatic variation
and land use on vegetation recovery after fire.
This research is advancing a long-term research program (initiated
in 1985) on how natural disturbance, climatic variability
and human activities have and continue to alter Northern Patagonian
landscapes. The expected results will quantify relationships
of fire behavior and effects to landscape heterogeneity at
spatial and temporal scales useful for resource managers.
The results will also provide a strong empirical basis for
realistic application of spatial landscape-models to predicting
fire behavior and fire effects in this landscape. The patterns
and causal mechanisms identified in this study will guide
similar approaches to understanding and predicting the ecological
effects of fire, livestock, and climatic variability in other
landscapes.
Forest dynamics and a massive bamboo flowering in the
southern Andes.
Sponsor: National Geographic Society. 2002-2003
In November 2000 a massive flowering of the bamboo Chusquea
culeou occurred in the Andes of southern Argentina and
adjacent parts of Chile at c. 40°S lat. This flowering
event affected most of the Andean forests over a 120 km north-south
extent, and is the first massive flowering of this keystone
species since 1940. A major population irruption of seed-eating
rodents followed the flowering event and resulted in an outbreak
of the hanta-virus in the human population. These tall bamboos
dominate forest understories and are a major source of forage
for native and introduced herbivores. The bamboos greatly
impede tree regeneration, and, consequently, the life history
of the bamboo is a controlling factor of forest dynamics at
a regional scale. The focus of the research is on how the
withering of the bamboo may be a window of opportunity for
the regeneration of the shade-intolerant tree species that
dominate these forests. We have installed permanent plots
and animal exclosures to examine the effects of the bamboo
flowering event on tree regeneration across five forest types,
in distinct structural types (young closed canopy stands vs.
old-growth stands with treefall gaps), and under differing
conditions of herbivory. The research is also providing baseline
data on the genetic structure of the bamboo populations in
relation to isolation due to geographical location as well
as timing of massive flowering.
RECENT NSF DISSERTATION
IMPROVEMENT AWARDS
The effects of climate and disturbance variation on post-fire
regeneration of Madrean pine-oak forests in Mexico’s
Sierra Madre Occidental. Stacy Drury. 2002-2003.
The historic range of variability of ponderosa pine in the
northern Colorado Front Range: Past fire types and fire effects.
Rosemary Sherriff. 2002-2003.
A multiscale analysis of natural and human influences on
the variability of subalpine forest fire history in Rocky
Mountain National Park. Jason Sibold. 2003-2004.
Causes and consequences of forest dieback in temperate rainforests across western Patagonia: A multiscale approach. Andres Holz. 2006-2007.
Environmental heterogeneity and insect outbreaks in Patagonian forests. Juan Paritsis. 2006-2007.
CURRENT AND RECENT POSTDOC FELLOWSHIPS
Disturbance and dynamics of Nothofagus forests in southern Chile: William Pollman, supported by the German science agency (DAAD). 2002-2004.
Regional and local influences on climatically sensitive disturbance
in the Rocky Mountains. Tania Schoennagel. NSF Postdoctoral
Fellowship in Biological Informatics. 2003-2005.
Impact of drought and competitive interactions on tree growth
and episodic tree mortality in subalpine forests of northern
Colorado. Christof Bigler. Swiss National Science Foundation.
2004-2005.
Fire risk and forest restoration in the wildland urban interface of the Colorado Front Range. Tania Schoennagel. David H. Smith Conservation Fellowship. 2006-2008.
DISSERTATIONS AND THESES
COMPLETED THROUGH THE LAB
2007
Characterizing historic fire regimes from understory vegetation composition in ponderosa pine-dominated forests of the northern Colorado Front Range. Robin Keith (M.A.), currently Research Technician, Rocky Mountain National Park, Estes Park.
Forest fuel mapping and strategic wildfire mitigation in the montane zone of Boulder County, Colorado. Kevin Krasnow (M.A.), currently Ph.D. student, Univ. of California, Berkeley.
2006
Effects of climate and disturbance on Madrean pine-oak forests in Mexico's Sierra Madre Occidental; Stacy Drury (Ph.D.).
2005
A multi-scale analysis of natural and human influences on the variability of subalpine forest fire history in Rocky Mountain National Park; Jason Sibold (Ph.D.).
2004
Regeneration dynamics of persistent quaking aspen (Populus
tremuloides) in western Colorado; Brian P. Kurzel (M.A.).
Tree regeneration responses to Chusquea montana bamboo
dieback in subalpine forests in the southern Andes; Andrés
Holz (M.A.).
The role of recent climatic variability on episodic Pinus
ponderosa recruitment patterns along the forest-grassland
ecotone of northern Colorado; Kevin League (M.A.).
Historic range of variability and stand development in pinon-juniper
woodlands of western Colorado; Karen S. Eisenhart (Ph.D).
The historic range of variability of ponderosa pine in the
northern Colorado Front Range: Past fire types and fire effects;
Rosemary Sherriff (Ph.D.).
Modeling wildfire mitigation and ecological restoration in
the wildland-urban interface: A study of the montane zone
of the Colorado Front Range; Rutherford V. Platt (Ph.D.).
2002
Effects of exotic pine on Paramo grasslands in the Ecuadorian
Andes; Kathleen Farley (Ph.D.).
Fire history of Araucaria-Nothofagus forests in the Andean
Cordillera of South-Central Chile; Mauro Gonzalez (Ph.D.).
Interactions among natural disturbances in subalpine forests
in northwestern Colorado; Dominik Kulakowski (Ph.D.).
2001
The forest fire regime of an upper montane and subalpine
forest, Wild Basin, Rocky Mountain National Park; Jason Sibold
(M.A.).
2000
Climatic and human influences on fire regimes in Pike National
Forest; Joseph Donnegan (Ph.D.).
Fire history at high elevation in the Colorado Front Range;
Rosemary Sherriff (M.A.).
The dynamics of alpine treelines in the southern Andes; Lori
D. Daniels (Ph.D.).
1999
Influences of dieback of the bamboo Chusquea quila
on tree regeneration in canopy gaps in south-centra Chile;
Mauro Gonzalez (M.A.).
Disturbances and tree species diversity along the elevational
gradient of a subtropical montane forest of NW Argentina;
Ricardo Grau (Ph.D.).
Dendrochronological identification of spruce bark beetle
outbreaks in northwestern Colorado; Karen S. Eisenhart (M.A.).
1997
The impact of flood frequency, permafrost distribution, and
climate variation on a northern treeline floodplain in Alaska;
Alison E. Arians (Ph.D.).
1996
A dendrochronological history of western spruce budworm (Choristoneura
occidentalis Freeman) infestations and outbreaks in the
northern Colorado Front Range; Steven W. Shimek (M.A.).
1995
Disturbance regimes and regeneration dynamics of upper montane
forests and páramos in the southern Ecuadorian Andes;
Philip L. Keating (Ph.D.).
Climatic influences on forest dynamics along the forest-steppe
ecotone in northern Patagonia; Ricardo Villalba (Ph.D.).
1994
Fire regime variation along a northern Patagonian forest-steppe
gradient: Stand and landscape response; Thomas Kitzberger
(Ph.D.).
1993
Climatic and disturbance factors influencing Pinus ponderosa
stand structure near the forest/grassland ecotone in the Colorado
Front Range; Joy N. Mast (Ph.D.).
1992
The use of remote sensing techniques in the old-growth spruce-fir
forests in the Rocky Mountains; Elizabeth M. Nel (M.A.).
1991
A dendrochronological method of studying tree mortality patterns;
Joy Nystrom Mast (M.A.).
The dynamics and disturbance regimes of Fitzroya cupressoides
forests in the Andes of south-central Chile; Antonio Lara
(Ph.D.).
The regeneration dynamics of Araucaria araucana in
the southern Andes; Bruce R. Burns (Ph.D.).
1990
Biogeography and ecology of timberline forest in north-central
Peru; Ken Young (Ph.D.).
Fire history of a Ponderosa pine/Douglas fir forest in the
Colorado Front Range; David Goldblum (M.A.).
Stand response and landscape response to western spruce budworm
and Douglas-fir bark beetle outbreaks, Colorado Front Range;
Keith Hadley (Ph.D.).
1989
The response of understory vegetation to major canopy disturbance
in the subalpine forests of Colorado; Marion Reid (M.A.).
Structural dynamics of a pine forest in the American southwest
under chronic human disturbance; Melissa Savage (Ph.D.).
1988
Successional change in vegetation and soils of southeast
Alaska; Lee Klinger (Ph.D.).
1987
Social dominance and the winter distribution of the Dark-eyed
Junco (Junco hyemalis); Peter Yaukey (M.A.).
Ecology of bamboos and their role in forest dynamics in the
Wolong Natural Reservem Sichuan, China; Alan Taylor (Ph.D.).
1986
Early forest succession on abandoned agricultural fields
on the loess bluffs of western Tennessee; David Shankman (Ph.D.).
1985
Vegetation changes associated with land use practices in
Mbeya region, Tanzania; Salome Kigongo Mashalla (Ph.D.).
1984
Influences of snow persistence on the regeneration of Engelmann
spruce and subalpine fir, Colorado Front Range; Christopher
Daly (M.A.).
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