Using Regression Analysis and Machine Learning to Investigate the Connection Between Mountain Pine Beetle (Dendroctonus ponderosae) Outbreaks and Human-Induced Climate Change

2026-03-14

The impacts of both natural and human-induced climate change are evident across the pine (Pinus) dominated forests of the Northern Rocky Mountains, USA. Paleoecological records have been used to investigate climate driven vegetation change and the complexities of fire disturbance in these forests over the Holocene, providing important information to the development of forest management plans and fire suppression protocols. Mountain pine beetle (Dendroctonus ponderosae) (MPB) outbreaks have also influenced ecosystem change in the Northern Rocky Mountains. However, little is known about the occurrence of MPB outbreaks beyond the historic time period (past 200 years). Without direct evidence (fossil beetle remains) to identify MPB outbreaks in paleoecological records, it has been challenging to identify the timing and frequency of outbreaks over a longer time period (Holocene) and to demonstrate how unusual the patterns of the past 200 years are. The increase in MPB outbreaks in the historic time period has been attributed to increasing temperatures affecting the reproductive cycle of the beetles and the weakening of the defense mechanisms in pine species. Understanding the frequency of MPB outbreaks and forest response over the Holocene is helping land managers better plan for the future management strategies of these iconic landscapes. This project used both traditional paleoecological time series analysis and quantitative analysis (regression analysis and machine learning) to investigate the frequency and timing of MPB outbreaks over the Holocene and identify patterns related to climate change. The data presented are from a series of sites across an elevational and latitudinal gradient in the Northern Rocky Mountains, USA and includes periods of high resolution (every cm) paleoecological proxy data. Initial findings indicate a positive relationship between MPB outbreaks and pine (Pinus) dominance on the landscape and more frequent MPB outbreaks during the historic time period than during any other time throughout the Holocene.

Reconstructing the Environmental History of the Bear River Massacre Site, Idaho, USA

2026-03-14

In 1863, the Bear River Massacre took place in Southeastern Idaho, USA, where about 400 members of the Northwestern Band of the Shoshone Nation were murdered by the United States Government. The massacre caused significant ecological land changes from the massacre itself but also from the colonization of the land, which presented land use changes and the introduction of invasive species. The tribe has since received 350 acres of their traditional land back from the government, but the land has been vastly altered since their ancestors lived on it. The Bear River restoration project, led by the Shoshone tribe, was created with the aim to bring the native vegetation back to the land and to allow the tribe to learn about the relationship between their ancestors and the resources they used. This research is contributing to the tribe’s restoration goals by reconstructing the past vegetation and environmental history of the Bear River Massacre Site using a quantitative, multiproxy paleoecological approach. The primary questions of concern that we aim to answer for the tribe are what was the native vegetation like when their ancestors lived on the land, and what is the environmental history of the site being a spring. The methodological approach to answer these questions will utilize pollen counts and loss on ignition from a wetland sediment core collected from a spring along the Bear River to reconstruct the paleoenvironment and identify past changes and disturbances in the environment.

Hydroclimate-driven ecological and fire regime shifts in a unique forest biome of Baja California since the mid-Holocene

2026-03-14

Baja California, Mexico occupies a climatically sensitive peninsular setting between the cool Pacific Ocean and the comparatively warmer Gulf of California. This Mexican state is home to a large spectrum of environmental conditions and diverse ecology, due in part to the compounding effects of variable precipitation from El Niño Southern Oscillation (ENSO) cycling and the North American Monsoon (NAM) across a topographical gradient. Near the center of the state resides Sierra de San Pedro Mártir, a high elevation mountain range at the tip of the California Floristic Region, forming a California Mountains ecoregion that is drastically different in biodiversity than the area that surrounds it. Sierra de San Pedro Mártir is a pine-dominated forest that receives ~75% of its annual precipitation during winter months, making it particularly sensitive to ENSO-driven hydroclimatic variability. Notably, this forest has only recently seen the emergence of fire management strategies.In a palaeoecological reconstruction from this region, a high-resolution fossil pollen record, coupled with macro-charcoal analysis, highlights shifting dominance between precipitation sources through the middle to late Holocene. More contemporarily, however, the impacts of fire suppression can already be seen in the palynological record. Methods of inferential statistics are employed alongside a traditional time series, and cohesion between these two methods of data analysis provides additional confidence in a compelling and robust precipitation-fire-ecology relationship detected through generalized linear regression. This finding has significant implications for the future of fire management in this unique environment, representing the integrative potential for high-resolution palaeoecological research. As this environment represents a natural laboratory for studying ENSO and NAM, this finding additionally has implications for how these two hydrological systems contribute to the future of more regional conservation and restoration.

Using Count Regression to Investigate Millennial-Scale Vegetation and Fire Response from Multiple Sites Across the Northern Rocky Mountains, USA

Fire · 2025-08-14

The Northern Rocky Mountains, USA contain a vast forested landscape, managed primarily by the federal government. This region contains some of the highest elevations forests and most iconic endangered and threatened species in the contiguous United States. The influence of human impacts and climate change are evident on the landscape today, with larger and more frequent fires impacting vegetation composition and recovery. This project uses paleoecological data from six lake sediment cores to investigate what drives fire across this region over the Holocene. Count regression was used to predict charcoal influx as a function of Pinus pollen accumulation rates (PAR) and percent. The results show that fire activity increases significantly with Pinus pollen, and that baseline fire activity varies significantly across sites, largely following an elevation gradient. The results of this analysis illustrate a novel way to use paleoecological data to provide valuable information to federal agencies as they prepare for future management of these ecologically valuable areas.

Using Paleoecological Methods to Study Long-Term Disturbance Patterns in High-Elevation Whitebark Pine Ecosystems

Fire · 2024 · 2 citations

• Environmental science
• Ecology
• Geology

Pinus albicaulis (whitebark pine) is a keystone species, providing food and habitat to wildlife, in high-elevation ecological communities. In recent years, this important species has been negatively impacted by changes in fire regimes, increased Dendroctonus ponderosae (mountain pine beetle) outbreaks associated with human landscape and climate modification, and the continued impact of the non-native Cronartium ribicola (white pine blister rust). This research investigates changes in fire occurrence, the establishment of Pinus albicaulis, and fuel availability at a high-elevation site in the Sawtooth National Recreation Area, Idaho, USA. Charcoal and pollen analyses were used to reconstruct fire and vegetation patterns for Phyllis Lake, Idaho, USA, over the past ~8200 cal y BP. We found that significant fire episodes occurred when the pollen accumulation rates (PARs) indicated more arboreal fuel availability, and we identified that Pinus albicaulis became well established at the site ~7200 cal y BP. The high-elevation nature of Phyllis Lake (2800 m) makes this record unique, as there are not many paleorecords at this high elevation from the Northern Rocky Mountains, USA. Additional high-elevation sites in Pinus albicaulis habitats will provide critical insight into the long-term dynamics of this threatened species.

A late glacial paleoenvironmental and climate record from the Sierra de Juarez, Baja California

Quaternary International · 2024-07-04 · 3 citations

Ciénegas are desert wetlands that are strongly correlated with the stability of the hydrologic cycle in arid landscapes. However, these environments are particularly vulnerable to climate change, drought, water diversion, and fire suppression which all have contributed to the degradation of ciénegas along the U.S.-Mexican borderlands. Therefore, identifying the timing of precipitation patterns in this region is of particular interest because of its relationship to many ecological responses of the landscape such as groundwater recharge and fire. Here, we present the first-ever fire paleoenvironmental record from Ciénega Chimeneas, a ciénega complex in the Sierra de Juárez of Baja California. We explore how changes in the amount and seasonality of moisture affected ciénega complexes and fire activity from across the southwestern North American region over the past 45,000 years. Our record suggests that during the late glacial period, 41,000–21,000 cal yr BP, the increase of Larrea and Quercus indicate an increase in summer precipitation. Subsequently, when summer precipitation increased, pollen preservation and pollen accumulation rates (PAR) also increased. Increased vegetation allowed for increased fire activity during the late glacial period. Regionally, most of the comparison sites also indicated wet conditions during the full glacial period. However, around 21,000 cal yr BP, effective moisture decreased resulting in a dramatic change in the vegetation assemblage. Specifically, the summer wet taxa disappeared, while pollen preservation and PAR decreased, suggesting a dry period until ∼14,000 cal yr BP. Little fire activity is recorded after 21,000 cal yr BP, likely due to the absence of fuels. At ∼14,000 cal yr BP, Larrea and Quercus reappear suggesting increased summer precipitation. However, the appearance of Cyperaceae and increases in grasses suggest increased winter precipitation. We suggest that the combination of summer wet and winterwet taxa ∼14,000 cal yr BP represents an increase in ENSO conditions, while the summer moisture controls remained relatively constant.

A Holocene Record of Vegetation Change and Mountain Pine Beetle Outbreaks at Lake of the Woods, Montana, USA

Western North American Naturalist · 2022 · 2 citations

• Humanities
• Geography
• Humanities

Los recientes brotes de escarabajos del pino de montaña (Dendroctonus ponderosae) se han caracterizado por no tener precedentes, en gran medida por la ausencia de información sobre su aparición antes de la documentación histórica. La capacidad de reconstruir brotes previos a los asentamientos, a partir de núcleos de sedimentos requiere la identificación y validación de indicadores apropiados. En este trabajo, proporcionamos un registro del cambio de la vegetación durante el Holoceno que indica posibles brotes del escarabajo del pino de montaña en un bosque de pino lodgepole (Pinus contorta) y de coníferas mixtas en Lake of the Woods, Montana. Utilizando un índice de diferencia de polen normalizado, identificamos positivamente brotes de escarabajos del pino de montaña posteriores al asentamiento, que sirvieron como puntos de calibración para identificar otros brotes a lo largo del Holoceno. El registro obtenido de Lake of the Woods indica que el cambio de la vegetación fue promovido principalmente por las precipitaciones y que los múltiples brotes de escarabajos del pino de montaña reconstruidos, contemporáneos y anteriores al asentamiento, se produjeron durante períodos en los que la composición del bosque estaba dominada principalmente por Pinus spp. La aparición de uno de estos brotes en ∼8200 cal yr BP es consistente con otros dos registros en las Rocosas del Norte, lo que sugiere un gran brote regional durante esta época.

The Potential for Pollen Records to Detect Mountain Pine Beetle Disturbance in a Pine-Dominated Forest, Idaho, USA

Western North American Naturalist · 2020 · 2 citations

• Ecology
• Forestry
• Geography

Mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) outbreaks are an important component in forest succession for Pinus (pine) forests in the western United States. The research presented here is the first attempt to use pollen data from lake sediment cores to identify MPB disturbance over the past 1600 years within a pine-dominated forest. With evidence of both current and presettlement MPB outbreaks in the surrounding forest, Fishstick Lake, a small subalpine lake in the Sawtooth Mountains of Idaho, is located in a Pinus contorta (lodgepole pine)–dominated forest. Previous work by Morris et al. (2010) and Morris and Brunelle (2012) used pollen data from lake sediment cores to identify Dendroctonus rufipennis (spruce beetle) outbreaks in a Picea engelmannii (Engelmann spruce) forest by identifying the tradeoff between host (P. engelmannii) and nonhost (Abies lasiocarpa [subalpine fir]) conifers following an outbreak. This research tested the hypothesis that pollen data can be used to identify disturbance events that affect Pinus within a Pinus-dominated forest. Because the abundance of non-pine taxa is low in pine-dominated systems, it was uncertain whether the response of non-pine, nonhost taxa would be detectable. This study used a normalized difference pollen index (NDPI) to test this hypothesis. The results indicate that proxy data (pollen) can be used to identify MPB disturbance in a pine-dominated forest.

POSSIBLE BENEFITS OF ECTOMYCORRHIZAL INFECTION OF CONIFER SEEDLINGS AT ALTA SKI AREA

Undergraduate Research Journal · 2017-06-08

Studying tree survival rates of conifers planted at Alta has shown that the project is struggling in terms of survival. I wanted to extend this research and see if there are any measurable benefits of ectomycorrhizal (ECM) root infection. I completed this research by harvesting small conifer specimens at Alta Ski Area, doing a series of analysis to define the health of each specimen, and then performing root analysis to determine the percent of ECM infection. Then by doing comparative analysis of these data I hoped to find that healthier plants had increased ECM infection percentages. I have not found that there is any significant connection between the two. This result leads me to believe benefits of ECM infection may be more in relation to ecosystem stability, and encourages me to ask more questions.

A HIGH-RESOLUTION RECORD OF MOUNTAIN PINE BEETLE OUTBREAKS FROM 7500-8500 CAL YR BP AT BAKER LAKE, MONTANA

Undergraduate Research Journal · 2015-01-01