Browsing by Author "Pelz, Kristen A., author"

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Open Access
Effects of mountain pine beetle on forest structure and fuel load 25-30 years after an outbreak in western Colorado
(Colorado State University. Libraries, 2011) Pelz, Kristen A., author; Smith, Frederick W., advisor; Jacobi, William R., committee member; Martin, Patrick H., committee member
Mortality of lodgepole pine (Pinus contorta (Dougl. Ex. Loud.) caused by mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins) has caused concern about long-term forest structure and wildfire hazard changes. In 2010, I identified and sampled areas affected by a 1980s MPB outbreak to quantify forest changes in the 25-30 years following mortality. Stands in Eagle County, Colorado with >30% 1980s lodgepole pine mortality were identified using USDA Forest Service aerial survey maps and inventory data. Stands fell into two forest type groups: lodgepole pine and mixed conifer. I sampled 20 stands to measure forest species and size structure and down woody fuel accumulations. I compared 1980s inventory data to 2010 data to find differences between forest type groups in their post-outbreak changes. Lodgepole pine stands recovered to pre-outbreak overstory total basal area, density, and species composition by 2010, while in mixed conifer stands basal area and density were significantly less in 2010 than before the outbreak. In mixed conifer stands, lodgepole pine overstory basal area was reduced from 66% of total in the 1980s to 51% in 2010.Understory tree density increased roughly six-fold in both forest types between the 1980s and 2010. The overall increase in understory density was due to a ten-fold increase in seedling/sapling (trees 0.6 m tall to 3.8 cm dbh) numbers. In lodgepole pine stands, the most abundant species in the 1980s understory was subalpine fir, followed by lodgepole pine. By 2010, lodgepole pine and subalpine fir were the majority of larger understory trees; aspen and subalpine fir were most abundant among smaller understory trees. In mixed conifer stands, subalpine fir and Engelmann spruce consistently dominated all understory size classes in the 1980s and 2010. Total down woody fuel load averaged 71 Mg ha-1 and did not differ between forest type groups. Overall, my results suggest that long-term forest recovery trajectories are dependent on pre-outbreak species composition, though understory densities are likely to increase regardless of non-host species abundances. These shifts in species and size composition by 25-30 years after outbreak likely have substantial impacts on forest health, potential fire behavior and ecosystem processes. We speculate that forest recovery following the current MPB outbreak will be similar to observed changes following the 1980s outbreak in these areas.
Open Access
Forest regeneration and future stand trajectories following mountain pine beetle-caused lodgepole pine mortality
(Colorado State University. Libraries, 2014) Pelz, Kristen A., author; Smith, Frederick W., advisor; Dickinson, Yvette L., committee member; Martin, Patrick H., committee member; Rhoades, Charles C., committee member
A mountain pine beetle (MPB) (Dendroctonus ponderosae) outbreak that began in the late 1990s has killed lodgepole pine (Pinus contorta var. latifolia) on up to 10 million hectares in western North America. Over one million hectares have been affected in northern Colorado and southern Wyoming. The large footprint of this disturbance has prompted widespread concern about the composition, structure, and function of forests as they develop following MPB. In this dissertation, I ask how variation in species composition and mortality level will affect the future forest in the Southern Rockies. I used forest growth models to predict forest structure and fuel loads during the century after MPB outbreak. I compared three lodgepole pine-dominated forest types (all > 80 % lodgepole by basal area) and the simulated effects of no-action and fuel reduction treatments. Forest with Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa var. lasiocarpa) became much more dominated by these species, resulting in highly hazardous canopy fuels. In contrast, stands of lodgepole and aspen (Populus tremuloides) did not shift composition and did not show a marked increase in fire hazard. The effects of management were also differed: hazardous fuels were best mitigated in the forest types with spruce and fir, but treatment had few positive effects in the stands of only lodgepole and aspen due to their lower hazard without treatment. The results show management of lodgepole-dominated forests must consider even subtle variation in composition to be effective. I also examined post-outbreak regeneration in these forests. In mixed lodgepole pine and aspen stands, I asked if regeneration is sufficient to reforest areas affected by MPB. Both species excel in high light environments that are created by overstory mortality, but lodgepole pine is thought to require ground disturbance to regenerate. Aspen regeneration can be prevented by browsing. I found lodgepole regeneration is occurring in 85% of stands, and all stands had aspen sucker density above 1000 stems ha-1. Many suckers are damaged by browsing, but my results suggest that sufficient quantities of down lodgepole pine may protect suckers and allow them to recruit to the overstory. Overall, I conclude aspen and lodgepole forests are regenerating successfully and that these areas will remain mixed forests of both species in the future. Finally, I measured the effects of mortality level on regeneration. I compared regeneration density and growth of lodgepole, spruce, and fir in high (85% of basal area) and moderate (40% of basal area) mortality forest. Lodgepole pine regeneration density and growth was high where outbreak was most severe, though all species grew faster in high mortality than moderate mortality. All three species will likely be important to future forest in areas with high mortality, and lodgepole pine will play a substantial role. In contrast, in moderate mortality areas lodgepole pine regeneration is nearly absent and spruce and fir are growing fastest. Here the forest understory will be made up of shade tolerant species, and the forest will become progressively more dominated by these species as this stratum develops.
Open Access
Mixed conifer forests in the San Juan Mountain region of Colorado, USA: the status of our knowledge and management implications
(Colorado State University. Libraries, 2021-12) Remke, Michael J., author; Chambers, Marin E., author; Tuten, Matthew C., author; Pelz, Kristen A., author; Colorado Forest Restoration Institute, publisher
Open Access
Mixed-conifer forests in southwest Colorado: a summary of existing knowledge and considerations for restoration and management
(Colorado State University. Libraries, 2010-04) Pelz, Kristen A., author; Colorado Forest Restoration Institute, publisher
Open Access
Monitoring forest cover spatial patterns with aerial imagery: a tutorial
(Colorado State University. Libraries, 2014-07) Pelz, Kristen A., author; Dickinson, Yvette L., author; Colorado Forest Restoration Institute, publisher
Open Access
Principles and practices for the restoration of ponderosa pine and dry mixed-conifer forests of the Colorado Front Range
(Colorado State University. Libraries, 2018-01) Addington, Robert N., author; Aplet, Gregory H., author; Battaglia, Mike A., author; Briggs, Jennifer S., author; Brown, Peter M., author; Cheng, Antony S., author; Dickinson, Yvette, author; Feinstein, Jonas A., author; Pelz, Kristen A., author; Regan, Claudia M., author; Thinnes, Jim, author; Truex, Rick, author; Fornwalt, Paula J., author; Gannon, Benjamin, author; Julian, Chad W., author; Underhill, Jeffrey L., author; Wolk, Brett, author; USDA, publisher
Wildfires have become larger and more severe over the past several decades on Colorado's Front Range, catalyzing greater investments in forest management intended to mitigate wildfire risks. The complex ecological, social, and political context of the Front Range, however, makes forest management challenging, especially where multiple management goals including forest restoration exist. In this report, we present a science-based framework for managers to develop place-based approaches to forest restoration of Front Range ponderosa pine and dry mixed-conifer forests. We first present ecological information describing how Front Range forest structure and composition are shaped at multiple scales by interactions among topography, natural disturbances such as fire, and forest developmental processes. This information serves as a foundation for identifying priority areas for treatment and designing restoration projects across scales. Treatment guidelines generally reduce forest densities and surface and crown fuels, enhance spatial heterogeneity across scales, and retain drought- and fire-tolerant species, old trees, and structures important for wildlife. Implementation of these guidelines is expected to enhance forest resilience to disturbance and climate change, as well as sustain important ecosystem services. Finally, this report emphasizes the importance of adaptive management and learning through monitoring and experimentation to address uncertainties inherent in the restoration process.