Department of Forest and Rangeland Stewardship
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These digital collections include theses, dissertations, faculty publications, and student publications from the Department of Forest and Rangeland Stewardship. Due to departmental name changes, materials from the following historical departments are also included here: Forest and Wood Sciences; Forest Management and Wood Utilization; Forest, Rangeland, and Watershed Stewardship; Forest Recreation; Forest Recreation and Wildlife Conservation; Forest Sciences; Forestry; Range Management; Range Science; Rangeland Ecosystem Science; Watershed Sciences.
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Browsing Department of Forest and Rangeland Stewardship by Author "Battaglia, Michael, committee member"
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Item Open Access Crown characteristics of interior western U.S. conifers with implications for canopy fire hazard evaluation(Colorado State University. Libraries, 2014) Ex, Seth, author; Smith, Frederick, advisor; Battaglia, Michael, committee member; Dickinson, Yvette, committee member; Ryan, Michael, committee member; Steingraeber, David, committee memberTree crown characteristics are important determinants of forest stand features such as their potential to sustain canopy fire. There are characteristic differences between crowns of shade tolerant and shade intolerant conifer species: shade tolerant conifers generally have longer, fuller crowns than intolerant species. In this work, I investigated the response of vertical foliage distribution to stand density for a suite of western U.S. conifer species of varying shade tolerance and interpreted results in terms of canopy fire hazard evaluation. In addition, I evaluated whether diameter-based foliage area allometries differ between geographic areas in the interior western U.S. in order to gain insight into the extent that local allometries can be applied outside their area of origination. I found shade tolerant tree species maintained a greater proportion of their foliage in low light environments than intolerant species. This was consistent with lesser sensitivity of crown ratio to increasing stand density for tolerant compared to intolerant conifers. Regardless of species shade tolerance or stand density, the center of foliage mass within crowns was nearly always above the crown midpoint. Foliage mass was shifted upward and concentrated in closed-canopy forest stands compared to open-canopy woodland stands, which is consistent with greater light competition in closed-canopy stands. Foliage area allometries differed between geographic areas, and differences were species-specific. Using realistic depictions of the vertical distribution of crown fuels in a canopy fire hazard evaluation procedure resulted in dramatic increases in estimated canopy bulk density for stands, with associated increases in estimated potential fire behavior.Item Open Access Forest range shifts under climate change: microenvironment impacts to tree recruitment at a climatic ecotone(Colorado State University. Libraries, 2019) Foster, Alison Connolly, author; Redmond, Miranda, advisor; Martin, Patrick, advisor; Battaglia, Michael, committee member; Rocca, Monique, committee memberWarming across the western United States is projected to cause dramatic shifts in tree species recruitment, with the most pronounced changes in composition at range edges where species are at their thresholds of reproductive tolerance. Yet microenvironments experienced by juvenile trees can be decoupled from regional climate due to variations in canopy cover, microtopography, and organic matter. As a result, tree recruitment may be strongly controlled by microenvironments and not follow species range projections based on regional climate, even at ecotone boundaries in which species at their upper range distributions are predicted to increase in density. This is likely especially pronounced in undisturbed forests with dense canopy cover in which microclimate is more strongly de-coupled from regional climate. To address these hypotheses of tree recruitment at species range margins we conducted a field experiment and observational study at the upper montane – subalpine ecotone on the Colorado Front Range. We characterized site microenvironment and observed germination and survival of six common conifer species, Douglas-fir, ponderosa pine, lodgepole pine, subalpine fir, Engelmann spruce, and limber pine. To quantify water availability and wildlife limitations, we sowed seeds from five study species and applied treatments of simulated precipitation and wildlife exclusion. Strong recruitment limitations were observed for nearly all species in experimental and observational studies, with strong negative effects of low soil moisture and maximum temperature. Notably, only subalpine fir exhibited increased seedling dominance, likely due to the limited light availability and cooler temperatures associated with shaded microenvironments. Recruitment success was unrelated to range position and do not match established migration predictions for these species. This research further illustrates the complexity of recruitment dynamics and the need to study regeneration at multiple scales.Item Open Access Horizontal and vertical forest complexity interact to influence potential fire behavior(Colorado State University. Libraries, 2022) Ritter, Scott Michael, author; Hoffman, Chad, advisor; Battaglia, Michael, committee member; Mell, William, committee member; Ex, Seth, committee member; Jathar, Shantanu, committee memberWildland fire behavior is a dynamic process controlled by complex interactions among fuels, weather, and topography. There is significant need to better understand the role of fuels and, particularly, complex arrangements of fuels, on potential fire behavior and effects as a there is a growing emphasis on forest treatments that emulate the heterogenous structures of historical forest ecosystems. Ideally such treatments are intended to reduce fire hazard while concurrently improving resilience to a wide range of disturbance agents and restoring the natural ecosystem dynamics that maintained these forest structures. One way to evaluate how the complex forest structures created by these treatments will influence fire behavior are modeling approaches that account for dynamic interactions between fire, fuels, and wind. These physical fire models build from computational fluid dynamics methods to include processes of heat transfer, vegetative fuel dehydration and pyrolysis, and gas phase ignition and combustion. In this work, several aspects of horizontal and vertical forest structure were evaluated to understand how spatial complexity influences fire behavior, with a particular emphasis on the transition of a surface fire into tree crowns. I used a combination of spatially explicit field data and a physics-based wildfire model, the Wildland-Urban Interface Fire Dynamics Simulator (WFDS), to deepen our fundamental understanding of fire behavior, inform the design of forest treatments that aim to achieve a variety of ecological and social objectives, and develop hypotheses related to the pattern-process feedbacks that contributed to the maintenance of resilient forests across millennia. Chapter 2 presents a simulation study focused on the relationship between horizontal forest structure and surface to crown heat transfer and crown fire initiation. The results indicated that relative to larger 7- and 19-tree groups, isolated individual trees and 3-tree groups had greater convective cooling and reduced canopy heat flux. Because isolated individuals and 3-tree groups were exposed to less thermal energy, they required a greater surface fireline intensity to initiate torching and had less crown consumption than trees within larger groups. Similarly, I found that increased crown separation distance between trees reduced the net heat flux leading to reduced ignition potential. These findings identify the potential physical mechanisms responsible for supporting the complex forest structures typical of high-frequency fire regimes and may be useful for managers designing fuel hazard reduction and ecological restoration treatments. Chapter 3 extends chapter 2 by investigating how different levels and types of vertical heterogeneity influence crown fire transition and canopy consumption within tree groups. These results show the importance of fuel stratum gap (or canopy base height) on vertical fire propagation, however vertical fire propagation was mediated by the level of horizontal connectivity in the upper crown layers. This suggests that the fuel stratum gap cannot fully characterize the torching hazard. The results also indicate that as the surface fire line intensity increases, the influence of horizontal connectivity on canopy consumption is amplified. At the scale of individual tree groups, the perceived hazard of small, understory trees and vertical fuel continuity may be offset by lower horizontal continuity (or canopy bulk density) within the midstory and overstory crown layers. Chapter 4 compares outcomes from four real-world forest treatments that cover a range of potential treatment approaches to evaluate their impacts of forest spatial pattern and potential fire behavior. My results indicate that restoration treatments created greater vertical and horizontal structural complexity than the fuel hazard reduction treatments but resulted in similar reductions to potential fire severity. However, the restoration treatments did increase the surface fire rate of spread which suggests some potential fire behavior tradeoffs among treatment approaches. Overall, these results suggest the utility of restoration treatments in achieving a wide range of management objectives, including fire hazard reduction, and that they can be used in concert with traditional fuel hazard reduction treatments to reduce landscape scale fire risk. Together this work shows that tree spatial pattern can significantly influence crown fire initiation and canopy consumption through alterations to net heat transfer and feedbacks among closely spaced trees. At the scale of the tree group these results suggest that larger tree groups may sustain higher levels of canopy consumption and mortality as they are easier to ignite and, in cases with small separation between crowns, can sustain horizontal spread resulting in density-depended crown damage. These findings carry over to vertically complex groups where the spatial relationship between small, understory trees and larger, overstory trees has a large impact on the ability of fire to be carried vertically. Further, in these vertically complex groups reducing the density (and/or increasing the horizontal separation) of the overstory trees, resulted in lower rates of crown fuel consumption, therefore, mitigating some of the "laddering" effect caused by the presence of small understory trees. These complex interactions between vertical and horizontal aspects of stand structure were born out in my evaluation of the measured forest treatments, where similar crown fire behavior reductions were observed across various stand structures. Overall, this work shows that forest managers can apply treatments to achieve a wide range of ecological benefits while simultaneously increasing fire resistance and resilience.Item Open Access The effects of climate on Engelmann spruce regeneration and vigor(Colorado State University. Libraries, 2017) Prolic, Curtis, author; Ex, Seth, advisor; Battaglia, Michael, committee member; Sibold, Jason, committee memberRecent climate modeling suggests that drought will become more frequent in the southern Rocky Mountains over the next century. Understanding how tree species will respond and adapt to this changing climate is vital to guide future management decisions by land managers. Future increases in drought frequency and severity will likely have an impact on the composition of forests. Modeling studies have been used to predict the effect that increasing drought will have on Engelmann spruce in southwest Colorado, but little field data has been gathered to validate this modeling. This study uses empirical data to test whether drought conditions are related to decreases in seedling establishment and tree vigor. Annual regeneration data from 1990 to 2009 was collected from 24 sites with 30-year PRISM precipitation normals ranging from 531 mm to 924 mm to determine if dry and wet sites respond differently to drought. Elevations of our study sites ranged from 3100 m to 3500 m above sea level. Among these 24 sites, we found the number of seedlings per hectare varied between 1804 and 18975. We used a mixed effects model to identify climate variables important to annual seedling establishment density. A separate provenance study on the White River National Forest was analyzed to identify drought effects on tree vigor. Engelmann spruce bareroot seedlings from twenty sources ranging from British Columbia to New Mexico were planted in 1970 at an elevation of 2930 m north of Vail, Colorado. Annual precipitation normals of the 20 seed sources ranged from 423 – 1918 mm. We collected increment cores from six to eight trees from each of the 20 seed sources in 2016, and standardized the chronology of each tree using standard dendrochronological techniques. We then analyzed the annual radial growth response of each provenance to a period of severe drought from 2000-2004 using both RWI and a resistance/resilience framework. For both parts of our study, we found weather variability and drought did not impact regeneration or vigor as much as hypothesized, suggesting regeneration and vigor of spruce in these high elevation forests are not reduced by contemporary levels of drought.