Browsing by Author "Binkley, Dan, committee member"

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Open Access
Effects of cultivation and recovery on soil organic matter and N mineralization in shortgrass steppe
(Colorado State University. Libraries, 1993) Ihori, Tamiko, author; Burke, Ingrid C., advisor; Binkley, Dan, committee member; Lauenroth, William K., committee member; Coffin, Debra P., committee member
Understanding cultivation effects on soil organic matter (SOM) and available nutrients to plants is important, because SOM is an important storage of C globally and available nutrients are an important factor in plant growth. It is also important to understand recovery from disturbance such as cultivation. I conducted two studies: one on total SOM and the other on in situ N mineralization in native, cultivated, and recovering abandoned fields in the shortgrass steppe of northeastern Colorado. I examined total C and N content in 30 cm depth soil of native fields, abandoned fields that were historically cultivated and then abandoned about 50 years ago, and cultivated fields that were cultivated more than 50 years, at 13 sites in the Pawnee National Grasslands. Both total C and N were highest in native, intermediate in abandoned, and lowest in cultivated fields. An average loss from cultivation for total C was 26% and for total N was 29%. Precipitation had a significant effect on SOM content in native fields, but did not have an effect on C and N losses from cultivation. C/N ratio differences among native, abandoned, and cultivated fields were not significant in 30cm depth soil. I estimated recovery of SOM using the CENTURY model. During 50 years of abandonment of lands, I estimate that 25 g/m² of C has recovered, but we could not detect N recovery. In situ net mineralization in 15 cm depth soil was also examined among three land management treatments (native, abandoned, and cultivated) and two microsites (under individual Bouteloua gracilis plants and between individual plants). Total C, N, and C/N ratios were highest in native, intermediate in abandoned, and lowest in cultivated fields, and higher under plants than between plants. In situ net N mineralization, % N mineralization, and moisture content in soils were highest in cultivated fields, but there was no difference between native and abandoned fields. In situ net N mineralization, % N mineralized, and soil moisture content were not significantly different between microsites. A ratio of field net N mineralization to lab net mineralization was highest in cultivated fields, but differences between native and abandoned fields were not significant. This ratio tended to be higher between plants than under plants, but there was not a significant difference. Because this ratio may be an index of environmental limitation to N mineralization, I infer that cultivated fields and between plant locations have less environmental restriction than native fields or underplant locations. I concluded from these results that nitrogen availability to plants is recovered in abandoned fields from the results of in situ N mineralization. However total C has recovered only 25 g/m², and total N did not show recovery in abandoned fields.
Open Access
From genes to landscapes: the distribution of western conifers
(Colorado State University. Libraries, 2013) Bisbing, Sarah M., author; Cooper, David, advisor; Angert, Amy, committee member; Binkley, Dan, committee member; Sibold, Jason, committee member
Managing and conserving forest ecosystems under a rapidly changing climate will require an understanding of the drivers of species distributions across a gradient of temporal and spatial scales. My dissertation research evaluated the relationship between distributional patterns of tree species and the processes driving these patterns from local to continental scales. I addressed three questions: 1) Which local abiotic and biotic processes are most important in determining the distribution of tree species along a hydrologic gradient in southeast Alaska? 2) How is genetic variation partitioned across the range of Pinus contorta, and is this variation explained by geographic or landscape variables? 3) How will Pinus contorta respond to predicted climate change? At the local scale, I assessed the role of abiotic and biotic constraints in limiting three tree species (Pinus contorta, Picea sitchensis, and Tsuga heterophylla) along a hydrologic gradient in southeast Alaska. I used a Bayesian hierarchical model to identify the strongest predictors of species' occurrence and biomass. Model predictions identified abiotic variables, including soil nitrogen, pH, and depth to water, as the primary factors limiting species' success in anaerobic wetland ecosystems. Competition was identified as the limiting factor in aerobic forest ecosystems. At the continental scale, I quantified the impact of historic evolutionary processes in shaping patterns of genetic diversity across the range of Pinus contorta, a widespread and morphologically variable species. I estimated gene flow and assessed the effect of the landscape on population structure. Gene flow is high across the range of the species, and patterns of variation are most strongly influenced by landscape barriers to gene flow and the environmental variation associated with its heterogeneous range. This suggests that, despite widespread gene flow, subspecies are adapted to local conditions. I then used correlative and mechanistic species distribution models to evaluate potential, future habitat suitability at the species and subspecies levels of Pinus contorta. Model results predict that P. contorta will maintain a large portion of its current habitat, but two of the more geographically constrained subspecies will lose a significant portion of suitable habitat. My work provides an understanding of the ecological and evolutionary processes shaping tree species distributions across a gradient of temporal and spatial scales, from historic to current timeframes and local to range-wide extents. Results from my research show that different processes determine patterns of distribution across this gradient of scales. Linking these patterns and processes will be essential for forest management and conservation in light of a rapidly changing climate.
Open Access
Plant selenium accumulation and the rhizosphere effect
(Colorado State University. Libraries, 2011) Alford, Élan Reine, author; Paschke, Mark W., advisor; Binkley, Dan, committee member; Borch, Thomas, committee member; Pilon-Smits, Elizabeth, committee member; Stromberger, Mary, committee member
To view the abstract, please see the full text of the document.
Open Access
Stand structure and wood production efficiency in Black Hills ponderosa pine
(Colorado State University. Libraries, 2011) Ex, Seth, author; Smith, Frederick, advisor; Binkley, Dan, committee member; Steingraeber, David, committee member
Contemporary North American forestry has moved away from management primarily for fiber production toward management for a suite of priorities, including aesthetics, forest health, wildlife habitat, and restoration of pre-settlement conditions. Multi-aged forest stands are better suited to contemporary management priorities than even-aged stands in many instances, largely because stand density can be held in check and regeneration initiated without wholesale removal of the overstory. However, competitive interaction between trees of varying size and inherent physiological differences between small and large trees make it unclear that multi-aged stands produce stemwood volume as efficiently as even-aged stands. In South Dakota's Black Hills National Forest, fiber production remains an important management objective, which raises questions regarding potential impacts to wood production associated with creating multi-aged structures. We used stemwood volume production per unit leaf area as a metric of production efficiency to compare productivity of different sized trees and cohorts of trees within multi-aged stands, as well as to compare productivity of multi-aged to even-aged stands of pure Pinus ponderosa var. scopulorum. Leaf area is a good measure of resource acquisition for productivity analysis both because it is closely related to light capture, and because multi-aged silvicultural systems can use leaf area per unit ground area (leaf area index) as a stocking tool to regulate density of individual cohorts within a stand. Direct measurement of leaf area is currently unfeasible in the context of daily forestry operations. Consequently, an explicit relationship between leaf area and a standard forestry metric is needed to allow managers to allocate leaf area among cohorts within multi-aged stands using available inventory data. A widely-used stocking tool called stand density index (SDI) is highly correlated with leaf area and has been suggested for this purpose. Yet, it is unclear that the relationship between SDI and leaf area is unbiased across cohorts within multi-aged stands. This work sampled 1,824 trees in 21 multi-aged and 10 even-aged stands to address questions of production efficiency and implementation of multi-aged silviculture. We found trees in the smallest cohort in multi-aged stands produced stemwood on average 20% less efficiently than trees in larger cohorts. Growth dominance analysis showed efficiency increased with increasing size for the smallest trees in multi-aged stands, but this relationship was inverted for larger trees. Despite size related efficiency differences between trees in multi-aged stands, there was no statistical difference in production efficiency between stand structures. SDI explained almost 90% of leaf area variation in multi-aged stands, with no statistical difference in the relationship across cohorts. Results suggested no penalty in terms of production efficiency for multi-aged stands compared to their even-aged counterparts. Furthermore, SDI provided an unbiased estimate of leaf area in multi-aged stands, supporting its use as a stocking tool for management of complex stand structures.
Open Access
The effect of mountain pine beetle caused mortality on subalpine forest stand and landscape structure in Rocky Mountain National Park, CO
(Colorado State University. Libraries, 2009) Nelson, Kellen N., author; Rocca, Monique Elisabeth, 1974-, advisor; Binkley, Dan, committee member; Martin, Patrick, committee member
Mountain pine beetle (MPB) eruptions in lodgepole pine forests are a disturbance process that shape forest structure and successional trajectories. Chapter one examines the effect that MPB have on overstory stand and landscape forest structure. I distributed 46 randomly located clusters of three plots across the west side of Rocky Mountain National Park (RMNP), and characterized changes in stand structure and lodgepole pine mortality through three stages in the eruption. Across the landscape, diameter at breast height, basal area, and density decreased by 37%, 71%, and 34% respectively. Environmental factors (elevation and moisture) and tree size greatly influenced the early stage of the eruption; whereas later stages showed stronger relationships with stand structure factors (tree size, basal area, proportion of non-host trees, density and stand age). Changes in forest heterogeneity depended on spatial scales; at the local scale, heterogeneity increased among subplots within clusters, while heterogeneity among clusters declined over time. In chapter two, I explored the effect of MPB-related mortality on aspen regeneration by examining whether suckering densities and growth rates increase with MPB-related mortality, and if ungulates utilize additional suckers through browsing. Conifer overstory mortality, aspen sucker density, stem elongation, total sucker height, and ungulate browsing rates were characterized in 48 plots over 8 stands. Heavy lodgepole pine mortality decreased conifer basal area by 80% and stem density by 50% of pre-eruption levels. This appears to relieve competitive pressure on aspen in mixed conifer-aspen stands. Linear mixed-effects model results show that as weighted mortality increased, aspen sucker density increased three-fold, aspen stem elongation increases by 2.5-fold, and mean sucker height increases by two-thirds. Additionally, as sucker density increased, I did not find evidence to suggest that the rate of ungulate browsing increased. Mountain pine beetle related mortality relieves conifer pressure and may lead to successful aspen recruitment.
Open Access
The impact of reforestation in the northeast United States on precipitation and surface temperature
(Colorado State University. Libraries, 2013) Clark, Allyson, author; Randall, David, advisor; Denning, A. Scott, committee member; Binkley, Dan, committee member
Since the 1920s, forest coverage in the northeastern United States has recovered from disease, clearing for agricultural and urban development, and the demands of the timber industry. Such a dramatic change in ground cover can influence heat and moisture fluxes to the atmosphere, as measured in altered landscapes in Australia, Israel, and the Amazon. In this study, the impacts of recent reforestation in the northeastern United States on summertime precipitation and surface temperature were quantified by comparing average modern values to 1950s values. Weak positive (negative) relationships between reforestation and average monthly precipitation and daily minimum temperatures (average daily maximum surface temperature) were found. There was no relationship between reforestation and average surface temperature. Results of the observational analysis were compared with results obtained from reforestation scenarios simulated with the BUGS5 global climate model. The single difference between the model runs was the amount of forest coverage in the northeast United States; three levels of forest were defined - a grassland state, with 0% forest coverage, a completely forested state, with approximately 100% forest coverage, and a control state, with forest coverage closely resembling modern forest coverage. The three simulations were compared, and had larger magnitude average changes in precipitation and in all temperature variables. The difference in magnitudes between the model simulations observations was much larger than the difference in the amount of reforestation in each case. Additionally, unlike in observations, a negative relationship was found between average daily minimum temperature and amount of forest coverage, implying that additional factors influence temperature and precipitation in the real world that are not accounted for in the model.
Open Access
The next west
(Colorado State University. Libraries, 2010) Hobman, Dirk, author; Knight, Richard L., advisor; Binkley, Dan, committee member; Fiege, Mark, committee member
The "New West" is a term with a history that spans almost two centuries. The following collection of photographs and text questions the longevity of this term while asking what lies ahead in the Next West. As viewers peruse these pages, the photographer asks that they keep in mind that the work presented herein complies with formatting rules set forth by Colorado State University. It unfortunately does not reflect the manner in which the work is intended to be seen. For further information, please contact the photographer at dh@dirkhobman.com.