Old-Growth Forest Dynamics After Fire and Drought in the Sierra Nevada, California, USA

Understanding forest ecosystems is important because forests cover approximately one-third of Earth’s land area, store half of Earth’s carbon, shelter half of Earth’s species, and absorb a quarter of new anthropogenic carbon emissions, slowing climate change. This dissertation provides insight into future forest habitat, fuels, species composition, and structure by investigating what happens to snags, seedlings, and trees in an old-growth forest after a low- to moderate-severity fire. Chapter II explores how low- to moderate-severity fire changes snag fall rates. Predicting how long snags will remain standing after fire is essential for managing habitat, understanding chemical cycling in forests, and modeling forest succession and fuels. Pre-fire snags––which tend to be preferred habitat because they include more large-diameter snags in advanced stages of decay––were at least twice as likely to fall as new snags within 3–5 years after fire. Pre-existing snags were most likely to persist five years after fire if they were \u3e 50 cm in diameter, \u3e 20 m tall, and charred on the trunk to heights above 3.7 m. Chapter III examines the effects of fire severity and microclimate on conifer regeneration after fire. Available seed, lower burn severity on the forest floor, more fire-caused tree mortality, and earlier snowmelt during the germination year gave Pinus lambertiana seedlings an advantage over Abies concolor seedlings, suggesting that lower-severity fire could naturally shift forest species composition toward Pinus species, which are more resistant to fire and drought. Chapter IV investigates the effects of lower-severity fire on tree growth by analyzing the tree-ring widths of seven mixed-conifer species throughout the Sierra Nevada. Post-fire growth patterns were not substantially different from growth fluctuations at adjacent unburned plots, suggesting that reintroducing lower-severity fire to forests where fire has been excluded over the last century will not prevent surviving trees from attaining pre-fire growth rates within five years after fire. Chapter V focuses on recruitment of large-diameter trees after fire, analyzing how local post-fire mortality within tree neighborhoods impacts post-fire radial growth of surviving trees. Cause of mortality influenced the relationship between neighborhood change and the growth of surviving trees, and this relationship was different for A. concolor compared to P. lambertiana, suggesting that species differences in cause of mortality could affect the species composition of future large-diameter tree populations. These findings demonstrate that low- to moderate-severity fire can promote Pinus seedlings and trees, exemplifying the concept that ecosystems shift toward species composition and structure that maximize resilience to challenging climate and disturbance regimes. This research was possible because of the existence of a long-term, spatially explicit, observational old-growth forest dataset with annual resolution

Recent Climate Change in Utah, 1870-2023

Climate change is impacting Utah. Forty-five years of temperature data show that Utah is steadily warming, which, in turn, is driving declines in winter snowpack, shifting the timing and amount of available water, increasing fire risk, and causing ecological change. This fact sheet addresses changes in Utah\u27s temperature, precipitation and snowpack, streamflow, wildfire, and ecology

Policies and Programs for Water-Wise Residential Landscaping in Utah

Water-wise landscaping is the practice of using plants in a landscape that are adapted to local conditions and only need small amounts of water. Converting yards to water-wise landscaping conserves water and is a climate adaptation action residents can take to benefit Utah as temperatures rise and drought becomes more common. Many policies and programs in Utah help residents use water conscientiously and make changes. This fact sheet provides information regarding current and future water-wise landscaping policies and programs in Utah

Artificial Carbon Sequestration in Utah

Carbon dioxide is an important greenhouse gas that helps keep Earth warm and habitable. But since humans began burning large quantities of fossil fuels during the Industrial Revolution, there has been a rapid increase in atmospheric carbon dioxide from approximately 280 parts per million in 1750 to more than 420 parts per million in 2024. Natural carbon storage processes have been unable to keep up with humans’ carbon dioxide emissions, and the sudden rise in atmospheric carbon dioxide has led to rapid global warming and climate change. One climate adaptation tool that may help rebalance Earth’s carbon cycle is artificial carbon storage. This fact sheet provides information on how geological carbon sequestration works and its potential in Utah

Rock Glaciers in Utah

Utah’s primary water supply––winter snowpack––is in decline due to climate warming coupled with more precipitation falling as rain instead of snow. As snowpack dwindles, other sources of cold stream water, such as rock glaciers, will become more important. Rock glaciers contain significant volumes of internal ice covered by debris. This internal ice provides cold meltwater to mountain streams, sustaining flows in summer and supporting biodiversity. Rock glaciers are common in Utah’s mountains and are projected to be more stable under climate change than Utah’s snowpack. Thus, rock glaciers are likely to persist in their current form even as snowpack volumes continue to decrease. Because rock glaciers may provide a critical, climate-resilient water source for Utah, more research is needed to quantify their relevance for present and future water availability and ecosystems

Climate Change and the Logan River: Past, Present, and Future

The Logan River runs through Idaho and northern Utah, beginning in the Bear River Mountains and flowing through Logan Canyon to Cutler Reservoir. The river is socially and ecologically significant to the Cache Valley community. Throughout its history, the Logan River’s water and energy have sustained life within the valley. However, climate change is threatening the Logan River’s support of both human and animal communities. Rising water temperatures and reduced flow caused by declining snowpack may impair the river’s ability to maintain healthy ecosystems

DNA: From rigid base-pairs to semiflexible polymers

The sequence-dependent elasticity of double-helical DNA on a nm length scale can be captured by the rigid base-pair model, whose strains are the relative position and orientation of adjacent base-pairs. Corresponding elastic potentials have been obtained from all-atom MD simulation and from high-resolution structural data. On the scale of a hundred nm, DNA is successfully described by a continuous worm-like chain model with homogeneous elastic properties characterized by a set of four elastic constants, which have been directly measured in single-molecule experiments. We present here a theory that links these experiments on different scales, by systematically coarse-graining the rigid base-pair model for random sequence DNA to an effective worm-like chain description. The average helical geometry of the molecule is exactly taken into account in our approach. We find that the available microscopic parameters sets predict qualitatively similar mesoscopic parameters. The thermal bending and twisting persistence lengths computed from MD data are 42 and 48 nm, respectively. The static persistence lengths are generally much higher, in agreement with cyclization experiments. All microscopic parameter sets predict negative twist-stretch coupling. The variability and anisotropy of bending stiffness in short random chains lead to non-Gaussian bend angle distributions, but become unimportant after two helical turns.Comment: 13 pages, 6 figures, 6 table

Irrigation Companies and the Great Salt Lake: Managing Water in Utah Amidst Climate Change

The Great Salt Lake, a key ecosystem and major component of Utah’s identity and economy, is threatened by rapidly declining water levels. This problem has caused widespread and ongoing concern from the public, and the Utah Legislature is faced with making water allocation and management decisions to adapt to the state’s growing population and changing environment. One important group in this discussion is irrigation companies. Here, we examine how irrigation companies receive and maintain water rights in Utah, their significant role in water management, and recent legislative efforts to incentivize efficient water use so more water reaches the Great Salt Lake. It is critical to understand the role of irrigation companies in water management as regional demands for water increase and supply decreases due to climate change

Sustainable Transportation: Transforming Utah Through Community Action

Transportation in the United States accounts for 4% of global greenhouse gas emissions. Over half of these emissions come from on-road vehicles. Nationwide, Utah has the third highest rate of car ownership, and the resulting air pollution from on-road vehicles has significant implications for the climate and public health. This fact sheet provides information on how Utah’s government and other entities are working to expand modes of transport that minimize harm to communities and the environment

Cap-and-Trade Carbon Pricing in Utah: Challenges and Potential Impact

Cap-and-trade programs are a market-based form of carbon pricing that allows companies to trade with each other using carbon credits. Carbon credits function as permission slips to emit a certain amount of carbon. The “cap” establishes the number of carbon credits an industry or region has available for trading. Companies are incentivized to emit less because they can sell their excess carbon credits to other companies. Several cap-and-trade programs exist in the United States, and these programs are effectively reducing carbon emissions while creating net economic benefits for their regions. A cap-and-trade program could help Utah reduce carbon emissions in the state while also improving air quality