Using Spatial Analysis to Evaluate Fire Activity in a Pine Rockland Ecosystem, Big Pine Key, Florida, USA

Pine rocklands are fire-prone ecosystems with limited spatial extent, and have experienced reduced area in the previous decades through habitat conversion and urbanization. The purpose of this dissertation research was to evaluate the historical range of variability of fire activity and spatial patterns of fires in a pine rockland ecosystem in the National Key Deer Refuge (NKDR) on Big Pine Key in the Lower Florida Keys. To investigate the temporal and spatial patterns in fire activity, I (1) evaluated the temporal patterns for fires in my study area in the NKDR, (2) analyzed differences in standard fire history metrics since the advent of land management in the 1950s, (3) mapped the spatial extents of fires that scarred \u3e 25% of the recording trees, (4) investigated how regression relationships fire activity and microtopographic parameters changed with aggregated scale, and (5) calculated global and local indications of spatial autocorrelation in the geographic fire-scar data. The 2011 fire was no more severe than other historic fires in the dataset, and was within a range of expectations for severe fires in the area. The relationships between fire activity and microtopography peaked at approximately 50 m (residual topography p \u3c 0.05; curvature p \u3c 0.10). Finally, spatial autocorrelation analyses found statistically significant (p \u3c 0.01) clustering in the fire-scar data network across the study area, and significant low-clustering (p \u3c 0.05) at the at smaller scales. Recent lack of fire return intervals consistent with pre-management periods confirms the influence that people have had on fire in this ecosystem, and the presence of the neighborhood adjacent to the study area in the south may have dampened fire activity in that area

Groundwater Modeling of the West Plains, WA

Located in Eastern Washington in the West Plains Region sits a plateau of Columbia River Basalts between Deep Creek, Hangman Creek, and south of the Spokane River. Primarily in Airway Heights, the amount of drinking water as well as the quality of the water has affected residents in the area. The most recent issue is PFAS contamination, which is thought to negatively affect human health and is found in drinking water wells across the West Plains. We can interpret subsurface geology using new well logs from Fairchild Air Force Base and in the Palisades area. When using ArcGIS PRO, well information can then be interpreted and projected as various data points. After this, it can be interpolated to predict multiple geological horizons and can be used to estimate the flow direction of groundwater. We will also use real PFAS results from across the West Plains to estimate if contamination can be linked to possible sources, including airports, fire stations, car washing facilities, or dumps. These models can help residences in the West Plains Region understand the possible sources of contamination as well as create a safer environment for them and their families. This research could put worried residents at ease and help them find clarity in this difficult situation

Depletion-Driven Morphological Control of Bundled Actin Networks

The actin cytoskeleton is a semiflexible biopolymer network whose morphology is controlled by a wide range of biochemical and physical factors. Actin is known to undergo a phase transition from a single-filament state to a bundled state by the addition of polyethylene glycol (PEG) molecules in sufficient concentration. While the depletion interaction experienced by these biopolymers is well-known, the effect of changing the molecular weight of the depletant is less well understood. Here, we experimentally identify a phase transition in solutions of actin from networks of filaments to networks of bundles by varying the molecular weight of PEG polymers, while holding the concentration of these PEG polymers constant. We examine the states straddling the phase transition in terms of micro and macroscale properties. We find that the mesh size, bundle diameter, persistence length, and intra-bundle spacing between filaments across the line of criticality do not show significant differences, while the relaxation time, storage modulus, and degree of bundling change between the two states do show significant differences. Our results demonstrate the ability to tune actin network morphology and mechanics by controlling depletant size, a property which could be exploited to develop actin-based materials with switchable rigidity.Comment: 22 pages, 10 figures. Authors James Clarke and Francis Cavanna contributed equally; Changes: Added modeling work, extended dynamic light scattering analysi

Advancing dendrochronological studies of fire in the United States

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Dendroecology is the science that dates tree rings to their exact calendar year of formation to study processes that influence forest ecology (e.g., Speer 2010 [1], Amoroso et al., 2017 [2]). Reconstruction of past fire regimes is a core application of dendroecology, linking fire history to population dynamics and climate effects on tree growth and survivorship. Since the early 20th century when dendrochronologists recognized that tree rings retained fire scars (e.g., Figure 1), and hence a record of past fires, they have conducted studies worldwide to reconstruct [2] the historical range and variability of fire regimes (e.g., frequency, severity, seasonality, spatial extent), [3] the influence of fire regimes on forest structure and ecosystem dynamics, and [4] the top-down (e.g., climate) and bottom-up (e.g., fuels, topography) drivers of fire that operate at a range of temporal and spatial scales. As in other scientific fields, continued application of dendrochronological techniques to study fires has shaped new trajectories for the science. Here we highlight some important current directions in the United States (US) and call on our international colleagues to continue the conversation with perspectives from other countries

The North American tree-ring fire-scar network

Fire regimes in North American forests are diverse and modern fire records are often too short to capture important patterns, trends, feedbacks, and drivers of variability. Tree-ring fire scars provide valuable perspectives on fire regimes, including centuries-long records of fire year, season, frequency, severity, and size. Here, we introduce the newly compiled North American tree-ring fire-scar network (NAFSN), which contains 2562 sites, >37,000 fire-scarred trees, and covers large parts of North America. We investigate the NAFSN in terms of geography, sample depth, vegetation, topography, climate, and human land use. Fire scars are found in most ecoregions, from boreal forests in northern Alaska and Canada to subtropical forests in southern Florida and Mexico. The network includes 91 tree species, but is dominated by gymnosperms in the genus Pinus. Fire scars are found from sea level to >4000-m elevation and across a range of topographic settings that vary by ecoregion. Multiple regions are densely sampled (e.g., >1000 fire-scarred trees), enabling new spatial analyses such as reconstructions of area burned. To demonstrate the potential of the network, we compared the climate space of the NAFSN to those of modern fires and forests; the NAFSN spans a climate space largely representative of the forested areas in North America, with notable gaps in warmer tropical climates. Modern fires are burning in similar climate spaces as historical fires, but disproportionately in warmer regions compared to the historical record, possibly related to under-sampling of warm subtropical forests or supporting observations of changing fire regimes. The historical influence of Indigenous and non-Indigenous human land use on fire regimes varies in space and time. A 20th century fire deficit associated with human activities is evident in many regions, yet fire regimes characterized by frequent surface fires are still active in some areas (e.g., Mexico and the southeastern United States). These analyses provide a foundation and framework for future studies using the hundreds of thousands of annually- to sub-annually-resolved tree-ring records of fire spanning centuries, which will further advance our understanding of the interactions among fire, climate, topography, vegetation, and humans across North America

Using Dendroecology to Strengthen the Historic Integrity of Cumberland Homesteads Tower in Crossville, Tennessee

The Cumberland Homesteads Historic District, located on the Cumberland Plateau in East Tennessee, is home to one of the first and largest Homesteads projects attempted during the New Deal era. Although the settlement did not succeed in its original objective, the history of the Cumberland Homesteads has become a valued foundation of the local community, which in turn strives to protect the legacy of the Cumberland Homesteads Tower. To preserve the integrity of the structure as well as the historical integrity of the landscape, the Cumberland Homesteads Tower Association sought to date and potentially remove trees that were not present during the period of significance (prior to 1938). The majority of the trees in close proximity to the Tower were identified as Eastern hemlock (Tsuga canadensis (L.) Carrière) and 15 trees total were sampled. Additionally, three post oak (Quercus stellata Wangenh.) trees located in a historic ‘triangle’ across the highway from the Tower and targeted for removal were sampled. Samples were successfully dated, and ca. half of the hemlock were confirmed to have been planted after the construction of the Homesteads Tower. Additionally, post oaks analyzed near the Tower were dated back to the early 1800s, which motivated their protection in the midst of a road project threatening their survival

Tree-Ring Based Reconstruction of Historical Fire in an Endangered Ecosystem in the Florida Keys

Big Pine Key, Florida, is home to one of Earth’s largest swaths of the critically-endangered dry forests. Known as pine rocklands, this fire-adapted ecosystem must experience regular fire to persist and remain healthy. Pine rocklands are composed of a sole canopy species: the South Florida slash pine (Pinus elliottii var. densa), along with a dense understory of various woody and herbaceous species, and minimal surface moisture and soil development. Slash pine record wildfire activity of the surrounding area via fire scars preserved within the annual tree rings formed by the species. Our study used dendrochronology to investigate the fire history of the pine rocklands on Big Pine Key, specifically within and around the National Key Deer Refuge (NKDR) because it is the largest segment of unfragmented pine rockland on the island. We combined the results found within the NKDR with those of a previous study completed in 2011, and incorporated historical documents and reports of prescribed and natural fires through November 2019 into our evaluation of fire history on Big Pine Key. We conclude that prescribed burning practices are vital to truly restore natural fire behavior, and repeated burning on these islands in the future must be prioritized

Tree-Ring Based Reconstruction of Historical Fire in an Endangered Ecosystem in the Florida Keys

Big Pine Key, Florida, is home to one of Earth’s largest swaths of the critically-endangered dry forests. Known as pine rocklands, this fire-adapted ecosystem must experience regular fire to persist and remain healthy. Pine rocklands are composed of a sole canopy species: the South Florida slash pine (Pinus elliottii var. densa), along with a dense understory of various woody and herbaceous species, and minimal surface moisture and soil development. Slash pine record wildfire activity of the surrounding area via fire scars preserved within the annual tree rings formed by the species. Our study used dendrochronology to investigate the fire history of the pine rocklands on Big Pine Key, specifically within and around the National Key Deer Refuge (NKDR) because it is the largest segment of unfragmented pine rockland on the island. We combined the results found within the NKDR with those of a previous study completed in 2011, and incorporated historical documents and reports of prescribed and natural fires through November 2019 into our evaluation of fire history on Big Pine Key. We conclude that prescribed burning practices are vital to truly restore natural fire behavior, and repeated burning on these islands in the future must be prioritized

Historia literaria hispanoamericana

This timeline was created by students in Spanish American Literature 1 (SN 403W) in Fall 2019 with Dr. Katherine Karr-Cornejo. This is a timeline of Spanish American literary history from pre-Conquest indigenous societies through 1900. It contains overview sections and sample works for each section. Its goal is to make legible to viewers a map of a culture and its artifacts

Comparing the impact of live-tree versus historic-timber data on palaeoenvironmental inferences in tree-ring science, eastern North America

Dendroarchaeological data from historic structures and artefacts have the potential to extend tree-ring chronologies spatially and temporally, especially where old-growth forests have been extensively modified or harvested. While these data may contribute to an improved understanding of past climate and ecology, critical differences in the properties of live-tree and historic-timber data might affect results and interpretations of large-scale studies, such as those relying on large datasets from public databases like the International Tree-Ring Data Bank (ITRDB). The objective of this work was to compare summary measures of live-tree versus historic-timber datasets likely to affect outcomes and inferences of typical paleoenvironmental applications. We used 99 live-tree (LT) and 41 historic-timber (HT) datasets collected in the Appalachian region of the eastern United States and compared common analytical measures for understanding past climate and ecology, including temporal coverage, species composition, recruitment patterns, segment length, series coherence/mean interseries correlation (as Rbar), expressed population signal (EPS), subsample signal strength (SSS) and response to drought and extreme climate events. We found that tree-ring data from historic timbers record some ecological events similarly to live trees and are sensitive to some climate conditions, with important caveats related to the influence of site and tree selection on analytical measures. In some cases, these caveats can be overcome through improved collection of metadata and additional analyses. In all cases, potential differences in LT and HT data should be considered by those who perform large-scale analyses using public tree ring databases, especially as more scientists contribute historic-timber datasets