Throughout the Central Hardwoods, fire return interval dramatically increased during the period of Euro-American settlement. Fire was used as a tool for clearing land and improving forage for grazing. The Shoal Creek study site is located in Jackson County, Illinois, 8 km southwest of Murphysboro. Shoal Creek is situated at the northern extent of the Illinois Ozark Hills, classified as a Subsection of the Ozark Highlands Section. The region is unglaciated and loess caps are 10 m deep on the ridgetops and 1-3 m deep on side slopes. Results show the site was frequently burned (MFI=2.95) from 1887 to 1946 during post-settlement. Fire waned from the site in the 1930's and the last major fire occurred in 1946. By this time, Shawnee National Forest had become established in southern Illinois and fire suppression was the preferred management technique. Thirty three fire scarred Quercus-Carya cross sections were opportunistically sampled from a southwest aspect. Cross sections were sanded to 600 grit and skeleton plots were used to determine signature years for cross-dating purposes. Year and seasonality of individual fire scars, and approximate pith date were determined for each sample to be utilized in FHX2. Recruitment history revealed that overstory oak-hickory species established under favorable conditions in the early 20th century. Timber was harvested from the site around 1900 and intense fires followed for the next 30 yrs. A small pulse of Acer-Fagus germinated as fire frequency decreased on-site during the 1930's and a significant pulse established immediately after the last recorded fire in 1946. Superposed epoch analysis (SEA) determines the influence of immediate weather patterns and overall climate trends surrounding fire event years. SEA was run to compare fire event years at Shoal Creek with PDSI climate reconstructions. For the 95% confidence interval, there was not a significant association between fire and climate. In the Central Hardwoods, lightning is associated with rainstorms and fires burn in both dry years and wet years so the relationship between fire and climate is not strong. The Shoal Creek study site will be compared with the Sugar Creek study site (located in the Shawnee Hills) to see if similarities in the historical fire regime and recruitment exist between the two physiographic provinces. If rehabilitation of oak-hickory dominated forest stands is the management objective, the results of this study will aid in fire cycle planning of frequency and seasonality. Managers may consider the MFI for rehabilitation burns, and range of fire intervals for long-term maintenance burns. However, prescribed burns are not the only answer for managers. Fire must be used in accordance with silvicultural techniques that mimic natural disturbance regimes such as TSI and shelterwood harvests which create large overstory gaps suitable for oak-hickory recruitment.

Fire-scarred trees provide an important source of data and direct evidence for understanding past fires and vegetation dynamics. Although dendrochronological fire scar records provide fine-scale temporal and spatial resolution, limitations exist in the development, analysis, and interpretation of these fire history datasets. In order to assess these limitations, we applied a systematic gridded sampling scheme to a 4-hectare study area located in the Ridge and Valley Province of northeastern Pennsylvania. We mapped and described a total of 155 fire-scarred trees within a 50-meter resolution grid, noting the species, health status, and basal scar orientation for each tree. Additionally, we cut a full or partial cross section from 58 fire-scarred pitch pine (Pinus rigida) for the purpose of assessing multiple "filtering" techniques and for the development of a fire interval simulation model. The simulation model randomly selected trees from each grid cell to estimate fire return intervals at multiple spatial scales. Our results indicate that fire return intervals are dependent upon the definition of "recorder" years and influenced by various filtering methods, including minimum number and minimum percentage of trees scarred. For example, the number and length of fire intervals was greater when years prior to the initial scar were considered "non-recording" vs. "recording" and when a percentage scarred filter was applied. The simulation model provides an additional range of fire interval estimations that can be used by land managers to guide forest restoration and fire management objectives. / Master of Science / Fire-scarred trees provide a valuable source of data and direct evidence for understanding past fires and vegetation dynamics. Although dendrochronological fire scar records provide fine-scale temporal and spatial resolution, limitations exist in the development, analysis, and interpretation of these fire history datasets. In order to assess these limitations, we applied a systematic gridded sampling scheme to a 4-hectare study area located in the Ridge and Valley Province of Northeastern Pennsylvania. We mapped and described a total of 155 fire-scarred trees within a 50-meter resolution grid, noting the species, health status, and basal scar orientation for each tree. Additionally, we cut a full or partial cross section from 58 fire-scarred pitch pine (Pinus rigida) for the purpose of assessing multiple “filtering” techniques and for the development of a fire interval simulation model. The simulation model randomly selected trees from each grid cell to estimate fire return intervals at multiple spatial scales. Our results indicate that fire return intervals are dependent upon the definition of “recorder” years are influenced by various filtering methods, including minimum number and minimum percentage of trees scarred at local and landscape scale. For example, the number and length of fire intervals was greater when years prior to the initial scar were considered “non-recording” vs. “recording” and when a percentage scarred filter was applied. The simulation model provides an additional range of fire interval estimations that can be used by land managers to guide forest restoration and fire management objectives.

Wildfire is an ecological disturbance that plays an important role in ecosystem function and interacts with climate and vegetation, relationships that may be altered by ongoing climate change. Insights from paleoecology can provide context for environmental change, including the natural range of variability. Here, the Holocene fire history of a small watershed in eastern Ontario, Canada is reconstructed. A high-resolution macroscopic charcoal series was derived from the lacustrine sediment of Mud Lake, north of Gananoque, Ontario and within the Frontenac Arch. Analysis of the charcoal record estimates a mean fire-return-interval (FRI) of 175 yr/fire around Mud Lake during the Holocene, and similar mean FRIs during different time periods indicates that it has been a largely stationary fire regime. The analysis suggests that fire activity may have recently increased, but a lack of documentary fire records for the area leaves this uncertain. There is no indication that humans have significantly impacted the fire regime, though anthropogenic ignition could have played a role in the area’s recent fires. The fire regime around Mud Lake does not appear to have shifted in association with major changes in regional vegetation. Fire activity does correlate with some paleoclimate trends. The estimated fire frequency decreased around 7500 yr BP, when wetter summers became more common in eastern Canada, and a recent increase in fire frequency would parallel with more frequent incursions of dry and cool air masses into the region. During other parts of the record, however, the fire activity does not appear to reflect the major climate impacts. The fire history of Mud Lake is relevant to the ecological management of eastern Ontario’s St. Lawrence Islands National Park and its restoration of a rare, fire-dependent tree species, the pitch pine. Though predictions vary, this area’s climate may become more favorable to fire through an increase in temperature and a decrease in summer precipitation. By providing information about the natural variability of fire activity in eastern Ontario, this research can be applied towards setting appropriate management goals during future environmental change. / Thesis (Master, Environmental Studies) -- Queen's University, 2010-02-01 00:14:00.711

At regional scales climate patterns (e.g., interannual wet-dry cycles) result in high spatial fire synchrony among Southwest forests. However, in the "Sky Island" forests of southeastern Arizona spatial and temporal patterns of fire history and tree age structure at landscape levels (i.e., within mountain ranges) are relatively unknown and therefore the focus of this study. In the Santa Catalina Mountains we reconstructed the fire history on a 2,900-hectare study area with two distinct landscapes, Butterfly Peak (BP) and Rose Canyon (RC) using 2-hectare "points" (i.e., collection areas). The RC landscape was dominated by shallow south-facing aspects and BP was dominated by steep north-facing aspects. Within each landscape, point mean fire intervals (PMFIs) were not significantly different between aspect classes. However, pooled PMFIs were significantly shorter in RC compared to BP. These results show that the fire history at any given point (i.e., 2 hectares or less) was primarily controlled by the broad-scale topography of the encompassing landscape, rather than by the fine-scale topography at that point.Using similar methods we also reconstructed the fire history on Rincon Peak, which is a small isolated mountain range with very step topography. The fire history of the 310-hectare forest area was a mixture of frequent low severity surface fires (from AD 1648 to 1763) and infrequent mixed-severity fires (from AD 1763 to 1867). This mixed-fire regime was probably due to a combination of climatic variability, the small area and rugged topography of this mountain range, and complex fuel arrangements. The distinct fire histories from these two study areas provided natural age structure experiments that indicated tree age cohorts (i.e., higher than expected tree establishment pulses) occurred during periods of reduced fire frequencies. In some instances these periods were likely caused by climatic variability (e.g., a wet and/or cool early 1800s) creating synchronous age cohorts across the region. At other times, extended fire intervals were a function of local topography (e.g., 1763-1819 in the northern half of Rincon Peak). Overall, these studies demonstrated that landscape and climatic variations combine to produce complex spatial and temporal variations in fire history and tree age structures.

Identification of effects that climate teleconnections, such as El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO), have on wildfires is difficult because of short and incomplete records in many areas of the world. We developed the first multicentury wildfire chronologies for northeast China from fire-scarred trees. Regional wildfires occurred every 7years from the 1700s to 1947, after which fire suppression policies were implemented. Regional wildfires occurred predominately during drought years and were associated with positive phases of ENSO and PDO and negative NAO. Twentieth century meteorological records show that this contingent combination of +ENSO/+PDO/-NAO is linked to low humidity, low precipitation, and high temperature during or before late spring fire seasons. Climate and wildfires in northeast China may be predictable based on teleconnection phases, although future wildfires may be more severe due to effects of climate change and the legacy of fire suppression.

Master of Arts / Department of Geography / Kendra K. McLauchlan / Whitebark pine (Pinus albicaulis) is a critically threatened North American conifer. In modern times, it has experienced a significant decline in population due to pine beetle infestations, blister rust infections, fire suppression, and climate change. While climate, fire, and vegetation are strongly linked on regional and global scales, the relative roles of these three factors are not well-documented during the Holocene in high elevation mountain sites of North America. Recent anthropogenic changes in climate and fire management practices are underway, but the potential responses of subalpine vegetation to these environmental changes remain relatively unknown. Here, I documented the paleoecology of a watershed surrounding an unnamed, high-altitude pond containing a large number of whitebark pine trees located at 2805m elevation in Grand Teton National Park, U.S.A. Using a 1.5 meter lacustrine sediment core collected in 2010, I generated a Holocene-scale fire and vegetation record using fossil pollen, charcoal, and macrofossils preserved within the core. I also conducted a dendrochronological study of the current stand of whitebark pine in the watershed to determine both approximate dates of establishment and responses to past climate change of this modern stand. Sedimentary charcoal data indicate significant variability in both fire frequency and fire intensity during the Holocene. The fire regime observed in the past 1000 years is seemingly unprecedented at this site, with lower fire frequency and higher fire intensity than any other time during the Holocene. Sedimentary pollen data suggest the study site has been primarily dominated by whitebark pine until the last 1000 years, with brief periods of vegetation dominated by non-arboreal taxa that indicate the presence of either successional dynamics or shifts in treeline location. Ages of individual living whitebark pine trees average 365 years, and dendrochronology data suggest that ring widths of the current stand have been declining since 1991. Statistical analyses of PRISM climate data with ring width data suggest that this decrease in annual growth is likely the result of decreased growing season temperature ranges driven by a warming climate. While this stand of whitebark pine is threatened by both warming climate and fire suppression, there is the potential for low-intensity prescribed burns to play a role in conservation and restoration management plans for this threatened conifer.

Although human land use in the industrial and post-industrial world has had demonstrable impacts on global climate, human land use may also improve or reduce the resilience of ecosystems to anthropogenic and natural climate change. This dissertation tests the hypothesis that low severity anthropogenic burning by prehistoric and protohistoric indigenous societies in the ponderosa pine forests of east-central Arizona improved the resilience of these forests to low frequency climate change. I use sedimentary charcoal, phosphorus, stable carbon isotopes, and palynology to reconstruct changes in fire regimes over the last 1000 years from seven radiocarbon dated alluvial sequences in five watersheds across a gradient of indigenous land use and occupation histories. Paleoecological evidence from occupied watersheds is consistent with small-scale, agricultural burning by Ancestral Pueblo villagers (between AD 1150-1325/1400) and anthropogenic burning by Western Apaches to promote wild pant foods (ca. AD 1550-1900) in addition to naturally frequent, low severity landscape fires. Statistical reconstructions of climate driven fire activity from tree-ring records of annual precipitation indicate that Southwestern forests were vulnerable to increased fire severity and shifts to alternative stable states between AD 1300-1650. In watersheds that were unoccupied or depopulated by AD 1325, paleoecological and sedimentological evidence is consistent with an increase in fire severity, whereas areas occupied and burned by indigenous people until AD 1400 did not yield evidence of increased fire severity. These results suggest that anthropogenic burning by small-scale societies may have improved the resilience of Southwestern forests to climate driven environmental changes.

No description available.

Questions remain regarding the impacts of late-Holocene human activities and environmental change on landscapes of the Caribbean islands. This dissertation examined the long-term environmental history of two sites in the northern Caribbean primarily through the analysis of proxy data sources contained in sediment cores. At Laguna Alejandro, a coastal lagoon in the southwestern Dominican Republic, we interpreted, from sediment lithology and stable oxygen isotope data, at least ten storm events over the past 1,000 years, producing the first long record of storm activity from the island. During the Little Ice Age (1400−1800 CE), we interpreted an increased frequency of hurricane landfalls at the study site with longer ecosystem recovery times and decreased fire activity versus during earlier, more moist periods of the late-Holocene. At Freshwater Pond, an inland pond on Barbuda, we interpreted vegetation disturbance from presence of disturbance pollen taxa and biomass burning near the pond from abundance of macroscopic (>125 µm) charcoal from sediments representing ~150 BCE–1250 CE, with consistency of burning and human history on the island informed by the archaeological record suggesting fire activity was primarily due to Pre-Columbian inhabitants. Microscopic charcoal analysis indicated that extra-local burning, primarily island-wide, continued until ~1610 CE then declined, possibly reflecting a change in land-use practices by Europeans who entered the region in 1492 CE and established a permanent settlement on the island in the 1660s. My study on modern pollen from surface soils and sediments, the first from lowland seasonally-dry vegetation of the Greater Antilles, informed our ideas on vegetation-pollen representation in different plant communities, including tropical dry forest, thorn forest, mangrove, mudflat, and lagoon. My modern pollen results also aided in the interpretation of stratigraphic pollen in the study of nearby L. Alejandro’s sediments and revealed changes in floristic composition at the study site through time. Pollen of maize (Zea mays) and Prosopis juliflora in sediments representing ~1760 CE document human subsistence agriculture and disturbance to tropical dry forest in the watershed. / PHD

Fire is a primary driver of environmental change that can originate from natural or human ignition. Macroscopic charcoal (>125 "m) deposited into lake sediment is a record of a local fire event, whereas microscopic charcoal indicates fire activity on a broad landscape scale. Patterns of charcoal deposition may shed light on both human activities and climate history over long-time scales. Whether lowland Caribbean forests have experienced natural fire regimes over the long-term is unknown. Laguna Limón is a little-studied, large, freshwater lake on the northeastern coast of the Dominican Republic. We extracted four overlapping sediment cores totaling 315 cm in depth, and conducted analysis of macroscopic charcoal (2-cm), microscopic charcoal (16-cm), and loss-on-ignition (1-cm) to examine the long-term fire and environmental history of the area. Loss-on-ignition data established that the lake has only recently become organic rich, and was likely open to the sea as a low energy bay until 1400 Cal. Yr BP. The lake existed briefly as a wetland before transitioning to the modern freshwater lake 1200 Cal. Yr BP. Macroscopic charcoal was most abundant in the freshwater section of the core while microscopic charcoal peaked near the bottom of the core, and aligns well with other regional microscopic charcoal records. Overall the charcoal record reflects a combination of climatic and anthropogenic related charcoal deposition suggesting that fire has played an active role in the environmental history Laguna Limón. / Master of Science