Browsing by Subject "Dendrochronology"
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Item ASSESSING THE DENDROCHRONOLOGICAL AND DENDROCLIMATIC POTENTIAL OF SHASTA RED FIR (Abies magnifica var. shastensis) IN NORTHERN CALIFORNIA AND SOUTHWESTERN OREGON, USA(2014-06) Torbenson, Max Carl ArneWe developed five ring-width records from Shasta red fir (Abies magnifica var. shastensis) stands in northern California and southwestern Oregon to evaluate growth trends and their relation to climate across the species' latitudinal range. The chronologies are made up of 173 trees in total, and earliest adequate replication ranges from AD 1624 to AD 1812. The oldest tree sampled has an inner-ring date of AD 1340. Tree age is only weakly correlated with size, and younger individuals (<300 years old) make up the majority of large trees (>100 cm DBH) in our data. Chronologies display shared variability in ring-width at inter-annual timescales; however, cross-dating across the full study region is not possible. The five records, together with one publicly available chronology, were compared to local and regional climate data. Significant correlations between red fir tree growth and local climate were found at all six sites but these relationships were not consistent throughout the latitudinal gradient. Prior analysis has suggested that the growth of the species is primarily limited by summer minimum temperature, but this relationship was not apparent at most sites within our network. Instead, the associations observed between red fir growth and climate are multivariate, dependent on the temporal resolution of climate data used, and may also be influenced by both latitude and elevation.Item Expanding the Tree Ring-Based Fire History Reconstruction of Itasca State Park(2022-06) Brumm, DanielItasca State Park is among the most iconic and visited state parks in Minnesota, and was established to protect the headwaters of the Mississippi River as well as to preserve an example of the old growth pine forests that once characterized the region. The red pine-dominant, fire dependent forest communities of Itasca support a close association between frequent fire events and forest composition, with many fire-scarred trees and remnant stumps preserving the park’s fire history within their annual growth rings. This research uses remnant, fire-scarred red pine stumps to expand upon previous fire history research by enhancing spatial coverage of tree-ring sample collection, strengthening the temporal assignment of fire events, and providing the first assessment of historic fire seasonality across the entire park area. Increasing evidence has been better documenting the role of people as critical ignition sources in fire regimes of the Upper Great Lakes. To better understand the role people may have had in influencing the fire regime of Itasca State Park, I investigated the cultural history of the area to provide important contextual information.I reconstructed a conservative fire history in Itasca State Park, dating 98 of 129 total tree-ring cross-sections that were collected in 2019, 2020 and 2021. I recorded 27 fire events from 348 individual fire scars between 1649 and 2015 (366 years), with the earliest and latest tree-ring documented fires recorded in 1697 and 1920 respectively. During this time, shorter and longer fire intervals were noted, with intervals being similar to other red pine fire history reconstructions. Fires tended to be synchronous across the park, with four fire years being recorded by at least 70% of the recording samples. Other fires with lower replication still exhibit a synchronous nature, as many events were recorded by samples collected at spatially distant sites. Fire seasonality could be determined on 180 (51.7%) fire scars, 78% of which affected the earlywood of the associated tree ring, indicating the early-growing season as the primary season of fire occurrence in Itasca State Park. Superposed Epoch Analysis found a significant relationship between fire occurrence and dry conditions the year before, and the year of fire events. Written records for the broader park area, however, indicate that most forest fires were ignited by human activities, and occurred in the spring, prior to the usual period of lightning strikes and fire occurrence (June-August). It is possible for Native American agency to have played an important role alongside dry conditions and lightning as an ignition source of historic fire events. Findings from this research affirm previous findings that fires were influential to the park’s forest conditions before Euro-American intervention. Results also identify the possibility of influence on the fire regime by Native American peoples who lived in or visited the park in the past. This fire history research may be a place to begin discussions, relationships, and partnerships with Native American communities in the area, as well as with management personnel to explore how fire may be returned to the park landscape with consideration of the park’s cultural history, and the association between fire and climate.Item Mixed-Silver Maple Forests Of The Upper Mississippi River Floodplain: Variations In Composition, Structure, And Growth Along Environmental Gradients(2020-05) Nielsen, DanielFloodplain forests of the Upper Mississippi River are characterized by complex interactions between biota and the physical environment, specifically aspects of hydrology. The role of environmental variation in overstory composition, structure, and growth is not well documented. Goals of this study were to 1) characterize current stand conditions along gradients of inundation and relative elevation, and 2) describe growth patterns of silver maple (Acer saccharinum L.) trees, and their relationship to hydrological patterns. Patterns of forest composition and structure were more similar for plots comprising similar environmental conditions than plots within a stand, suggesting that current methods of stand delineation do not capture the full extent of within-stand environmental variation. I found evidence that growth patterns of silver maple had positive relationships to hydrology at a plot-level and a stand-level. These results suggest that forest managers may need to “rethink” how they summarize stand condition and develop silvicultural prescriptions.Item Mountain hemlock (Tsuga mertensiana [Bong.] Carr.) growth and cool-season precipitation in Crater Lake National Park, Oregon(2015-04) Appleton, Sarah NicoleThis study describes the development of a new network of mountain hemlock (Tsuga mertensiana [Bong.] Carr.) records at high-elevation sites in Crater Lake National Park (CRLA), Oregon, and uses these data to make inferences about past climate in the park during the last five and a half centuries. The seven hemlock chronologies, which are constructed from 53-80 tree-ring samples at each location, are highly synchronous over time, which suggests that tree growth across the Park is controlled by similar sets of environmental factors. The climate signal preserved in tree-ring-width series was estimated by comparing them against local monthly climate data, and that analysis showed an inverse relationship between tree growth and cool-season precipitation (previous November, previous December, January, March and April) and a more modest positive relationship with growing season temperature (April-August). The inverse association between cool-season precipitation and hemlock growth is opposite to the relationship displayed by most tree-ring records in western North America. Based on the observed association between hemlock growth and climate, I identify several periods during the past five centuries where snowpack in CRLA was persistently high or low. Tree growth was combined with observed anatomical anomalies, including locally absent rings, traumatic lenses, and light latewood, to estimate past hydroclimate conditions within the park. The sequence from A.D. 1809, 1810, and 1811 stands out over the last five centuries because of its low growth and high concentration of anatomical anomalies, which are interpreted as evidence for the early onset of winter in A.D. 1809 and an exceptionally short growing season in A.D. 1810.