Browsing by Subject "dendrochronology"
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Item Earlywood vessel area analysis of Quercus macrocarpa tree rings at the Cedar Creek Ecosystem Science Reserve in Minnesota(2021-07) Crawford, DanielQuantification of various wood anatomical characteristics in annually resolved tree rings has been shown to reveal environmental information on seasonal or shorter timescales that is often not present in ring width alone. The genus Quercus is particularly important to dendroclimatology, and Q. macrocarpa tree rings are particularly useful for studies of regional climate. Further, the ring-porous anatomy of this species positions it as a prime candidate for quantitative wood anatomy. To date, the majority of dendroclimate studies involving Q. macrocarpa have been based purely on ring width. Very few quantitative wood anatomy studies have been conducted in North America, and virtually none in the Western Great Lakes states. Measurement of earlywood vessel area may provide an avenue for extracting information on past environmental conditions, even at forest interior locations which fall outside the typical schema of dendrochronology site selection. When related to tree height measurements, earlywood vessel area can provide key insights into the hydraulic properties of individual plants, water use strategies, and the history of tree height throughout ontogenesis.This study examines the interannual variability in mean vessel area as well as the reliance of vessel area on tree height in savanna and woodland habitat types at the Cedar Creek Ecosystem Science Reserve, in Minnesota. The relationship between vessel area and tree height is statistically and practically significant, and far stronger at this site than the relationship between inter-annual mean vessel area variability and climate, for which no clear process-based relationships were detected. This finding holds true when other metrics than mean vessel area are explored, including percentiles of mean vessel area, hydraulic diameter, and vessel area variance. The overall positive trend in vessel area throughout ontogenesis and the adherence of this trend to a functional allometric power curve further support the body of literature showing that tree height is a deterministic driver of vessel size in these individuals. Given the clear dependence of hydraulic characteristics on tree height, and the possible role of tree height as a factor in plant vulnerability to myriad factors associated with global environmental change, I advocate for tree height to become a standard datum in dendrochronological sampling, and encourage future studies involving quantitative wood anatomy to further examine the role of tree height on individual trends in xylem size through time.Item A False Ring Chronology of Red Pine (Pinus resinosa): Border Lakes Region, MN(2014-12) Crawford, Daniel J.; Kipfmueller, Kurt F.The presence of false rings was documented for over 100 samples (increment cores and cross-sections) from the Border Lakes Region. Marker years were characterized as years in which three or more trees at a site exhibited a false ring. The two modern false ring events were cross-referenced with instrumental precipitation data, and the full chronology was overlain with the nearest North American Drought Atlas PDSI reconstruction. The largest contributing factor to widespread false ring formation in this area is likely moisture stress.Item Multi-Scale Topographic Influences on Tree Growth: A Case Study of Quercus lobata in the Tehachapi Mountains, California(2022-12) Trumper, MatthewComplex topography can facilitate climatic and hydrologic microenvironments that buffer plants against climate change and extreme drought. However, the extent to which topographic position mediates tree growth response to climate remains an open question. Dendrochronology, the study of precisely dated tree rings, has been a valuable tool for assessing tree growth response to climate variability across topographic gradients. In this study, six new tree-ring chronologies were developed from valley oak (Quercus lobata), a long-lived, endemic species in California. Trees were sampled growing in upland and riparian hillslope positions along a 1,300-meter (4,265-feet) elevational transect in the Tehachapi Mountains of California to understand how topography acts as a mediating factor on tree growth and drought sensitivity. Valley oaks are thought to be highly dependent on groundwater, so I hypothesized that higher groundwater availability at the riparian sites would mediate growth sensitivity to drought. Results showed that tree growth patterns and drought sensitivity varied substantially in association with hillslope position and elevation. Valley oak radial growth showed a consistently weaker response to precipitation at riparian sites, supporting my hypothesis. The influence of hillslope position on drought sensitivity varied with elevation, such that the riparian buffering effect was strongest at the low elevation sites and weaker at higher elevations. At upland sites, precipitation and tree growth covaried on annual to decadal time scales, depending on elevation. The strong topographic influence on valley oak growth and drought sensitivity observed here has implications for climate refugia planning and paleohydrology using this species.Item A Tree-Ring Fire History Of The Upper Bois Brule River, Northwest Wisconsin(2019-01) Martin, LiamThe Bois Brule River is a 44-mile-long, northward flowing Wisconsin waterway. From 1650 – 1830 the river served as part of a popular fur trade route, used by the Ojibwe, the British, and the French, that connected Lake Superior to the Mississippi River. The route eventually reached such prominence that it was termed “The Historic Highway”. I developed fire histories at three discrete sites along the Upper Bois Brule River in Northwest Wisconsin in order to (A) determine the rate of historic fire along the Upper Bois Brule River, (B) provide fire history information within the context of changes in Native American and European American land use, (C) investigate the influence of seasonal drought patterns on fire occurrence and (D) provide crucial and necessary baseline information to be used in land management decision-making. The fire history is comprised of 60 fire scarred trees, 344 individual fire scars and 68 unique fire years. The mean fire interval ranged from 15.7 – 22.4 and the mean fire interval for the entire region was 5.1. The rate of fires began to slow in the early 1900s, before eventually ceasing in 1918. There was no consistent relationship between fire events and regional climate patterns when each site was considered individually. When all fire years were considered in aggregate there was a significant relationship between the event year and regional drought. Results suggest that lighting, as a lone ignition source, cannot fully explain the reconstructed fire regime. It seems likely that human land use activities may have influenced the rate of fire along the Upper Bois Brule River. These findings have important implications for future land management and can be used as a guide to achieve site specific goals.