The dendrochronological statistic mean sensitivity quantifies the environmental stress experienced by trees; however, researchers have not applied mean sensitivity to interpretations of macroclimatic tolerance, because, in the southwestern United States, where the metric was developed, species' discontinuous distributions on mountains obscure range-wide patterns, and because topoedaphic factors disproportionately influence mean sensitivity in these semi-arid environments. In this thesis, I examine geospatial patterns of mean sensitivity in temperate, humid regions, specifically for Pinus strobus.
I developed P. strobus chronologies for sites across an elevation gradient in North Carolina. Correlation analyses of topography and individual tree data reveal that no topographic factor influences mean sensitivity. Conversely, broad-scale trends are evident in a collection of range-wide chronologies; specifically, mean sensitivity is lowest in the range core and increases toward range margins. These results suggest that mean sensitivity can be interpreted to reflect macroclimatic suitability. Such interpretation facilitates the identification of populations that are poorly adapted to their climatic conditions. Further, geographically weighted regression of mean sensitivity allows one to determine the specific climatic component that precludes complacent growth at any location. By accounting for non-stationarity, geographically weighted regression could even identify ecotypic responses.
Applying these methods to Pinus strobus helped to identify the species' western populations as the most sensitive, due to moisture stress. Results indicate that the high-elevation, southern populations are the least sensitive, due to abundant moisture. The geographically weighted regression only elucidated the quadratic relationship between mean sensitivity and climate, while ecotypic responses were not evident with such sparse data.
|Advisor:||Knapp, Paul A.|
|Commitee:||Liu, Zhi-Jun, Royall, P. D.|
|School:||The University of North Carolina at Greensboro|
|Department:||College of Arts & Sciences: Geography|
|School Location:||United States -- North Carolina|
|Source:||MAI 49/06M, Masters Abstracts International|
|Subjects:||Physical geography, Geographic information science, Forestry|
|Keywords:||Climate-growth relationship, Dendrochronology, Eastern white pine, Geographically weighted regression, Mean sensitivity, Pinus strobus|
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