Abstract
Historical GIS involves applying GIS to historical research. Using a unique method, I recovered historical tree survey information stored in bar chart figures of a 1956 publication. I converted PDF files to TIF files, which is a format for a GIS layer. I then employed GIS tools to measure lengths of each bar in the TIF file and used a regression (R2 = 97%) to convert bar lengths to numerical values of tree composition. I joined this information to a spatial GIS layer of Indiana, USA. To validate results, I compared predictions against an independent dataset and written summaries. I determined that historically (circa 1799 to 1846) in Indiana, oaks were 27% of all trees, beech was 25%, hickories and sugar maple were 7% each, and ash was 4.5%. Beech forests dominated (i.e., >24% of all trees) 44% of 8.9 million ha (i.e., where data were available in Indiana), oak forests dominated 29%, beech and oak forests dominated 4.5%, and oak savannas were in 6% of Indiana, resulting in beech and/or oak dominance in 84% of the state. This method may be valuable to reclaim information available in published figures, when associated raw data are not available.
Highlights
Researchers increasingly are applying Geographical Information Systems (GIS) to a range of topics, including historical research (Gregory & Healey, 2007)
Mean absolute error and root mean square error for predicted values compared to observed values were 2.75 and 3.34 for beech, 1.97 and 2.61 for oaks, 2.49 and 2.64 for hickories, and 3.38 and 3.84 for sugar maple (
Despite the poor quality of the original figure (Potzger, Potzger & McCormick, 1956), the TIF image was clear as a GIS layer (Fig. 1)
Summary
Researchers increasingly are applying Geographical Information Systems (GIS) to a range of topics, including historical research (Gregory & Healey, 2007). There is a great amount of information stored in publications that do not have associated, archived datasets, and in some cases, it may be possible to access that data using GIS. One example is published information about historical tree surveys. Surveyors recorded two to four tree species at section corners and halfway between section corners. These records provide information about forests before sustained Euro-American settlement and disturbance. Despite availability of valuable ecological data that provide a record of historical forests, transferring survey notes from the 1800s to a more accessible format is time-intensive
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