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Revisiting historical beech and oak forests in Indiana using a GIS method to recover information from bar charts

Posted date: July 10, 2018
Publication Year: 
2018
Publication Series: 
Scientific Journal (JRNL)
Source: PeerJ. 6: e5158.

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.

Citation

Hanberry, Brice. 2018. Revisiting historical beech and oak forests in Indiana using a GIS method to recover information from bar charts. PeerJ. 6: e5158.