In addition to the written records, repeated photographs of the plots have been taken since 1906. Those photographs are in the Desert Laboratory Collection of Repeat Photography at the USGS in Tucson, Ariz.

Over the years, botanists and ecologists have helped census and re-census the plots. Co-author Turner took over the work when he came to the UA as a botany professor in 1957, continued while a botanist for USGS and continues to do in retirement. In 1993, co-author Webb took up the project and is keeping the censuses going.

Sorting through data recorded from 2012 back to 1906 was a huge challenge, said Rodriguez-Buritica. She had something to build on: Janice Bowers of USGS had begun to archive the records but retired before finishing. Initially, Rodriguez-Buritica and Venable thought a year would do it – but the task ended up taking much longer.

The records were in several places – some at the library or in storage at Tumamoc and some in the UA library's Special Collections.

One of the challenges Rodriguez-Buritica faced is that methods of collecting and recording information about plants have changed over time.

Spalding, who established the very first plots in 1906, worked long before the age of computers – he recorded his observations in a small notebook. Ecologists continued to record their field observations in paper notebooks and created maps on graph paper well into the latter part of the 20th century.

All those paper records had to be digitized.

Only in the last 20 years have scientists been pinpointing plant locations and other observations directly onto a map within their computers by using GPS and GIS technology.

Upon reviewing and checking the data, Rodriguez-Buritica realized that she needed to standardize the information collected over a century so that other scientists could analyze it.

Her expertise in applied statistics and spatial ecology was perfect for the job.

She also computerized the series of maps created over time so new investigators could see all the plant location maps created since 1906.

By putting all the information into a standardized digital format and making it easily accessible on the Web, Rodriguez-Buritica, Venable and their colleagues have ensured that other researchers can build on and expand this unique data set.

Tumamoc Hill is one of the birthplaces of plant ecology, Venable said.

"In the first half of the 20th century, all the great plant ecologists either worked here or came though here," he said. "Plant ecologists from the Desert Lab were key in founding the Ecological Society of America and its flagship journal, Ecology. It is satisfying to see the project come full circle and be permanently archived 100 years later by the journal that these researchers started."

The Desert Lab and Tumamoc Hill have been designated as a National Environmental Study Site, a National Historic Landmark, an Arizona State Scientific and Educational Natural Area and are on the National Register of Historic Places.

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